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TWiP 37 Letters

Cam writes:

Dick Despommier is often talking about the importance of ecology when understanding parasitism. Does he have any suggestions for good introductory texts to the subject for someone of my lowly level?

I recently came across this article, which led me to the idea of Oogst. Has Professor Despommier come across this, and how does he view it in relation to the idea of Vertical Farming?

Raihan writes:

Hello Guys,

Sorry but I wanna share a non-parasite related news story with you guys.
Came across this article about how the government in Singapore is deciding to invest in roof-top gardens here, as a measure of controlling the recent cases of flash flooding here.

When I read it, i was reminded of Dr Despommier's brain child, the Vertical Farm. I guess this is not exactly a farm but it has a lot in common and displays another way of how incorporating fauna in cities can help solve problems in an urban setting.

You guys may choose to read this email on your Vertical Farming Podcast instead of TWIP.

That should be coming pretty soon right? *cheeky grin.

Love the show

Matt writes:

Dear Dickson and Vincent,

(Not sure if I sent this to the right place on the microbe world website, but as I noticed that you gave this email address at the end of the podcasts I thought I'd try it as well...)

Thanks for your wonderful series of podcasts; I have been working my way through all of TWIP and you are currently keeping me sane whilst I data-enter several thousand clinical records from a malaria prevalence survey. I also have TWIV on CDs which I listen to in my car on my commute route to my workplace in Muheza, North East Tanzania. And I'm very excited by TWIM which I will indulge in soon.

I am a medical entomologist currently working on insecticide-treated materials against malaria vectors and have a question which I hope you'll discuss on TWIP in relation to malaria but also in a broader context. It is this: do you think we already have enough tools to control (many) infectious diseases and that funding should be channeled into improved application/delivery of those tools and away from the search for novel techniques and 'blue sky' research? For malaria, we already have a diverse arsenal of proven weapons and auxiliary tools including bed nets, indoor residual spraying, intermittent preventative treatment, house screening, rapid diagnostic tests; GPS and mobile phone systems have vastly improved surveillance, we have subsidized and highly effective frontline drugs for treatment, amazing repellents and lures for mosquitoes etc. etc. People like Fred Soper and Malcolm Watson were incredibly successful at reducing malaria 60+ years ago with a much more limited arsenal. You might say that there was much less resistance to insecticides and anti-malarial drugs in those days, but in recent times two brilliant weapons emerged that are still being used, to which there was no resistance, i.e. pyrethroid insecticides and artemisin-based combination therapy (ACTs). What do you think are the major stumbling blocks in infectious disease control? Is the health sector too slow to act on research findings*?

Many thanks and keep up the good work.

Matt, National Institute for Medical Research, Tanzania & London School of Hygiene and Tropical Medicine

p.s. I wrote this before I saw the topic of Twip 35! I hope this question is still relevant (and I'm going to listen to that episode now once I can download it!)

p.p.s. I thought you might like to know that my two dogs are named after you! (Vincent and Dickson - jpg)

Dr Matthew J Kirby
Fieldsite Project Manager PRISM
Amani Research Centre
National Institute for Medical Research

Heather writes:

Dear Doctors R&D,

I love your podcast! It is wonderful to listen to commuting to work and while I am working as the support technician for the chemistry and microbiology teaching labs at our small state college. My favorite thing about your show is that the format is similar to the "seminar" or "journal club" courses that were my favorite in graduate school (that was back when I too wanted to be a "dr.", before I became a lapsed microscope jockey. Maybe I will go back to grad school....maybe...some day). Basically these 1-2 credit courses consisted of grad students getting together with a professor to pick apart papers in specific disciplines such as microbiology (we went over the "old" "elegant" research that was the foundation of modern microbiology), microbial genetics (we called that one "cloning club), current topics in molecular biology, current topics in elasmobranch biology, and current topics in shellfish aquaculture. My background is in fish and shellfish pathology, specifically the microbial and parasitic (and molecular aspects thereof) diseases of cultured fish and shellfish. Bearing that in mind, while I realize that you focus your podcasts on human/public health issues related to parasitism, might you consider doing an episode about epizootic parasites (or microbes or viruses) that impact humans economically and/or ecologically? Some examples that come to mind are my good friends QPX (quahog parasite unknown) or Perkinsus marinus in the New England shellfishery, "bumper car" disease in Long Island Sound lobsters, or the recent controversy surrounding the ISAV (infectious salmon anemia virus) outbreak in the Pacific Northwest. Then of course there are always parasites that are just fun for their "gross" factor like "salmon poisoning disease". Regardless if your decision regarding the discussion of parasitism of non-human animals I will continue to look forward to your TwiP, TwiV, and TwiM podcasts.

Thank you!


P.S. I read "Parasite Rex" as a freshman in college and it is still one of my favorite books!

P.P.S. "Monsters Inside Me" sometimes grosses me out, and that is saying a lot for it's accuracy!

TWiP 36 Letters

Trudy writes:

Dear Drs. Despommier and Racaniello,

I am almost caught up listening to TWiP! I look forward to your future efforts and eBooks, etc., however, in TWiP # 32, I thought I heard you mention that there would be a link to Dr. Despommier's lectures. I couldn't wait to go to your website and check them out. Unfortunately, the link was missing. You know what they say about the missing link, don't you? It must be a cryptid! But seriously, hope you will post the link to the lectures at your next opportunity. Please? :-)

I am dreading listening to # 33 because there are no more TWiPs available yet. I live in a semi tropical climate in SW Florida so tropical diseases and parasites are especially interesting. The only good thing about being current with your series, is that I can start to catch up on TWiVs and TWiMs. I did find Dr. Racaniello's lectures in Virology on iTunes and am watching this series. I started with the hepatitis Delta virus. It is of special interest to me as are all forms of viral hepatitis.

Dr. Despommier, please consider doing a podcast on vertical farming and even throw in some other tidbits of gardening wisdom.

I took the user survey as you request. Perhaps the results will help you in your future efforts. The way you two work together on TWiP makes for a delightful experience. Science, medicine and pathogens "float my boat" so it is a great pleasure to have two learned professors so engaged in interesting discussions.

I have written before. Hope this isn't too much. Consider that you are talking (via my earbuds) straight into my noggin: I feel like I know you both and it is an honor.

Best regards,

Peter writes:

Brian writes:

Vincent & Dickson,

My wife pointed me to TWIP and what a blast. My 23 year old son and I are making our way through the early episodes during our commute to and from work and loving every minute of it. After listening to the tapeworm episodes I will NEVER pet a dog from Wyoming or any other of the sheep states.

I'm not sure if you have covered the evolution of parasites, we're only up to episode 9, but that must be as crazy as ever. Surely you have enough material for several years worth of podcasts, but I'd like to hear a bit about how an animal accumulates such a bizarre life history.


Peter writes:

Dear TWiP team.

I was speculating about parasites that modify host behaviour and a possible strategy that may have evolved in those transmitted by blood feeding vectors.

To achieve optimum transmission of the parasite uninfected blood feeding insect vectors should find infected hosts more attractive than uninfected ones and once the insect vector had itself become infected its behaviour should change so that it would then preferentially seek uninfected hosts.

Has any research been done to determine whether any parasites that employ blood feeding vectors actually do modify host smell and vector preference in this manner?

As I was writing I was thinking of arthropod vectors such as mosquitoes and biting flies but it occurred to me that there are other possible blood feeding vectors such as vampire bats and leaches whose behaviour could also be potentially modified in this way.
Are there any zoonotic infections that are transmitted by leach vectors?

Lastly, I have seen blood feeders described as Hematophagous and Sanguivorous are these synonymous, and if not what is the correct/preferred term?


Gopal writes:

Hello, Vincent & Dick,

This month's issue of The Scientist has this interesting article:

Can't help wondering, somewhat uneasily, what our own parasites make us do!



Don writes:

In your discussion of Wolbachia in filariasis, Vincent suggested tetracycline for therapy. Dickson opined that it was too toxic and expensive . Au contraire, in the QID form it is "dirt cheap" and has been used widely since the mid 50's. Prolonged use does cause mottling of the teeth, and florescence of the bones under Woods light, not a problem for most of us. Wonderful Podcast, and deeply appreciated. Thanks

Kyle writes:

Top O' The Mornin' To Ya! (I'm not Irish - I just like the phrase..)

I would like to thank you for putting together such an excellent podcast. I'm currently a Med Tech working in a parasitology laboratory and enjoy my days searching through blood and pooh for those tiny life forms that you describe so well. I was introduced to the world of parasites by a course I took as an undergrad. The course instructor was one Dr. James B. Jensen. Judging from your earlier talks, I trust that this name will sound familiar. As you can imagine, the course taught by such a well known parasitologist was an amazing experience. I have a great passion for parasitology, and I'll see what kind of future I can put together. Thanks again for the great shows. I encourage you to continue, and add my voice to those that are calling for more. It is This WEEK in parasitism, you know! :)


Jim writes:

Vincent and Dick,

Delighted to hear the latest TWIP on the malaria vaccine. You guys mentioned using impregnated bed nets to reduce malaria. The NY Times had an article at:

This article described using poisoned bait to reduce the mosquito populations by a bunch like 90%. Would love to hear your thoughts on this.

Was also delighted to hear you guys are going to have more TWIP.

Am still devoted to TWIP, M, V.
Thanks much and 73

Kelly writes:

Hi, Vincent and Dickson.

I'm a PhD student at the University of California Davis and a long-time listener of This Week in Parasitism and This Week in Virology. I have a great appreciation for the fact that you two are successful scientists who take time out of your busy schedules to share your love of parasites and viruses with the general public. In fact, I was so inspired by This Week in Parasitism that I have since begun podcasting about science topics myself! Thanks for the inspiration!

I thought you two might be interested in an "experiment" in science crowdfunding called the SciFund Challenge. One exciting aspect of this experiment is that we're exploring a potential new source of funding (i.e., the general public) for small science projects at a time when everyone seems to be complaining about how difficult it is to get grant money. While this aspect of the experiment is certainly exciting, the most exciting part to me is the fact that crowdfunding forces scientists to engage with the public. Not only does the public get a chance to learn about cutting edge research, but they get the opportunity to have a voice in deciding the direction of future research through the money they donate.

While I think you might be interested in learning about a program incentivizing scientist engagement with the public, my motives are not entirely altruistic. I have a SciFund project focusing on how trematode parasites manipulate the behavior of their hosts, and I'm wondering if you would be willing to help me get exposure to my RocketHub proposal for this project (URL is here:, or go to and search "Support Zombie Research"). I study Euhaplorchis californiensis (EUHA), a trematode parasite infecting the brains of California killifish. EUHA manipulates the neurochemistry and behavior of their fish hosts, a fact which I find endlessly fascinating. These parasites have essentially had millions of years to figure out how the fish's brain works, and to figure out how to manipulate brain chemistry to achieve their own goals. I'm working on quantifying the extent to which the parasites modify the behavior of their host, and am trying to figure out the mechanism by which these parasites achieve their extraordinary behavioral manipulation. I believe parasites have a lot to tell us about how brain chemistry influences behavior, and I think of my research as an exercise in coercing EUHA to tell me what it has learned over millions of years about brains and behavior.

If you would be willing to tweet about my project or mention it in any other way, I would be endlessly appreciative. I'm happy to answer any questions you might have about my study system, as it's pretty much my favorite thing in the world to discuss!

Trudy writes:

Dear Drs. Racaniello and Despommier,

I just discovered your wonderful Podcasts! I am a registered nurse who has an unusual background. I worked as a diener at a teaching hospital while working my way through college. My mom was an RN also when there were few vaccines. She graduated in 1935. She would often discuss what she had seen as a public health and Army nurse anesthestist in WWII. She had a library of medical textbooks that I enjoyed reading . I spent part of my career as a nurse epidemiologist (county public health practice) and as an STD clinician, where I got to work with all kinds of infectious diseases and conditions (viral, bacterial and of course parasitic.)

I have been interested in infectious diseases and conditions since I was a young child when I got my first microscope. Also I have been lucky enough to live in semi tropical Florida for over 30 years. The University of S. Florida still has a great series of podcasts from their medical school's Division of Infectious Diseases. They also discuss tropical medicine and have a College of Public Health.

My first in person experience with a parasite specimen which really "hooked" me on microbiology was that of a tapeworm which was in a huge (tall) container in the foyer of Abbott Labs in Chicago. I was with a group of High School students which had a NSF grant in collaboration with Northwestern University's College of Medicine.

I have been fortunate to see a lot of interesting things because I also did some bio-medical illustrations. I am both an artist and a nurse.

To make a long winded email shorter...Your podcasts are infectious...I believe there is no cure or treatment other than continuing as a listener to you discuss microbes in your most engaging fashion.

Thank you for sharing your knowledge and experiences!

Trudy in Naples, Florida

Paul writes:

Hi guys

Just discovered the podcast.
Listening to 2 shows a day ...working my way up.....absolutely love dr. House ..parasite rex....and monsters inside me:)
While gathering information about parasites i often see these so called zappers little devices that kill parasites ..what are your thoughts on these.....and the history of using electric devices in killing parasites.

Greetings from switzerland

Josh writes:

Dear Drs. Despommier and Racaniello,

I am an auditor. To occupy my mind while I work I started scouring iTunes for science rich content. I saw your show "TWIP" and thought why not? I think the first TWIP I listened to was #33. I was immediately hooked. I went home and subscribed to TWIP, TWIM, and TWIV that night.

Currently I am listening to all of the TWIPs in a row before I start the other shows. I love the education, the ick factor is pretty high but this show provides me with an EXCELLENT free education, and helps me confront fears that were boogey men in my mind by giving me real quantifiable behaviors and characteristics of many things I have had uninformed fears about ( i.e. Trichinella, Toxoplasmosis, and tapeworms).

I am very saddened that I didn't know who Dr. Despommier was prior to November of this year. In the Spring of 2011 I was writing a business plan for my entrepreneurship class and I advocated that my group do our project on vertical farming. We were unable to find any resource that would provide us with information on how to successfully integrate a vertical farming business into an urban area such as Phoenix AZ, where our fictitious business had to be. We had thought about potentially buying a tall structure like an empty condo tower, or office building and converting it into a farm, or placing farms on roof tops (kind of like they do in Cuba). Sadly we couldn't find any cost to benefit analysis, yield per acre data, or potential profit margins with which to build our fictitious business plan. We ended up using another idea of mine, recycled building material sales. I remain sad that we were unable to write a plan for vertical farming.

Thank you for providing me with such a wealth of free information. Thank you for presenting it in such a content rich way, without spoon feeding the listener. Please continue to do these shows. I am indifferent to frequency as long as I can continue to have access to your knowledge and experiences.


Rachel writes:

Dear Dr. Racaniello and Dr. Despommier,

I'm in the process of choosing a career (PhD or MD)

I would love to follow in your footsteps and become a professor, researching parasites and leading the young minds to new discoveries! However, when talking with my parasitology teacher it seemed like he was discouraging me due to the lack funding and interest in the subject. I wanted to know your opinion, especially Dr. Despommier's. Do you think part of your success in your area of research came from the 'newness' of the subject or is there still an opening for hopeful parasitologists.

Thanks for all the work you both put in to the TWI series, I am a huge fan.

I am waiting anxiously for the next installment of TWIP.

TWiP 35 Letters

Trudy writes:

The more I listen to your fantastic podcasts, the more I love them. wO0t. I am the Naples, Fl nurse/artist who has written before.

Because I did get the pleasure of tracking reportable diseases and conditions in Florida, I was struck to know that other states did not require reporting of giardiasis.
Thought you might find the link to the list in my state interesting.

I do have a question...if you answered it can you mention the podcast number, please? It is more of a TWIM question, but I would like both of your comments because of the urban gardening interest by Dr. D. When tomatoes were suspected of being the source of a widespread salmonella outbreak in the not too distant past, there was speculation that the organism was contained within the tomatoes' cells!!! I garden, was a biology art major before finishing my BSN. This made absolutely no sense considering the differences between animal and plant cell structure. Also, what does Dr. D. think of organic gardening?

You also may find it interesting that Florida does allow land application of bio solids after processing in a wastewater treatment plant. Considering some of the encysted pathogens, I always felt this was unwise. Not every County allows it.

All the best from your very loyal long learner with ear buds which are rapidly embedding as a result of your "infectious podcasts"...


Dang, you are the best, guys. Listening to the podcast about crypto right now.

Gave you 5 stars and wrote a "glowing review" (ala Mark Crislip) on iTunes.

Alexander writes:

Dear Drs. Despommier and Racaniello,

I've really enjoyed listening to your podcast and learning about all of the fascinating parasitic diseases that they don't teach us enough about in medical school. I'm a student at Boston University School of Medicine but currently taking a year off to do HIV research in Uganda. Among other things, I'm hoping to perform a retrospective study looking at the impact (if any) of soil-transmitted helminth infection on antiretroviral treatment outcomes in a cohort of HIV-infected individuals in rural Uganda.

At any rate, my real question for you has to do with treatment of schistosomiasis. I happened to be swimming in Lake Victoria last weekend (self-preservation is not one of my strong points...) and am thinking it may not be a bad idea to take some PZQ. My question is: how long does one need to wait after potential exposure to schisto for PZQ to be effective? My favorite new textbook, Parasitic Diseases 4th Edition by Despommier et al (have you heard of it?) says that PZQ is effective against the adult organism. However, it sounds like it takes several days for schistosomulae to migrate from the infection site to the liver, only then at which time they develop into adults. Provided that schistosomulae are also susceptible to PZQ and the drug has good subcutaneous tissue penetration, it should be fine to prophylax even within the first days after exposure. However, if this is not the case it may be necessary to wait some period of time to ensure that any schistosomulae have had time to transform into adult worms before administering PZQ. Any thoughts on this?

Finally, I just wanted to say thanks for taking the time to create and sustain TWIP. It's always a pleasure to listen in, and I'm actually finding the information you provide in the podcast (coupled with your wonderful textbook) to be quite clinically relevant here in Uganda.

Thanks, and all the best,

PS - here's an idea for a future TWIP episode: a review of clinically relevant (or otherwise interesting) interactions between parasitic infections and other infections, e.g. genital schisto increases susceptibility to HIV infection in women. I think one important and possibly under-emphasized point by Peter Hotez and others at the forefront of advocacy around NTDs is that it is valuable to target NTDs not only for the purpose of eliminating these infections themselves but also for mitigating any pathogenic synergy they might have with other more "sexy" diseases like HIV.

Cedric writes:

Dear Vincent and Dickson,

I recently read this paper discussing the phenomenon of self medication in animals. The authors speculate that this behavior was selected for, at least in part, due to the antiparasite properties of many of the plants, animals, or materials consumed by animals for reasons other than nutrition. I was wondering if Dickson had any more information on this process, and what his opinions are regarding the origin of self medication in regard to parasites.

Thanks so much for all of your work in developing TWiV, TWiP, and TWiM. Your discussions have given me a real head start in my undergraduate biology classes, and I look forward to every episode.


Ricardo writes:

Novel Drug Wipes out Deadliest Malaria Parasite Through Starvation

Theodore writes:

Good day (or night),

Starting from October I've listened to about half of the TWIVs, all the TWIMs and the TWIPs. I find them to be very enjoyable, the semi-Socratic method of teaching is quite refreshing. However, two particular subjects have been underplayed.

First Toxoplasma. The papers by Fekadu, Lindova and McAllister are great primers for the studies regarding the behavioural effects of T. gondii. The Gaskell one is by far the most interesting though. So, hands down, the leading theory for schizophrenia's etiology is an inappropriate level of L-dopa, the precursor for such molecules as dopamine and epinephrine. Depending on the population studied, seroprevalence of T. gondii induced IgGs among patients with schizophrenia is as high as 97.7%. Though there is some ambiguity as certain studies report a 42% seroprevalence amongst schizophrenics, compared to 11% in controls. Regardless of the exact rate, it has a statistically significant presence in schizophrenics and people with other mental health problems.

Just a correlation though. A tongue in cheek refute of correlative studies is the stork theory (will be paraphrased/butchered). The idea is that from 1970-1985 there was a surge in the German birth rate. At the same time, there was a surge in the stork population of Germany. Their coincidence was statistically significant. Of course, we know this is bupkis. Storks and babies aren't actually related. However, if we found that there was a drop in condom sales, we could have an aha moment, due primarily to the fact that we can name the mechanism for why that correlation actually matters.

Back to Gaskell, and the aha mechanism for toxo and schizophrenia. Their group shows that T. gondii has two fully functional enzymes specific for producing L-dopa, and they show that these genes are transcribed specifically when the parasite infects neural tissues, and that the enzymes produced do make L-dopa. We really can't prove that toxo causes schizophrenia with Koch's postulate since putting a brain parasite into a volunteer isn't all that nice. However, I'm flummoxed to think of anything else that is needed to point at T. gondii as the causative agent for some types of schizophrenia.

Ricardo writes:

Global warming wilts malaria

TWiP 34 Letters

Raihan writes:

Hello Professors Racaniello and Despommier,

In TWIP #33, Dr Despommier said that certain parasites do not need receptors to enter cells, while Dr Racaniello then said that all viruses require a receptor for entry. I might be wrong but don't certain paramyxoviruses like Respiratory Syncytial Viruses enter the host cell by mere membrane fusion? I hope I'm not missing the point here, but i remember being taught in my undergraduate course that there are a certain class of viruses that don't need a receptor at all.


Steve writes:

I first read of the Red Queen's Hypothesis in Parasite Rex by Carl Zimmer, which list Dr. Despommier in the acknowledgements. Recently there was an story in The Wall Street Journal: "Why Sex? To Keep Parasites at Bay, of Course" by Matt Ridley. I believe it would be very helpful to hear your thoughts on the Red Queen's Hypothesis.

Thanks, we appreciate all of your great podcasts.

Scott writes:

Vincent & Dickson,

I listened with great interest this afternoon to the TWIP story on malaria vaccine (via Science360 - I am not an academic, but a true science junkie). My keen interest is due to the fact that I lived in Nigeria for some time and suffered from P. falciparum infection seven times before I was finally able to build enough immunity to not suffer mightily. No cerebral, thank goodness! But it left me with a passion for watching developments in the study of the parasite and the science of malaria control.

In listening to the part on the TWIP podcast about the locus of injection site being critical to efficacy for this possible vaccine candidate, a thought occurred to me: Since mosquitos are so adept at finding blood vessels from which to suck their bloodmeal, why not create a genetically modified mosquito that would produce the candidate vaccine protein in its saliva, so that when it inserts its proboscis into the blood capillary, the host gets a tiny injection of the protein at the same time. While I do expect that not a single mosquito bite would produce immunity, of course, the many thousands that one receives over time, might do the job, and would maintain it over time, as "booster shots" would be received daily. Since this vaccine seems to be efficacious against all the strains it has been tried against, it would suggest that the parasite's docking protein is highly conserved in evolution, making the evolution of resistance much less likely.

If the same genetic sequence were also used to invoke immunity to Plasmodium by the mosquito itself, it would give the mosquitos an evolutionary advantage in the environment, in that there is also a cost to the mosquito as well in carrying the parasite. This would ensure that the genetic modification would become dominant in the mosquito population over time. It would also provide a double-pronged attack on the parasite - both at the mosquito and human blood stages of the parasite's life cycle would be suppressed.

While I recognize that there are surely some formidable barriers in the way of creating such a system and deploying it in the field, my thought is that it might have enough promise to be worth looking into.

Warmest regards from (so far) malaria-free Cartago, Costa Rica,

Trudy writes:

Listening to you in Podcast #6 on tapeworms. You are making me laugh. I live in Florida. Not everyone is retired in Florida. Not even people who live in South Florida are all retired.
FYI Whole Foods does list the country of origin of the animal proteins sold in their stores.
With my background in Public Health epidemiology and communicable disease clinic (STD clinician...TB outreach), I have never seen a tapeworm in a specimen since moving to Florida. I had seen on in the teaching hospital I worked at in Grand Rapids, Michigan in a specimen from an immigrant. Now I said not everyone in Florida is retired and they are not...but I am retired (early).

Cattle ranches are not just in the panhandle either...many of these ranches are all over the state. Florida is a big state, we have a lot of open land used for all types of agricultural purposes. While there are beef cattle grown in Florida, many more farms/ranches are devoted to dairy production.

I am a nurse, an artist and a Florida Master, microbiology and infectious diseases continue to be of tremendous interest to me.

Charlotte writes:

In TWIP 33 you asked which protozoa should be discusesed in future episodes. If you discuss Acanthamoeba as a "Trojan Horse" you can correct errors made on two episodes of TWIM regarding Legionella as endosymbionts of Acanthamoeba.

I think listeners would find comparisons of Acanthamoeba, Neglaria and Hartmonella (in terms of pathogenesis and as bacterial reservoirs) interesting.

Thank you for the podcasts, without which I would never sleep.


P.S. The "Trojan Horse" term was coined by Barker & Brown, but everybody uses it now.

TWiP 33 Letters

Howie writes:


Great podcast!!!

A while ago, Dick made a comment along the lines that Sir Ronald Ross was a dim bulb. Ross did much more than "just" discover that bird malaria is transmitted by mosquitos. He was a closet mathematicians and published about 20 papers and books on pure mathematics (see

He was also a superb infectious disease transmission modeler.

Germ theory was developed in the 1850s. Before then, people believed that diseases such as cholera were caused by a miasma, a noxious form of bad air. About 60 years latter, Ronald Ross, a public health physician, developed two ODE (ordinary differential equation) transmission models for malaria [Ross, 1910] that made the following predictions:

Germ theory was developed in the 1850s. Before then, people believed that diseases such as cholera were caused by a miasma, a noxious form of bad air. About 60 years latter, Ronald Ross, a public health physician, developed two ODE (ordinary differential equation) transmission models for malaria [Ross, 1910] that made the following predictions:

1: One does not need to kill all the mosquitos in an area to prevent malaria epidemics. There is a threshold value of vector capacity,  below which the disease quickly dies out in humans. This conclusion was at first rejected by the experts, but proved correct by field trials in Malaysia where malaria transmission essentially ceased after draining the mosquito larval habitats.

2: Malaria can not be eradicated by treating humans alone. Even if the number of infected humans is reduced by 99%, if the mosquito population remains unchanged, then the disease prevalence will rebound to its former value.

3: The endemic level of infections is lower for longer lasting infections, e.g., it is lower for P. vivax than for P. faciparum infections.

Of course, mathematical models can not prove anything, but they generated novel hypotheses which were found to be correct and saved countless lives.

Ross was also the first to present a mechanistic model of the transmission of a generic infectious disease.

Not bad for a dim bulb!

Please, never stop TWIVing.


Professor of Mathematics

Georgia Institute of Technology

Spencer writes:

Dear TWIP,

I really enjoyed your analysis of the Malaria Vaccine article from the New England Journal of Medicine.    You guys had an interesting discussion about the different phases of clinical trials and I thought it was incumbent upon me to clarify these phases.  As a clinical investigator, I oversee several Phase 1 clinical trials.  A Phase 1 trial is a dose escalation trial:  It is simply carried out to assess safety at various potential clinical doses of a compound.  Obviously, before a compound makes it to such a trial, there has been some demonstration of effectiveness in animal models, or some reasonable suspicion that the compound will be a useful treatment for the disease.  Phase 1 studies are small - typically 20-80 people and it is in this phase that side effects can first be seen.  A Phase 2 trial targets the maximum tolerated safe dose in a specific population that either has the disease or is at risk for the disease.    There are usually 100-300 people in a Phase 2 tri al.  In addition to looking at continued safety at the studied dose, the compound in question is studied for its effectiveness in treating the condition or disease in this phase.  In Phase 3, the compound is compared to standard of care treatment, often in a head-to-head blinded fashion.  In some cases, there is no defined standard of care treatment.  Alternatively, in some cases, such as you discussed about HIV, it would be unethical to withhold conventional treatment while evaluating the new compound.  This makes Phase 3 trials very difficult to complete.  Also, Phase 3 trials usually require thousands of participants and take a long time.  Phase 4 trials are post-marketing trials.  The compound has already been approved for sale and prescription by the Food and Drug Administration.  Many of the side effects and sometimes disasters associated with some medications are not apparent until the drug is taken by 10s of thousands of people after it is already released.  I hope this is helpful to listeners and I just want to remind you guys that there are still some interesting parasitic lifecycles and histories to discuss for which we are still waiting.  Keep up the great work.

Jim writes:

I was jolted to hear the casual mention in TWIP 28 by Dr Gwadz of chiggers and scrub typhus.  I thought chiggers were one of the local pests I could ignore other than itching during routine encounters with them each summer.  This summer at the worst point I had over 50 on two legs despite deet all over my shoes, socks and lower pant legs.  One or perhaps two adjacent bites produced a large blister in contrast with the usual small, red, itchy nodules.  No other symptoms, but now I'll be alert associated symptoms.  During scrub typhus research with Google I saw instructions for soldiers about tucking trousers into the tops of their boots as a protective measure.  I assume this is the reason for "blousing boots" done by the Army, but don't recall ever hearing that was the reason.

Another great TWIP, by the way.  A small group discussion seems to produce the most interesting results.

Thanks again.


Smithfield, VA

Michael writes:

I love TWiP!

I am starting my parasitology class (for a Medical Lab program) this fall. I am also excited to be able to learn and understand many more of the details now that I have the basics down because of TWiP.

I also have enjoyed being able to use all of the TWi_ podcasts to form questions for my friend in Physician Assistant school who then often asks her classmates the same questions (I bring up topics you say are not often taught in medical schools and the unusual cases, and put them into a type of case study, adding the most vague hints as she and they get stumped). Due to your podcasts I will be able to better grasp everything I learn and be able to help impart critical thinking skills to other health care professionals.

Also, Do I remember hearing that a 6th ed may be coming out of the Parasitic Diseases book? I would love to add that to my studies! If so, any idea when? Did you say it may be avaliable on ibooks? I also encourage you to consider Kindle, for it is easier to read the text on a Kindle, and anyone with a computer, ipad, iphone, android, ect. Can get the free Kindle app and read it and view any color pictures.

I would still like a higher frequency, but so long as you just don't stop, I will be happy with whatever you can do!

Anything associated with Infectious Diseases and how humans interact with and are affected by them is my passion!

Thank you for giving me chopped and dried wood to put onto the fire!


Jim writes: (incomparable TWiP 30)

Just incomparable!  Pure knowledge; so much expertise in one place; another podcast in my Best Podcasts folder.  All the TWIV, TWIP and TWIM podcasts are great, but they are readily accessed, too, so far, and I'm capturing a collection of less easily retrieved audio files for times when I can pass on the collection to interested folks which has already occurred twice.  A couple TWIP's are there to capture attention and alert listeners to where similar files are available.  I'm sure your backup plan is excellent, Vince, but I'll happily store copies of everything, if you need another remote site.


Smithfield, VA

Alan writes:

What creature/parasite/worm can I catch from eating a cockroach snack late at night?

I can't decide which entertainment personality I like more, Vince or Des Pom. Its not just the subject its you guys that I listen to.

Have fun,


P.S. I am with Dixon on the orchids.

Scott writes:

Hi guys!

This article popped up on a facebook feed I subscribe to; probably you already are familiar with the material, but just in case I thought I would pass it along. I have an interest, but no expertise, in tropical medicine, and would like to hear your opinions.

Ricardo writes:

Alex writes:

Hello Doctor Racaniello and Despommier,

Curious if you might have some incites on a particular malaria life cycle. I've been reading on Plasmodium vivax.  We know that Plasmodium vivax can relapse via the hidden agents stored in the liver, termed 'hypnozoites'. But time and time again through multiple sources it's stated that vivax malaria relapses much more quickly in patients in tropical regions over non-tropical regions, on the magnitude of several months.  For the life of me I cannot explain this, the parasite would seemingly detect the same body temperature and conditions within the host regardless of where they are living. I have two theories here; Perhaps the hosts are indeed different, with varied levels of nutrition and other factors causing the hypnozoites to convert earlier in tropical cases and later in better nourished non-tropical cases. Or, on the other hand, the cases of "relapses" could be muddled by actual cases of re-infection. Since you are more likely to get an infection in a tropical region the relapse rates seem lower in non-tropical regions. Any thoughts?

In TWIP#31, Doctor Despommier mentioned that a man by the name of 'Macgregor' conducted a statistical analysis to determine the number of cases needed to maintain malaria infection within the population?  I was unable to find this paper, and curious if you might be able to link in within the show-notes next time.  I'm extremely interested to see these figures. It seems to me that we might be on the cusp of a medical paradigm, with a vaccine that's 50% effective it may be the extra push with the combination of mechanical preventative strategies (bed nets, ect.) needed to eradicate the disease.  Is there such a thing as 'vector-based herd immunity'?  Conventionally, 85% of individuals within a population must be immune to maintain herd immunity within the entire population.  I know this is complicated by the fact that it must be essentially eradicated within two populations (humans and mosquitoes), and therefore likely to result in a much higher threshold of immunity.

Keep up the great work!

Todd writes:

I'm reading this article and take a small issue with item #5 :

The first part of this paragraph makes perfect sense:

If it's parasites or other risks associated with sushi that worry you more than mercury, Andy Bellatti suggests you put your mind at ease. "Fish served in sushi restaurants has been previously flash frozen, which kills parasites as effectively as cooking," he explains.

Particularly confusing to me though, and if memory serves, contrary to a comment that Dick made about farmed fish (though I think it was in reference to a sheep borne parasite (liver fluke maybe?)) is the second part of the paragraph:

[Andy] also points to Steven Shaw's book Asian Dining Rules: Essential Eating Strategies for Eating Out at Japanese, Chinese, Southeast Asian, Korean, and Indian Restaurants, which explains that most fish used for sushi in restaurants around the world are farmed to avoid the problems with parasites in wild fish. "Fish like tuna are not particularly susceptible to parasites because they dwell in very deep and cold waters. Sushi restaurants typically use farmed salmon to avoid the parasite problems wild salmon have," he explains. The fish that are at times likely to have parasites, like cod or other whitefish, aren't used for sushi anyway and are generally served fully cooked.

I suspect it is more about which parasite they're referring to than the absolute of "all parasites."  Can you clear up my confusion?

Keep up the great work guys!  TWIP and TWIV are both part of my commute routine.  It makes me wish my drive was longer...well...maybe not...but your penchant for educating the masses is earning you karma points daily!


P.S. Ronald Jenkees *ROCKS*!  You should hear his unreleased music, which he has linked from his website.

Luca writes:

Dear Vincent and Dick,

Once again I write to you after listening to TWIP episode 32, where Vincent went off on a tangent to discover the meaning of acta in the various scientific journals.

Here I am to shine some light upon it. As an Italian, I learned that word in primary school, when we were taught that every day, in Ancient Rome, all that had been discussed and decided in the Senate would be put up on a poster in the Forum, the public square, so that the people could know about it. This was called Acta Diurna (loosely, record of the day) - of course there's a wikipedia page for it: Here it is! It goes into much more detail than I ever would be able to. I probably got it wrong in some details, too. Primary school was long time ago.

Once again thanks for your constant, excellent work in education and public outreach, I have now expanded my weekly podcast schedule to include TwiM, but I have to admit that TWiP is still my favourite.

All the best


PS: here's an added bonus - I knew the meaning of Despommiers, but was curious about Racaniello, so looked it up online - there's no meaning as far as I can tell, although to me it sounds like some kind of edible root in Italian. However, I found the Racaniello coat of arm, in the corresponding wikipedia page - - did you know about it? And you have a (rather mean) family motto, too: Dominus exquisitus artis saeviter quis revocas malum memet (I possess a refined art, that to hurt cruelly whoever does me evil). Cheery-o!

TWiP 32 Letters

Raihan writes:

Hi Guys,

I saw this video during the course of listening to TWiP. Is there any parasitic truth behind this phenomenon?

Amazing Podcast. You guys are revolutionizing education.


from @Sophie on Twitter:

Please do a TWiP on Baylisascaris procyonis

Jim writes:

TWIP 26 on the schistosomes was equally interesting. I did some serious thinking about a swimming episode done in Cam Rahn Bay, Vietnam in 1971, but never had any problems, yet. I heard that shistosomes either stopped or prevented invasion of Quemoy and Matsu Islands by the Chinese by wading across an isthmus probably in the early 1900's. Neat analogy with Schwarzenegger.

Smithfield, VA

Suzanne writes:

I think most wild salmon are caught at sea. Would any parasites they picked up as youth in rivers stick with them then?

I've been told that from an economic/environmental point of view Alaska does a very good job fishing (and not overfishing) for wild salmon. That's one reason I buy Alaskan wild salmon. I don't think I'll stop, but most of what I buy is canned and cooked. Or smoked. I do like salmon sushi occasionally, though... hmmmmmm.

Chad writes:

I came across an organism named Naegleria fowleri while I was going off on tangents from a wikipedia search.
This looks like an interesting organism for your podcast, (assuming it is considered a parasite.)

Thank you,

Jim writes:

Prof Despommier:

In your excellent TWIV 22 about hookworms you noted that after the Civil War lethargy was a major problem in the South due to hookworm infection. My local newspaper today contained a long article about difficulties US troops have in training and working with Afghan troops, stating in part that "...American forces often characterized their Afghan counterparts as drug abusers and thieves who were also incompetent, corrupt and lazy with 'repulsive hygiene.'" Do you know of parasites in that part of the world which could lead to a person being seen as incompetent and lazy, especially if they have poor hygiene, or if studies have been made to identify prominent parasites in Afghanistan or that region? No other details about these characteristics were offered in the article, so we don't know, for example, if the repulsive hygiene description is by necessity, due to cultural differences, or laziness.


Smithfield, VA

Alberto writes:

Dear Vince and Dickson

Following the release of TWiP #27 (Trematodes) I attended grand rounds at our hospital where an interesting case was presented that was coincidentally relevant to this recent episode.

A middle aged man presented at our hospital with severe liver dysfunction and was eventually found to have a Fasciola hepatica infection (a single egg was seen in a stool sample). The CT and NMR scans clearly showed tracks of necrotic tissue in the liver but the most impressive graphic was a video of the gall bladder ultrasound where multiple flukes could be seen moving in and out of the field of view of the scanner.

The presenting infectious disease registrar believes the source of infection was fresh watercress consumed with a traditional Lebanese dish of raw beef (Kebbeh nayyeh). The watercress was obtained from the patient's friend in Forster on the Northen New South Wales coast, in sheep country.

Apparently there have been other cases of F. hepatica infection including one in Melbourne associated with cultivated watercress.

I am still catching-up on old episodes of both TWip and TWiV. I look forward to hearing more about molecular hydrogen generation by parasites. Is anybody looking at cloning the enzymes involved in this pathway for commercial exploitation.

Keep up the amazing effort guys.
Molecular Haematology Lab, Institute of Haematology
Royal Prince Alfred Hospital

Ryan writes:

Just so you know...

I could listen to Bob tell stories all day long! Great episode, guys!

Ryan Rogers
Texas Parks and Wildlife Department
Possum Kingdom Hatchery

Jim writes:

Professor Despommier,

I realize both you and Dr Racaniello are concerned about public health issues, but this seemed at first glance to be of greater interest to a parasitologist than a virologist. However, please don't prevent Vince from commenting. So, may I get your comments about this Thirstaid Bag from Britain ( Despite its small size it looks like another possible item for my emergency equipment box for use in a local disaster, or for travel anywhere water quality is questionable. It's compact, tough and lightweight and has a filter shelf life of 5 years. Of course some iodine pills or small bottle of clorox would be much cheaper, so is it a cost effective item? I wonder, also, how temperature affects the filter and also how a user in the field could test the water it produces to verify filter effectiveness. For example it could be on the shelf for 4.5 years and have just produced some 200 or 300 liters of water out of its 350 maximum. The manufacturer says the filters are stamped with a production date and once placed in use are effective for a year, or I presume, the 350 liters. Let's say the bag and a 3oz bottle of clorox are stored in a car glove box or car trunk in Florida for 2 years and then in Massachusetts for 2 years, before a need for them occurs. Do you think both will be as effective as when produced?


Smithfield, VA

James writes:

Dear Vincent and Dickson,

I have finally caught up with all the TWIP podcasts! In October, I will start a position as an assistant professor in host-pathogen interactions at the Faculty of Veterinary Medicine at the University of Calgary. My background is in biochemistry and bioinformatics. I completed a PhD at the University of Edinburgh on genomics of parasitic nematodes and a postdoc in Toxoplasma gondii at the Hospital for Sick Children in Toronto. In my new position, I hope to return to nematodes - if the funders will permit me!

Although my work is focused on genomics, I readily see the importance of classical parasitology, e.g. taxonomy and systematics, cell biology and ecology. In recent podcasts, Dickson has referred to the end of the golden age of parasitology and the closure of parasitology departments. Rest assured that there are still groups of Young Turks telling anyone who will listen and shouting at those who won't about the importance of all aspects of parasitology, not just DNA-sequencing.

I want to thank you both for your efforts in TWIP - I continue to learn a lot, especially the history and social aspects. With respect to the basic biology, I am continually blown away by the invasion and survival mechanisms of these parasitic critters. Trying to understand them better is what gets me out of bed in the morning, that and a cup of tea!

Listening to Robert Gwadz was inspirational and I look forward to hearing from other legends in the field.

best wishes


Faculty of Veterinary Medicine,
University of Calgary

TWiP 31 Letters

Chandler writes:

Hi Dr.'s Racaniello and Despommier,

After listening to your podcast on Onchocerca volvulus I decided to contact you in hopes of enlisting your expertise. I am a PhD student of biology at Northern Arizona University and while my research is in novel antimicrobial gene discovery using halophilic Archaea I am also currently working with Onchocerca lupi. There has recently been an increase in incidence of Onchocerca lupi infections in dogs in the Southwestern United States. My dog, at 2 years of age, began showing symptoms of an eye infection that persisted after several different rounds of antibiotics. After seeking out an ophthalmologist, exploratory surgery was performed and a single nematode found. Almost a year and four surgeries later, his infection is still present. The worms have been coming to the outside surface of his eyes where I see them and pull them out as well as forming several nodules in his eyes. He is given monthly injections of ivermectin and takes doxycycline daily (200mg) in hopes of killing the Wolbachia and rendering the parasites sterile. Between only two vets I have seen in the Phoenix area they have seen nine cases of Onchocerca lupi recently. I am receiving nodules removed from the eyes of my dog as well as parasite samples from California and Utah cases. I am currently sequencing the partial mitochondrial genes from all samples in hopes of comparing the parasites in the U.S. to others published from Central Europe where Onchocerca lupi is endemic. I wish to sequence the entire biome of Onchocerca lupi in hopes of discovering highly conserved unique DNA as a potential treatment target as well as other possible endosymbionts as potential targets. I also would just like to see this information available to others who specialize in parasites. Funding, however, seems very difficult to secure for this parasite.

I have a couple of questions I hope you can answer and if not perhaps you can point me in the direction of someone who can. I have not found any literature on O. lupi that shows these subcutaneous nodules throughout a canines body. The samples I have received have all been found in nodules on the eyes. However, I am finding several 'bumps' on my dog's body and am wondering if these might be nodules or if they are a calcium build up from the high, long-term dose of oral prednisone. Secondly, after recently dissecting a newly formed eye nodule, I found several worms that I believe are calcified ( I have not yet tested to be certain) and several worms that I am not sure if were alive or dead or perhaps unhealthy. Are there ways of testing whether these are healthy/living parasites? Will all dead parasites become calcified? Do you have any ideas why several of the worms have migrated to the outside surface of his eyes?

I feel I had a million questions to ask you and now can only remember these. I did want to point out that recently in areas where this parasite is endemic (Europe) a couple of papers have been published on Onchocerca lupi being zoonotic. These findings are based on molecular analysis. This seems like reason for concern in the United States where it looks like it is also soon to be endemic.

I have included a picture from one of my dog's surgeries of what we are calling a drainage tract. It seems too large to be created for the adult worms to migrate through, could it be for the microfilaria? Have you seen anything like this before? The vets and I are at a loss for what it is, but after having all surrounding tissue removed several months later another one formed. Thank you for taking the time to read my ridiculously long email and any information you can give me is greatly appreciated.


Tommy writes:

Hi Vincent and Dick,

Loving the podcast, and I'm glad that you guys finally got around to the wonderfully peculiar and complex trematodes! Having worked with various different species of trematodes for the last few years, I am
glad to finally hear them make an appearance on TWiP. When you were discussing schistosome cercariae penetrating their host, I was reminded of some videos I filmed over a year ago which can be found here:

There, you will find the video of some cercariae of a fluke call Curtuteria australis (which I wrote a post about for the Parasite of the Day blog:
penetrating the foot of its second intermediate host, a bivalve called Austrovenus stutchburyi.

Back on the subject of the schistosomes, some recent research indicate that schistosomes can get "divorced":

Beltran, S., Boissier, J. (2010) Male-biased sex ratio: why and what consequences for the genus Schistosoma? Trends in Parasitology 26: 63-69.

Beltran, S., Cézilly, F., Boissier, J. (2008) Genetic dissimilarity between mates, but not male heterozygosity, influences divorce in schistosomes. PLoS ONE 3(10): e3328.

Beltran, S., Cézilly, F., Boissier, J. (2009) Adult sex ratio affects divorce rate in the monogamous endoparasite Schistosoma mansoni. Behavioral Ecology and Sociobiology 63: 1363-1368.

Steinauer, M.L. (2010) The sex lives of parasites: investigating the mating system and mechanisms of sexual selection of the human pathogen Schistosoma mansoni. International Journal for Parasitology 39: 1157-1163. (interesting supplementary video for this paper)

Also on the subject of trematodes in general, it is true that the majority of them have a snail first intermediate host, but there is a handful of families (e.g: gymnophallid, fellodistomatid, bucephalid, etc) which have bivalve first intermediate host. Finally there are a few very odd species which use polychaetes of all things as first
intermediate hosts (e.g: Cardicola forsteri), however such examples are very rare. So generally speaking all digenean/trematodes have *mollusc* first intermediate hosts, and the majority of them have snail first intermediate hosts.

Keep up the good work, the podcast is always informative and I look forward to more fluke talk!


Kenton writes:

Are there hieroglyphics indicating schistosomiasis was a recognized disease in ancient Egypt?

Thank you. I enjoy listening to your podcasts on TWiP.


TWiP 30 Letters

Jim writes:

How about using compost that includes road kill? I heard a billion pounds of animal byproducts go to landfills rather than into animal feed to prevent spread of mad cow disease. Compost that, too?

Virginia may compost roadkill

Boosters say it could save money and help the environment

By Cory Nealon, This email address is being protected from spambots. You need JavaScript enabled to view it.

April 21 2011, 10:42 PM EDT

The Virginia Department of Transportation is considering composting roadkill, a move boosters say will save money and improve the environment.

The complete article can be viewed at:,0,6568729.story

Visit at

Peter writes:

Cutaneous leishmaniasis

Whilst perusing NEJM

Open access.

hookworm, cutaneous larva migrans

chronic schistosomiasis

Colleen writes:


My questions is: can a traveler to a South American country acquire a bacterial infection that lies dormant after an initial presentation of high fever, headache and GI disturbance, with recurrence of bowel issues months later? Are there bacteria that can lie dormant for months and have recurrence of acute symptoms?



Scott writes:

I can't be the first one to think of "Another TWIP is hosted", can I? Keep up the good work.


Ben writes: (subject: an odd thing about texas)

Dear sirs:

Recently there has been an explosion of "stumbling poultry disease" in my neighborhood in south Texas, it abounded after all the nearby gineaus (however its spelled) died of it and stopped eating all the ticks.

This makes me think it is Babeecia (I hope I spelled it right) but one of neighbors thinks it might be a worm. Would this classify as a parasite? Have you ever heard of anything like this before?



Beware the man with a gun for he knows how to use it


Pps: you don't have to read this on the podcast, but I don't mind being read

Benjamin writes:

Hello again sirs:

I am the one who wrote you about stumbling poultry disease.

Two things: on T gondii, Vince asked Dr Despommier a how question about toxo, to which Dr Despommier said something to the effect of: "Vince, I believe in creationism" I resemble that remark, and would politely ask you to refrain from doing so again, at least as a joke.

Second, on TWiP 19 Dr Despommier mentioned that some kids have pica. It's pronounced PEE-kah not PI-kah. Pika is a small rodent that lives in south America.

Benjamin writes:

Hello again sirs:

I just was listening to TWiP 15, so I no don't feel guilty for sending you so many emails.
Two more things: on the end of TWiP 18, Vince randomly says "your narration is impeccable" have you fixed this? maybe it was just an editing glitch, it just disturbs me late at night when I have trouble sleeping.
Number two: what happened to the just released TWiM? Was it removed? My collection is mismatched, so by logic, it was removed at the turn of the year.

Greetings from south Texas, the home of the golden-cheeked warbler

Ps: Dick's volume keeps me on my toes trying to hear/keep from hurting my ears, something to look into.

Ivan writes:

Hello Professors Vincent and Dickson,

I am writing from Cozumel the island on the Caribbean and I found your podcast of Strongyloides stercolaris what I think is great. I was looking for data and pictures of different parasites and I would like to know if you can help me identificating the species of this parasite that I start seeing very often in my practice I think is an Ancylostoma caninum but I am not sure. I would appreciate your help.

I attached the files with the pictures, excuse me for the quality of the images but the camera in the microscope does not aloud me to take better pictures

Thank you in advance.

MVZ Cert. Iván

[see the TWiP 30 show notes for the images]

Liam writes:

Dear Vincent and Dick,

Thank you both for reigniting my interest in these fascinating organisms. I am a medical student from Western Australia with a particular interest in infectious diseases although our clinical teaching seems mostly oriented around bacteria, viruses and the occasional fungus. I have only recently discovered these podcasts but have found them immensely educational and entertaining. If I might offer a suggestion for a future episode you seem to have avoided the free-living neurotropic amoebae such as Naegleria, Acanthamoeba and Balamuthia in your episodes about protozoa. While they might be considered opportunists rather than parasites, Naegleria in particular causes one of the deadliest eukaryotic infections and I would be very interested if you could offer some further insights.



TWiP 29 Letters

Dylan writes:

Dear Professors Racaniello and Depommier,

I hope this email finds you both in good health. I am a second year medical student from Ireland studying at the University of Cambridge, UK and I have been following the TWiP series with considerable interest. Please allow me to compliment the marvellous work you both are doing for science communication, which I am certain will help inspire both researchers and clinicians alike as well as the general public to learn more about infectious diseases. If I may, I would like to request that an episode be devoted to the helminth, Schistosoma mansoni.

Wishing you the best of luck with all the podcasts,

Yours faithfully,


Clint writes:

Love your show.

Have you seen this

The news clip covers a Chemotherapy Drug that Also Kills the Parasite That Causes Malaria.

It may be a malaria breakthrough could you give us your thoughts.

Thanks Again for a great program.


Ryan writes:

Hey Guys,

Thought I'd follow up with you on my email you read on #24.

You asked which university I attended and who taught parasitology there. I attended a smaller to medium size school in Texas called Tarleton State University, where I studied Limnology. My parasitology professor's name was Dr. Russell Pfau. Most of his work is with genetics and currently based around the cotton rat (Sigmodon hispids).

I also thought I would tell you guys how I have put my parasitology classes to use, as it might interest Dickson.

After I graduated with my B.S. I started working at a state run fish hatchery, where we produce game fish and do a fair bit of aquaculture research. We produce striped bass, smallmouth bass, channel catfish, and rainbow trout that are stocked in public water bodies around the state for angling enjoyment. We do regular sampling of our fish for various parasites and bacterial infections, so I've kept my microbiology skills fresh over the last few years.

Our arch-nemesis, however, is a single cell algae: Prymnesium parvum (golden algae).

It is a common algae found in estuaries around the world, but wreaks havoc when introduced to inland waters. P. parvum was first identified in Texas in the mid-eighties, and has gone on to destroy fish populations in several of our drainage basins throughout the state. Since then, it has reared its head in many different states in the U.S. Much of our resources (and most of my time) are spent dealing with golden algae at our facility and providing assistance to private land owners who have experienced blooms on their property.While we have good controls for dealing with it on a small scale, there is currently no solution for treating on a large reservoir scale.

Here is a link to more info on our website if anyone is interested:

Thanks again, for the great podcast. Since finding TWiP, I've also added your other podcast to my weekly downloads. They're all great.

(semi-professional phycologist)

John writes:

This show has stimulated an interest in the subject in me, an unlikely candidate.

Thank you

Coincidentally my dog is currntly being treated for heart wrom.

If you ever need an alternative name for the show I have;

1) Hold my hand, I'm a stranger in parasitism

2) Parisitism lost - paristism found.

3) Another shitty day in parisitism.

I hereby assign all rights.

Keep up the good work.


Alberto writes:

Dear Vincent & Dickson

Thanks for your wonderful podcasts. I have recently subscribed to both TWiP and TWiV and am slowly working my way back through the back catalogue.

I am a diagnostic molecular biologist working in the haematology department of a major teaching hospital in Sydney, Australia. Our lab's main tasks are PCR detection of various mutations and gene rearrangements found in leukaemias. This year marks the 20th anniversary of the first official diagnostic PCR report issued by our lab, so we have been involved in the field from the early days

I was particularly interested in TWiP #23 re. Strongyloides stercoralis since it is relevant to my work in molecular diagnostic haematology. One of the diseases that our lab works with is chronic eosinophilic leukaemia (CEL), particularly the myeloid subtype that is characterised by the presence of PDGFRA and PDGFRB gene rearrangements; this subtype is particularly sensitive to kinase inhibitors such as imatinib. Curiously, these gene rearrangements are almost exclusively found in males and they do not involve the sex chromosomes.

(Note for your listeners: Eosinophils are white blood cells that form part of the innate immune system. They are full of toxic protein granules that are released to kill invading organisms. However, if these granules are released in the host's tissues in large quantities they can cause significant systemic toxicity. Commonly affected tissues in hypereosinophilia [eosinophil blood counts above 1.5x10^9 /litre] include the skin, heart, lungs & gastrointestinal tract. )

Therefore, it is very important that patients with eosinophilia are correctly diagnosed so that the clinician can determine if they are eligible to receive this very effective targeted therapy. CEL is very rare compared to reactive eosinophilias, including those caused by parasitic infections. Other idiopathic eosinophilias are treated with corticosteroids which suppress immunity.

In my CEL powerpoint that I have presented to clinical haematologists I have a couple of slides stressing the importance of screening patients by Strongyloides serology prior to commencing corticosteroid or kinase inhibitor treatment for eosinophilia. It was not until I heard TWiP#23 that I really understood how serious strongyloidiasis is and why it is so important to avoid it.

Having no background in parasitology and very little in immunology beyond undergraduate biology, I appreciate that Dickson instructs us in the correct pronunciation of the names of the organisms and diseases that you discuss.

I hope you guys continue to keep up the good work and that you mentor a new generation of podcasters who will produce other interesting podcasts. I only wish there was a podcast of equivalent content and production quality in molecular haematology. Thanks again and I look forward to hearing more from you both.




Molecular Haematology Lab, Institute of Haematology

Royal Prince Alfred Hospital


TWiP 28 Letters

Chris writes:

Dear Dick and Vincent,

I am a doctor of pharmacy and I have listened to all of your podcasts and have read many of your book suggestions (TWIV and TWIP). I thoroughly enjoy them and hang on every word of Dick's stories. I would like to say a few things. First may I point out the obvious flaw with your name; This WEEK in Parasitology, and yet we don't have it weekly. I feel that we need more shows just to catch up with all of Dick's anecdotes. You also mentioned the island of Ceylon changing to Madagascar but in fact it is now Sri Lanka. The USGS was formed in 1879 as a bill signed by president Rutherford Hayes and I can't seem to find anything in it's history that relates to the Rockefeller Foundation. As best as I can tell Thiabendazole is not available in the US or Canada and Mebendazole oral is the current treatment for hookworm. I hope this helps. Keep them coming.


P.S. Why not have a TWIP/TWIV app for your iphone? All of the contacts, emails, shownotes and shows and access to literature can be in one place. Just a thought.

Lars writes:

Hello Vincent Racaniello and Dick Despommier,

this is my second mail to the TWIV/TWIP team. Thanks for some more background information last time about the Plasmodium falciparum/Gorilla story.

By now I have listened to all TWIP podcasts more than once and have been able to listen to nearly all the TWIV podcasts. I can understand that with your schedule does not allow to have a TWIP and TWIV podcast every week and I think in this field it is better to have less podcasts but the ones that are there go really into the subject. I think with a weekly but much shorter version a lot of the public learning benefits are reduced. So it would be great to have these long TWIP and TWIV podcasts in future as well.

I am sure you have heard about the The Carter Center and its fight against Guinea worm. It would be great to have a podcast about the Guinea worm topic since its said that this will be the second disease (the first parasitic disease) to be eradicated. And the first disease eradicated without the use of a vaccine.

Greetings from Germany


Jim writes:


What a terrific cohesive and comprehensive approach to hookworms. Such a delicate handling of the political and social issues, too. You may receive some response from listeners upset about the civil war and slavery and southern lethargy, but hopefully it will be balanced by positive reactions.

I just finished an article about a visit to Biloxi, Mississippi, in an 1865 edition of Harpers Weekly Magazine that talked about the lethargy that infects not only locals but visitors, too, referring more to the weather, I suppose, than parasites. Even in the 60's while living in California folks would refer to the much slower pace of life and speach in the South that supposedly derived from culture and weather. Interesting idea that parasite-derived group actiivity or mores might lead to social changes that perpetuate it.

Thanks for a terrific netcast. Looking forward to the rest of the story.

Smithfield, VA

David writes:

Love the show....

This delightful book has a section that is germane to your show and you might want to quote a few lines and discuss.

It details the occupation of Tongue examiner of pigs who would look for signs of parasite infection and sometimes cover it up.

Also....I have been a victim of Giardia three times as I was outdoor type of fellow who had a dog I traveled with extensively.

I got the classic symptoms each time: Painful abdomen often after eating, foul smelling stools that persisted, changes in stools consistency and color and it lasts until some form of treatment
Round one cured by Flagyl aka Metronidazole

Round two cured by Wheat Germ and I mean cured followed by Flagyl

Round three cured by Wheat Germ alone.

some research is here

here is a health page recommendation

scroll down for wheat germ



Jeannine writes:


I was a fellow graduate student at Notre Dame, graduating in 1970. I remember your discussions on parasites in the break room with pleasure. Your name keeps popping up everywhere, most recently on the TWIV netcast I receive, I suppose, as a member of the ASV. So I just wanted to say 'hello'.

Following a post-doc at the University of Chicago I had the good fortune to be hired as a grants manager by the Office of Naval Research in Chicago, where I lived at the time. I was hired at the recommendation of Morris Pollard, a friend of my soon-to-be boss. I went on to be transferred in 1982 to ONR Headquarters in Arlington, VA, where I still reside. I retired, sort of, in 2002. My 30 years in government work proved to be a delightful continuation of graduate school, as I site-visited hundreds of scientists most eager to discuss their research in areas ranging from shark behavior to fluid resuscitation of hemorrhage. I probably attended at least 200 conferences during my career as well. As a parting shot, so to speak, I fielded a battlefield hemorrage treatment used by the Marines in Iraq. During most of my government career I conducted part-time research in virology as a visiting professor at Loyola Med. School in Chicago, Uniformed Services University in Bethesda, University of Tennessee and Washington State University. My primary objective has been to understand how viruses make you sick--a field of minimal interest to virologists I must conclude following many hostile letters from journal editors. I have recently completed my work at WSU and plan to write a few more articles and then read books unrelated to virology! Three of my most recent articles are attached.

I am pleased that another student of Notre Dame has had a rewarding career.

Best wishes to you and your family,

Laura writes:

I am currently studying Zoology at university and starting a masters degree in Molecular parasitology and vector biology in september. I have recently seen a story on monsters inside me (its on the discovery channel) about a fireman who became infected with Ballamuthia an amoeba where there have only been a few cases in humans. Would you be able to tell us more about opportunistic amoeba?

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