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TWiP 96 letters

 Ella writes:

Long time listener, first time email.

I am surprised that no one got the diarrhea case, although I would have been wrong as well, so many familiar parasites!

I was diagnosed with Blastocystis hominus in 1990 when I came back from a year in Nepal. The symptoms were more like Giardia than anything else, but were not self-limited. I did the series of three stool tests and got told by college health services that this was a "new" pathogen being found in HIV patients. I was given the # to CDC by the lab and told to call. I did, they recommended 7 days of metronidazole, which the college doctor gave me and my symptoms went away and have never returned. Dickson said there is no treatment, was I just lucky?

I later had Entamoeba histolitica during my Peace Corps Service in the Central African Republic. I'd forgotten the bit about it being non-invasive. Good stuff. I also had Giardiasis during my first trip to Nepal. Now I never catch anything when I travel.

I went to Dartmouth Medical School (before the Seuss conversion) and was taught microbiology by the incomparable Elmer Pfefferkorn, the kindest man alive.

I was turned on to the TWIX podcasts by a friend who is a bench scientist and really love the intellectual stimulation and memories it brings up. I must say, overall Dickson is my favorite, and I dread the day that Vincent tells us how he really feels. (I like all of the other co-hosts as well but on TWiV Dickson's role of audience surrogate, and his function of winding up Vincent makes him precious.)

The weather in Kathmandu is 71F, 21C, 94% humidity, likely to rain either tonight or tomorrow.

Thanks for everything.


Lynn writes:

Dear TWIP Team,

I'm a molecular biologist who has spent the past 2+ decades raising 5 wonderful children (a zoologist, a veterinarian, 2 engineers and the youngest is a freshman). My many and unanswered job applications have informed me that I'm no longer 'lab-worthy' so I fulfill my love for biology by taking Coursera courses (Dr. Racaniello's of course), reading fascinating books (D. Crawford's Deadly Companions for instance), and listening to TWiV, TWIP , TWIM and Urban Agriculture!

My guess for the case study of TWIP 95 is Ancylostoma braziliense, a type of hookworm which thrives in sandy soils of subtropical regions and is an intestinal parasite of cats and dogs.. It is the major cause of cutaneous larval migrans in humans. Humans are dead end hosts - the hookworm larvae do not develop further. However, they cause intense itchiness which I would imagine could lead to secondary bacterial infections in the affected area. Treatment is administration of oral thiabendazole, 500 mg, 4 daily dose. I think the ceviche is a 'red herring'!

Many, many thanks for such informative and entertaining podcasts!

Robin writes:

Cutaneous larva migrans

The question to ask is how the anterior thighs were in contact with contaminated sand. Perhaps lying prone with the cloth being short and only up to the region of the hips. The anterior legs may have been spared by the angle at the ankles.

Benedict writes:

Hi, i think the lady has cutaneous larva migrans from the wild dogs' helminths

Joseph writes:

Cutaneous larva migrans

Peter writes:

Diagnosis, Cutaneous Larvae Migrans, possibly due to A. Caninum.

Nicholas writes:

Dear Drs. of TWiP,

I have to admit I took a slight hiatus from your program only to return to what is an even more informative and entertaining program through the addition of the clinical expertise provide by Dr. Daniel Griffin. I applaud you all and extend my deepest gratitude for your efforts in disseminating knowledge in your respective fields.

I'm currently an anatomical veterinary pathology resident at Louisiana State University. Attending veterinary school in Kansas, many of the things I’ve diagnosed while in Louisiana I either never learned about, or resulted in a margin note of “this disease is only a problem of the south, don’t worry about it for the examination”. As the always hot and humid southern Louisiana would have it, those diseases have now become my everyday reality and a love for infectious disease has followed.

In regards to the 28 year old female beach goer, as a veterinarian a mental image of a puppy with pale mucous membranes and a small intestinal lumen full of hookworms and hemorrhage comes to mind. I believe this is a case of Ancylostoma caninum (hookworm), a zoonotic agent that claims canids as a definitive host. Humans become infected through exposure to L3 larvae that develops from morulated eggs deposited in the feces of infected canids. The L3 larvae directly penetrate the skin and manifest clinically as erythematous and pruritic serpiginous tracts, which is a classic presentation for cutaneous larval migrans. This woman was predisposed to developing this condition through her adventurous nature, which led her to secluded beaches inhabited by feral canids. These animals are typically not tolerated at popular public beaches and thus people are less likely to be exposed to the infective L3 larvae stage. I find it interesting that her companion somehow didn’t also display evidence of cutaneous larval migrans, but maybe he was more interested in surfing than sunbathing. I also anticipate there wasn’t much beach romance going on, at least without the use of a towel or tent. With that in mind, sex on the beach is best served cold. I frequently see this species of hook worms in young puppies, which I presume is due to repeated transmammary exposure through ingestion of milk and/or lack of repeated deworming in puppies. In contrast, I rarely see this parasite in domesticated adult canids, which I attribute to the high compliance of monthly antihelminthics, which are routinely prescribed in veterinary medicine for various parasites including heartworms, hooks, ascarids, and whipworms. For everyone’s viewing pleasure, I’ve attached a gross image from a case I had in a puppy that died from severe anemia attributed to ancylostoma caninum. In the future I’d be happy to share gross or histologic images from my cases, so please don’t hesitate to to shoot me an email if you’re presenting a zoonotic agent that is prevalent in the southern U.S. I’ll be beginning a PhD next fall at the Tulane Primate Center and will be commuting daily from NOLA, which means I'll finally have an opportunity to catch up on TWiP, TWiV, and the likes!

Thanks again for all you do,

Christine writes:

Dear Vincent, Dickson and Daniel,

Greetings from sunny brisbane where the temperature is a delightful 26 degrees C and a light breeze gently rustling in the Macadamia leaves in my backyard.

Although the past 2 twips have not appeared in my podcast feed (hence I missed the last one entirely) I finally got grumpy while listening to twiv (which is showing up) when you said you had recorded 4 podcasts that week, and found them on microbeworld.

This weeks patient is showing the classical signs of Cutaneous Larval Migrans. It is, as you know, an infection with hookworm larvae in the skin. A number of species are associated with it depending of location of infection. Ankylostoma braziliense is most common in Central America and South America and infects dogs and cats. Humans are a dead end host and therefore the infection is self limiting, although the discomfort and unsightly appearance leads to treatment using antihelminthics such as tiabendazole, albendazole, mebendazole, and ivermectin.

Without going into the lifecycle etc., the patient most likely contacted the infection by lying on the sand on her light 'sari' material through which the larvae could pass when they hatched from eggs deposited in/on the sand in the faeces of the wild dogs seen in the area.

The boyfriend may have simply been luckier where he lay or if he lay on a more substantial towel it may have been sufficient barrier to the larvae. The larvae may lie dormant for weeks or months or may migrate straight away, therefore we cannot be sure exactly when/where she was infected but as she did not notice the bumps till she got back it was probably towards the end of her trip.

Yours in anticipation of more great stories and learning,
Christine from Brisbane.

Dave writes:

Dear TWiP Trio,

In the case of the 28 year old woman who visited Belize, I believe that she has a case of hookworm infection, specifically cutaneous larva migrans caused by Ancylostoma braziliense. Humans are accidental hosts to these parasites (which typically parasitize dogs and cats). When contaminated feces come in contact with skin, the larvae of the hookworms burrow under the skin and begin to travel through the skin. The fact that there were wild dogs on the beach is a major red flag, and along with the serpiginous rash, locale, and sensation of movement, this points point to cutaneous larva migrans.
Recommended treatments: albendazole, ivermectin, thiabendazole.

The weather in Shrewsbury, MA is a cool and cloudy 62 degrees F.

PS, i think you will be happy to know I recently purchased my membership to the American Society of Parasitologists! I plan on reading the journal as much as I can, and I hope this decision helps potential graduate professors show my passion for parasites (what I want to study for a PhD).

Elise writes:

Dear TWIP Trifecta,

How are you? I hope this finds you well. It is suddenly a bit cooler here in Lower Manhattan: 72 F/22 C, but the weather is very nice, so I’m not complaining.

After failing to correctly diagnose TWIP 94, I am picking myself up again and attempting to sort out whatever is going on with the Young Woman who Went to Belize.

I believe the patient has Cutaneous Larva Migrans. The infection/infestation is usually caused by hookworm larvae (Ankylostoma caninum and Ankylostoma braziliense are the dog and cat hookworms). Everything seems to point to hookworm. CLV is quite common in South America (and Dr. Griffin pointed out that he had another very similar case in Lima, Peru). In addition, the patient spent a lot of time on rather remote, non-touristy beaches in Belize that were frequented by wild dogs. Since the hookworm larvae is transmitted to new hosts through dog or cat feces, it is not at all unlikely that the dogs she saw were once or future hookworm hosts. She spent a lot of time lying on the sand, and while she used a thin sarong type fabric as a blanket, the fabric’s weave may have been loose enough for the larvae to get through or she may have spent some time exposed directly to the sand. (Many cases of CLM manifest themselves on people’s feet and between toes because walking barefoot on the beach is so common.) I was thinking that the fact that she frequented more remote beaches was significant because more touristy spots, especially those close to resorts, tend to be cleaned up more regularly and are busier so that animal traffic may be somewhat more limited.

In addition, the patient’s symptoms are consistent with a CLM infection. When Dr. Griffin first described the patient’s distress, I was confused, because his very gentle discussion of a little raised nodule with a red “serpiginous” line coming out from it didn’t sound so dramatic, but when I found images of CLM infections online, I see that it would indeed be very upsetting. Also, severe itching is another symptom of a hookworm infestation and that is awful, indeed.

While these infections are self-limiting (after what sounds like a miserably itchy and rashy series of weeks), they can be treated with topical medication (Thiabendazole) or with oral medications (Albendazole, Ivermectin). Is there a reason for preferring the oral drugs to the topical or vice versa?

After an off week, last week, I do hope I did better this time.

As always, thank you so much for your wonderful work.

Best wishes

Andrew writes:

Dear TWIP Team,

My conclusion is that the patient is suffering from cutaneous larva migrans, most likely caused by Ancylostoma braziliense. The presence of dogs on the beach and the use of thin fabric support the evidence. The hookworm eggs were likely passed through canine feces which landed on the sand, where they hatched. The larvae were then able to penetrate the patient's skin through the thin fabric. The symptoms of red, itchy bumps and lines are consistent with cutaneous larva migrans, as the worms creep through the skin. Although human hookworms are able to cause intestinal problems, A. braziliense, an animal hookworm, lacks the enzymes needed to burrow deeper through human tissue (normally, the worms travel to the lungs first and then end up in the intestines.) Finally, there is geographic evidence, as A. braziliense is known to be found in Central America.

Andrew writes:

Hello Twipanosomes,

I am an electronics engineer based in Christchurch, New Zealand. My diagnosis of the current case is scabies, key symptoms being the itchiness and wavy lines.

Many thanks for the many hours of fun and information. I'm a keen listener of TwiP, TwiV and TwiM.


Eric writes:

Dear TWiP triumvirate, thank you for another fun case of the week. All clues given seem to point to a clear case of leishmaniasis. The described wild dogs were likely the reservoir hosts on these secluded beaches. An infected sandfly likely bit the woman while she lay on the beach and the infection ensued. Treatment will not be fun.

It is sunny and 70 degrees here in Seattle, a beautiful fall day.

Carol writes:

Greetings Team TWiP,

After a busy summer during which I have been listening to the podcasts but not finding time to write in, even when there has been a multi-week gap between episodes, I've finally managed to send this before then next episode has aired. I suppose the structure of a full semester can be beneficial after all, compared with the relative freedom of taking a single summer class.

I am going to resurrect a previously-incorrect guess for this episode's case study. If it is again incorrect, I will continue to guess it every episode until it is correct. Foul-smelling steatorrhea? I will make the same guess. Long worm removed from an ankle lesion by twisting it around a stick? I will make the same guess. It will have to be right some day.

The woman with the serpiginous red lines creeping out of papules on her thighs has cutaneous larval migrans, presumably Ankylostoma braziliense. The wild dogs, beach, pruritis, and many other things point to this being correct. If not... there's always the next case study.

Thank you always for an enjoyable series of podcasts,

Carol from Victoria, where is it currently raining gently and 16C.

AJ writes:

Hello Twippers!

I'm writing a guess for the case introduced in Arsenic and Leishmania. What fun, contemplating all of the subcutaneous visitors you can acquire at the beach! This sounds to me most like a case of cutaneous larva migrans. I know a couple of species could be culpable, but considering most of what I know of this condition comes from one House MD episode, I won't speculate a precise species. I hope this poor lady got those pesky zoonotic hookworms removed without issue.

Also, the TWiP website appears to be down at the moment! I can still access TWiV and TWiM though.

Keep it up!

Clarke writes:


I have been enjoying your podcast during my compute for quite some time.

Knowing how Dixon likes fishing, and both of your thoughts on parasite/non-parasite co-evolution, I thought you might find the attached paper interesting.

My interest is in foodborne (particularly fishborne) parasites that may infect humans.

Recently the Japanese have linked Kudoa spp. with gastrointestinal illness.

Please keep up the podcasts.

Best regards,

Clarke Beaudry
Division of Seafood Safety
Center for Food Safety and Applied Nutrition
US Food and Drug Administration

John writes:

This video is worth a watch or a listen. Jimmy Carter talked about neglected tropical diseases at AMNH last winter:

Ramon writes:

Tale of the tapeworm...squeamish readers stop here.

James writes:

Kia ora folks,

Thought of you lot when reading this article. Reminded me of some of the stuff Dickson has mentioned in the past.


Michael writes:

I’ve become quite the fan of TWIP (as well as TWIV & TWIM.) In addition to listening to the current episodes, I find myself spending far too much time working my way through the backlog and dreaming of the day where I placate my more OCD aspects and have listened to them all.

I love listening to them while cooking and eating which may sound strange to some since the topics aren’t necessarily typical eating friendly topics. But on the other hand, it does serve to keep me from avoiding any shortcuts in my food prep, cooking and clean up.

One nit-pick (which is yes a parasitic joke – please and thank you), the sign off. While “Another TWIP goes parasitic” does nicely parallel the one for TWIV – I think I’d prefer “Another TWIP worms its way into your hearts…” as being far more topical….


PS: So does the fact that all the acronyms for your respective podcasts start with “twi”, an admission of your secret Twilight (movies, books) fandom – leading us to the inevitable descent in Gothdom by you all and the release of “This Week In Vampirism?” ;-)




TWiP 95 letters

Ruben writes:

Dear Day-Twippers,

I am a big fan of TWIP. You do so many things right, that a little problem in your TWiP94 broadcast is not a big deal. As you may already know all three drugs in the Nutman et al. study are small molecules, not monoclonals, they are -tinibs, not -mabs. That is why they work on an intracellular target, the tyrosine kinase domain.

Vincent had the right questions and hesitations about what was claimed to be an orally available antibody, but Dickson and Daniel convinced him that it should be fine with the right capsule :-(. A good lesson from this situation is that it would be a good habit for at least one of you to check the facts with Wikipedia as they emerge and doubly so if there is even a slight doubt, especially outside the area of expertise of the three co-hosts.

Keep up the good work and please continue. In the future you may consider including a pharmaceutical chemist every now and then.

Ruben Abagyan, Ph.D.
University of California, San Diego
Skaggs School of Pharmacy & Pharmaceutical Sciences

Ken writes:

Hi Vincent,

This week during my daily commute, I was listening to TWiP episode 94. It was a very good episode; however, as I was listening, I noticed an error with regards to the description of the mechanism of action of the drugs in the filarial paper that you discussed. Gleevec (imatinib) and the other two drugs are small molecule inhibitors of tyrosine kinases rather than being monoclonal antibodies. I imagine you have caught this error or had other listeners write in, but just case in not, I figured I would write in to let you know. Looking forward to more TWiX episodes in the future along with the newer Urban Agriculture podcast. They are a great way to stimulate my mind during my daily commute to and from MedImmune!

Best wishes

Anthony writes:

On TWiP 94 around 1:05 Prof. Despommier mentions ". . . Gerds (?) and other weird mammals . . ." as model organisms. What are Gerds and these other mammals? I made some attempts at a Google search but got listings for acid reflux disease in dogs.

Thank you.

Steve writes:

Hi Vincent, Dickson, and Daniel!

Good to have you back after the hiatus, and thanks for ‎filling me in on the 'usefulness' of the dreaded ticks!

Dickson was wondering if it was possible to freeze fish quickly and cleanly, and the team seemed vague on how it was done. This reminded me of the superb, but harrowing, documentary on the soulless way we produce and treat our food: 'Our Daily Bread'. It is made all the more effective by having no narrator: just the machines and the human robots who mind them.

The section beginning about 1hr 10 min in shows how farmed salmon is prepared. I think you will find it to be one of the most soulless parts of the whole piece.

Everyone should see this film.
And wonder what it is to live in a world run by humans: only for humans.

All the best,


Where it is a pleasantly cool and quiet night.


Steve Goff writes:


Robin writes:

Sounds like Cryptosporidium. Could be hominis, but with the Chilean cattle / beef industry parvum is a consideration.

Jerry writes:


Varun writes:

Greetings Professors,

First, I wish to point out an error in the episode. A lot of discussion about the Protein kinase inhibitor for CML therapy (i.e Imatinib) rested on the idea that it is a monoclonal antibody. To the best of my knowledge it is a 2- phenyl amino pyrimidine derivative and not a mAb.


Coming to the clinical case challenge, I would like to know if there are CD4/CD8 counts available and is there a current HIV viral load status available. I would like order a stool examination for a iodine wet mount and an AFB stained stool examination.

Considering HIV status, there is following plethora of possibilities. Not sure which one to pick.


Cystoisospora belli


I just have a curiosity. I wonder if Dickson would do a parasitology course hosted at Coursera. That would be a blast.

I love the way you people deliver excellent educational content every single time without fail.

Thank you
TWiX Fan

Varun C N

Junior Research Fellow
Department of Neuromicrobiology
NIMHANS, Bangalore

David writes:

Dear Daniel, Dickson and Vincent,

Thank you for another riveting parasitic podcast, which makes busy work at my lab seem but a breeze. It is truly a treasure - listening to three brilliant scientific minds wax poetic the wonders of the parasitic world.

The symptoms that the patient featured in the case study of episode 94 seems to point to none other than Isopariasis caused by Cystoisopora belli. This parasite is ubiquitous, but is found in many tropical/subtropical areas of the world, including Chile. The patient shows the classic signs of isopariasis (diarrhea + headaches); and the smoking gun - isopariasis often occurs in immuno-compromised individuals - finalized my hypothesis.

The weather in Boston is overcast with clouds, 20% chance of precipitation, 74% humidity.

Best wishes,

Elise writes:

Dear TWIP Trifecta,

Well, this time I was away (but not for SO long) so please forgive me if this diagnosis shows up late.

After days of murky heat and piles of rain, it is lovely here in lower Manhattan, 79 degrees F / 26 degrees C, but thunderstorms are returning, so it will be moist again in no time.

I am going to attempt a diagnosis of the 33 year old Chinatown resident who has been suffering from intermittent diarrhea for months. I suspect that he has a Giardia infection (giardiasis). It is possible (and as a dog owner, I know this very well) to become infected with giardia in the Northeast but the parasite is extremely common in Chile, where the patient has been recently.

Often, people infected with giardia have no symptoms, but watery diarrhea of the sort that the patient describes, is one of the most common. The infection is spread through contaminated water and food, but it can also be spread through oral and anal sex. The patient describes a very varied sex life with many partners, so it is very possible that if he did not encounter the parasite in his food (and he does say he is an “adventurous” eater), one or more of his recent partners could have infected him.

I do have some questions, though. My reading suggests that giardiasis is usually self-limiting, so for this case to linger, in a relapsing fashion, for months is a little unusual (however I have found mentions of post-infectious irritable bowel syndrome, which would cause the symptoms to persist). Does his HIV status make him more prone to giardiasis or do the medications he takes make him more vulnerable to gastric symptoms?

Finally, I had found some descriptions of tapeworm (Diphyllobothriasis) infections that have some similarity to the patient’s experience, but I am still inclined to think that giardia is a more likely suspect. I am prepared to be wrong with this diagnosis.

Thank you so much as always for your terrific work.
Many best wishes

SJ writes:

Greetings from the Eastern Sierra!

The entire state of California is on fire currently, and the small system that moved through yesterday did nothing to dampen that fact. Currently, it is 18 C with a 22 percent chance of precipitation. Lots of smoke in the air.

For the 33 year old Chinese male, I have to say this was an interesting one. As was pointed out, there are MANY causes of recurring diarrhea. Thankfully, the viral, fungal, and bacterial options have been ruled out due to this being TWIP. Otherwise we could look at traveler's diarrhea (given our patient's love of travel) as a possible diagnosis.

I'm going to guess that it's cryptosporidiosis. The symptoms are relatively minor, which rules out more serious parasitic infections. It could be giardia, which occasionally recurs, but the main reason I picked a cryptosporidium infection has to do with the patient being an HIV infected male. For one, immunocompromised individuals have a difficult time fighting off cryptosporidiosis and often see symptoms return. For another, certain sexual practices can cause direct infection and do not require the patient to ingest infected food or water. Finally, according to wikipedia, cryptosporidium is the most common organism isolated in hiv infected patients presenting with diarrhea.

The headache could simply be a coincidental symptom, or perhaps is due to mild dehydration.

Thanks, and I look forward to the next episode as always.


Robin writes (guess for man from El Salvador):

Seems like Chagas'. Left heart failure sans right heart failure may account for both the absence of reported dependent edema and the "throat closing" when supine. The throat hurting might be dysphagia related to loss of the nerves plexus of the esophageal musculature. Damage to Auerbach's plexus could account for constipation: sort of like a diffuse acquired Hirschsprung's disease. Serologic testing might keep him out of the blood bank. PCR or blood film exam could confirm the diagnosis. The chronic upper body and upper extremity rash may be unrelated, an unusual manifestation, or an indication that the gent has something other than Chagas'.

1. The quote about one death being a tragedy and a million deaths being a statistic is routinely misattributed to Josef Stalin; its origin is unclear.

2. Scrubs should be used in areas where procedures are being done, and should be forbidden elsewhere. No entering or leaving any medical facility in scrubs.

Peter writes:

Hi TWiP team I thought this paper from Parasites and Vectors would be of interest:

Not every worm wrapped around a stick is a guinea worm:
a case of Onchocerca volvulus mimicking Dracunculus medinensis

Dylan writes:

What's your opinion on flagging patients as delusional when they bring their physician suspected parasites? It seems that many of the "symptoms" or signs of what to look for with suspected delusional parasitosis is the same behavior and actions one would take if they were actually infected with a "worm". I'm including a link to a couple photos of one of the many very large flukes that I brought to my Dr., only to have them inquire where I got the vial that it was in, and to be diagnosed with obsessive compulsive behavior. Please look.

Scott writes:

Dear Daytwippers,

Here is an interesting paper on a newly discovered antimalarial protein found in mosquitoes, that has some potential for use in a vaccine. I would be interested in your comments on it during the podcast:

Cartago, Costa Rica

Robin writes:

With regard to the question of why mammals have non-nucleated red blood cells, while the other classes of vertebrata do, mammals emerged about 150+ million years ago, nearly contemporaneously with the reptiles, but were presumably homeothermic from the outset.

This demanded higher metabolic rates, that were partly fulfilled by denser networks of smaller capillaries, which in turn required smaller and more flexible erythrocytes. Discarding the nucleus allowed for a reduction in size without a corresponding loss of haemoglobin, and with the additdonal benefit of enhanced flexibility. The downside to homeothermy was limitation of body size imposed by those much warmer climates through constraints on thermoregulation.

So the poikilothermic dinosaurs got bigger. Homeothermy in the saurischian dinosaurs and their bird descendants was presumably a rather late development, and the evolution of denser networks of smaller capillaries with their concomitant of non-nucleated erythrocytes, a chance happenstance in our lineage, has not occurred in them.

Ola writes:

Dear TWIPers,

Hope you are all well.
I am writing to you to ask whether at any point you have covered the subject of microRNAs found in secretory products of nematodes. I've searched through the microbe world website, but couldn't find anything relevant. Do you think the fact that immunomodulatory microRNAs were found eg. in H. polygyrus suggest that they are used by other parasites? This is probably mediated by gene silencing by microRNAs, but how about other genetic material? How about transferring mRNA or DNA to the host? What do you think about it? Also, can you think of any potential therapies if microRNAs turned out to play a big role in parasite world. I am very curious of your opinions on this field.
Best Wishes,

Heather writes:

Hello Doctors!

The conscientious eradication of most over-talking has greatly improved the TWiP listening experience. Thank you!

Here is an article you might like to address on a future TWiP:


TWiP 94 letters

Elise writes:

Dear TWIP Trifecta,

How are you? It is lovely here in lower Manhattan, 82 F / 27 C with blue skies and not much in the way of humidity to make things wilt.

Since you are all going on the road, I’ll be on the edge of my seat waiting to hear about the patient from TWIP 93, and here is my diagnosis. I believe the patient has Chagas disease.

There are two phases of the disease (acute and chronic) but people often don’t develop the acute symptoms or they pass and the disease becomes chronic and unnoticed until other symptoms develop. It can take quite a number of years before chronic infections reveal themselves. Chronic chagas infections can lead to a wide range of problems including: cardiac damage, digestive problems, difficulty swallowing, nervous system problems and even dementia.

The patient has been feeling pretty well, but his low-level complaints are consistent with a chronic Chagas infection. His intermittent constipation is probably the result of digestive tract problems caused by Chagas disease. (Chagas is apparently the cause of a large percentage of the cases of “chronic megacolon” in Central and South America. I think I saw a megacolon at the Mutter Museum in Philadelphia. It is very hard to know how someone could get around town with that.) Since he spent a large portion of his life in El Salvador, where Chagas is common, it makes sense that this is something he contracted when he was living there and now continues to harbor it.

In addition, his difficulty with the feeling of his throat closing when he lies down, and his sore throat are also consistent with chronic Chagas disease (which can also lead to “megaesophagus”— which sounds extremely dangerous and hard to live with as well).

His rash can also be a symptom of Chagas disease (and his description of it that it is not hugely bothersome and comes and goes intermittently is also consistent) but most descriptions I have found suggest that the rash is more of an early symptom of the disease.

I assume that until the blood bank referred him to his physician, he would have been content to live with these symptoms since they aren’t really interfering with his life, but now that he knows what is going on, he should get rid of the parasite before it can cause more damage. Has his heart been damaged at all? What is the best way to treat a patient with this chronic an infection and will he be able to recover?

I hope you all have wonderful August excursions and come back with all kinds of stories. Until you return, I will have to track down case studies and diagnostic riddles wherever I can find them.

Many thanks and best wishes

Mark writes:

It is 37 degrees centigrade in Oklahoma today and humidity feels quite high.
I live in the American South so I am extra interested in the 39 year old El Salvadoran American's case. There has been some concern that the disease described may be endemic in warmer climate areas of US.

I am guessing the patient has the symptoms of American trypanosomiasis, or Chagas disease. The rash and the constipation and upper GI strictures are symptomatic of this disease, (due to thickening of smooth muscle tissue of colon and gi tract). American trypanosomiasis has recently been added to the CDC list of blood borne pathogens screened for in US.

Problem is that the blood bank refer patients diagnosed with this disease to physician and patient may be asymptomatic and physician, lacking familiarity with the disease, may not notify CDC for treatment advice. Treatment advice from CDC includes free medication.

Also in some locales physician may not refer patient to infectious disease physician. The symptoms do not only include what were described in Daniel's case, but can also include cardiomyopathy.

I am a Clinical Pharmacy coordinator and am trying to get the news out regarding Chagas Disease to physicians who practice at my hospital. Chagas disease may sound rare and unknown, but I have seen a cone nose kissing bug of the variety described in Chagas Disease reviews at my residence. Also where I live we are blessed with a Hispanic American and migrant worker community, some who are recently from Latin America.

Thanks for this interesting case.

Clarification on guess of diagnosis. Mega colon results from dilation of Colon due to nerve damage and decreased smooth muscle tone and same happens to esophagus, Difficulty swallowing is a symptom that can cause malnutrition in patients.

Here is a fact sheet from cdc on Chagas' disease, American trypanosomiasis.

Lee writes:

Dear TWiP;

I am a long time listener and lover of your podcast, but have never written. So, hello!

The combination of a skin rash with intestinal problems, along with the fact that the problem was identified during blood donor screening. leads me to a diagnosis of Chaga's Disease (Trypanosoma cruzi). This is consistent with the patient's history of living in rural Central America where both the trypanosome and its kissing bug host are endemic. As you pointed out on a previous TWiP, rural South and Central American houses with thatched roofs are a perfect habitat for T. cruzi's triatomine vector. An immunologic test for Chaga's antibodies would confirm the diagnosis. Alternatively, a microscopic evaluation of a blood sample should show the presence of trypanosomes. Furthermore, the patient's file, specifically his mother's heart attack history, suggests that other members of his family may be affected by the parasite and should be screened.

Treatment with antiparasitic drugs will not entirely eliminate the patient's parasite load, but may improve his quality of life and reduce his risk for further complications from the disease.

The weather in Portland is hot (27 C), sunny and dry. This is not what I expected when I moved to the Pacific Northwest; I'm hoping it cools down by the time your next podcast rolls around.

Hope you're all enjoying your August holidays,

SJ writes:

Hello TWIP team!

It's currently 32 C with scattered clouds here in the beautiful Eastern Sierra. Unfortunately very smoky due to due forest fires. Watching the Perseid meteor showers is difficult this year as a result of all the smoke.

Being from El Salvador and due to being rejected as a blood donor, my first thought was Chagas disease for this episode's case study. At work we were discussing the insect vector diseases that are threatening to cross the border from Mexico and the subject of Trypanosoma cruzi being included in the blood donation screen was brought up. In some cases, Chagas causes enlargement of the colon and the esophagus, which may be the root of the patient's bowel and swallowing problems. The rash is also indicative of chagas, though I understood that to be more of an acute phase symptom than a chronic phase symptom.

Lastly, Dr Griffin mentioned that his facility has become the local 'experts' on the disease in question. I believe I recall him mentioning in previous episodes that they had become a Chagas disease center of sorts.

Hopefully the patient doesn't suffer from cardiac damage as well.

Thanks as always for putting together these wonderful podcasts.

dr wink writes:

The man from El Salvador

As a protozoology major in college (OSU let me create my own major), I'd better get this one! I say Chagas' Disease. I suspect megacolon and achalasia, but I don't remember anything about a rash -- can't wait for you to resume pod-casting to hear the discussion.
Wink Weinberg

David writes:

Dear Daniel, Vincent, and Dickson,

I was disheartened to learn my guess of the salmon tapeworm (which didn't make it on time to be aired, sparing me some minor embarrassment) was the incorrect diagnosis, but Anisakis was indeed my second guess, so that gives me a bit more confidence.

As for my guess regarding the 39 year old immigrant from El Salvador, I was quite puzzled as to this particular combination of symptoms, including skin irritation, throat closure, constipation, and rejected blood.

After much research, I will venture the guess that this is Chagas disease brought on by Trypanosoma cruzi. This parasite enters the bloodstream through the bite of a reduviid bug affectionately called the kissing bug. This protozoan parasite causes the megacolon symptom which manifests as constipation and causes skin lesions manifesting in his irritation. The patient's trouble swallowing also points to Chagas disease, and I am assuming the patient was denied blood donation due to the discovery of trypomasigotes in the bloodstream.

The weather in Shrewsbury, Massachusetts is 62 degrees Farenheit, a nice respite from the interesting heat wave Massachusetts has been enduring, a rather fitting fate after the Noreaster that slammed the region this winter.

Best wishes,

David writes:

Good afternoon, all! I hope I am not too late

My name is David, I am currently a research technician at Mass General Hospital. I am interested in becoming a parasitologist, and figured listening to your podcast would be a great way to continue my already-powerful attraction to the parasitic world. I am going to venture that the parasite in the case study is none other than Diphyllobothrium pacificum/latum- also known as the salmon tapeworm. The reason for selecting his parasite is due to the symptoms that our patient suffered (nausea, abdominal pain, vomiting, fever) as well as the ubiquitous nature of the parasite - found along the entire northern hemisphere. The fact that none of her other friends suffered symptoms is also a clue to the culprit - according to Scholz et. al (, four out of five cases can be asymptomatic. Diagnosis includes identifying eggs in the feces, treatment includes Praziquantel (although not FDA approved)

The weather in Boston is an extremely balmy 88 degrees F, with a 50% humidity.


Steve writes:

Hi TWiPers,

Looking forward to your next podcast. They seem to be a long way apart once one has caught up.

Just a quick question for Dickson:‎ I was just about to listen to a webinar on a new Lyme vaccine, and, there at the start, is the usual picture of a tick. Looking at the loathsome creature, I find myself wondering: what is their ecological function? If they were all to disappear tomorrow, would it be anything other than a blessed relief to everything but the diseases they carry?

I can usually think of something good to say about most creatures, but these seem to have no function other than to cause suffering.‎ Pure parasite with no redeeming features.

I wonder if Dickson knows of any good purpose they might have? Maybe it's just to slay animals that don't have any larger predators, but it seems to me that they are a pure pestilence that the World would be well rid of, and it really is against my nature to say it.‎

Even the dreaded mosquitoes provide food for a wealth of other creatures, but ticks: a few birds like Ox Peckers may feed on them, but I bet more feed on them than they catch themselves!


All the best,

Rather grey and windy, but quite warm at the moment.

Morgan writes:

Dear TWiP friends,

This is my first time writing to you after discovering TWiP and the rest of the Twix series last fall on iTunes. I greatly enjoy all of the Twix podcasts, but TWiP is without a doubt my favorite. Like many of your listeners, I too am enjoying the “new and improved” format with the case studies and the inclusion of Dr. Griffin – he brings a vibrant new energy to your discussions, and his insights and stories about parasites from his perspective as a medical practitioner bring a new level of fascination and entertainment to the show. As an amateur entomologist I have especially enjoyed episodes involving medical entomology (particularly enjoyed TWiP 28 w/ Robert Gwadz). Do you think it would be too corny if I said I wanted to ‘put a bug in your ear’ encouraging you to include an occasional guest entomologist on TWiP?

I do not have a guess at this time for the recent TWiP 93 mystery case, but I do have a question for you. One recurrent topic on TWiP is the acquisition of certain parasites by eating certain meats or raw/undercooked meats. What about insects? With entomophagy on the rise, should we begin concerning ourselves with parasitic infections we might get by eating insects? While many insects have their own parasites, are there any human parasite infections we could acquire only via the consumption of insects (versus transmission via insect bite)?? Or is this the sort of thing we will only begin to learn with time and experience as more people become comfortable with the idea of eating things like cricket flour and cockroach kabobs? Advocates of entomophagy claim that insect protein is healthier than the protein obtained from beef, chicken, pork, etc., and that it is more “green” to raise insects for food than it is to raise cows, chickens, pigs, etc., but I am curious if humans can expect to encounter parasites in their undercooked caterpillar sushi (if that is even a thing yet) just as we do in undercooked meats. I have not done enough reading to know whether or not the statements about health and the environment are accurate, but like to think that, if they are, people will eventually catch on to entomophagy as part of the “green” movement and transition to a diet that includes insects. As a vegan, I would also encourage skipping the whole entomophagy thing and transitioning directly to a plant based diet, but tend to think of entomophagy as a baby step for a culture that will someday hopefully cease eating animals altogether. But for a new experience, next time you are in D.C., try Oyamel Cocina Mexicana for their chapulines (Oaxacan grasshopper tacos), margaritas and cool décor. This can be done before or after a visit to the Smithsonian Museum of Natural History’s insect zoo J

On an unrelated note, but to provide you another bit of color to add to the diverse tapestry of that is your listening audience - I am a 27 ½ year old student attending community college after a 7ish year hiatus from school. Guess what I am interested in studying? If you guessed entomology, you are correct. I also work full time as a legal secretary, part time as public relations director for a local small animal rescue, and am mom to a houseful of animals big and small. My daily commute involves a bus ride, followed by a ferry ride (or a ferry ride followed by a bus ride, depending which way I’m going…), so you can imagine how TWiP has become a wonderfully welcome addition to iTunes listening library. TWiP has also become my default listening selection for summer Sundays spent relaxing on the sands beside the Atlantic Ocean in Virginia Beach.

The weather this morning in Norfolk, VA is unnaturally pleasant for this time of year with the temperature around 23°C with 85% humidity; a bit of rain around daybreak and more forecast this afternoon. No worries though as the weekend calls for plentiful sunshine on the beach. Thank you for TWiP and for your sensational efforts in “edutainment”. Keep up the good work.


PS: I’d also like to mention that I find it highly entertaining when Vincent says “Reduviid bug” and would like to encourage him to say it on air at every given opportunity, regardless of its relevance to the current conversation topic. Such flair and enthusiasm in his pronunciation! Vincent, you might appreciate the fearsome and magnificent Arilus cristatus. In the event that there is such a thing as reincarnation, this is exactly what I want to be on my next go ‘round J

Trudy writes:

Dear Twip Trio,

Just listening to the last Parasitic

TWiP 93 letters

Sandra writes:

Daniel: I was fascinated by your answer to the case from TWIP 91 - the life cycle of the southeast Asian worm (I won't even try to spell it.) Re early symptom coughing & wheezing: if the ED did a chest X-ray out of concern about the lungs, would the X-ray give any clue as to the true cause?

Sandra in Dallas

Anthony writes:

If memory serves me correctly, in dogs and cats, roundworms evacuated after a dose of piperazine tend to coil in a "watch-spring" shape unlike any other worms. Is this not the case with human roundworms?
Is the watchspring shape in dog and cat roundworms an effect of piperazine? Or is the lack of this form in the human parasite images an effect of preservation?

Tangentially,the reason for the parasite jumping ship in the case study was attributed to the stress of acquiring the craft of medicine. If this wasn't meant as dry humor, should such apprenticeship be
questioned? If a parasite senses their vessel to be sinking, it would seem that these conditions could be defined as cruel and unusual punishment for a mass murderer. Is there really a need for every
doctor to have experience functioning under extremes of sleep deprivation? And should patients be exposed to a judgement impaired novice?


Robin writes:

Human infection by Anisakis simplex (herring worm) and other nematodes, or roundworms, is caused by eating certain raw or undercooked fish. Ingestion of the worm can result in severe abdominal pain, nausea, and vomiting within hours of ingestion and has been misdiagnosed as appendicitis or other abdominal diseases. If the worms don’t get coughed up or vomited out, they can burrow into the walls of the intestines and cause a localized immune response. The worms eventually die and are removed by the immune system. In severe cases, physical removal of the worms by endoscopy or surgery is needed to reduce the pain. People who produce immunoglobulin E in response to this parasite may subsequently have an allergic reaction, including anaphylaxis, after eating fish that have been infected with Anisakis species. Albendazole may be used to treat mild cases.

Anisakis species have complex life cycles which pass through number of hosts through the course of their lives. Eggs hatch in seawater, and larvae are eaten by crustaceans, usually euphausids. The infected crustacean is subsequently eaten by a fish or squid, and the nematode burrows into the wall of the gut and encysts in a protective coat, usually on the outside of the visceral organs, but occasionally in the muscle or beneath the skin. The life cycle is completed when an infected fish is eaten by a marine mammal, such as a whale, seal, or dolphin. The nematode excysts in the intestine, feeds, grows, mates and releases eggs into the seawater in the host's feces. As the gut of a marine mammal is functionally very similar to that of a human, Anisakis species are able to infect humans who eat raw or undercooked fish.
The known diversity of the genus has increased greatly over the past 20 years, with the advent of modern genetic techniques in species identification. Each final host species was discovered to have its own biochemically and genetically identifiable "sibling species" of Anisakis, which is reproductively isolated. This finding has allowed the proportion of different sibling species in a fish to be used as an indicator of population identity in fish stocks.

"If you copy from one person it's plagiarism. If you copy from ten persons it's a topical discussion. If you copy from a hundred persons it's a subject synopsis. If you copy from a thousand persons, it's a comprehensive literature review."

Christine writes:

Dear Vincent, Dickson and Daniel,

Thank you again for a great twip. Today's case of the young woman with abdominal bloating and pain, vomiting and nausea is most likely a case of Anisakiasis (also known as herring worm disease) caused by an infection with Anisakis simplex or Pseudoterranova decipiens.

Infective larvae are found in the sea water having been deposited as eggs in the faecal material of seals. The infective larvae are taken up by crustaceans that are then consumed by fish or squid. Humans ingest the nematode larvae when they eat raw or undercooked infected fish or squid. The larvae can invade the gastrointestinal tract. Eventually when the parasite dies it produces an inflamed mass in the oesophagus, stomach or intestine.

Diagnosis is generally made by endoscopy, radiography, or surgery if the worm has embedded (worms may invade the intestine 1-2 weeks after infection). The history of raw fish consumption is helpful for diagnosis.

Signs and symptoms include abdominal pain, nausea, vomiting, abdominal distention, diarrhoea, blood and mucus in stool and a mild fever. Allergic reactions of rash and itching, or less commonly anaphylaxis can occur. The symptoms can occur within hours of eating the infected fish.

The patient therefore was most likely infected during the sushi preparation.

It is recommended that the fish, having been wild caught is gutted and processed immediately to stop the worms moving into the muscle from the fish's body cavity. If the partner who caught the fish did this quickly only very few worms may have migrated to the muscle nearest the belly which the patient may have consumed while preparing the sushi using meat from nearer the top of the fish where the meat is thicker and more colored.

The worms are white in colour and 1.8 to 3.6 cm long and < 1cm wide.

Treatment is recommended for his patient to avoid gastrointestinal invasion and further symptoms.

Successful treatment of anisakiasis with albendazole 400 mg orally twice daily for 6 to 21 days has been reported in cases with presumptive (highly suggestive history and/or serology) diagnoses. ( although it is not FDA approved for this indication and there are notes on its use in pregnant and lactating females as well as use in children.)

Today's weather in beautiful Brisbane is 20C with 53% humidity and a light, but cool breeze, ( I finally had to find my sweater).

Blue skies with 20% cloud cover, a great day for a BBQ.

Keep them coming,

Christine (from Brisbane).

Peter writes:

I would suggest ingestion of Anisakis species as the diagnosis in this case.

April writes:

Hello gentlemen,

First things first! I would have thought, given your background Dr. Despommier, that you would know what third shift is! Although, at this particular moment, I can't remember if you were an assistant in a hospital lab. My particular schedule is 10:30pm to 0630am.

Our hospital is also a reference lab for many clinicians and other hospitals in Wisconsin and Illinois. Because of this we have a robust third shift workload that handles a lot of the molecular testing (it's more cost effective to batch those tests) and all the regular microbiology testing that the hospital requires (think stat gram stains, positive blood cultures, etc.)

Anyways. You say fish and I automatically think Diphyllobothrium latum. If I am correct, then other listeners will be as well and I'm sure they'll go through the lengthy task of explaining life cycle and mode of transmission.

I will add this though-I'm wondering if the patient ingested the salmon as soon as her boyfriend brought it home, then froze it for about a week before serving it to her friends. After that one fateful undergrad parasitology course I freeze ALL meat before ingesting it!

Thank you so much for the camaraderie, you three are fabulous!

Elise writes:

Dear TWIP Trifecta,

As always, thank you so much for your challenges. It is truly summer in lower Manhattan, quite humid and warm (83 F / 28.3 C)— the kind of weather that makes the dogs exhausted and seek out cool spots to sleep.

The case in TWIP 92 is curious because the young student’s onset of symptoms is so sudden and Dr. Griffin seemed to imply strongly that they were brought on by something about her most recent sushi meal as opposed to anything consumed in prior days or weeks. With so many of the parasites discussed in other case studies, it takes some time before the parasite makes itself known through symptoms, so this one is unusual for having such a rapid onset.
My guess is that the young woman has an anisakis infestation, causing gastric anisakiasis contracted from the salmon or the tuna she ate. (Anisakis is one of the more likely parasites that can be transmitted by marine fish.) The patient’s sudden abdominal pain, particularly the tenderness in the upper left quadrant, and vomiting suggests that the anisakis larvae have penetrated her stomach wall (the stomach, spleen and some of the colon are in this quadrant of the abdomen) within a few hours of her having ingested it. 

As to why the patient is the only person from her sushi dinner party to get sick, it is likely that she was the only one to have the bad luck of eating a piece of fish that contained the larvae. (It is possible, though, for people to develop intestinal anisakiasis, the symptoms of which set in after 7 days. There is also a frightening sounding anisakis induced anaphylaxis, ) 

The literature is quite matter-of-fact about the treatment for gastric anisakiasis because the larvae can’t survive in a human host (we are called a “dead-end host” for the parasite, which needs to be passed from a fish or a squid to a marine mammal in order to complete its developmental cycle). Patients can be treated by having the larvae removed with endoscopy and patients can also be treated with albendazole.

I am not sure if I am correct with my diagnosis, but this was the most likely parasite I could find that causes such sudden symptoms. Where did the student’s boyfriend catch the salmon, by the way? I know that the tuna could also be the culprit, but I was curious.

As always many thanks.

Eric writes:

Dear TWiPpers, , I am writing with a guess for the case of the week from TWiP 92. This case seems quite a bit harder than the last two, and I don’t feel as confident that the clues lead to a clear answer. The question I wish I could have asked before I had to make my guess: how often does this patient engage in sushi making events? And especially NOT using commercially-caught “sashimi grade” fish?

I will go out on a limb and guess that this sushi-making event is not an isolated event, and that the patient has engaged in this activity many times. I will guess that the current symptoms are not from this recent event, but rather caused from an event long past, perhaps one where a fresh-water fish was consumed, perhaps caught by the patient’s brother. I will guess that this hapless young woman is suffering the effects of infection with Dioctophyme renale, a giant kidney worm. This would perhaps explain the tender abdomen, and fever, and perhaps the enlarged abdomen, although that is a stretch. I am haunted by the anemic mom factoid. How can this be relevant? Or is it a red herring (raw)?

I eagerly await the unfolding of this fishy tale.

The weather in Seattle is 29 °C, cooler than last week, but still hot for Seattle, under skies devoid of clouds, but hazy with the smoke from wildfires raging in Beautiful British Columbia™. For those interested in a sensational blog about the Pacific Northwet’s weather, climate, and related, I highly recommend following the Cliff Mass Weather Blog ( It provides amazing insights into current atmospheric phenomena by University of Washington atmospheric science researcher Cliff Mass. Definitely my “listener pick”. The posts from July 8 and July 6 discuss this smoke and its effects and some great satellite images and other striking visuals.

Best wishes,


Jan writes:

Dear sirs,

This case is fun indeed , great anecdote to casually mention during diner with squeamish people. Earth worm lookalike, coming out both ends; Taenia sollum.

Keeping it short, my higher brain functions have melted out of my ears due to the heatwave we're suffering from. Temperature around 30 degrees C, no clouds and lots of horse flies where I'm currently working.


SJ writes:

Greetings TWIP trio!

I was happy to get the answer to the episode 90 case study. I polled some of my coworkers and we came up with several options, (naegleri fowleri was one but the patient was not an outdoorsy type) but none of them quite fit. I missed the HIV diagnosis despite noting the candidiasis. I guess I was so focused on the single diagnosis that I forgot to consider how important it is to remember that immunocompromised individuals often develop unusual conditions that are not present in the general population.

By the way, it's 18 C at 0730 but we expect it to get very hot today, perhaps 38 C here in the Eastern Sierra.

For this week, I strongly suspect anisakiasis. The patient is an adventurous eater, the parasite comes out of both ends (a common symptom in those infected with anisakis) and the size and vermiform features also match.

The fact that he has traveled a lot may or may not be a red herring here. Anisakiasis comes from eating raw, undercooked, or preserved fish. While it is uncommon in the US due to flash freezing of sashimi grade fish, it is not unheard of. However, because he travels, he could have developed it from eating fermented cod liver, ceviche, or any number of local fish dishes all over the world. One could almost feel bad for the nematodes in question, since we humans are a dead end host.

Keep up the good work as always gentlemen. I look forward to the answer to this case study.

Mark writes:

I am neither physician, nor microbiologist, but a pharmacist who finds your show fascinating. My guess for this weeks riddle is neurocystercosis of spine complicated with neurocytercosis of the brain. Intravenous drug abusers can acquire this parasite through shared needles, and the behavioral changes, the seizures and the radiculopathy of the left arm could be the result of a cyst in the spinal cord. I don't know what to make of the white mouth, so all this is a guess. This is an interesting case. I look forward to hearing the diagnosis next twip podcast.

Dennis writes:

Doc, for twip, here's a new Leishmania vaccine.



Eric writes:

Hey Doctors!,

Hopefully this hasn't already been plugged!, but I wanted to share a link to a case studies column on the nyt:

This month's case is a type of case that Dr. Griffin has promised, but has yet to deliver (I won't spoil it more than that!). While not all of the cases that the columnist, Dr. Lisa Sanders, writes up are about parasites, a fair amount are! If you're the first to guess the right cause, she'll send you a signed copy of her book. She almost always includes any pertinent physician notes and more than once I've made sense of a test or note because i had already learned about it on TWIP!

I also provided a link to another case that I thought you or the listeners might enjoy:

Thanks for all of the fun!,
eric from irvine where the sun is too bright and the temperature is too high.

Steve writes:

Hi TWiPers,

I think #90 was one of your most amusing and informative TWiPs. I was particularly impressed with the case history guesses by Daniel's daughters: very bright young women indeed!

Your bot fly case reminded me of my old friend Peter, who used to write the Belize Rough Guide. We rather thought he was taking his research for the book a bit far, sometimes, as he always seemed to come back with another parasite or disease! He was a regular visitor to the London School of Tropical Medicine and Hygiene, where they used to look forward to seeing what he came back with next!

People really do need to be careful in Belize, because Peter 'test drove', unintentionally, both malaria, and Leishmaniasis, and, on one occasion, also brought home, what he called his 'pet': which was a bot fly larva growing in his forearm. He was quite proud of it and enjoyed grossing people out by showing his pet to them! He successfully brought it to 'term', but I don't know what happened to it after that!

Peter was, actually, very careful when travelling, and researched health advice thoroughly for each of his books: he knew more about malaria than our local hospital, where they flatly wouldn't believe he could have it, when he went through a relapse episode of it while back home, and needed more medicine in a hurry. The fact that he collected several TWiPs'-worth of parasites, despite knowing the risks, and advising others on them, should serve to illustrate how vigilant one needs to be while travelling.

Sadly, despite never having smoked, Peter died, much too young, of throat cancer. I did wonder if it might have been caused by something else he 'collected' in his travels. With any luck, your triumvirate of podcasts, may help educate people to be at least a little wary, whilst enjoying their exotic holidays.

All the best,


Where it is rather grey, but refreshingly windy today. (Which started rather strangely, with a massed gathering of noisy Jackdaws, Crows, and Magpies, all together in the small cherry tree at the bottom of the garden! I have no idea what they were up to: there are often Red Kites overhead--they have come back very quickly, after reintroduction in the '80s--but I couldn't see them this morning.)

PS: great about the belugas. I looked for youtube reports after your show, and was interested to see the locals saying they were diving for 'bunker'--a fish that I hadn't heard of. The Wiki on it is quite interesting, and Dickson might have something to say about how the native Americans used to use it for fertiliser. I seem to recall reading advice to plant a sardine with each maize seed, before, and it is nice to find out where the idea came from.

Apparently, the fish is now overfished for oil and animal feed, which, in turn upsets the ecology of the bay, so, maybe, it is a very good sign that there seem to be enough about to attract the beluga. (Belugas? Belugae?)

Also wondered if this might clear up a mystery to me, as to where all the 'cod liver' oil on our supermarket shelves was coming from, when there is supposed to be a shortage of cod. I once asked our Food Standards Agency if they ever checked fish oils for authenticity, and was surprised to be told that they did not…

Curt writes:

I believe a head CT will reveal juvenile Taenia Solium encysting on being in the patient's brain tissue. If the CT doesn't reveal neurocysticercosis, the CT is still a good idea for new onset of seizures without prior history.

Bill writes:

Vincent, In a recent podcast you discussed the practice of using water bottles to sterilize water via sunlight.

Raw PET allows over 50% of UV to penetrate, down to about 320 nm.
Peak antibacterial activity is around 260 NM, but duration of 8 hours in the sunlight compensates for this attenuation and a very high % are killed via a day in the sun.
Spores are more resistant, but are removed to the filtration you spoke of.

This paper cover it quite well.

there are PET formulations that protect from UV light, that block almost all the UV from the product, these are usually colored.

link to the use of sunlight to sterilize water.

Heather writes:

Hello Doctors!

I have not had time to write to TWiP in a long time because I am back in graduate school! This is significant because my return is partially inspired by the TWiX podcasts, which were my only link to science during the years I worked "out-of-field". I am currently finishing my master's degree part-time, while working "in-field" as a laboratory manager at a small state college. I am very happy that you have added Daniel to the show, he brings a lot of energy and an interesting perspective. I have been enjoying the case studies, maybe I will have time to guess one of them soon. Would you be open to doing a fish or shellfish case study if I can find you a good one to send to you? Keep up the good work!


Dan writes:


I just discovered your podcast and immediately became a fan. Great work!

Now to my question. I am somewhat of a parasitophobe but I love smoking cigars. Cigars happen to often come from central american countries which, I learned from your tapeworm episodes, have widespread problems with tapeworms.
Do you know if there is any risk in contagion from hand rolled cigars? If the person rolling is contaminated there could possibly be contamination of the cigar itself right? I am curious to know if I should start cleaning my cigars before smoking them. While cleaning them might cause the things to break, I'd rather have a broken cigar than a tapeworm infection...

Would to get a reply, thanks in advance/ Your new fan Dan

Brigitte writes:

I read about an interesting theory in Carl Marx's Parasite Rex. The book did not go into great detail, but I would like to hear your thoughts. The book talked about parasites and allergies. Do you think that parasites can actually prevent allergies? People have used parasites for illnesses and infections for decades. Though, many of them did more harm than good.

Thank you,

Justin writes:

I thought this might be worthy of a TWiP since everyone loves pathogens that are implicated in behavior changes.

"Researchers from the University of Leeds, Queen’s University Belfast and Stellenbosch University in South Africa found a tiny parasite, Pleistophora mulleri, not only significantly increased cannibalism among the indigenous shrimp Gammarus duebeni celticus but made infected shrimp more voracious, taking much less time to consume their victims. "

Right now on the Cross Island Ferry heading to Orient Point and it's Sunny 0C and a calm windy open water day.


TWiP 92 letters


David writes:

Dear Vincent, Dickson and Daniel,

I am one of the co-authors (from the London School of Hygiene & Tropical Medicine) of the PloS Pathogens paper you highlighted on the malaria parasite as part of TWiP 91 on June 20th. Thank you for dealing with the paper so well. I was wondering what to expect after some of the online interpretations and comments that arose from our work. For obvious reasons it received some media attention. Catherine Lavazec (Institut Cochin, Paris) who co-led the study (with Gordon Langsley) was understandably keen to take advantage of that possibility.

Just a brief comment to say that the use of sildenafil in our study was a proof of concept (as you pointed out). So even though sildenafil has been used in children (a question that arose on TWiP 91), the aim is not to use this drug to control malaria. In fact, sildenafil is quite a poor inhibitor of the malaria parasite phosphodiesterases (mid micromolar as you pointed out). My lab is exploring the possibility of identifying a much more potent selective inhibitor of the malaria parasite phosphodiesterases (of which there are four) with no side effects. Phosphodiesterase enzymes are expressed in multiple stages of the complex malaria parasite life cycle. So we hope that developing such an inhibitor as a drug would allow us to both treat disease (by targeting the asexually replicating blood stages) and also to block transmission (by killing the gametocytes). So in this case, the issue of altruism will not arise.

I enjoyed your TWiP podcast. Thank you.

Best wishes,


Professor David A. Baker

Faculty of Infectious and Tropical Diseases
London School of Hygiene & Tropical Medicine
Keppel Street
London WC1E 7HT

Jenn writes:

Hi twip team,

The "over-talking" thing is really a New York manner of speaking. You are absolutely correct when you say it's due to enthusiasm, and is not meant out of rudeness or to interrupt the other person.

This is something I try to convey to my non-NYC friends (they get irritated when I interrupt them, and I get irritated when they stop talking to " wait their turn").



Christine writes:

Good morning Dickson, Vincent and Daniel,

Thank you again for another enjoyable and interesting twip podcast.

I believe that our young trainee physician has an ascarid infection.

The infection with Ascaris lumbricoides may present with the emergence of a 15-30cm long whitish round worm from either mouth or anus. It usually resides in the small intestine and mild infections may be asymptomatic or rarely experiencing nausea, diarrhea and abdominal pain.

Treatment is a 3 day course of albendazole or mebendazole, repeated after 2 weeks.

Unsurprisingly the infection has a faecal/oral contamination cycle, with eggs excreted with faeces. Fertile eggs will embryonate in the soil and are infective after 18 days to several weeks depending on conditions. Larval hatching after ingestion and mucosal invasion leading to portal circulation and then systemic circulation and traveling to the lungs where the larvae further mature for 10-14 days, break through the alveoli, climb the bronchial tree to be swallowed in order to locate as adults in the small intestine.

The weather this morning in Brisbane is a brisk 11C with a beautiful sunny winters day of 21C to come, light breeze, and clear skies. Couldn't be better.

(Brisbane, Australia)

April writes:

Good morning gentlemen,

I'm a public health microbiologist in Milwaukee, WI. I work in a hospital lab currently, on third shift, and have been an avid listener for for some time now, though this is my first time writing.

Ascaris lumbricoides is my official guess. What else could be so long, besides a tapeworm! And having dissected a gravid Ascaris in a Parasitology class I can indeed say they look like earth worms to the untrained eye.

I'm taking a real guess here, with one of my only resources being the "Atlas of Human Parasitology" by Lawrence R. Ash and Thomas C. Orihel. I think Dickson gave it away though when he mentioned the case of the little girl who had visible worms coming out of her nose, because one Google image search of the parasite in question brings up that very picture!

The weather in Milwaukee is a balmy 69 degrees fahrenheit with a nice thunderstorm on the horizon.

Thank you so much for the wonderful learning opportunity, especially for this nocturnal parasitophile (is that even a thing?).


Robin writes:

Earthworms are annelids. Annelids are segmented. The segmented human helminths are cestodes. Cestodes are flattened with elongated segments. That might not have been the case in this instance. Annelid segments are short like a rouleaux, and also like a rouleaux, approach a circular cross section.

Nematodes also approach a circular cross section, and hence the name "roundworms"; however on closer inspection, they show no evidence of segmentation. They can vary in size from microscopic free living soil dwellers to earthworm size; most of the larger ones tend to be parasitic, including human roundworms such as Ascaris lumbricoides.

Varun writes:


In response to the recent case challenge presented the description is matching that of Ascaris infection. Given that the patient left with the worm itself in the examination table, there isn't any additional required lab tests. Just check the morphology of worm. An additional simple stool wet mount maybe done but isn't required in this case.

Guess: Ascaris lumbricoides infection

Elise writes:

Dear TWIP Trifecta

I hope very much that this finds you all well. It is pretty balmy here in lower Manhattan 87 F/30.5 But the skies are clear and the humidity a reasonable 36%.

I do have an attempt at a diagnosis for the young resident in Salt Lake City, but I also have a bunch of questions. In looking around at what sorts of earthworm-shaped parasites could have found their way into his digestive tract, the most likely culprit seems to be a roundworm (Ascariasis lumbricoides). Certainly, the remarkable photographs one can find online match the description that the patient gave of the worms he saw and their behavior is also consistent (they emerged, alive and motile). People with intestinal ascariasis, as is the case with this patient, don’t always have elaborate symptoms beyond a range of abdominal discomforts. He felt well and has no fever, edema, discomfort, or neurological symptoms beyond the vomiting incident that first introduced the possibility that he might have a parasite (or perhaps it would be better said that the parasite introduced itself to him).

Ascaris lumbricoides is among the most common helminthic human infections, and it is most prevalent in tropical and sub-tropical climates such as the ones the patient likes to visit (he’s been to India and Southeast Asia). It is transmitted by people ingesting roundworm eggs that can be found in contaminated soil or food. The patient, an adventurous eater, could easily have been exposed on his travels.

Roundworm infestations often are asymptomatic until they have a final glaring symptom. They are typically discovered when they are either in the early stages and the worm larvae are small and migrating through the lungs causing coughing and wheezing OR in the late phase (6-8 weeks after eggs were ingested) and when they can cause abdominal pain, nausea and vomiting, and the dramatic “passage of worms” from the mouth, nose or anus. In extreme cases (usually in children) massive infestations can cause intestinal blockages.

So assuming I am right and the patient has a roundworm problem, why did the roundworms emerge both from his mouth and his rectum? Do the large worms move back and forth through the digestive tract or did one (or more) end up in the stomach and others in the large intestine? Also, was it a reaction of the worm with the beer that made the patient throw up or was it the presence of the worm in itself that did it? Finally, in the examining room, why did the worm crawl out at that time? In the cases I read, most of the times worms make dramatic appearances from orifices while their human hosts are sedated.

As always, thank you so much for your wonderful work. I look forward to hearing TWIP 92.

Best wishes

Eric writes:

Dear TWiPsters, I am writing with a guess for the case of the week from TWiP 91. I thoroughly enjoyed your tale of the emergence of the motile flesh colored worm from your young patient’s tail. I can think of only one common critter that fits the description, Ascaris lumbricoides. Perhaps there are others, but I do not know them, nor are the common I suppose. And the treatment would be the same regardless? But no guessing is needed as the patient was kind enough to supply a fresh sample right at the visit. The only mystery is: why are they emerging? I recall Dickson saying in the early Ascaris episode that fever is a common reason that Ascaris will seek to emerge, but why else? Dickson was asking here about fevers, but there were none reported. Daniel seemed to be hinting that stress in the form of sleep deprivation may be the answer? I await eagerly to hear if there is a clear reason for the Ascaris emergence. How many did he have?

Seattle is currently experiencing its first heat wave of the season. It is currently 27 °C at 8pm. We are under an “excessive heat watch”, with predicted highs of 32 for the next week, phew, very uncommon for Seattle.



TWiP 91 letters


Heather writes:

Dear Dr.s R, D & G,

I really hate to criticize learned professors, especially my elders. I suspect I may be being overly - sensitive or perhaps it is a cultural difference. However, the "over-talking" is decreasing the quality of the TWiP podcast. I think the quality would be improved if certain hosts made a concerted effort to not speak over other hosts, but to pause and insert their wonderful insights (which I do really want to hear) only when others have finished speaking. I know it is hard to teach an old dog new tricks but the over-talking makes the discussion hard to understand at times. Please don't be offended: I love TWiX, especially the party guilty of over-talking.


Ann writes:

Dear Dickson, Vincent and Daniel,

I have wanted to write in to your show for a while now, and am finally doing so because of something mentioned in the last podcast (#90). I was in Hopland, CA busily obtaining blood samples from western fence lizards while listening to your podcast, when Dickson mentioned that reptiles get malaria. As it turns out, I was taking blood samples as part of a long-term saurian malaria research project I have been working on since 2003. I study Plasmodium mexicanum, a lizard malaria parasite that uses two species of Lutzomyia sand fly as vectors. I was so happy to hear you mention lizard malaria that I had to write in (if you ever want to chat about P. mexicanum, I am more than happy to oblige- this is a fascinating parasite!). Also, I was interested to hear Vincent’s thoughts on viruses infecting red blood cells. As a PhD student, I scanned hundreds of lizard blood smears and sometimes found small, purple-stained inclusions within the red blood cells. I was told that that these were viral particles/clusters. It appears that viruses can infect nucleated red blood cells. I attach the following article as a reference.

Thank you so much for your podcasts- it is refreshing to listen to scientists as passionate about parasites as I am. I teach Microbiology, Parasitology, Invertebrate Zoology and Ecology at Penn State York, and often refer my students to your podcasts, and utilize them as discussion tools in class. I enjoy the new additions of Daniel and the case studies. I have gotten all of the cases except the one posed in podcast #90. I cannot wait for the ‘big reveal’ in the following podcast. Thank you again for you stimulating lessons.

Anne Vardo-Zalik

Dr. Anne M. Vardo-Zalik
Assistant Professor of Biology
Biology Program Coordinator
Penn State York

Steen writes:

In case you are still curious about the origin of the name of the c(ellular)-JUN protein ( ubiquitinated by FBW7, the target of the apicomplexan prolyl isomerase you discussed in TWiP 88):

"This putative cell-derived oncogene of ASV 17 is termed jun, abbreviated from Japanese ju-nana, the number 17."

So the gene was in fact named after the relevant virus.

Vogt gives a perspective on the rapid identification of JUN as a transcription factor 28 years ago: " we see how convergences of seemingly unrelated research led to important insights."

Perhaps June 17 should be declared 'national oncovirus day'.

Christine writes:

Dear Doctors Vincent, Dickson and Daniel,

The 28 year old patient described in today's twip with non-acute arm and hand weakness, behavioral/mental changes and a seizure, together with oral Candida albicans "infection" and high risk behaviors is suggestive to me of a multifactorial diagnosis.

The Candida in an adult suggests to me reduced immune function ( although he does report toxic habits and a cessation of smoking may help clearance of the Candida). Given his sexual history and lack of protection used I am concerned about HIV, and both he and his partner should be tested.

As a consequence of reduced immune function he would be at increase risk of Toxoplasma gondii. This may cause focal brain lesions that can explain the weakness, seizure and behavioural/mental changes. Given the seizure an MRI or CT would be my first instinct, with serology for toxo via IgG agglutination, and a stained blood smear for the presence of an active infection. If indicated in the scan and supported by blood work I may request a lumbar puncture to do PCR for toxo in the CSF.

Given that toxo is such a successful parasite and the initial infection can be asymptomatic it is likely that he has encountered this parasite possibly without knowing it. With reactivation as a consequence of immune reduction toxo can become a serious and life threatening infection.

Treatment for the toxo, Candida and if diagnosed, HIV should begin promptly for best outcomes.

The weather here in Brisbane is partly cloudy, currently 24C with a predicted max of 28C , 30% chance of any rain (0-0.2 mm), a moderate UV alert between 10.50 and 1.40, and a low-moderate fire danger.

A beautiful late autumn day, it's hard living in paradise ;-) .

Christine from Brisbane (enjoying my Sunday morning twip.)

Jan writes:

Hi sportsmen,

What better way to spend a rainy Sunday afternoon then trying to solve a puzzle using ones brain, instead of shutting it down in front of the TV watching a game ? Especially since I'm on a winning streak in my personal league. ( the pin worms were foul play ) Daniel didn't want give the results of the blood tests but I'd be surprised if the guy didn't have HIV/Aids. Do his toxic habits include needle sharing when using intravenous drugs ? Not that it matters, the unsafe sex , probably including anal, with multiple partners is dangerous enough of its own. Combining the presumed aids with the symptoms leads me to think it's toxoplasmosis. My cats agree and they're never wrong.



Congratulations to Vincent on the pronunciation of my name, and I don't watch sports, not even the stereotypical ones.

Elise writes:

Dear TWIP Trifecta,

I hope all is well. It is soggy and stormy and suddenly chilly (56 F, 13 C) here in lower Manhattan, as I am sure it is for you all uptown.

For once I almost hope my diagnosis is not correct because if I am right, this is a sad one.

This diagnosis was tricky for me and as a result is multipart but I’ll just say first that all of the clues suggest to me that the patient has Toxoplasmic Encephalitis (or cerebral toxoplasmosis). I’ll try to explain my thinking.

The first thing I sorted out was that the patient’s symptoms seemed most like a form of encephalitis (personality/ behavior changes, left side weakness, seizure, persistent headache, low fever). I got a bit stuck trying to figure out what sort of encephalitis he might have because most of the parasites that wind up in the brain didn’t fit the profile of this patient— especially given that he has not left the United States and doesn’t have other lifestyle choices that might expose him to some of the parasites that you have discussed in other patients (tapeworms, for instance).

While I was slightly stymied by the encephalitis, I set it on the back burner and looked at some of his other symptoms. I was intrigued by the patient’s non-encephalitic symptom of having a white coating on his tongue and lacy white mucosa in his mouth. This sounds quite a bit like thrush (oral candidiasis), which can be a symptom of an HIV infection and suddenly a lot of things made sense.

The patient maintains a high risk lifestyle that could lead to him having contracted HIV. He has a lot of sexual partners of both sexes and admits to not taking any precautions to protect himself from sexually transmitted diseases. In addition he uses recreational drugs, and while you didn’t mention whether he injects himself, if he does, this is another unsafe behavior that could lead to a lot of infections, HIV among them. If the patient is HIV positive or otherwise has a diminished immune system,

Many, many healthy people have toxoplasmosis and are entirely unaware of it. (The literature tends to describe these infections as “latent and asymptomatic”). When, however, the body’s immune response is compromised, the toxoplasma gondii protozoan parasite can become “reactivated” and, if they are in the brain, cause lesions that trigger the encephalitis symptoms.

Since the patient had not been to a doctor in quite some time, it is possible that he doesn’t know about his HIV status and that all of these symptoms are a horrible surprise.

I would be very interested to hear how the toxoplasma parasite “reactivates” without a strong immune response to keep it in check. How does it remain dormant?

This was a tricky diagnosis so I’m prepared to be wrong but I am very much looking forward to hearing whatever the answer may be.

As always, tons of thanks for your wonderful work.

I await your next podcast on the edge of my seat.

Many best wishes

Shane writes:

My guess for this case is Toxoplasmic Encephalitis caused by T.Gondii infection coupled with HIV infection. The give-away was the very active unprotected sex-life with multiple partners.

Weather here in Queensland Australia is a beautiful 20 Degrees C as you entertain me on my commute home from University of Queensland.

Kind Regards,


Eric writes:

Dear Dickson, Vincent, and Daniel, I am writing with a guess for the case of the week from TWiP 90. But first, let me say as a long time listener but first time caller, errr writer, that I find your podcasts sensationally well done and informative. I started with TWiM several years ago when I finally got a smartphone with a good podcatcher. I moved to TWiV after exhausting TWiM’s back catalog around the time of the most recent Ebola outbreak, and then later discovered TWiP. I love to learn, and find it brilliant that I can turn commuting time and driving-the-kids-around time, which otherwise feels wasted, into learning time with TWiX episodes! My degree is in astrophysics, but I have since moved to the field of proteomics and have picked enough biology to follow along even when you dive deeply into the papers. Mostly.

Regarding the case of the 28 year old man with the seizures, the information is rather limited, but for the huge advantage to know that the answer must involve parasitism. I strongly suspect that this is a case of encephalitis caused by toxoplasma. Since this gentleman reports unprotected sex with multiple partners, he must be considered high risk for HIV infection, and I fear he might be immunocompromised due to early stages of AIDS. Toxoplasma in an immunocompromised individual may well cause encephalitis that can cause the symptoms described. This was the case with tennis star Arthur Ashe, who then founded the Arthur Ashe Foundation for the Defeat of AIDS. The first questions I would try to answer are: are the lymph nodes swollen? Then is he HIV positive? And then a test for toxoplasma, perhaps there is a good PCR test?

A question for you: would the signs and symptoms be any different for a new toxoplasma infection in an immunocompromised individual, and a long-latent toxoplasma infection becoming active with the onset of immunodeficiency?

I love TWiP. The new case of the week with each episode is a great idea. It turns a one-way show into a two-way experience! Brilliant! I started with episode 1 many months ago and now have finally caught up and can participate in the cases in real time.

Today’s weather in Seattle was pure “June Gloom” aka June-uary (, a common pattern this time of year where a low heavy cloud cover is drawn in from the ocean and hangs overhead all day. But the 10-day forecast starting tomorrow is nothing but sun. Summer in Seattle begins tomorrow!

Best regards,
Eric from Seattle

Varun writes:

Greetings Profz,

In relation to the paper discussed, I want to cite an earlier work Patrick Duffy and colleagues identifying the importance of CD55 and CD59 in malaria. The study found also that the CD55 and CD59 levels dropped with age of RBC. Maybe by using the CD55, falciparum is trying to get into those RBC that are much younger which makes a lot of sense.

In the podcast there was a discussion on is there a possibility of virus replicating inside RBC. As Vincent explains, for obvious reasons such as lack of cell machinery this doesn't seem to be possible nor I could find any published examples. This has fueled some scientists to look into use of RBC as viral traps. This has been tried with little success for HIV too.

The second question that came up was why does human RBC lose their nucleus during development. The answer is that RBC is mostly a bag of hemoglobin and nucleus is expelled through a specific mechanism so as to accommodate more hemoglobin. Additionally, loss of nucleus makes the cell extremely flexible allowing the RBC to move easily inside very small capillaries. The flexibility of RBC is also attributed to a protein called Spectrin, problems with which lead to spherocytosis leading to anemia. This automatically brings into question why does some animals have nucleated RBC. Straight answer is I don't know. Perhaps somebody can chime in.

With respect to case described, I want to ask is the patient HIV and HBV status. Bisexual Men are known to acquire parasitic infections related to GIT (such as Giardia and Entameoba). The only parasitic STD I know of is Trichomonas. But I'm not sure if this is even a case of STD.

I'm not able to correlate the case to any organisms to explain the symptoms described. Sorry, but no guess this time.

Rebekah writes:

Dear TWiP doctors,

My guess for the case study is Toxoplasmosis. It is easily Transmitted is by eating raw meat or ingesting the fecal Oocysts (which can be anywhere). Most healthy individuals do not become ill, however I have suspicions that our patient is not entirely healthy. The white film on the patients tongue suggests an infection with Candida spp. which can occur in patients with an immunocompromising disease. With this patient's risky sexual behaviors he very easily could have picked up an infection such as HIV/AIDS. Toxoplasmosis can cause flu like symptoms and encephalitis in immunocompromised people. Historically Toxoplasmosis has been a problem for the HIV/AIDS population. I am a bit nervous that I have read too much into this patient's case, but it was the only thing that made sense logically to me.

Thanks again for this truly enjoyable podcast!

Microbiology Section Head
Hastings MI

Bjorn writes:

Dear Twippers ;)

Case of the week, twip 90

So on this one I’ll guess encephalitis caused by toxoplasmosis caused by an infection of the parasite Toxoplasma Gondii. The short reason why I think this is a reasonable guess is that the patient has a history of high frequency unprotected sex with both men an women and recreational drug use. This means that this guy has multiple risk factors for acquiring a HIV infection. Since this patient does not seem to visit a doctor very frequently, he may also not have had a HIV test, so may in fact be HIV positive without knowing it. Assuming that he has HIV, he may be immunocompromised and on his way to developing AIDS. The clinical signs and symptoms are consistent with too:

dull, constant headache
intermittent fever
Symptoms may also include focal neurological deficits, such as:
weakness, or even paralysis, of one side of the body;
speech disorder, especially slurred words;
weakness or loss of sensation in any limb;
loss of an area of vision.

The actual infection he can have gotten from many places e.g. from direct contact with feline feces or through eating raw or undercooked meat. Toxoplasmosis Gondii is one of the most common parasites on the planet, it’s very easy to get in contact with it. It’s not easy to get sick from it unless one is immunosuppressed. Foetuses may be infected in the womb and this infection may cause abortion or serious disease in infant children (congenital toxoplasmosis), but I don’t this is a relevant aspect of the disease for this guy.

He presented with seizure and weakness on one side of the body. The “not being himself” could be consistent with the above list, but it is of course hard to tell. To firm up this diagnosis there are a number of tests that can be done:

T cell count (CD4). Less than 200 cells / mm^3 would be consistent with 3 AIDS.
HIV antibodies or virus would pretty much determine if he has or hasn’t got a HIV infection.
Wikipedia says that diagnosis of toxoplasmosis can be done through "biological, serological, histological, or molecular methods, or by some combination of the above.” so I guess that would be a good idea to do. It also says that it can be tricky and another way of diagnosing would be to start medicating and see how well the patient responds.

Another thing that can be done is to MRI/CRT to look for signs (

Guess that’s it.

Love twip. I don’t think I’ll stop trying to work on the case studies, even if I don’t find the right diagnosis every time, which I don’t :-)

Best wishes


Alberto writes:

Dear TWiP Triforce,

I'm a long time fan of the TWiX universe and always wanted to write in expressing my admiration and gratitude for your efforts to disseminate science on the internet, and now with Daniel's case mysteries I finally do it.

I'm a PhD student in Immunology in Berlin, but I'm originally from Rio de Janeiro, Brazil, where I did my Bachelor's degree in Pharmacy and Laboratory Medicine. Even though parasites are not present in my daily work (my thesis' subject is tumor immunology and T-cell biology) I find them absolutely fascinating and think there's much to learn about human immunology by studying them. Vincent, have you ever considered starting a TWiI (This Week in Immunology)?!? Even though I like to think that by combining TWiV, TWiM and TWiP the end result is already a big TWiI, since in almost every single episode there is mention of a function or cell type of our immune system!

But I should get to the case! My guess is that the patient is suffering from complications of Toxoplasmosis due to a weakened immune system caused by HIV. When not properly controlled by the immune system Toxoplasma gondii can cause neurologic symptoms, which would explain the seizure and the pain in the left arm and hand. The white coating on the tongue can be caused by Candida. If the patient really has AIDS a low leukocyte count would be visible in the complete blood count. CD4+ T-cell count and serology for HIV would help the diagnosis. I would also ask for IgG and IgM serology for T. gondii.

Thank you all for doing this extraordinary, informative and fun podcast! The case studies are really a good idea to engage in conversation and thought about infections and biology! Keep it up!

All the best,

Robin writes:

Left upper monoparesis. Subacute mental status change. White coating mouth and tougue, candidiasis? Seizure with post-ictal state. Low grade fever.

Toxoplasmosis is the most common cause of space-occupying brain lesions in AIDS. Neuroimaging usually reveals multiple nodular or ring-enhancing lesions with edema and mass effect.

Usually, the patient with CNS toxoplasmosis will present with focal neurologic symptoms and signs often superimposed on a global encephalopathy. Mild hemiparesis is the most common focal finding. Headache, confusion, lethargy, brain stem and cerebellar disorders, and seizures are also observed

Evaluation and management of intracranial mass lesions in AIDS
Report of the Quality Standards Subcommittee of the American Academy of Neurology

I left Africa 50,000 years ago.

How Homo sapiens populated the Earth:
PBS: The Journey of Man
Coleoptera, diptera, hymenoptera etc. are insect orders, rather than genera.
Entomology started long before Cornell.
A group of primordial arachnids passed through a bottleneck, with only a hexapod four-winged form emerging. From it in 300 million years has radiated today's diverstiy of Insecta.

Tissue stains to antimcrobials... shoulders of giants.

It was the great Rudolf Virchow who mused on the possibility of differentially staining tissues with dyes so that some dyes might be specifically toxic to microbes.

That led to experimenting with aniline dyes, leading to Prontosil rubrum, then Prontosil album, sulfanilamide, and the rest of the sulphonamides.

Blood group antigens presented on the surface of red cells are handles: for what hands, present or past, is yet mostly unknovn.

We've prabably had malaria since our shrewlike ancestors or even our reptilian ancestors, the disease co-evolving with us.

Erythrocytes have the glycolytic (pentose phosphate) pathway. Without the nucleus the cell size is smaller (hence lower viscosity), and there might be some greater flexibility.

IRIS immune reconstitution inflammatory syndrome


TWiP 90 letters


Christine writes:

Dear Vincent, Dickson and Daniel,

I think the latest case describes cutaneous furuncular myiasis.

The lesion on the young man's buttock is suggestive of a botfly infection with the larvae most likely of the species Dermatobia hominis. The eggs deposited onto a smaller vector-fly or mosquito which lands on the person. The eggs are deposited onto the skin of the person (or other mammal) and the body heat causes the egg to hatch the the larvae penetrate the skin, often through the mosquito bite or along a hair follicle. Six to twelve weeks later the larvae leave, exiting through their original hole, and fall to the ground to pupate.

It is this exiting that I expect lead to diagnosis on that fateful Sunday.

Infections are most commonly located on exposed skin where flies and mosquitoes most often land, usually the limbs, but have also occurred on the scalp, neck, back, breast, scrotum, tongue and eye.

The condition is self limiting but most patients prefer its removal prior to its own exit. This is done through killing the larvae followed by surgical removal.

The weather here in brisbane is delightful, a mostly sunny autumn day with blue skies, a smattering of clouds temps from 16 to 23 degrees C. A 60% chance of any precipitation between 1 and 3mm.

Christine from Brisbane, Australia.

Robin writes:

Local treatment of human botfly myiasis in Belize.

The human botfly (Dermatobia hominis) is found from Mexico to northern Chile and Argentina. The larva of this forest-dwelling fly develops in the skin of birds and mammals, including man. The female botfly captures and lays her eggs on the legs of a dipteran, usually a mosquito, although at least 48 species of dipterans and one tick are confirmed vectors. Upon contact with the host, eggs immediately hatch and larvae penetrate the skin. Pre- existing lesions are not required for entry into the host. The developing maggots form furuncular lesions with a central respiratory orifice. A pair of spiracles located on the caudal extremity re- main in this orifice allowing the maggot to breathe. Transverse rows of epidermal spines anchor the maggot within the muscle. Maggots do not wander and development to pupal stage requires about six weeks, although infections up to three months have been reported. At maturity maggots measure up to 25 mm long and 7 mm in diameter. Pupae exit the host and pupation is completed in the soil.

Cutaneous Myiasis: Diagnosis, Treatment, and Prevention:

Cutaneous Myiasis Merck Manual

Peter writes:

Greetings DayTWiPers

Here are my thoughts on the TWiP 89 mystery infectious disease case.

Daniel's description of this as a 'fun case' leads me to think that it is an interesting but not a serious or life threatening condition.

Based on the information given in the programme I would say that the patient has furuncular myiasis caused by Dermatobia hominis, the human botfly, this parasite is common in Central America.

The location of the infection in this case is unusual as botfly larvae are usually carried by mosquito vectors and the head and neck are more common sites of infection, the buttocks are not normally that accessible to mosquitoes.

Having done further reading on botflys, I see that they also utilise some tick species as vectors, so I think it probable that the EIS trainee received a bite from a tick that was carrying a botfly larvae which then parasitised him.


Rebekah writes:

Hello TWiPers three,

My guess for the case study is the Myiasis caused by a screwworm. The CDC page that discusses myiasis states that the flies may lay eggs on drying clothes that are hung outside. Which may have been how this person caught this infection by hanging his swimsuit out to dry.

Thanks as always for providing me with hours of edutainment as I sift through the piles of culture plates on my otherwise lonely weekends at the lab.

Microbiology Section Head

SJ writes:

Hello proffessors,

First email, thanks for the TwiX series of podcasts, I've been enjoying them since the start of the ebola outbreak, when someone suggested TwiV to me on Facebook. It's 21 C, windy, with possible thunder showers forming out here in the Eastern Sierra of California.

I'm a lab assistant at our local hospital, looking to go back to school to become a lab tech sometime in the near future. Unfortunately we send out our parasitology testing with the exception of a rapid giardia/cryotosporidium test so I haven't gotten to see any eukaryotic parasites in person.

Anyhow, is it Dermatobia Hominsis? There are bot flies in Belize, the symptoms match, the only thing that doesn't quite work is the larvae should have waited about 3 more weeks before dropping out, but perhaps the patient noticed other signs that the larvae was present? That's all I could come up with. Not super happy with the location of the bite, given the fact that he stayed in a screened room.

Anyhow, keep up the good work! Looking forward to hearing the answer to this puzzle.

Elise writes:

Dear TWIP Collective

I hope this finds you all well. It is very warm and sticky here in lower Manhattan, about 25 degrees C but humidity is 65%, having the effect of making everyone cranky, except me because I am working on your new puzzle.

I’m going again to hazard a guess diagnosis, this time for your Superbowl watching Belize-traveler and I hope my guess can also satisfy the answer the question: what happened as he was watching the Big Game?

It sounds as if the EIS trainee patient has Dermatobia hominis cutaneous myiasis. I believe he may be hosting botfly larvae.

The botfly (Dermatobia hominis) is found in Central and South America (generally— Belize specifically). Its eggs usually get transmitted to non-human mammals, which is why the symptoms of this infestation are often misinterpreted or misunderstood as being something like an infected cyst or boil, leishmaniasis or cellulitis.

Typically, mosquitoes inadvertently deposit the botfly on a mammalian host when feeding. (This is fascinating because the mosquito is carrying around eggs that only hatch when they sense the warmth of the mammalian body.) This transmission can also happen by the mosquito (also inadvertently) leaving eggs on clothing that has been hung out to dry, as the patient’s likely non-Speedo-type bathing suit was. (For this reason, an account I found in the UK Daily Mail publication advised that travelers iron the clothing they have left out to dry. This seems like well meaning but pretty impractical advice at best given the circumstances under which most people are traveling in these locales.)

The patient’s symptom, a bump that gradually grew and developed a small central hole or impression, that seemed almost like a boil or a pimple are consistent with what happens when one is hosting botfly larvae. The indentation in the center of the bump is the spot where the larvae’s spiracles are enabling it to breathe. There is not usually excessive pain for the host, but I did find accounts of itching and occasional sharp pains when the larvae moves around. The patient didn’t describe either of these symptoms, but perhaps that is because of where he was hosting the botfly larvae. Some of the accounts I read involved the eggs taking up residence on the scalp or beside patients’ ears or even in their eyes, so those may be much more sensitive areas.

The other thing that leads me to suspect cutaneous myiasis is your collective secretiveness about WHAT HAPPENED to the patient during the Super Bowl after he had been incubating the larvae for 5-6 weeks. Did he “give birth” to a 3rd stage botfly larvae? According to accounts I have read, if the larvae isn’t removed, after 4-10 weeks, the larvae needs to fall away from its mammalian host and finish developing underground.

If this event wasn’t so dramatic, perhaps the patient just felt the larvae moving, which is probably pretty freaky, and went to an ER or a clinic. It is interesting that so many of the sources I found recommend home remedies for removing the botfly larvae, by covering the bump (especially the spiracles) with vaseline or nail polish or anything else that would prevent the larvae from breathing, and then extracting it as it moves to the surface in an effort to breathe. Removing that larvae is the cure for the infestation and there are no accounts of lasting side-effects. Would it be wise for the patient to take some sort of antibiotic after getting rid of the larvae?

Often I want to discuss my amateur parasite sleuthing with the people around me, but I must say that in this case I have restrained myself because it is a little too gross for my audience. But not for me.

As always, thank you so much for your wonderful podcast. It it great fun.


James writes:

Dear TWIP Team,

I think that I finally have a reasonable guess. It's for TWiP 89! I am a graduate student in analytical chemistry, so I don't know much about parasites (though I'm slowly learning!). Though out of my field, I find the TWiV, TWiM, TWiP, & UrbanAg enriching listening while I perform experiments in lab. Keep up the good work.

Now onto the guess...

I think that what was ailing the young EIS trainee was botfly. When I was a junior in high school, we took a class trip to Belize and heard all about the botfly. I even got to see an active case of it. One of the guides on the trip had a large bump on the back of his neck, he convinced a second guide to cut open his large red bump with a "sterilized" (read: rinsed with vodka) pocket knife. The second guide then took a can of Raid Roach Killer and sprayed it onto the wound. The whole procedure looked quite painful, but the two acted in a way that made me think this wasn't the first time they'd done it.

Hopefully, this guess isn't too off the mark, but the botfly ordeal makes for a good story even if I am wildly incorrect.

Oh, almost forgot, the weather here in central Illinois is rain with a high of 51 F (10.5 C). It's quite chilly for springtime, but it will be warming up this weekend.



Carol writes:

Greetings Team TWIP,

My guess for this episode's case study is cutaneous larval migrans, or creeping eruption. Whether I'm correct or not, it sounds unpleasant! The more parasites I learn about, the less I want to leave my house... At least treatment for many parasites is relatively easy, in case reasonable precautions fail.

Looking forward to the next episode,


Heather writes:

I finally have time to make a guess on the case study: the young man has a butt fly....I mean a bot fly, otherwise known as a "warble".

Joseph writes:

dematobia hominis

Grace writes:

Dear Day Twippers,

Grace and Caylee here again. We write to you from the parking lot of the closest pizza parlor with free wifi after getting rained-out from a day of squirrel trapping.

We guess that the young man who traveled to Belize and returned with a red bump on his rear was bitten by a mosquito or other biting insect carrying the eggs of the human botfly (Dermatobia hominis).

If we are right, then we extend our sympathy for the poor man's right buttock. We occasionally run across chipmunks and deer mice harboring botfly larvae and don't envy them the experience. I hope your case subject's team won the Superbowl, however, a larval botfly emergence probably made for an exciting halftime show regardless.

Wishing you sunshine and squirrels,
Grace and Caylee

Allan writes:

Aloha Doctors,

The weather in Kona today is a pleasant 77ºF/25ºC, partially cloudy with VOG (volcanic fog) so thick I cannot see the horizon, although its there somewhere.

I like your new podcast format but as you’re now turning podcasts out weekly, by the time I finish listening to an episode in the car and am ready to take a stab at the case study a new episode arrives… but don’t slow down!

Fun case study this week:

I got to spend two full years between the 1984 and 1990 living and working in Belize and Guatemala, helping start community health training programs, volunteering in the out-patient clinic at the national hospital in Belmopan and working in the refugee camps that were scattered at that time around the capital.

On hearing this week’s case, I immediately suspected the patient has a simple botfly larva myiasis (most likely from Dermatobia hominid), although I have seen a few non-typical myiasis over the years in Belize and Guatemala as well, where the larva would develop in a tight spiral just under the skin, which is not typical of my experiences with the human botfly larva. My guess is that these were probably from other dermatobia species, but I never followed up. (perhaps I can dig up an old photo for you to identify).

My guess is that on SuperBowl Sunday the small larval breathing hole opened up on your patient’s lesion, or perhaps the larva actually emerged at that point.

We always used to treat by covering the breathing hole with vaseline and if the larva was small enough, it would emerge on its own far enough to grab with forceps and remove. Larger botfly larva needed to have a small incision made to fully remove intact. In Guatemala or Belize, this could be done in 20 minutes by a minimally trained community-based health care worker. Take a botfly larva back to the states and the treatment can becomes a circus with consultations from four medical specialties.

While a botfly myiasis fits the symptoms described, I would want to rule out a Primary Stage Onchocerciasis nodule, however Onchocerciasis in Central America is just in the Sierra Madres, where there is highly oxygenated falling water. In Belize you would only see it in refugees, but back in the day the thought was you could control River Blindness by popping out the subcutaneous Primary Stage nodules before they matured (we didn’t realize how many hid out in the deep tissue.)

I don’t know if botfly larva would find albendazole or ivermectin disagreeable, as I never needed to treat it systemically.

In reviewing the “modern” botfly literature today, I learned for the first time of the Botfly’s use of transitional vectors, such as houseflies and mosquitoes to deliver botfly larvae to their hosts like guided missiles. (This might help explain the nodule’s location on a less accessible area.) Nor had I realized the Inuit people apparently consider the larva quite tasty….perhaps an acquired taste. (wait of the groan)

I always enjoy your perspectives and interaction.

Regarding your discussion on water purification.
I have a little experience teaching and using solar disinfection (about 30 years). The first research I ever saw on Solar Disinfection came out in 1979 from the American University in Beirut, later confirmed repeatedly by WHO-Geneva, Ireland’s Royal College, Texas A&M and many others, because no ones believes it. Solar Disinfection has its place for some situations, (in refugee situations after the media/money intense spotlight disappears and the donated reverse osmosis filter breaks down), but before real health-security/development conditions are re-established. Solar Disinfection, on non-turbid water in 2L PET containers left in intense sunlight for some 5 hours, seems to really kill the diarrheal disease causing bacterial and viral organisms. While solar heating of the water from 30-50ºC makes this process more efficient (3X more at 50º), the heating is not the essential element, highly oxygenating the water by shaking for 20 seconds probably helps as much. I’ve used it with our teams for up to 3 months and while it works, it is inconvenient. If I can afford $18 Sawyer 0.1micron micro-tubular filter with no moving parts to break, and a 1 million gallon warranty, I now typically use that… or their $80 0.01 micron viral filter, both using basically kidney dialysis tubules. We were apart of the wide scale testing of this filter in 70K families after the 2010 earthquake in Haiti, and its now what most thru-hikers on the AT or PCT trails carry.

Always value your thoughts and experience.
Vince are you aware if Solar Disinfection has been tested against poliovirus?
Dickson, whether or not the glacial ice is contaminated, I’m with you in guessing that as ice cubes in a glass of Scotch, the organisms don’t stand much of a chance.

Best regards and keep up the great work


Jan writes:

Hi guy's

Since you started calling me a friend, I suppose I can be a bit more informal. I didn't have the time ( changed jobs) to look up the most likely species, but my guess would be an insect which deposited an egg in the poor man's posterior. Why did he find out during watching a game ? Must have been the bouncing on the couch and the agitating moving sports fans exhibit when watching something completely inconsequential.



PS the weather in Rotterdam is 15 C with light overcast

Eloise writes:

Dear TWiPers,
I totally deserve an award. I am a twelve year old girl who wants to be a writer, and I listen to TWiP. Of course I must admit, I did not start of my own volition. My father a “humble scientist”, wrote a letter and appeared on the show and did not mention me. This letter is a reminder, Father, that you better start mentioning me. Anyway, in your last episode I found the case very interesting, and I am dying to know what happened on Super Bowl Sunday! My guess for the case is Pilonidal Cyst, but it’s probably not because that’s not a parasitism. My sister, Daisy, swears (ohh, sorry, she’s yelling at me that she “ thinks” that, not swears it.) that it bot fly larva, and my friend, Cricket, (who I forced to listen to the show), says she thinks it a leech bite. I have never been right on a case before, but I thought you might want to hear from a “Fangirl” of TWiP.
With all due respect and ANNOYANCE AT MY SISTER,

Daisy writes:

I think that the guy in the last episode had a botfly larva buried in his skin. This insect lays its eggs on a mosquito, tick, or fly and the eggs hatch when the vector feeds on a host. The lesion seems like the bump that would be made by a botfly larva, which would be raised, painful, and have redness around it, usually mistaken for a mosquito bite. This will swell as the larva grows, which would be why the bump got bigger. The central part of the lesion could be the hole in the skin the maggot creates so that it can breathe. If left untreated, the larva will mature and emerge in about 5-10 weeks, which is consistent with the time between his trip to Belize and Super Bowl Sunday. The human botfly is also found in Central and South America, which is also consistent with this case. Getting a botfly on a visit to those areas is rare, but cases are increasing as tourism increases to those areas. If the man had discovered what his bump was before Super Bowl Sunday, he could have done something to cut off the larva’s air supply and kill it.

Bill writes:

Vincent, Dickson,

I recall that humans have one aspect that resembles camels. In certain tropical areas they both store fat against leaner times. In women this is called Steatopygy aka steatopygia

It seems to have become part of the beauty ratings of African women, as manifest in booty-worship - a certain KK being renowned in that respect.

Logically, a beauty aspect is a proxy for a survival attribute - women with stored fat will live on while their fashion model sisters = seen as more beautiful, will starves in droves.... I wonder if some camels are also seen to be more attractive for similar reasons?

As for the hapless student in Belize, I wonder if his growing red nodule has a breathing hole, which might indicate a possible Dermatobia hominis infestation carried to him by some intermediate host?


TWiP 89 letters

Robin writes:

Cerebral cysticercosis


Left shift:
This is from the days when dinosaurs roamed the earth:
Manual counters for the differential count had the buttons left to right for neutrophils, bands, eosinophils, basophils, lymphocytes, and monocytes. More of the one hundred button presses on the left buttons constituted a left shift.

differential counterFive key differential counter



When this one is needed, the patient has a problem.

Christine writes:

The case described sound like neurocysticercosis caused by brain infiltration of larvae of the pork tapeworm Taenia solium and the immune systems response to it. Although she claims to not currently eat meat other than chicken (for economic reasons) this does not exclude consumption at celebrations or on rare occasions in the more distant past.

This diagnosis is supported by the lack of eosinophilia and the neutrophilia without left shift is most likely due to demargination.

As a side note Dickson's explanation of left shift is right on the money as I was taught.

The weather here in Brisbane is changeable after a devastating east coast low that brought flooding, intense rains on Friday, to a delightful, sunny autumn day with 26 C temps for Saturday, we have clouded over with light showers again today (Sunday) but still a delightful 26 degrees and a light breeze.

Christine from Brisbane.

Jan writes:


Is it Cystiscerosis ? That would fit the complaints, it's common in that part of the world and the fact that you can acquire this parasite from fecal contamination of foodstuffs by infected animals without eating meat makes me lean that way.




the weather is 15 c, occasional drizzle and the cherries are blooming.

Wink writes:

With the information provided, you must expect neurocysticercosis. If it's a zebra, my wild and crazy guess would be an errant Echinococcus vogeli.

Bjorn writes:

I’m making a wild guess on this one. Wild in the sense that it’s atypical, but not entirely
impossible: I’m guessing tht this was a case of latent malaria breaking out, possibly
in the form of cerebral malaria. The reasoning is this:

o The patient is from central america, where she lived for many years.
She might very well have picked up Malaria there. The shaking chills she presents
is a typical symptom that may well be caused by malaria.

o The seizure she had is consistent with cerebral malaria, so this is consistent.

o If the form of Malaria she picked up was Plasmodium Vivax or p. Ovale or p. Malariae,
since these particular species have an abiity to hibernate in the liver for many
years or even decades in the form of clinically “invisible” hypnozoites.

o She might not even have had any malaria apparent infection previously, so this could
be the first time she experiences malaria symptoms. It is also possible that she
has had malaria previously, but has ignored it. The family only took her to the
ER after she had multiple seizures, so a little bit of shaking chills might not have been
enough to make medical attention seem necessary.

To confirm or reject this diagnosis use a quick diagnostic test for all the known malaria forms,
and if any of them are positive start medication immediately. Blood smearr (thick + thin) would
also be nice to confirm/reject malaria and also identify the species.

The internet tells me that he weather is nice outside, but since I’m in a train, in a tunnel on my way to work
I really couldn’t tell.

Elise writes:

Dear TWIP Trifecta,

I hope this finds you all well and frolicking in this gorgeous moment of New York springtime. It’ll only be here for a few moments before summer swamps in, so frolic while you can.

I think I have a diagnosis for the patient featured in TWIP 88. I suspect strongly that the patient has Neurocysticercosis, caused by tapeworm larvae (taenia solium). (There are two types of neurocysticercosis — the parenchymal and extraparenchymal — and I don’t know if both can cause the seizures the patient has so I can’t be more specific, diagnostically.) I know the patient was emphatic about how she doesn’t eat any meat, but it is much more likely to become infected with tapeworm larvae through fecal-oral contamination than from eating undercooked meat (which would lead to intestinal tapeworms, anyway). Fecal-oral contamination also makes it possible for the larvae to make their way to the brain, eventually creating cysts that can lead to seizures of the sort that brought the patient to the emergency room.

There are a lot of possibilities as to how the patient got infected. She came to the United States from El Salvador ten years ago. Cysticercosis and neurocysticercosis are both quite common infections in developing countries, and the incubation period can be extremely long. In addition, she could have contracted the parasite from someone who visited who was infected. In general, most cases of cysticercosis and neurocysticercosis in the United States do occur in immigrants from Latin American countries, but they can also show up in people who travel to countries where tapeworm infections are common or patients who have contact with carriers. Cases in the United States are on the rise. The CDC was very clear about how widespread this sort of infection is and has put it on its list of “Neglected Parasitic Infections” (which is a great name) that need public health attention.

I was interested to read that neurocysticercosis is a leading cause of adult onset epilepsy in developing countries. I didn’t realize that the diagnosis of “epilepsy” could refer to this sort of seizure disorder.

What would be the best thing to do for this patient? Her seizures are not the sort that would necessarily regulate with epilepsy medications. Most of the sources I found noted that antiparasitic medications would cause more brain swelling and pressure. (And also, unless I misunderstand, it seems as if the seizure activity occurs as the larvae are dying, so does it stop once the larvae are dead? Will this eventually resolve?)

As always, thank you so much for your work and for your wonderful podcasts. I truly look forward to them.


AJ writes:

Hello parasailing parasitologists!

Another interesting case! I’m shooting from the hip here, but sounds like neurocysticercosis. Not eating pork keeps her from acquiring the adults, in her intestines, like the worm wants. But if one of her meat eating friends had adult worms, got eggs on their fingers, and then made everyone a salad… well then she could very well have dead or dying larvae in her brain. Then no one wins! Taenia solium is still very common in many South American countries, and while it seems unusual that she could be experiencing symptoms from a ten year old exposure, the adults could easily live that long in a friend or family member’s intestines. Or, maybe a friend visited San Salvador and picked up some worms more recently.

Looking forward to hearing the answer!

PS. The weather in San Diego: still dry.

Grace writes:

Dear Twippees,

This is another joint effort by me, Grace, and my science girlfriend, Caylee. We think the culprit in the case of the seizure-ing woman from El Salvador is Taenia solium, the pork tapeworm.

This lovely parasite may have taken up residence in the patient years ago through contaminated pork before she ever moved to the U.S. and found purchasing meat too costly.

We write to you from mile-marker-18, Idaho, the closest place to our field residence that gets cell service. The small mammals of Idaho send their greetings.

Best wishes,
Grace and Caylee

Carol writes:

Greeting, TWIPpers,

I missed writing in last episode, but I was pleased to hear that what I had guessed was correct. This time I'm managing to write before the next episode is up.

My guess for the case study this episode is neurocysticercosis; just because she reports not eating meat due to the expense now doesn't mean she didn't eat it during the 23 years before she immigrated. I don't eat meat now, partly for ethical and partly for economic reasons (finding meat that has been raised in a manner I can accept is possible, but it's out of my price range), but my entire extended family does and I did while growing up.

The weather here in Victoria is, again, sunny and mild, with a nice ocean breeze. Vincent will be happy to hear that there are no longer any cherry blossoms messying up the trees, though he might be disappointed that the lilacs are in full bloom.

Looking forward to the next TWIx podcasts eagerly, as they provide a nice break from studying for summer courses without making me feel guilty for not learning things,


Dona writes:

Heard your recent podcasts and am writing re the case study this week. First though, feel obliged to update you on the weather in Oxford, UK today - warmish (up to 18 degrees) and cloudy but no rain.

Is the case study cysticercosis caused by Taenia solium? If it is, would you treat the family, especially the infant?

Found this paper from 10 years ago, suggesting cases were going up in US - is this true today?


Varun writes:

Greetings Professors,

In response to TWiP# 88 case..

There is a series of parasite to be considered when it comes to parasites related to seizures. Ref:
From the given list of symptoms is probably pointing towards Neurocysticercosis. Though classically it is a meat derived condition, there are sufficient conditions described by transmission through unwashed vegetables, with fecal contamination. Am also considering that it also can sometimes have a unusually long incubation periods.

I would like to know if there was any significant findings from brain imaging, what was the differential count, an IgG ELISA for cysticercosis and Toxoplasma.

My guess- NCC (Neurocysticercosis), casued by cystic larvae of Taenia solium

Anne writes:

Dear TWIP team,

My thoughts for the woman from El Salvador are that the case description best fits that of cerebral cysticercosis (neurocysticercosis.) It is acquired through ingestion of tape worm eggs in the feces of an infected human carrying the intestinal tapeworm Taenia solium. This represents an aberrant form of the life cycle. Typically, the lifecycle would be completed by a pig ingesting material contaminated with human feces containing the eggs and humans would then in turn acquire the tapeworms through ingestion of undercooked pork containing the larval stage. It is an important cause of acquired epilepsy in areas where Taenia solium infection is common and sanitation is poor.

Turns out it occurs in my home state too :
O'Neal S, Noh J, Wilkins P, Keene W, Lambert W, Anderson J, Compton Luman J,Townes J. Taenia solium Tapeworm Infection, Oregon, 2006-2009. Emerg Infect Dis. 2011 Jun;17(6):1030-6. PubMed PMID: 21749764;PubMed Central PMCID: PMC3320238.

I am mildly disappointed with Dickson’s dismissive comments this week about current veterinary education. Certainly the scope of knowledge required to become a board certified veterinary pathologist is extensive. I will point out that we don’t have the luxury of studying only one species.

I adore the show and look forward to the podcasts as they come out. Thanks as always.

Beaverton, OR

Adam writes:

Hello my good sirs,

In response to TWIP 88's case, unless the little 10-year bit is a total red herring, I believe this may be Chagas disease, or Trypanosoma cruzi!

A quick story about why this comes to mind: A few years ago, I was in rural Nicaragua working on a water sanitation project. We had a Peace Corps volunteer accompany us who woke everyone up in the middle of the night because she found one of the "kissing bugs" that we learned were vectors of T cruzi. She explained that if we were to see one in the stable where we were staying (yes, we were sleeping in a converted stable), to trap it and find her so she could capture it and give it to the government health organization, presumably for epidemiological purposes. This raised lots of questions and she had to explain that these bugs can give people a parasite that can cause sudden death 10 or 20 years after being bitten. Needless to say, this freaked a whole bunch of people out and kept them up all night. I, for one, thought it was fascinating and it made me seek out more information about parasites when I got back home!

On this same trip, I went swimming barefoot in a lake with some locals (spectacular idea, I know...). I thought this was really great and all until I came out of the water and noticed that grass leading into the lake was littered with cow pies! Within 24 hours, I had some nasty diarrhea that passed within a day. Luckily I had some Lomotil to keep me "stopped up" for the bus ride home. Wish I could figure out the pathogen that made me sick!

Anyway, sorry for the lengthy reply and story. Thanks for all you do to promote scientific literacy! I am a middle school science teacher in Chicago who is applying to medical school this year. The podcast trifecta give me lots of great lesson ideas for my kids, and keep me intellectually stimulated after long, monotonous days. Keep up the incredible work.


PS - Is it weird that I hope I picked up some parasite in Central America? I went to school in Eugene, Oregon, which happens to be just about the grass pollen capital of the world around this time of year, and developed some severe allergies while there. It would be cool to see if they persist after my trip - my own little "hygiene hypothesis" experiment!

I emailed a heme/onc doc I have been shadowing who guesses that "she has neurocysticercosis - a form of T. solium, the pig tapeworm. The fact that she doesn't eat meat doesn't mean anything, It can be transmitted fecal-oral, so if no hand washing she can get it."

After researching this a little bit more and learning that T. solium is the leading cause of adult onset epilepsy worldwide, it seems like neurocysticercosis is a much better guess than Chagas disease!


Someone wrote:
This is a review but is gamma interferon the intrinsic factor described by Dixon versus leishmania?

AJ writes:

Hello fellow parisamaniacs,

This week's case study seems to me to be a case of Leishmaniasis. The ulcer sounds much like leishmaniasis, especially as it is painless, and the subject knows he's been bitten by some sort of dipteran or another. Italy isn't an unreasonable place to pick the disease up, although it isn't terribly common.

I'm not sure if the hep C would tie into that. Also, Dick kept asking about fish and beaches, which made me consider vibrio and mycobacteria briefly, but those are outside the scope of twip. I'm not sure if phlebotamous would bread near beaches specifically, and they only feed at night, so I'm not sure it's relevant.

Keep up the great work! I love the clinical cases, although this is the first time I've had any clue as to what the diagnosis might be.
Thanks always,

Grace writes:

Dear TWIP Team,

This attempt at cracking the case study is a joint effort. It comes to you from a duo of small mammal biologists searching for enzootic plague out in west central Idaho. With no good radio stations, downloading episodes of TWIP and TWIV for our long commute to the field each day helps keep us sane.

Apologies if the format of this letter is wrong, and if our answer is totally off the mark. We researched what we thought were the pertinent clues in a sunny cafe in Boise, and our most educated guess is Cutaneous Leishmaniasis caused by Leishmania infantum. The patient could have been bitten by a sandfly during one of his trips to southern Italy. Sandflies are at their lowest levels during the time of his trip (winter), but the incubation for L. infantum can be long, lasting up to years.

Thanks for the great podcast! It's lots of fun for those of us in the uncertain purgatory that is the time between undergrad and grad school to have a reason to use our brains again.

Best wishes,

Buboes from Idaho

George writes:

Hi Vinny. Nice discussion brought to my attention by Monica. Of course, I had to explain the story to everyone in the lab

TWiP 88 letters


Robin writes:

Cutaneous leishmaniasis.
CL has been endemic in Italy at a relatively constant level since the 1970s, in the same areas that are endemic for VL. CL is largely underreported to the MoH. Only cases that are diagnosed and treated in hospitals are reported, but those diagnosed in private clinics are not. It was estimated that 450–500 cases occurred both in 2004 and 2005.

Christine writes:

Dear Doctors Vincent,Dickson and Daniel,

Having listened to your latest podcast I am less disappointed that I was stumped over twip 86. I had excluded most things I could think of due to a lack of fever or diarrhea.

This week however sounds like a case of cutaneous Leishmaniasis. This would have been transmitted by the bite of a sandfly. Would be worth sampling the edge of the lesion to id.

The weather here in brisbane has been beautiful blue skies, fresh westerly winds and a high of 25C.


Wink writes:

If this is leishmaniasis, my question for Dixon is where do sand flies live -- beach, desert, grass?

Bjorn writes:


My guess would be is cutaneous leishmaniasis. It’s not that common in Italy, but it’s certainly not unheard of.

He could have been bitten by a sandfly vector while on the beach. A definitive diagnosis can be made by demonstration of the organism in the tissue surrounding the lesion. If the organism spreads beyond the skin, it can establish a visceral leishmaniasis. Here are some signs one can look for to confirm a diagnosis for that condition:

* There may be hypergammaglobulinemia and hypoalbuminemia
• Liver enzymes commonly elevated
• Pancytopenia very common
• Diagnosis by demonstration of the organism
• Commonly done through splenic puncture, liver or bone marrow biopsy, lymph node aspiration, or staining of peripheral blood buffy coat.

Assuming that this is cutaneous leishmaniasis, the treatment may be just to let the thing heal itself. However, do observe for signs of visceral leishmaniasis since that will require treatment. Most commonly utilized medication is pentavalent antimonial compound
stibogluconate. Alternative options can include liposomal amphotericin B, pentamidine, azoles and miltefosine.

All of this is fresh off my notes from the wonderful Coursera course in “Tropical Parasitology: Protozoa, Worms, Vectors and Human Diseases". As a software engineer I don’t know much about parasites, but what little I do know comes from "this week in parasitism" and that single coursera course. Parasites are fascinating :-)

Keep it up doctors, you are an inspiration.

Elise writes:

Dear TWIP Gang,

How are you? Many thanks again for your case studies. I love working on these and was not event remotely mortified by not getting the answer to TWIP 86 correct. I never would have guessed pinworms would be the culprit. (And that is a sentence I am glad I have never had an opportunity to compose prior to today.)

For TWIP 87, I have done some research and it looks very much like cutaneous leishmaniasis. All of the symptoms the patient exhibits pretty much line up. The lesion he presents is consistent with cutaneous leishmaniasis: large, painless, unhealing sore (beginning as a small painless bump), with a fibrous scabby covering, with the infection limited to the lesion, and not spreading beyond.

The patient was in Southern Italy and spent time on the beach, where he very well may have offered up an appealing meal for the sand flies that spread the infection through bites. The CDC and other sites report that cutaneous leishmaniasis is widespread (present in large parts of: Asia, the Middle East, Africa, southern Europe, Mexico, Central America, and South America), and the incubation period is about right. I suspect the patient’s elevated blood pressure is unrelated to the lesion.

(I should also add that the glee with which all of you introduced the description of the symptoms and the patient profile made me think that this would probably be a less subtle problem than the one in TWIP 86, which is why I am offering a not-uncommon diagnosis.)

Finally, I read in a number of places that these lesions cause permanent scarring. Would it be possible to minimize the scarring if the diagnosis is made sooner or is the damage inevitable?

Thank you so much again. It is 68 degrees F (20 degrees C) in lower Manhattan and the skies are blue, and it is hard to believe that it is going to pour in a couple of hours.

Cheers and best to all of you

Scott writes:


As a longtime listener, I have enjoyed your case presentations, and though I have no competence as a diagnostician, have enjoyed speculating about possible diagnoses.

The case presented in the current TWIP struck a chord with me. Living here in Costa Rica, where myiasis caused by Dermatobia hominis is fairly common (there are some really gruesome photos to be found on the web), the presentation sounded actually quite familiar. I can't speculate as to the species involved, as I am not that familiar with the species of parasitic flies that are found where the patient had been traveling, but myiasis would be my guess at a diagnosis.

Somewhere I heard a story about a biologist who was infested here, and decided to let nature take its course once he got back home, so he could document the development of the larvae to its emergent stage. As I recall, it got just too painful to tolerate and he had to remove it prior to the emergence, but even so, doing such a thing strikes me as being truly heroic dedication to science. I was infested with one once, and removed it as soon as I discovered it - I can testify that it was painful even when still quite small.

Cartago, Costa Rica


TWiP 87 letters


Jan writes:

Hello doctors,

This was indeed not easy to Google; one of my attempts even had a dr oz page as one of search results. Clearly a dead end. However with some persistence I came up with Entamoeba Histolytica.
As for clean water; I use the boiling method when hiking and camping, and if you take a thermos flask along you can boil extra water while making your morning coffee and have tea or other hot beverages during the day. If you want cold water, just boil it in the evening when preparing dinner and let it cool overnight.

Greetings and thanks,


Robin writes:

Seems like Katayama's syndrome if a diagnosis is clinched in the parasitology lab.

Stool exam for cysts in amebic liver abscess is unhelpful, and trophozoites would not be expected in the absence of dysentery.

Murphy's sign as classically understood, is an inspiratory catch at the right costal margin at the midclavicular line, and not, as is now commonly described, as just right upper quadrant tenderness. The classic Murphy's sign is also well localised, and is a reliable indicator of a problem gall bladder.

Wink writes:

No, I’m the chump!!

You got me this time. I considered trypanosomiasis: the incubation would be OK but the presentation is wrong. Anisakiasis is not common there. He shouldn't have been walking around barefoot or wading in fresh water. I think the incubation for ascariasis is longer and a tourist would most likely be asymptomatic, but -- common things being common -- I'm making a wild bet on A. lumbricoides.
Wink Weinberg (Atlanta)

Richard writes:

I think that this gentleman has some sort of intestinal helminth infection, my vote is ascaris because it is soil-transmitted and the patient lacks high risk food exposures.

Further wikapedia-ing indicates that one still has to ingest ascaris eggs, but they are hard to kill so I think even the "westernized" food chain at a big hotel may be the culprit.

Else writes:

Dear TWIP Collective,

How are you? It seems that spring has finally settled in here in New York, so in spite of the high winds here in lower Manhattan (where it was in the lowest of 60’sF — 15-ish C) it has felt great.

I am again, trying my hand at a diagnosis. I know you were going for a trickier case study this time, and without a medical or science background I may be out of my depth, but here is my attempt.

I think that the young man who has recently returned from a trip to Kenya may be experiencing amebiasis brought on by entamoeba histolytica.

It was a bit tricky to think about what was going on with the patient because his symptoms were not particularly dramatic (which is great for him, but hard for this highly amateur detective), and the primary symptoms: stomach pain and decreased appetite, occur in many instances (or even without the help of a parasite, when exposed to too much family, at holiday time).

Amebiasis is apparently a common parasitic infection in many parts of the world but for the purposes of this case study, parts of Africa including Kenya and it expresses itself in many ways. 90% of people who are infected are asymptomatic. In people who are symptomatic, the symptoms can show up in 2-4 weeks, so given the duration of the patient’s visit and the fact that he has been home for a week, the time frame makes sense.

For people who are symptomatic, the range of symptoms includes abdominal pain as a primary symptom. (The patient does not have fever or other GI symptoms, but infected people don’t always exhibit these.)

As for how he could have contracted this parasite in spite of such care he took, staying at a hotel that caters to Western visitors and avoiding the water, I think it is possible that he slipped a little. It was mentioned that he ate salad at the hotel, which is raw and if it had been washed in local water, some parasites could have found their way to the patient. Also, he did drink soda, but if he had any ice cubes, again, this could have been a point of contact with the parasite. They are common, hard to avoid and it sounds like people can be colonized and have no idea.

As for the diagnosis, it is recommended that multiple stool samples get tested because the parasite can be hard to find.

I fear I have missed something critical, but this is the best I could come up with.

What was the vaccine that the patient should have gotten before he left that he did not get?

Many many best wishes. I am very grateful for your fascinating and brain-stretching (for me) podcast and challenges.



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