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TWiP 54 Letters

Tommy writes:

Hi Vincent and Dickson,

I was listening to the new episode of TWiP (episode 52) and one of your listeners wrote in asking about tree parasites. While plant parasite is not my main field of research, I have written about one such parasite on the Parasite of the Day blog - the nematode Bursaphelenchus xylophilus which causes the tree disease known as Pine Wilt.


The basis for that post was actually a PLoS Pathogens paper on the genomic characteristics of that particular parasite.

In addition, there are also numerous insects, nematodes, and bacteria that can infect plant tissue and induce gall formation. I feel that
Dickson might be fond of those plant parasites because much like Trichinella spiralis, these organisms are capable of manipulating the
architecture of the host's tissue, forcing it to grow structures that both house and feed the parasites - much like T. spiralis with its
nurse cell.

Mike writes:

Dear doctors Racaniello and Despomier,

I just wanted to write in with a bit of praise. I have been a regular listener of TWIV for over a year now, and I'm just now catching up with both TWIM and TWIP. I have to say after having listened to the episode on hook worm and the remarkable back story given by Dickson about that organism in a historical context, that I am truly impressed. I spent ten years reading about history outside of school in my youth, and I must say that I am deeply impressed by both the depth and breadth of Dickson's knowledge.

Thank you both for a wonderful show and the hours and hours of edutainment.


Suzanne writes:

RE: earthworms

They come out when it rains because they can. It's not so much that they avoid wet tunnels when it rains as they usually avoid dry ground. When the ground is wet they can come out so they do.

Jeff writes:

Hello twip hosts,

I just listened to TWIP 52 and all the emails had to do with you guys mentioning stopping TWIP. I just discovered TWIP last summer (2012), and I've caught up with all the episodes! I just wanted to let you guys know that TWIP has kept my mind constantly busy during half day hikes in the Pacific Northwest Cascades! I thoroughly enjoy the report Vincent and Dick have. I love the jokes. It is one of my favorite podcasts.

I was trained as a Chemist at San Diego State, so I have a special connection to TWIM, with the SDSU hosts that are often on there. I now live near Portland, Oregon and hike quite frequently.

I hope none of the TWI's die, and I thank you two for all your work and information you've given to thousands of people.


Rick writes:

Hello Dr. Racaniello and Dr. Despommier!

I, like many, had a sinking feeling in my stomach when cancelling the show was proposed earlier. I was refreshed to hear this will not happen! Dr. Despommier, do you know the Komuniecki's at The University of Toledo? I had the opportunity to do some work in her lab (Patricia) working with Ascaris suum. Ah, the trips to the slaughterhouse.

If I may make a suggestion for a TWIP, TWIM, and TWIV: drugs. A review of antiparsitic agents and resistance mechanisms. Likewise antibiotics and resistance mechanisms (the New Delhi metallo-beta lactamase, cfr resistance, erm resistance, effluc pumps, gyrase mutations and everything TB has). What a show(s) that would be. TWIV, well i know there are not as many antivirals (for non-retroviral infections) but why not. Then again there is no shortage of TWIV episodes (sorry Dr. D).

Thank you both so much for all of the education and the history lessons. I am always captivated by Dr. D's stories.

Best regards,
Rick in Toledo OH, patiently waiting for spring to come

Spencer writes:

Dear Vincent and Dickson,

Attached is a letter which I think represents a sad state of affairs for parasitologists, epidemiologists, physicians and particularly for patients. It is a decision probably driven purely by cost. In the past year, I have treated a patient at this hospital with amoebic dysentery. Was this patient part of the 0.3 percent? Could you address the quoted statistic about the overwhelming giardia/cryptosporidium being found nationwide?


Spencer Kroll MD PhD

Frank writes:

Dr. Racaniello,

It is 50F and sunny today in Central Illinois, with plenty of flooding in low lying areas.

I would like to start by saying Thank You for the three TWiX podcasts. I enjoy listening to them during my commutes and while I am out walking. They are helping to keep my skills in Immuno/Micro/Etc while I am busy with my medical school studies in many other topics also.

I want to point out one clarification that applies to this weeks TWiP #53. You stated that a positive PPD indicated an active TB infection. It actually indicates that the patient has been infected with TB at some point. Most individuals that are PPD positive will not develop active TB unless if there is an issue with their nutrition or immune system.

The active disease is when there is clinical or radiographic evidence of the disease. Without either of these the patient at worst has a latent form of TB. This is important to know because latent TB is virtually non-transmissible.

It is also important to note that some patients with HIV and other immune disorders that effect the T cell population will not react appropriately to a PPD test due to a lack of T cells that cause the skin reaction.

SIU School of Medicine

PS I will be at the ASM conference in Denver. Do you know where and when you will be recording any TWiXs while you are there?

Marcel writes:

Hello TWIP team,

I love your family of shows, but while listening to TWiP 53, I noticed that Dickson used the word Eskimo. I hate to play politically-correct police, but Eskimo is now considered as fairly derogatory (at least in Canada and Greenland). The word, meaning "eaters of raw meat" by some accounts, has been replaced here by the word Inuit.

Just something to consider. Love the show!

Marcel in Canada

Justin writes:

I bought crabs from a local grocery (Pathmarket ) and noticed these small black ovals the size of sesame seeds (image attached and compared to the size of a quarter) on one of the legs and I was hoping you could identify this and confirm its normal and an ectoparsite. I love the show.

Thank you!

IMG 20130426 231444

TWiP 53 Letters

John writes:

Dear Vincent and Dickson,

I just heard your most recent TWIP. Please keep these podcasts going! I love listening to your podcasts and hearing your enthusiasm for my favorite biological topic, parasites. Remember that for every fan that takes the time to write to you there are probably 20 other fans who have not written. Plus many "new" fans are still catching up on the archived episodes (I began listening to TWIP at around episode 35 and it took months to catch up). These podcasts make an excellent teaching tool and I certainly plan to incorporate them in my Parasitology courses. And they expose the parasitologist to other areas of research that they may not otherwise have explored.

Let me suggest some topics and guest for upcoming shows.

Parasites and behavior: You've touched on this, but I think the topic deserves its own show. I recommend asking Janice Moore at Colorado State.

Parasites and Ecology: Again, you've touched on this topic (especially in episode 44), but it left me wanting more. I recommend asking Kevin Lafferty at USGS and Tommy Cheung at UNE (who has written to you previously)

Insect parasites: parasitoid wasps would be fun to learn more about. You could also focus more on fleas and lice as parasites (as opposed to vectors of parasites).

Plant parasites: not my area, but it's something I'd like to learn more about.

John Janovy teaches Field Parasitology at the Cedar Point Biological Research Station at U of Nebraska. I'm sure he would enjoy being a guest on your podcast.

And Shelly Michalski would enjoy talking about her work with FR3.


Saint Aardvark the carpeted writes:

Hi there -- I came across TWiP, TWiM and TWiV recently after following
a link from this article:


I downloaded the episode and was aghast...the idea of volunteering for a norovirus study was incredible. The entire episode was fascinating.
I could not stop listening, and ran around afterward telling everyone about what I'd learned.

I've added all three of your podcasts to my regular listening, and will be catching up on old episodes as well. I'm not a scientist, but
an interested amateur, and the level of detail is great -- I'm learning a lot, and I'm challenged to learn more. The atmosphere is
great, the guests are wonderful, and for the record I *love* the digressions and the weather reports...they make it feel comfortable
and casual.

I'm sending this to TWiP because I just listened to the episode about malaria and was sad to hear that you're considering giving it up.
Please don't! The episode was fascinating, and I'm currently downloading more back episodes. I hope you continue to produce more.

Thank you very much for your work, and the generosity of you and all your guests.

Tom writes:

A few months ago my wife asked me to look at and photograph a moribund grasshopper lying atop the leaves of a bush in our front yard.

It appeared to me that it was a grasshopper covered with eggs. My wife wanted no more such grasshoppers fearing they might eat some plant she treasured in our garden. I knocked it to the ground and stepped on it and the kicked it under the bush.

I did immediately send the photo to my friend who has a Ph.D. in entomology and she informed me that those were NOT eggs but a rare form of grasshopper mite. The mites had infested the grasshopper and killed it by sucking its vital juices. She wanted to know if I could find the dead grasshopper and stick it in a Zip-Lock bag and cool it with dry ice and give it to her. She had contacted the leading mite expert in the USA, I think some fellow in Michigan, who said he could only identify the species with certainty if he had one to examine.

By this time it was the next morning and while I did find the grasshopper's remains, alas, the mites were gone I suppose because the grasshopper was dead and no longer capable of giving them a delicious meal. I did provide her with the carcass with the hope that there might be a mite or two left on the carcass, but apparently there were none present.

Have you ever studied or become aware of mites of this type before? I did learn there are grasshopper mites but the common one[s] look nothing like these.

You just never know when you will find something rare.

I have added photos to my flickr account that you might enjoy, as you did last time I mentioned this site to you:




I have also attached a beaver I photographed a couple of days ago in one of the ponds near my house.


Rie writes:

Hello, professors. This is neko from NZ again.

I just listened to twip episode 50. You mentioned you haven't got any email and you might stop your podcasts. Now that you've mentioned it, I can imagine your mailbox is overflowing with email from all over the world, but here is another one, from land of the long white cloud.

When I started listening to twip, I was fascinated but also couldn't help feeling uncomfortable. I used to love steak rare but I no longer feel like risking it. I can't help but cook them well done for my family now. I now wash my hands and cutting boards often with detergent after handling raw meat. On the other hand, I can eat pork without hesitation after defrosting. All thanks to your educational podcasts. If you are looking for some ideas for future episodes, I'm really interested in food safety, just every day risk factors and preventive measures, associating with parasites.

At the end of episode 50, you talked about toxoplasma. One of my favourite podcasts from Japan mentioned toxoplasma being able to manipulate some neurotransmitter in the brain. I think he was talking about this article.

That Japanese host said that toxoplasma might be responsible for some suicidal cases if this article is true. That, the people committed suicide might have been infected by toxoplasma. He was wondering weather it will bring down the suicidal rate if we systematically carry out a test to find the infected and treat them. What are your thoughts on that?

Lastly, I don't mind if it's monthly, or bi-monthly, but please do continue educating us.

Thanks always,

Alexandra writes:

Dear TWIP,

I recently wrote to TWIV to express my admiration and ask a question about viruses of fungi. However, I have not previously written to TWIP, though I listen to it almost as often.

I am an undergraduate, and I work as a tutor for the biology survey class which all new biology majors must take. We're currently covering Biodiversity, and I cannot express to you how fabulous it has been to be able to enliven our discussions on Phylums Nematoda, Platyhelminthes, Apicomplexa and so on with the stories I've gleaned from TWiP. I take a particular (perhaps a little sadistic) pleasure in relating the story about how outhouses perched over lakes and rivers led to endemic fish tapeworm, or how toxoplasma gondii can cause radical behavior changes in rats (and maybe humans).

Every now and then, I even manage to turn on another person to TWiP, TWiM, and TWiV. Keep up the good work! You help to remind me of the inherently joyful and curious nature of science - which undergraduate coursework often obscures or obliterates entirely.

Peter writes:

Hi guys.
Another tool for field work.


202 specimens of Astronotus ocellatus (Oscars), were collected from a freshwater lake in the state of Amapá, northern Brazil.
A total of 6,308,912 parasites belonging to 11 different taxa were found. Protozoa was the most abundant; flukes, worms were also prevalent and abundant.

No Amazon sushi for me. 

I used to keep Oscars. Didn't realise the parasitic load would be that high.

In relation to parasitic species being 40% overall.
The link also examines the notion of the food web and the role of parasites.



peter w

Jim writes:

See http://www.smbc-comics.com/ for the latest, and you can go back to this one if you wish...

Oh - and thanks for the continuing podcasts, too!

Yet another Jim from Virginia

Maureen writes:

Another innovative idea used in Africa:

Scientists diagnose intestinal worms -- using an iPhone microscope


Robin writes:


also: How to pronounce Shankar. It's a name widely recognised in India. The first pronunciation is the Indian one, the second is akin to the way the British overlords butchered the local languages.

Robert writes:

Dickson's first two choices of people he would like to meet (Lincoln and Darwin) shared a birthday, February 12, 1809.

All the best,

TWiP 52 Letters

Jason writes:

Hi Drs. Despommier and Racaniello,

This week you wondered why the immune-activating receptor for Toxoplasma gondii, TLR11, is present in mice but not in humans. You noted that it looks like there's no selective pressure keeping it around in us and it has become a pseudogene. You asked why mice then need it since it doesn't harm the host.

Is it possible that rodents need extra defenses against T. gondii because it changes their behaviour and makes them more susceptible to predation? "Toxo" could be killing the mice indirectly. We descended from tiny crawly things, but when our ancestors moved up the food chain, they wouldn't need this defense any more. If it is true that T.gondii increases your risk of auto collision then perhaps we will see a selective sweep over the next million years!



Houston, TX

Kim writes:


I just finished listening to TWIP 50 and got sad when you guys were partly demoralized to continue the series. I would like to suggest you merging TWIP and TWIM, to make the burden of making these excellent podcasts a little less exhausting.  You could find a parasitologist every now and then (if Dickson is not availabe) and speak about these things in a larger group. For example Elio would probably know something and Michael, as he seems to have knowledge about almost everything! This could be embedded with doing like a ratio of 1:3 with bacteria (meaning every fourth podcast on parasites or so). Please consider this, as I object to quitting the series but am also worried about Vincent’s mental health with his work-burden!

I would also love to hear Dickson explain the vertical farm-thingy. The name is pretty obvious what it is, but a little more in depth. The book is on my list of books to buy, but I have still a few to read before buying new ones so I would like a little preview!

Thank you for the great podcasts.

Best regards,

Kim, biomedical undergraduate from Stockholm.

Jan writes:

Hello doctors,

Just a thank you from the Netherlands. I'll keep listening. And if you could do an episode on tree parasites (with external expertise ) I'd be ever so grateful. I never took any biology in school, but I can still understand the podcast ( I am a science nerd though ). What is your opinion on Carl Zimmer"s Parasite Rex ? It seemed quite accurate to me, and is very well written, but I'm no expert. Would you recommend it to the general public?



PS Majored in medieval history, now a tree-worker

Maureen writes:

To Our Esteemed TWIP Duo:

I waited with bated breath for #50 TWIP for a month. TWIP is my favorite of the tri-TWIs! Imagine my dismay when the discussion at the end of it was about whether you should end TWIP (I listen to the end). We are listening!  We just didn't write because there was no TWIP to write about for a while. I find TWIP to be the most informative and comfortable to me. Vincent and Dickson have a great rapport. I work in infectious disease with patients with Toxoplamosis, Leishmaniasis, Lime disease, Malaria, Loa Loa, Strongyloides, Giardia, etc., and always look to understand these parasitic diseases better. Your discussions clarify so much for me so please keep TWIP. I would like a TWIP that includes information regarding Sarcocystosis. Long live TWIP!


Clinical Research Nurse

Justin writes:

Good morning Dr. Depomier and Dr. Racaniello,

I listened to episode 50 on Monday, congratulations, and nearly had a panic attack when I heard that the show may come to an untimely end. I have not listened to all the episodes but have been listening sind late summer early fall and always excited to listen though as of yet I don't understand much about parasitic life cycles. Anyways, my contribution to saving TWIP is proposing a topic that I would like to see discussed. Chagas disease recently trended on the news and twitter and I thought it was pretty cool. I know you have discussed T. cruzi before but here are two links I'm interested in, a news article.

http://www.sciencedaily.com/releases/2013/02/130214092353.htm and the corresponding paper


Thank you and God save the TWIP

Mabry writes:

first - to let you know how much i am enjoying your podcasts.  my husband steered me your way with #38 about dracunculiasis. i am working my way though all them now  while i am quilting on my sewing machine. then i will go through the viruses.  i was trained as a chemist; my biology education has just been picked up over the years (many now).  this is a great way to learn, and you two are fun to listen to.  thanks

second - i have great-grandparents who left the mississippi valley for oregon in 1845 & 1853 because of malaria.  in one family account, one was so sick from it that he could only lay in the wagon for the first month of the trip.  (as an aside - can you imagine walking all the way from iowa to oregon?)  i have heard that one/perhaps the major reason why we don't have malaria in the u.s. now (and italy & other places) is that because of our mosquito eradication programs, principly with ddt, we dropped the human resevoir of the disease enough so that there is not enough to propagate the disease.  we certainly have drained a lot of swamps. that helps, but i doubt that it is the answere. mosquitos will always still have more than enough places to breed. i know that ddt had a bad rep, justifiably so.  but it broke the cycle of transmission, and then it was no longer needed.   what sort of studies have there been on transmission rates vs rates of infection in the population vs the others transmission factors?

Trudy writes:

I love this podcast.  I learn so much from you two...just listening to #50.  Will be thinking of what other topics or papers might make an interesting episode.  Was very excited to see that there was a new episode!  I am subscribed via the iPhone and iPad podcast app.

All the best from a fan in Naples, FL


Rufus writes:

Yes, I'm still listening.  Fine episode.

I think I now know a bit about what complement is.


Portland, Oregon.

Nick writes:

What is your guys' favorite parasites and why?


Neal writes:

Dear Vincent and Dixon,

I am not too proud to beg.

Don't stop TWIP-ing.

I am a recent devotee to all things TWIx.  Love it.  

You have made my commute much more productive; like a journal club while I am behind the wheel.

I just listened to TWIP podcast 50.  My colleagues work on Factor H and Neisseria (maybe good for a TWIM podcast); so I found this mosquito/malaria/complement business was very cool.  Of course, mosquitos have their own complement C3 like factors that are involved in controlling malaria.  Maybe complement is the achilles heal for this parasite that we should think about more?

As an "insect immunologist", I am looking forward to listening to episode 51.  Lost of great mosquito immunology that you might consider for TWIP.

Don't stop TWIP-ing.  If you build it, they will come.

Keep up the great work!



P.S.  I won't tell Shankar that you butcher his name.


Neal Silverman Ph.D.

Professor & Research Director

Division of Infectious Diseases and Immunology

Department of Medicine

University of Massachusetts Medical School

TWiP 50 Letters

Alaric writes:

Hello Vince and Dick,

I just found your podcast and I love it! You have some wonderfully witty banter.

I am only on my 4th episode (that's what you call a podcast segment right?), and have a question pertaining to my original reason for searching out your podcast.

I am working on the research portion for a short story I am wanting to write about what the world would look like if we knew exactly how different parasites effect behavior. Think of it as a thought experiment dealing with the nature of environmental determinism and the concept of free will. Say, would people purposefully expose themselves to a parasite for a desired effect, or use one as an alibi for an act of bad faith? I may bring in epigenetics into this story as well, but I'm not sure how it will fit. It is meant to be science fiction with a bioethical slant.

Importantly, I don't want it to seem too sensationalist though, so I am trying to base as much of the story in reality as possible. Hence listening to your podcast! Do you have any suggestions on where I should look for information about this? Do you have a podcast/episode/segment about this? It's validity as an idea? Conspiracy theory or reality?

Also, love the mini-history lessons. Myself, I am a student of history of science/medicine/technology and seriously appreciate it! A++ will listen again.


C. Alaric

Robin writes:

If he is of Indian origin, the first name is not pronounced as in chancre


But as:

Robin writes:

Minas in Portuguese means ‘mines’.

James writes:

Hi folks,

You wanted to know how many NZ listeners you have so now you know you have one more. :p

Keep up the great work.

Kind regards,
New Zealand

Jacob writes:

Hi all,

I saw this in my inbox this morning and thought that it would be a good TWiP pick of the week.



Peter writes:

Dear Vincent and Dickson

I thought that this paper from PLOS one would be worth a mention on TWiP

Tapeworm Eggs in a 270 Million-Year-Old Shark Coprolite

The fossil from Brazil has been found to contain the oldest known examples of tapeworm eggs.

The specimen was so well preserved that a worm larva could be seen in one of the eggs.



TWiP 49 Letters

Jim writes:

Professors, you've discussed this idea before, but I thought you'd enjoy this nice summary from Nature:


And I do enjoy your podcasts. Thank you for sharing your wonderful conversations!
Sincerely, another "Jim" from Virginia

Alan writes:



Virginia writes:

I've been fascinated with parasites for years, ever since reading Peeps, a novel by Scott Westerfield. While it is fiction, every other chapter focused on a particular parasite and described its life cycle.

When I found this podcast, I nearly burst from happiness! While I am no longer a wildlife biology student (I recently switched to an English major - what a change, eh?), I still love learning more about parasitism. So many people find it odd that I'm so enamoured with such "gross" creatures, but I think they're just nifty.

Anyway, I just wanted to thank you for starting this podcast. It is both informative and entertaining. Keep up the excellent work!

Ethan writes:

Saw this and it instantly reminded me of Dickson's heavy breathing in the background.


Don writes:

Dear Sirs.
I became intersted in parasites of the gills in fresh water fish, esp Myxoma fundubli, and was surprised to learn tha this animal produces spores. How common is that? Your TWIPMV is marvelous, thank you so much.

Spencer writes:

Dear Vincent and Dickson,

Here's a link to an interesting study published in the Journal of Clinical Endocrinology and Metabolism that was done in China suggesting that schistosome infection may curb diabetes risk. The researchers detected an association between previous schistosome infection and a lower prevalence of diabetes in patients. This may hint at a link between glucose metabolism and T cell mediated cytokine secretion. Before I tell patients to go seek out schistosome infection, perhaps more studies need to be done.

Association of Previous Schistosome Infection With Diabetes and Metabolic Syndrome: A Cross-Sectional Study in Rural China


Spencer Kroll MD PhD

Noor writes:

I apologize in advance for the large volume of correspondence, and for not knowing the entire catalogue of what has and has not been covered. I send these e-mails with only the utmost respect and admiration.

I was so ready to roll my eyes into the back of my head for that story, but found myself captivated. I believe I sense the gift.

Also any chance of exploring the facts of the great Candiru myth?

From Wikipedia:

William S. Burroughs wrote about the candiru in his 1959 novel Naked Lunch, describing it as "a small eel-like fish or worm about one-quarter inch through and two inches long patronizing certain rivers of ill repute in the Greater Amazon Basin, will dart up your *censored* and hold himself there by sharp spines with precisely what motives is not known since no one has stepped forward to observe the candiru's life-cycle in situ."[22] Burroughs also mentioned it in The Yage Letters: "At that time I was stationed at the remote jungle outpost of Candiru, so named from a tiny eel like fish that infests the rivers of that area. This vicious fish introduces itself into the most intimate parts of the human body, maintaining itself there by poisonous barbs while it feeds on the soft membranes".[23] The fish is also referred to in David Grann's The Lost City of Zand in Chuck Palahniuk's Fight Club (novel).

Not knowing anything about its reproductive or life cycle, its difficult to say if this should be classed a predator or parasite, but in my book anything that "allegedly" swims up your urethra and needles itself in there permanantly should be classed a parasite, although one that certainly shows no regard for the life of the host, although I'm sure there must be surgical interventions to prevent kidney rupture.

It should also be noted that the Candiru is a major plot point in the Season 1 Episode 9 of the animated Adult Swim show "The Venture Brothers" entitled "Are You There God? It's Me Dean."

The episode appears to have been available for free some time in the past, but is now certainly $2 on iTunes. http://itunes.apple.com/us/tv-season/the-venture-bros.-season-1/id256218414

Being a Johnny Quest kid I have a special place in my heart for The Venture Brothers.


Robin writes:

With regard to TWIP & TWIM & TWIV: Keep 'em comin' !

Possible reservoirs in a vertical farmer:

Many hares
Ten little piggies.
Two soles.
Two calves.
A large variety of ducks:
Thoracic, R lymphatic
(R & L & common) hepatic, (cystic & common) bile, pancreatic etc.

Visceral pain:

All viscera except the central nervous system have pain receptors. They are activated by stimuli appropriate to the organ, which are not necessarily the same as the stimuli for somatic receptors. The intestine can be cut with a knife without pain, but just about everyone has experienced the pain from stretching of the gut. The pain receptors in most solid organs is located in their (fibrous) capsules, and are stimulated by ACUTE stretching or ACUTE inflammation.

Insects, bugs & arachnids:

It was quite clear to me in school that all bugs were insects, but that not all insects were bugs. I would not have graduated if I were not clear on that point. I had to unlearn English after coming to the uS of A (lower case "u", as that is the way it was originally intended, in the Declaration of Independence).
Likewise, I would not have graduated if I had lumped ticks and mites with insects. But of course in the uS, one must not expect to hear about Medical Arachnidology.

Mosquito swarms:

In my childhood, I remember swarms of male mosquitoes swirling above the heads of people in the evenings. One knew that they were male because they had mustaches (feathery antennae). Therefore one was not concerned about being bitten by them.

TWiP 48 Letters

Ruth writes:

Dear Dick Despommier

My name is Ruth
I am a listener of twip and recently I decided to look into your vertical farming that you mention on the podcast.

While I was watching a video of you explaining vertical farming you mentioned soil-less growth in an urban environment and I immediately thought of another video that saw earlier this week.

The video is about a man named Eric Maundu - who combined aquaponics with fish farming in an amazing way. Using a very small amount of space he set up a system with a fish tank . The fish water with the fish waste is carried on a basin of rocks (in which sit plants). Bacteria break down the fish waste and the plants use the nutrients. Afterwards the water -minus the waste is returned to the fish tank. Maundu also mentions that the fish could be edible types - so you could grow two resources at once.

I just thought it was so amazingly efficient and thought you may be interested also.

Here's the link to the video .

Also I would like to thank you and Vincent very much for This Week in Parasitism and this week in virology - both wonderful entertainment and education :)


Maureen writes:

I'd like to learn more about sarcocystis, a parasite that usually only affects animals but seems to have infected some of our military.


Carl writes:

To: This Week in Parasitology podcast (Vincent Racaniello, Dickson Despommier)

Here's evidence-based advice for cat owners unwilling to get rid of their pets:

"...cat litter should be changed daily, and pregnant women should delegate this task to others.

"Many scoopable cat litter manufacturers suggest scooping fecal lumps daily and changing litter weekly, but this is likely to give a false sense of security because the oocycts might sporulate in the leftover feces; in addition, the scooping spoon is likely to become contaminated with oocysts; hundreds of oocycts may be present in a milligram of infected feces. There is also the risk of cats tracking infected feces throughout the house.

"We do not currently have a practical recommendation for safe disposal of cat litter other than disposing it in a heavy duty plastic bag with the hope that anoxia will kill T. gondii oocysts."

Dubey et al: Survival of T. Gondii in Cat Litter.
Journal of Parasitology, Oct 2011 at 753.

"Gloves should be worn while gardening, while changing litter and while handling soil potentially contaminated with cat feces.

"Owners may also be advised to keep dogs away from the cat litter box to prevent ingestion of and passage through of oocysts.

"Vegetables should be washed thoroughly before eating, because they may have been contaminated with cat feces."

Dubey: Toxoplasmosis of Animals and Humans,
2d ed. 2009 at 54.

Practical suggestions:

Here's what I'm doing with 3 cats my wife insists on keeping:

Using a small open litter box, arrange a big plastic bag covering the bottom and extending up over the sides. Add the litter. At least once every 24 hours, wearing disposable examination gloves, lift the bag containing all the litter, knot the top and take it outside to the trash container. (No scooping.) Replace bag and litter.

We switched to pine pellets for litter, which is much cheaper--especially from farm or horse supply stores.

Public health risk:

Although most vets believe that cats shed oocsyts once for a few days, the leading researcher says, "Whether naturally infected cats shed oocysts more than once in their life is unknown."

Dubey: Toxoplasmosis of Animals and Humans, 2d ed. 2009 at 36 - 39.

While everyone was skeptical of the initial reports of brain cysts leading to mental illness and car crashes, the more recent research has made such claims more plausible. Given the limits of research tools and funding (and how small oocysts are and how hard it is to evaluate brain cysts...), it seems prudent to minimize our individual risk of toxo from cats and encourage more effective public health efforts (like changing the labels on cat litter.)


I assume you've been trying to get JP Dubey on your podcast. Please
keep trying....

TWiP 47 Letters

Liesbeth writes:

Tomorrow starts the XVIII International Congress for Tropical Medicine and Malaria Conference here in Rio de Janeiro. I read Peter Hotez will be participating in a round-table session on “What is the future role of academic journals in the research, control and prevention of tropical diseases?”.I myself will be presenting partial results of my graduate project on the zoonotic potential of Giardia duodenalis in the past. Dr. Racaniello recently participated in the Brazilian Virology Society meeting congress in São Paulo, but what about Dr. Despommier? It would have been awesome meeting you both here! But well, too many congresses, too little time, right? (and money, for that matter!)

All the best


Sophie writes:

Hello Twipsters

I have a pick of the week: Windowfarms, it's a non-profit vertical gardening project: How to make your own vertical window garden. If you want a full description listen to Britta Rileys TED-talk, I can't do it justice. I don't know if this is a fitting pick, as it's more a Dickson pick, than a parasitology pick. But I think it is amazing, I'm definitely doing this:)

Keep up the good work

Peter writes:

Dear Vincent and Dickson.

I would like to point out that the "Female Owners of Cats More Prone to Suicide" article mentioned in TWiP 43 is rather misleading. The study mentioned made no mention of cat ownership and men were not included in the study as it was only mothers who were included in the cohort.

Most human infections are from contaminated meat, not from handling infected cats.

If a cat is infected with Toxoplasma gondii the oocysts are only shed for a short period of time, typically less than 14 days, before the cat's immune system stops oocyst production. The cat should then be immune to further infection.

Dr Postolache has noted limitations to the study, such as the inability to determine the cause of the suicidal behaviour.

He said:

"T. gondii infection is likely not a random event and it is conceivable that the results could be alternatively explained by people with psychiatric  disturbances having a higher risk of  becoming T. gondii infected prior to contact with the health system.”


Could the high rate of infection reported in France be due to the popularity there of rare meat?

Further information on Cats and toxoplasmosis:



Peter writes:

Dear Vincent and Dickson.

Thank you for a fascinating and informative TWiP, I thoroughly enjoyed the linking of parasitism and ecology.   Following your request for listeners to find more information on the life cycle of  nematomorphs I did some reading and found that many nematomorph species use a "paratenic" or transport host in which the larva forms cysts and do not develop further until the paratenic host is eaten by a scavenger or predator.(1)

Crickets are generally omnivorous but some species are carnivorous. A wide range of species can be used as paratenic hosts including flatworms, snails ans some nematomorph species make the transition from water to land by forming cysts in aquatic insect larvae, with the cysts surviving the host's metamorphosis to an flying adult which can then convey them to land. Adult nematomorphs are short lived and do not feed, they die after mating. One species of nematomorph has been  discovered from Kenya that is parthenogenic and lacks males(2) Some sites I looked at mentioned the morphological similarity of the larval nematomorphs to some adult marine worms(3)


(1)  http://digitalcommons.unl.edu/dissertations/AAI3064559/

(2)  http://www.plosone.org/article/info%3Adoi%2F10.1371%2Fjournal.pone.0034472

(3)  http://www.bumblebee.org/invertebrates/NEMATOMORPHA.htm

continuing: I came across a bit more information on  how  nematomorph worms  influence insect behaviour.

David Biron,  Frédéric Thomas and  colleagues at the  Laboratory of Genetics and Evolution of Infectious Diseases at Frances National Scientific Research Center in Montpellier., France, have found the worms produce proteins that mimic some found in the insects nervous system. Somehow these prompt the insect to jump into water, allowing the adult worm to swim away. http://news.nationalgeographic.com/news/2005/09/0901_050901_wormparasite.html http://www.youtube.com/watch?v=76BnVsaLiR0

Tommy writes:

Dear Vincent and Dickson,

I really enjoyed your episode on the horsehair worm and food web ecology. In case if you haven't already found it, here is a review on the biology of nematomorphs which you might find useful:

Hanelt, B., Thomas, F., and Schmidt-Rhaesa, A. (2005) Biology of the Phylum Nematomorpha. Advances in Parasitology, 59: 243–305

Also, I was pleasantly surprised to hear you talk about the New Zealand cockle-trematode system. Those papers you mentioned originated from the lab where I did my PhD - in fact, my PhD thesis (and a small part of my postdoc work) consisted of research which followed up on some of the questions which were raised by those initial studies you cited, delving deeper into the ecology of that host-parasite system. Here are a small selection of publications which pertain specifically to the cockle-trematode system.

Leung, T.L.F. and Poulin, R. (2007) Interactions between parasites of the cockle Austrovenus stutchburyi: Hitch-hikers, resident-cleaners, and habitat-facilitators. Parasitology, 134: 247-255.

Leung, T.L.F. and Poulin, R. (2007) Recruitment rate of gymnophallid metacercariae in the New Zealand cockle Austrovenus stutchburyi: an experimental test of the hitch-hiking hypothesis. Parasitology Research, 101: 281-287.

Leung, T.L.F., Poulin, R. and Keeney, D.B. (2009) Accumulation of diverse parasite genotypes within the bivalve second intermediate host in the digenean Gymnophallus sp. International Journal for Parasitology, 39: 327-331.

Leung, T.L.F., Keeney, D.B. and Poulin, R. (2010) Genetics, intensity-dependence, and host manipulation in the trematode Curtuteria australis: following the strategies of others? Oikos, 119:393-400. Leung, T.L.F. and Poulin, R. (2010) Infection success of different trematode genotypes in two alternative intermediate hosts: evidence for intraspecific specialisation? Parasitology, 137:321-328.

Leung, T.L.F. and Poulin, R. (2011) Intra-host competition between co-infecting digeneans within a bivalve second intermediate host: dominance by priority-effect or taking advantage of others? International Journal for Parasitology, 41: 449-454.

Vincent was wondering how the cockles become infected with the trematodes - I can answer that as I conducted (and came up with the protocols for) experimental infections of those cockles, and spent many, many hours observing and documenting the process. The free-living cercariae are initially sucked in through the cockle's inhalant siphon, once inside the cockle's mantle cavity, they immediate cling to the foot and begin penetrating into the muscle. Once within the foot, they then migrate through the muscular tissue for some time (a few hours at most) before encysting at a suitable spot (usually the tip of the foot). During one of my observation periods, I recorded some footage of the cercariae penetrating the foot tissue - the link to which I recall I've sent to you in another e-mails, but to save you the trouble of wading through masses of old e-mails, here it is again: http://www.youtube.com/watch?v=k4-m3IsAlAQ


P.S. I really appreciate all the effort and time which must go into making all the "This Week In" podcast series and the role they play in educating the public about the unseen and overlooked majority of life on this planet. I am the writer and co-administrator of the Parasite of the Day blog (http://dailyparasite.blogspot.com), where I write about newly published research on parasites that I happen to come across, in a manner that is accessible to the general public. I consider that my small contribution, as a scientist, for public education and promotion about parasites, parasitism, and parasitology.

Robin writes:

A Conversation with Robert Sapolsky


A few years ago, I sat down with a couple of the Toxo docs over in our hospital who do the Toxo testing in the Ob/Gyn clinics. And they hadn't heard about this behavioral story, and I'm going on about how cool and unexpected it is. And suddenly, one of them jumps up, flooded with 40-year-old memories, and says, "I just remembered back when I was a resident, I was doing a surgical transplant rotation. And there was an older surgeon, who said, if you ever get organs from a motorcycle accident death, check the organs for Toxo. I don't know why, but you find a lot of Toxo." And you could see this guy was having a rush of nostalgic memories from back when he was 25 and all because he was being told this weird factoid ... ooh, people who die in motorcycle accidents seem to have high rates of Toxo. Utterly bizarre.

What is the bottom line on this? Well, it depends; if you want to overcome some of your inhibitions, Toxo might be a very good thing to have in your system. Not surprisingly, ever since we started studying Toxo in my lab, every lab meeting we sit around speculating about which people in the lab are Toxo-infected, and that might have something to do with one's level of recklessness. Who knows? It's very interesting stuff, though.

You want to know something utterly terrifying? Here's something terrifying and not surprising. Folks who know about Toxo and its affect on behavior are in the U.S. military. They're interested in Toxo. They're officially intrigued. And I would think they would be intrigued, studying a parasite that makes mammals perhaps do things that everything in their fiber normally tells them not to because it's dangerous and ridiculous and stupid and don't do it. But suddenly with this parasite on board, the mammal is a little bit more likely you go and do it. Who knows? But they are aware of Toxo.

Don writes:

Dr. Racaniello,

On TWIP 42 you decried the lack of a Microbe World search engine.  Well here's a little used Google feature that can help.  To find the TWIP episode about toxoplasma simply type this as a Google search:

site:microbeworld.org toxoplasma "this week in parasitism"

As long as the site allows the Google crawlers the result is usually better than site search features.  Unless of course the site search feature is an embedded Google search.

Looks like the TWIP you were looking for was #12.

Love TWIP, TWIV and TWIM.  I have heard them all.  Some multiple times.  But my favorite has to be TWIP largely because of the happy accident of a world class parasitologist and a world class raconteur being embodied in your co-host.   Dickson Despommier is without peer.

Dickson's modest erudition and your nagging straight man routine make for a very entertaining show.  Please don't think I am belittling the part you play.

That you could do what you do so graciously, given all your accomplishments, is rare.  Lesser men would let their egos get in the way.

That I can also learn something is also much appreciated.  Don't change a thing.

Thank you, Don

Kyle writes:

Dear Dr. Despommier,

I am a student doing post-bac work in premed, and was intrigued by your discussion of a possible study of the contamination of dog run soils by Toxocara Canis.  I'm designing a study in the Chicago Land area to gather this data, and was wondering if you could recommend a method of testing for eggs in the soil, i.e. if there is any preferential methods in your opinion.  Also, I heard on your podcast that there is some graduate work being done in New York, and was also wondering if they would want to compare data after both our studies are done.  Thank you for the great work both you and Dr. Racaniello put out every week, your podcast is an absolute joy to listen to.

Sincerely, Kyle

Ronald writes:

I love your TWIP and TWIM and am sharing a balance of them with students as time permits. My absolutely only complaint is that ... as an old geezer ... my hearing is not what it once was and for me ... there are often times when a speakers' voice seems to almost disappear ... sort of a mumble for me ...  I believe this is because you speak ... and this is natural ... as if you are speaking to someone sitting close to you. I believe it would help if you each spoke as if you were speaking to an audience ... maybe with a microphone and never allowing your mouth to point away from the audience ... aiming the sound down instead of forward ... without losing the cordial atmosphere. Trivia, I know and I doubt anyone else has described similar issues. Keep up the great work. It is great to have a chance to learn from your discussions. I know you spend a lot of time preparing these and I am truly grateful. Enunciate is the word that has been escaping me but I believe that is the core of my problem.


Nick writes:


Firstly I'd like to say I am a huge fan of your shows- TWIP, TWIV and TWIM. I am a student in Perth, Australia and am in the final year of my zoology major, and first year of my microbiology major. I am extremely interested in getting some experience in a lab to do with viruses, parasites and microbiology, so I was wondering if there was any help or advise at all you could give me?

Thanks, Nick

Amanda writes:

Good morning Drs. Racaniello and Despommier;

My name is Amanda and I just love your TWIP podcast.  This article caught my eye and I thought it would be of interest to both of you considering that it seems to be about a virus parasitizing another virus!


Also, a recent study on DNA methylation in Trich: http://www.the-scientist.com/?articles.view/articleNo/32932/title/Genomic-Methylation-Collector/

Keep up the good work!   Can't wait to hear another podcast…you guys keep my brain active when doing routine lab tasks!


Research Technician at Massachusettes General Hospital

Jim writes:

FYI for Dick just to show where the subject is appearing, with comments.

Jim Smithfield, VA

Singapore Builds First Vertical Vegetable Farm

via Slashdot by samzenpus on 11/5/12

kkleiner writes "Short on arable land? One solution would be to plan up. Singapore, a small country that imports most of its food, has now begun selling vegetables from its first vertical farm. And even while they're more expensive the vegetables are already selling faster than they can be grown. If the farms prove sustainable – both technologically and economically – they could provide a much desired supplement to Singapore's locally grown food and serve as a model for farming in other land-challenged areas."

Michael writes:

Dear Professors Vincent Racaniello and Dick Despommier,

I am a long retired biochemist who spent his career in Public Health. The two things that I miss the most are access to journals, and the round table discussions that I held in my office every morning. I accomplished this by providing free coffee, and often Danish. Soon my office was bursting with those wishing to talk about what they were doing, where they were having problems, and what they were going to do about them. These were not meetings in the normal sense, but rather verbal free-for-alls where many problems were resolved, many friends made, and aptitudes which were dormant came alive.

While I often worked with the biochemistry of microbes, I never had occasion to do any work with parasites other than see an interesting slide or specimen that someone wanted to display to everyone in sight. When I started listening to TWIP,  I first I thought it was the filling of an enormous cavern of personal ignorance that drew me towards your show. But then I realized it was the Socratic method that formed the backbone of your lectures. With Professor Racaniello so often playing the foil, and the general banter it was almost like being back at my favorite time of the day at work. As I now live in a rural area and can no longer have such conversations with my old colleagues, this has truly gladdened my heart and filled in a missing part of my life that goes far beyond the knowledge provided. While I realize that this is not your primary intent, it is a delightfuly serendipitous collateral benefit. I would like to urge you to ignore those curmudgeons and martinets who demand a formal, structured and pedantic presentation. You are at your best when you allow your personalities to show through.

This is particularly significant to me as I had been in an undergraduate honors program that had about 40 profs and a dozen students. We were completely self directed, and met either one on one, or in small groups with the profs. We got to know them as people, and as a result leared more and did more than we ever would have under more normal circumstances. It was unfortunate that this outstanding experiment was far too expensive to be broadened to the rest of the students.

Before I wear out your patience, I would like to note that I listen to many such podcasts, but that yours is the only one that does not request financial assistance (which I usually provide.) You program is most worthy of some mechanism of recognition. So I thought perhaps a donation in your names and TWIP to be a possible method of recognition of your outstanding work. Would you please advise me as to your favorite charity or research facility in parasitology that you would prefer the donation to be made.

Truly gratefully yours, Michael

Robert writes: Sirs, In September 1903 the British satirical magazine Punch published an insomniac's ode to the students of tropical disease:

Men of science, you that dare

Beard the microbe in his lair

Tracking through the jungly thickness

Afric's germ of Sleeping Sickness

Hear , oh hear my parting plea

Send a microbe home to me.

Sometimes it is better not to get what you ask.

Todd writes:

Thank you so much for the parasitology podcast. I am encouraging my children and nephews who will probably pursue health related careers to listen to it, first because it is such an interesting “fly through” of the related science, and secondly because I find you two so interesting. However, my family eats a whole lot of sushi, and I haven’t been able to find the sushi episode on iTunes. Did that end up getting made?

Regards, Todd

P.S. I had been imagining myself to be a sort of forager, and would eat the semi-fermented pears that fell from my tree after cutting away the portions containing ants and worms and washing them a bit,  but after watching some YouTube videos about roundworm infections, I got a little bit afraid, since I don’t know but that the pears had fallen onto soil or leaves that had traces of dog, opossum, squirrel, rabbit, raccoon, or bird feces. However, a professor friend of mine told me that our immune system kills roundworms for us, and it’s only children who are at risk.

PPS. Since I also occasionally dip into alternative health websites, I wonder if you have ever podcasted related to the “clean hypothesis” of allergies and the alleged cures of asthma and other allergies  from exposure to roundworms (in controlled situations) and hookworms in uncontrolled situations. I think a lot of people are interested in auto-immune disorders lately, and those of us who live somewhat dirty and untidy lives wonder if somehow environmental stimuli are keeping us robustly healthy.

TWiP 44 Letters

Todd writes:

Hello Dixon and Vincent!

Your research and real life experience is slowly getting summarized by researchers so that it can be understood by reporters (aka those who
have a disproportionately loud voice in society):


The article is attempting to tie lack of MPV (microbes, parasites, viruses) to inflammatory diseases, which might be a stretch. I don't know if there is a dearth or an abundance of research for either side of this proposed relationship. But it's promising on the surface and hopefully the political forces at work destroying science in our country won't do the same for this research.

An excerpt from the concluding paragraphs:

"Since time immemorial, a very specific community of organisms - microbes, parasites, some viruses - has aggregated to form the human superorganism. Mounds of evidence suggest that our immune system anticipates these inputs and that, when they go missing, the organism comes unhinged."

Have a fantastic week fellas!

Josh writes:

Hello Parasite hosts!

I have written twip before to express my appreciation for the show. I still appreciate it very much and it still helps me get through my days auditing.

I ran across this article on reddit.com/r/science, http://lifestyle.iafrica.com/wellness/813618.html , which makes this discovery sound like a guaranteed cure for all forms of Malaria with just one oral dose. Thinking that was a rather large claim I did some digging and found the original story, http://www.science.uct.ac.za/news/?id=8220&t=dn , this article is a little more reserved, though not much, with its language. I am interested in what both of you think of this? Is this the wonder drug they make it seem like?


Phoenix AZ

Ricardo writes:

South African researcher find single dose cure for malaria: http://www.treehugger.com/health/south-african-researchers-find-single-dose-cure-for-malaria.html

Dirk writes:

Dear parasitology lovers,

Just came across your blog through recommendation of a colleague and heard your conversation on the worm in the eye.

The name seems to be the local meaning of "worm" as quoted on page 643 in the book "A HISTORY OF HUMANHELMINTHOLOGY by DAVID I. GROVE (link: http://www.scribd.com/doc/57580301/Book) from the publication #49: GUYOT. Ophthalmie produite par des vers dans les yeux à la côte d'Angole. Abstracted in J N Arrachart's Mémoires, Dissertations et Observations de Chirurgie, Paris, pp228-233, 1805. (Originally presented to the Academy of Surgery in Paris in 1778).

And if I understand correctly you claimed that Cobbold was a German. Although being a German myself Cobbold was British, a son of a Suffolk clergyman (Principles and Practice of Clinical Parasitology, Gillespie /Pearson, 2001, page 3.

Best regards,


Lisa writes:

Dear Vincent and Dickson,

I am a veterinarian with a PhD in virology, and I am in my second year of anatomic pathology residency at the New England Primate Research Center. I just recently discovered the TWiM, TWiV and TWiP series of podcasts and they are great! I am training for my first marathon and my long runs were becoming quite tedious with the same old songs on my iPod every day. Now, I download another episode of TWIP every time I head out for a long run and I always have something interesting to listen to. I enjoy TWiM and TWiV, but TWiP is especially great while I am studying for my pathology boards. Although TWiP is based mainly around human diseases, most of these parasites are, of course, also quite relevant to veterinary medicine. Your amusing anecdotes and interesting stories help to cement the life cycles of these fascinating creatures in my head and your entertaining banter makes me feel like I am running with company every time. Thanks for helping the miles fly by and keep up
the good work!


Rufus writes:

Topic suggestion -- I noted recently a news article regarding a treatment method for malaria that addressed the parasite's ability to cause an infected red blood cell to lodge in a capillary and thus avoid being filtered by the spleen. I don't recall you discussing this aspect of the infection. I don't know how effective the treatment is, but the fact that the parasite does this is way cool.

See for example: http://www.ncbi.nlm.nih.gov/pubmed/6348780

Best regards,


Software engineer (for a SEM manufacturer)

TWiP 43 Letters

Robin writes:


Trematodes are commonly referred to as flukes. This term can be traced back to the Saxon name for flounder, and refers to the flattened, rhomboidal shape of the worms.

Robin writes:

re men stealing meat from lions

Check out this video on YouTube:


Liesbeth writes:

Dear Vincent and Dickson,

Let me start thanking you for encouraging me to carry a healthier life. Since taking the bus to the lab each day meant a 20 mins ride, and your podcasts are usually longer, I decided to start waking up earlier and walk every day instead, that way I can hear the whole episode! I feel somehow infected by a parasite podcast that modifies my behaviour in order to be listened, reaching its objective when I arrive at the lab commenting on the last episode heard.

After your discussion on the origins of the term Loa loa, I did some internet research and came up with an article published in 1991 by John D. Ruby and John E. Hall. Since it's really short, I copied it here for you to read:

"It has recently been called to our attention that the word 'loa', used for centuries, first by Africans and later by parasitologists, to refer to the 'eye worm', also appears in the terminology of voodoo or Vodun where it refers to a large pantheon of deities that may possess one's soul or being. The word 'loa' may be derived from the Yoruba word 'l'awo' meaning 'mystery', but according to Bourguignon its origin remains uncertain. To the devotees of vodun, the noon hour, when the sun casts no shadow, is a perilous time. A man without a shadow is a man without a soul and therefore vulnerable to possession by such spirits as 'loa'. To ward of these spirits, believers wear amulets and cast spells. African vodun evolved in Benin, formerly Dahomey, and was brought to Haiti with slavery during the seventeenth and eighteenth centuries. Since both adults and microfilariae of the 'eye worm' Loa are diurnal, with maximum activity occurring at noon (when the West African would be most susceptible to spirit possession), and since West African vodun and the 'eye worm' share a common geographic origin, we have reached the tentative conclusion that one is probably the etymological source for the other. Whether the helminthological Loa predated the anthropological one remains a matter of conjecture"

Knowing something about the origin of the name and the way the parasite was discovered really helps to remember things better!

Looking forward to your next infectious TWIP,

Todd writes:

Found the following reference for the origin of ‘Loa'. Still don't know what it means...


Love the show!

Laboratory Technician III
Georgia Perimeter College

Peter writes:

Just to get you started <grin>


Alice writes:

Drs. Racaniello and Despommier:

Did you see this about Toxoplasma gondii?



Spencer writes:

Dear Vincent and Dickson,

Here is a news piece very relevant for TWIP: The first congenital case of Chagas disease in the US. With a great video from Dr. Jim McKerrow.

Here's the link:


Thanks and keep up the great episodes!

Spencer MD PhD

TWiP 42 Letters

Jesse writes:

Dear Doctor's Racaniello and Despommier,

Huzzah! I have tracked down Dick's missing book on tropical medicine, or at least another copy of said book. While listening to TWIP #40, my ears perked up when Dick said he had lent a book to a student only to have it never return. A quick Google search found the following book: "Tropical Medicine and Parasitology: Classic Investigations" by Mott and Kean of Columbia University circa 1974, which I believe is the book in question. I managed to find a copy online for a steal (less than $10, including shipping!) and immediately ordered it. In 4-14 business days, I should receive a copy, which I will gladly send along to Dr. Despommier as a token of my gratitude for everything that he has done for me (more than you would think).

As a pharmacist working the night shift at a popular chain store, I quickly grew tired of listening to internet radio at night and needed some further stimulation. Your podcast was one of the first that I found and I quickly listened to every episode (multiple times even). This podcast, along with a few other life changing experiences, has inspired me to completely change the direction of my life. I now have solid plans in place to go back to medical school (once my debts are knocked down a bit) with hopes of becoming an infectious disease specialist. My dream is to join Paul Farmer's organization (Partner's in Health) and practice "tropical medicine" while helping those most in need.

Thank you both for all that you do and for taking the time to read my email. If you reply with a mailing address for yourselves at Columbia University, I will gladly send along the missing book once it arrives. As always, looking forward to your next TWIP!



P.S. Are you missing any books Dr. Racaniello? Your work on Polio is greatly appreciated, as my grandfather suffer's from a mild case of Polio myelitis -- so it is obviously a topic that is near and dear to me.

Keely writes:

Hello Dr. Racaniello.

To introduce myself, my name is Keely, and I'm currently a second-year graduate student at UCLA. I work on parasitic worms under Elissa Hallem, and I TA for the undergraduate parasitology class taught by Patricia Johnson.

First off, thanks for all the podcasts. I really enjoy them, and they keep me reading new and interesting papers that are a bit outside of what is usually on my radar. Also, though I was a microbiology major with a strong interest in parasites, my undergraduate institution lacked a full parasitology course, so I learned most of my parasitology from my own reading. I really appreciated the review that TWiP gave me before I started working on parasites for my graduate program.

Anyhow, I was listening to an older episode that I missed somehow, and you mentioned at some point having listeners on the show as a guest. If you ever decided to try and do this, I would love to toss my name in the hat.

Thanks again!

Michael writes:

I am 63 years old. I became ill while serving in Vietnam at the age of 20. For 43 years I have been going to one physician after another physician. Army, VA and private physicians have never been able to identify or diagnose my illness correctly, because every treatment or medicine they gave me, oral and topical, never worked.

For years I argued that I felt that it was parasitic, but the VA eventually convinced me that I had Agent Orange related illnesses and that my idea of parasites was not only futile, but hypochondriasis (a diagnosis, which they actually gave me).

Well, I am still hopelessly suffering. Boils are breaking out all over my body, particularly on my scalp and arms, and I truly feel that I am in late stage severe and chronic Parasitosis, but the VA has me diagnosed with Delusional Parasitosis. Last year in November, I had three very large lesions/boils that grew so large that they burst and left large continuously draining holes (blood and infection) in my arms and scalp. I became interested in the fluid samples and began collecting them in small plastic jars with tight lids. I took these samples to the VA and asked them if they would have them tested/cultured or examined under a microscope to see if anything could be determined or diagnosed. They refused and said that their blood tests for parasites was all that they needed and it had come back negative and there was nothing else that they could or would do. So to date, after years of complaining and arguing, all that they give me in medicines is anything medicines for para

After that I decided to buy a USB 200x Microscope that could take photos of what I focused on underneath the lens, which I found on Amazon marked down from $250 to $80, and examine these fluid collections on my own.

Doctors Racaniello and Despommier, both of you may be surprised. Thus far (for five months now), I have 200x photographed over 3000 pictures of the fluids draining out of these non-healing, large, deep, open wounds. In January I took nearly 1000 (what I had at the time) of these photos to the VA and they wouldn't even look at them, notwithstanding that they also did not give me the necessary wound either. If what I am looking at in the photos is correct I am acutely infected with millions of nematode microfilariasis worms and flukes.

Lastly, is it possible for me to send you a few of these photos (I can send them all on a snailmail CD or post them to Photo Bucket) for you to look at and advise me on whether or not they are in fact one or more of the over 10,000 nematodes that find humans as a desirable host? Thank you.


Raphael writes:

Good day, doctors!

I did not hesitate to write this right after hearing an email you responded on TWiP 39.

I would like to thank cytotechnologist Rebecca for the comment and Dr. Dickson for additional info on how tricho is vertically transmitted from mothers to female newborns and how it could be lifelong. Not so many years ago, I had a rare opportunity to have a urinalysis result that came out which was trichomoniasis positive. The female patient who was in her early twenties denied that she had no history of sexual contact but knowing very well that tricho is a sexually-transmitted infection, I immediately did not believe her. Nevertheless, I treated her with an antiprotozoal drug.

Now that I know how tricho is transmitted, I owe that patient my apology.

Tracy writes:

Dear Dick and Vincent (if I may be so bold)

I listened to the podcast on Leishmania this week as I prepped for my Leishmania lecture in Medical Microbiology. I was struck by Dick's comment that we didn't know what the amastigotes ate while in the the phagolysosome. I ran across an annual review in Microbiology article that seems to address the metabolic needs and potential nutrients sources for the amastigotes while in the phagolysosome.

Here is the link to the paper: (Metabolic Pathways Required for the Intracellular Survival of Leishmania)


I enjoy your podcasts and my students find them an easy way to approach very complex material.

Keep up the good work!

Laura writes:


Firstly i would like ot say that I followed your podcasts whilst i undertook my undergraduate degree and found them useful for revision. I am now starting a PhD at Nottingham University in England this year and would like to thank you for providing such great podcasts.

I would like to ask, as mosquitoes carry a number of parasites/viruses that can infect humans, is it possible for one mosquito to infect a person with more than one species of parasite/virus, for example could a person get malaria and leishmania at the same time from the one mosquito?

Jon writes:

Ok, this sounds rather unpleasant - but may explain a lot about the world :)

The Brain: Hidden Epidemic: 
Tapeworms Living Inside People's Brains


Suzanne writes:

Maybe Dickson knows or maybe someone else has mentioned it, but if you wash immediately with soap and cold water poison ivy oil washes off more easily. Wash all your clothes in cold water, too. Most people want to wash with warm water (I've done it and boy did the rash spread) but cool or cold water works best. I hope his has cleared up by the time you get this!


Jim writes:

Dickson mentioned this 2 vol set on the last TWIP. This link from the World Catalog may have specifics as well as where Vol 1 can be bought, and cheaply too, it appears. Volume 2 is in the World Cat database, but not linked to any library or store -- odd. The key thing is that the title may be "Tropical Medicine and Parasitology." I found a few Vol 1's, but no Vol 2. Might a Vol 2 be sold as a Vol 1? Here is a link that at least shows a Vol 1 & 2 set has at one point been listed on Amazon, so a periodic search may eventually be productive. I like looking at old books and will keep an eye out in this area. Maybe a mention on a TWIP would alert listeners to also watch for the set. Not an expensive item.

Ref deer flies: I have used these tred-not patches on my hat for several years and they are quite good. Just ordered another big batch. Sound like something Dickson can use, if he is not doing so already. Only negative aspect is that they are only good for one day. The last of my current batch were purchased last year and worked just fine.

Beautiful shows, all!


Smithfield, VA

Stephen writes:

This is actually for TWIP, FYI

(BTY: It's not easy to send to TWIP from the Nature app, because it assumes an email address.)

Bovine TB disguised by liver fluke

Nature News,Published online: 22 May 2012; | doi:10.1038/nature.2012.10685


Meika writes:

I have been one of your silent fans for about a year now. And I absolutely LOVE all three of your podcasts. I am a scientist at heart and by training, but a horse trainer for my living. I recall a past podcast about a dressage barn that had an outbreak of toxoplasmosis, and I am trying to search for it, but Toxo is a very popular subject for you guys and the list is long. While I am willing to listen to all episodes again to try to find it, can you give me a hint as to which episode it was and shorten my search?

Your show has been an inspiration to me as well as a fun link to my past life as a scientist. Listening to TWIM has prompted me to go on a several days long spree of reading reprints of my grandmother's research. The earliest I can find is 1933 and she is the lead author in The Journal of Bacteriology on carotenoids and Vitamin A in bacteria. She also was interested in nutrition and color inheritance in Serratia and published her research for four decades. I cant help but think that she was the rare woman bacteriologist who led by example for so many women back then. Thanks for keeping me interested and helping me know my grandmother better.

Meika (pronounced: mica, like the mineral.)

Mike writes:

Doctors, I have recently discovered podcasts and the very first thing i searched for was one on parasites. I have been fascinated with parasites since grade school and will be starting my 3rd year of veterinary school in the fall so i was very excited to see a podcast devoted entirely to parasites. granted a bulk of my parasite knowledge is animal based i still very much enjoy TWIP. I started your first episode and have just finished the episode on hookworms. a few things i wanted to bring up, from the perspective of a budding veterinary parasitologist. First: A. caninum is capable of infecting young pups through the bitches milk and i was wondering if any human hookworms have been documented to do the same, at least for animals, hookworms can also be contracted from eating the 3rd larval stage (generally pica) or from eating a variety of other animals that have eaten the 3rd larval stage and act as a transport host, for example, the larva eaten by a mouse, enter a hibernation state until a cat or a dog comes along and eats the mouse. as the tissues are digested away the larva wakes up, receives environmental cues and will proceed to develop to an adult, this is a particularly common way for cats to contract A. tubaeforme given their predatory nature. Has anything similar ever been documented with a human species of hookworm?

Second: as to the question of prevalence of hookworms in dogs in America, yes they are definitely endemic. they are a problem across the nation especially shelters, as are whipworms, ascarids, coccidia.

Third:in one of the episodes on tapeworms Dick was comparing the pork tapeworm to the beef tapeworm and mentioned that horses and cattle are different from pigs and asked Vince why. Dicks answer was that cattle and horses are both ruminants while a pig is an omnivore, i don't know if this was an accident but horses are not ruminants, they do not have the complex foregut fermentation system of cattle, sheep, goats, deer and other similar animals, horse are hindgut fermenters and do a bulk of their digestion in their colon and cecum (appendix) but both are herbivores.

and last, to Vince, you had peppered Dick with questions on what animal species had what nematode parasites, to broaden your list, ascarids are found in horses, pigs, cats, dogs, cattle, raccoons, wild canids and felids and mostly any other mammal. hookworms are just as ubiquitous in the animal kingdom. that's all for now but i am sure i'll write again, keep up the great work gents. I understand that this is a long email and will not be offended if you don't read it on the air but i would greatly appreciate answers to my questions if possible

Mike writes:

Doctors, again i write to you because a few things had slipped my mind while writing my last email. Dick, when you were describing the live cycle of ascaris, you said there was an operculum on ascarid eggs. I have seen many ascarid eggs of several species and have never seen an operculum, did you miss speak or have i just not been looking carefully enough? or is it specific to A. lumbricoides? it has always been my understanding that the operculum is rather rare in nematode species save members of the orders Oxyurida and Enoplida. speaking of Enoplida, one of the many parasites we discussed in parasitology course that is part of our curiculum was Dioctophyma renale, the giant red kidney worm, a particularly cool video of a dog in canada that was unfortunate enough to contract a few of these has been posted on youtube: http://www.youtube.com/watch?v=5ob6S_EqR1c Has there ever been a case in people that you know of?

Lastly, I just listened to the Strongyloides podcast, do pigs, like people often pass the larva in their stool but in the veterinary world they are the exception, most of the time in other domestic species the eggs are what are passed does this ever happen with people? have you ever seen a Strogyloides egg? This particular parasite can be debilitating and even fatal to piglets but with the modern management techniques in the American swine industry the problem has ceased almost entirely.

thanks again for humoring me gents,

Daniel writes:

Hello again professors. Sorry to keep bugging you but I thought you might be interested in a website I happened upon the other day.
It's a crowd sourced pseudo-video game designed by UCLA students in which the players have to identify RBCs that are infected with malaria. Here's a bit of text from the site and the link.

The Idea

Analysis and related diagnosis of medical images, regardless of the source and imaging modality, are tasks that require a great deal of expertise, demanding significant training of medical practitioners prior to being able to accurately interpret and diagnose such images. This is particularly true in analysis of microscopic data, creating challenges in resource-limited settings and developing countries, where properly trained health-care professionals are difficult to find.

We have shown that by utilizing the innate visual recognition and learning capabilities of human crowds it is possible to conduct reliable microscopic analysis of biomedical samples and make diagnostics decisions based on crowd-sourcing of microscopic data through intelligently designed and entertaining games that are interfaced with artificial learning and processing back-ends. We demonstrated that in the case of binary diagnostics decisions (e.g., infected vs. uninfected), using crowd-sourced games it is possible to approach the accuracy of medical experts in making such diagnoses.
Specifically, using non-professional gamers we report diagnosis of malaria infected red-blood-cells with an accuracy that is within 1.25% of the diagnostic decisions made by a trained professional.


Wish you both the best and let me apologize again for bombarding your inbox.


Nick writes:

Hi Vince and Dick,

I'm writing hoping that you haven't already been flooded with emails regarding heartworm treatment and resistance, and if you have, maybe I can still be able to contribute something. I'm a dual degree student (DVM/PhD) at Cornell University and am studying the mosquito vector ecology of heartworm. As your listener mentioned, there have been some reports of persistent microfilaremia in dogs on preventive medication. Some of the issue has been shown to be due to lack of owner compliance to administering the drug, but, after controlling for that, there have still been dogs identified with persistent microfilaremia despite preventive treatment (and often after the adults have been killed or removed), which currently is the only standard method to clear the microfilariae.

This loss of efficacy is specifically of the microfilariae to clearance, not to melarsomine (Immiticide), which is the adulticide. Ivermectin formulations used as preventive/microfilaricidal, which you eventually got to during the podcast anyway! There have been some studies looking into the effect of doxycycline on clearing the Wolbachia in Dirofilaria immitis to reduce their ability to reproduce and possibly reduce microfilarial and larval fitness for transmission, which I thought you'd find interesting.

I'll be sure to chime in on veterinary topics or, more likely, vector biology topics that I know something about. Also, I was surprised to hear that Dick came to speak at Cornell but I had missed it! I'll have to be more attentive next time,

Keep up the good work!


Alberto writes:

Dear Parasite Hosts

I thought Dickson would be interested in this story from ABC's ( Australian Broadcasting Corporation) Science Show which features an interview with A/Prof Daryl Davies of USC, LA in which he discusses the potential use of ivermectin for the treatment of alcoholism.


I found this recent article in Neuropharmacology from the Davies lab which describes the experimental use of ivermectin in a mouse model of alcohol dependence.


I quote from the abstract:
".. in the present study we investigated the effects of this agent on several models of alcohol self-administration in male and female C57BL/6 mice. Overall, IVM (1.25-10 mg/kg, intraperitoneal) significantly reduced 24-h alcohol consumption and intermittent limited access (4-h) binge drinking, and operant alcohol self-administration (1-h)."

The mechanism of action appears to be via antagonism of a purinergic receptor in the brain. In the interview, A/Prof Davies explains that in parasitic organisms, the drug acts by stimulating an excitatory glutamate chloride channel.

Keep up the great work guys.


Ethan writes:

I found this in the mail today from my water department and had to forward it to you guys. Looks as though my city's water is clean of any cryptosporidium parasites, but inhabitants of other middle Tennessee areas perhaps are not so lucky!



Peter writes:

Watching 'Origin of Us' a BBC2 documentary on Human evolution. In Episode 2, 'Guts', the host Dr. Alice Roberts mentions an interesting hypothesis relating to tape-worms.

It appears that the lion tape worm and human tape worm are very closely related. A DNA study is used to determine the time of worm
speciation. It is assumed that around this time Humans began to steal or eat the same prey as lions. Eventually the worm evolves from Humans as the intermediate, host to becoming the definitive host. Aprox 800k to 1.7 million BCE.

She does not cite the work but, being a BBC doco, I have no reason to doubt the work is genuine and published somewhere.

Novel idea to use tape worms for plotting meat eating in Humans.

Stephen writes:

Might this help to learn how Cobbold named Loa loa.

I don't have access to the journal, and didn't find the full text on line. Pubget.com finds it at the nearest university library, but it's $31.

A bit steep just to satisfy curiosity.


Rohit writes:

Dear Dr Racaniello and Despommier,

I listened to the fascinating episode Worm in the Eye: TWIP 40 earlier this week. Coincidently, I saw this news story, about a doctor taking out a worm from the eye in Mumbai India today. http://www.bbc.co.uk/news/world-asia-india-18640495

I thought that it would be interesting to hear Dr Despommier's expert comments about this worm/case. I apologize if this worm has already been discussed and I have just not caught up with that particular episode yet. I am curious if the doctor's statement "The worm could have travelled deeper into the eye or gone to the brain through the optic nerves, which could have been fatal" is true. Being a virologist, I know that Polio and other viruses travel through nerves but can worms too travel through nerves?

Dr Despommier is a wonderful story-tellier. I find it amazing how much he can remember. Keep the awesome worm-stories coming along with some very intriguing questions from Dr Racaniello.



Postdoctoral Fellow, Chandran Lab
Department of Microbiology and Immunology
Albert Einstein College of Medicine

Ethan writes:

Dickson mentioned how crazy it is that ticks can live up to 50 years in a dormant state without taking a blood meal, and it immediately reminded me of this:


After subjected to conditions within a vacuum and being blasted by an electron beam, the tick keeps ticking.

Joann writes:

Hi Drs. Racaniello and Despommier,

Great podcast!

I'm a graduate student in epidemiology and am completing my practicum this summer working as a health inspector in a coastal town. One of the health agents I work with used to be a chef at one of the local restaurants. She described to me (warning this is gross!) how they used to use tweezers to pull out little (~1" worms) from cod and swordfish that would later be cooked in served. My questions for you: do you have any idea what these worms might be? And, is there any chance that ingesting them (or perhaps eggs/larvae, etc.) of these worms would make humans sick? Regardless, still pretty nasty.

Keep up the great podcasts! I have a long commute usually and have been twipping and re-twipping.


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