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TWiP 70 letters

Robin writes:


While it is true that Taenia saginata tends to be benign as helminthic infestations go in humans, the same cannot be said for Taenia solium.

In both cases, ingestion of (encysted) larvae leads to enteric infestation with adult worms. In the case of Taenia saginata the eggs do not produce the encysted forms in human tissues.

Not so in the case of Taenia solium, where the eggs, even on vegetation, can be ingested by vegetarians, producing larval stages encysted in tissues, known as cysticercosis; an infestation in the brain, called neurocysticercosis, is particularly undesirable.

Segments of Taenia solium regurgitated from distal locations into the stomach can have their very numerous eggs all simultaneously activated by gastric juice, resulting in rather severe cysticercosis.

A species is an organism with a distinct group identity that can be maintaintained through multiple reproductive generations, even when hybridising across the entire group. Genetic drift limits species identity over time.

Jim writes:

Here's a link to an hour-plus podcast from EconTalk (!) by a journalist about the growing interest in exposure to pathogens to promote better immune responses. Looks like the related book has been out a year, and has only 54 reader reviews. It sounds like the interviewer, Russ Roberts, was reluctant to do the interview, but relinquished after prompts from several folk. I've not heard of the author or the book, but both may show up elsewhere, and the interview may provide enough insight to determine if the book is worth reading. Thought Dickson might be interested in listening and commenting on the concepts.


Smithfield, VA

Tim writes:

Hello Drs D and R!

I just listened to TWIP #66 where Vincent expressed his “I’m not mad, just disappointed” feelings towards the lack of emails received lately – so I’ll do my best. I would like to take the story of Schistosoma mansonii resistance to oxamniquine that you presented and appeal to Dickson’s ecologist side. It was found in the presented study that a single amino acid change inactivated the sulfotransferase activity of a Schistosoma mansonii enzyme, interfering with activation of the prodrug and conferring resistance. Assuming Schistosoma mansonii evolved the sulfotranferase enzyme for a reason, this inactivation must have come with some kind of trade-off. In the presence of the oxa drug, this trade-off is clearly beneficial. I am wondering if these resistant parasites are somehow at a disadvantage during the “normal” life cycle in the absence of drug since they are short an enzyme. Is anything known about this? Do you think that by removing the drug from the equation the parasites will eventually revert back to the active enzyme form by “fixing” the single amino acid change, thus restoring the enzyme function? Thanks for another great podcast!

- Tim

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!

Heather writes:

Dear Doctors R&D,

I'm catching up on old episodes and I very much enjoyed Dr. D's reading from his new book. I see that his vertical farm book is in audio format, will the new book also be available in audio format? Dr. D telling "stories" is one of my favorite parts of TWiP and I would love a whole book of them.

I also wanted to tell you how far-reaching your podcasts are. My husband works coordinating volunteers for a state park. A science club from a community college in Tennessee came to volunteer in the park during their spring break. My husband was very taken with how industrious and intelligent the group was. I work managing chemistry and microbiology labs for undergraduates at a state college, so I was naturally slightly suspicious of these assertions. The students and their advisor invited us to have dinner with them and I must admit I found them very engaging young people. Due to my interests and previous work with parasites and microbiology the conversation naturally turned in that direction. One of the young ladies, who couldn't have been more than 18 years old, mentioned that she absolutely LOVED all the TWiP, TWiV, and TWiM podcasts and is pursuing microbiology as a field with an interest in cyanobacteria. I thought you would enjoy hearing how your work inspires some of the youngest of the new generation of scientists. Thank you for the excellent podcast. I look forward to more "stories" and I really like having guests like Sagi on TWiP.

Peter writes:

Dear Dickson and Vincent.
I saw this paper and thought that it could be discussed on TWiP:


Interview with lead author of the study Rebecca A. Cole, PhD, Parasitologist with the US Geological Survey’s National Wildlife Health Center


Fiona writes:

Dear Vincent and worm enthusiasts. I have been listening to your podcasts for a few years now. I have personally seen and have pictures to prove that there is new species that is infecting millions. Myself included. I copied the following url and am interested to know what you think about the following? http://ropeworms.com/ This is prolly TMI but to get these things out of me I have been administering MMS enemas and every single time I do these rope worms come out of me. WTF. I love your how you are both very witty and your worm info is awesome.
HELP. Fiona

Angelica writes:

Hi, my name is Angelica. I have a question regarding Lamblia intestinalis. How long antibodies are produced in blood against lamblia if infection occurred? Can we detect infection by blood test even if it is chronic infection? I will be very grateful for answer by email
Kind regards,

Paul writes:

Hi, I recently listened to your podcast on Giardia and have a question about treatment and life cycles that I can't seem to find anywhere in research papers I have read on the subject.

I understand the 2 stage life cycle of this parasite and that antibiotics will kill it during the trophozite stage, but what about the cysts? Do they survive the antibiotics and therefore will just develop and reinfect once you've finished the treatment?

Consensus seems to be that it is a pretty difficult infection to get rid of, is this the reason why? It would seem to make sense to me to do a second round of antibiotics to kill all the Protozoa that were in the cyst stage during the first round, but I can't find any mention of this in the literature or anything on the life-span/timing of the life-cycle to know when to administer a second dose to ensure complete eradication?

I found your podcast to be very helpful in understanding this parasite and thought you might have the answer to my questions?

Many thanks,


Dave writes:

Those who get precise about ice ages say it something like this: "The last three million (I'm guessing) years have been an 'Ice Age'. During this ice age, there have been several discrete glaciations."

The height of the most recent glaciation was ca. twenty thousand years ago. It tapered off for a few thousand years before entering the (recently ) current interglacial.

Keybrd gone back.



Dave writes:

El Niño is the Boy Child (Jesus). It is the warm anomaly in the Pacific. La Niña is a girl child, named for contrast, and is a cooling period in the area of the Pacific anomaly.

I don't know squat about the identification or naming of the anomalies in the Atlantic, but I wish I did. If somebody put La Nina in the Atlantic, it's news to me.

PS The Cali drought is the worst on record, beyond past dry periods associated with Niños. It is unknown if it will resolve, repeat, or persist for decades. The decline of glaciers in the Sierra (over past decades) may interact with decreased snow pack. In any case, a dry year means a decreased snow pack, the melting of which has been the primary source of water for ag and people in Central Cali. 0% of water contracts is going to most farmers this year. It is a big big deal.

Love, dave

TWiP 69 letters

Richard writes:

Hi Vincent and Dickson,

I enjoy TWIP, and often recommend it to my students. I'm a parasitologist, primarily a Leishmaniac, but I have learnt a lot from TWIP. I find it both more educational and entertaining than Car Talk.

The discussion on TWIP67 about nitrile drugs for Chagas disease was excellent, but I wanted to point out a common misconception about the amastigote, which does in fact have a flagellum. It is a non-motile, intracellular stage, but it retains a short flagellum, which is clearly visible in electron micrographs. The same is true for the Leishmania amastigote.

The flagellum, in all stages of these trypanosomatid parasites, arises from a structure called the basal body and emerges from the cell body in a specialised region of the cell surface called the flagellar pocket. The flagellar pocket is an invagination of the surface membrane which appears to be the only site of endo-and exocytosis in trypanosomatids. While in motile forms (promastigotes, epimastigotes or trypomastigotes) the flagellum extends for some distance outside the cell and gives the cell motility, in amastigotes it does not emerge from the flagellar pocket. However, while the non-emergent flagellum cannot confer motility, this does not mean it has no function. One possibility is that the flagellum is a sensory organelle, reporting on the environment of the parasite. In fact, the trypanosomatid flagellum is structurally and evolutionarily related to organelles that are responsible for sensing in vertebrates - olfactory sensors in our nose are a good example.

We have shown that motile stages of these parasites can respond to chemical stimuli in the environment, by swimming towards or away from them. Amastigotes can't swim, but it may still be important for them to sense changes in their environment.
Maybe we could compromise amastigotes by perturbing their sensory apparatus?

One other point. You cited Plasmodium as an example of a protozoa that does not have a flagellum. In fact, the male gametocyte undergoes a striking process called exflagellation to produce motile, flagellated gametes in the mosquito gut. This is the only flagellate form in the complex plasmodium life cycle - there are more exceptions than rules in biology.

Thanks so much for doing a great job with TWIP.

All the best

Institute of Infection, Immunity and Inflammation
Glasgow Polyomics
College of Medical, Veterinary & Life Sciences
University of Glasgow

Hilary writes:

Hi there, professors Despommier and Racaniello!

I'm a final year student doctor from sunny Melbourne (today: 24 degrees Celsius, sunny, with a 15km/h southeasterly) just writing to let you know how much of an inspiration your podcasts have been! I have always had a passion for parasitology, ever since my undergraduate microbiology days - not to mention an unfortunate encounter with the 1998 Sydney giardia outbreak. The entertaining, insightful and always educational content of your TWIP podcasts has kept me inspired and engaged through many long commutes. I count you guys amongst my greatest insipirations and must confess I have named two of my favorite zebrafish after you ( along with other luminaries such as Freddie mercury and sir Ed Hilary, as well as some very inspiring pharmacology professors). Nothing more to add, just keep up the amazing work,


Pete writes:


Hi professor guys, emeritus or otherwise!

I have been listening to the trio for a couple of years now, ever since you were on Sceptics Guide. Recently, for some unknown reason, I downloaded the early TWIP episodes.

So, to the question: about 6 months ago I had a holiday in Laos: probably the best I have ever had.

I was in the country-side one day, at a village home stay, when my host invited me to a celebratory lunch at a small local school. I ate some (well cooked, and delicious pork), but eschewed the dish based on blood, which I am glad they warned me about.

After many rice wines and a few local beers, we retired to the guest of honour's home. Where we ate and drank even more. One of the dishes was produced from a banana leaf, and I had a nibble. Whereupon someone informed me it was cured pork, with spices. It was delicious. But I do distinctly remember saying "that is not good falang [foreigner] food".

So, to a couple of questions:

1. Could there have been Trichinella in the blood based dish? I have no idea how much it was cooked.

2. How many organisms could I have possibly ingested in a few grams of cured pork?

3. Could I have developed an immune response from that that will benefit me in later years?

Thanks you guys,

Josh writes:

Drs. Despommier and Racaniello.

Thank you so much for the show! I think I speak for many listeners when I say that both of you have had a profound personal affect on my life through your (mostly) weekly teaching. TWIP was the major inspiration behind my decision to leave a career in woodworking and cabinetmaking to pursue a degree in biochemistry (which is off to a great start, by the way).

Onto my picks: I've been meaning to pick this first one for a while. I came across the blog of Nathan Shields when it was feature in a brief by the New York Times. He's a math teacher who started making fun pancakes for his kids.


I thought they were hilarious, so I scrolled through and hit the weekly pick jackpot:


A TWIP listener, maybe? My other pick is The Winged Scourge, a Disney propoganda film about the spread of malaria featuring the Seven Dwarves. It was apparently created for the Coordinator of Inter-American Affairs in 1943 for a Latin-american audience. The eradication methods seem a bit dated, but it's pretty educational and very entertaining!


Thanks again, gentlemen!

John writes:

Dear Professors,

You requested more reader email, so here is more reader email.

It is below freezing outside and I have a bandage on my finger.

I am writing again to share a paper about squirrel parasites. Again, there is more than enough here to fill an episode.

Franklin's Ground Squirrel, Spermophilus franklinii, lives in the northern prairie. Unlike the gray squirrel that bit my finger by accident, these squirrels often eat meat, catching prey as large as hares and mallards.[1]

As omnivores they have more parasites than their herbivorous cousins. Here is a parasite inventory from a paper.[2] I only recognize one
genus name from TWiP. I hope a parasitologist on your show can discuss life cycle or habits of some of the others.

Apicomplexa: "Eimeria bilamellata, E. callospermophili, and E. spermophili."

The last two species names are derived from genus names of ground squirrels. Do they only infect ground squirrels?

Cestodes: "Hymenolepis citelli was the most common cestode, Choanotaenia spermophili and Taenia mustelae were found in the liver,
and larval T. taxidiensis was found in distal muscles in the rear leg."

I do not recognize the first two genera. Taenia is the genus including common human-infecting tapeworms. The Latin names translate
as "weasel tapeworm" and "badger tapeworm." I assume squirrels are among the intermediate hosts.

Trematodes: "The trematode Alaria mustelae was found in lungs of 6 S. franklinii and in the spleen of 2 individuals. Plagiorchis proximus,
also a trematode, was found in the small intestine of 1 individual."

I found a list of hosts and stages of Alaria mustelae in another paper: "A snail which harbors the sporocysts producing cercariae, a
tadpole or frog into which the cercariae penetrate and in which they become immature metacercariae or agamodistomes, here to be called
mesocercariae, a mammal (mouse, mink, or raccoon) which carries the metacercariae, and another mammal (mink or weasel) the host of the hermaphroditic adult." [3]

I would have designed a simpler life cycle, but nobody asked me.

Nematodes: "The most common mature nematode, Physaloptera spinicauda, was found in the stomachs of 13 individuals. Spirura infundibulifomis was found in the stomach and esophagus. Capillaria cf. hepatica was found in the liver, and Citellinema bifurcatum occurred in 3 individuals."

I do not recognize any of these genera from human-centric TWiP.


[1] Sowls, Lyle K. 1948. The Franklin Ground Squirrel, Citellus franklinii (Sabine), and Its Relationship to Nesting Ducks. Journal
of Mammalogy 29(2):113-137 (http://www.jstor.org/stable/1375239)

[2] Ostroff, Andrea C. and Elmer J. Finck. 2003. Mammalian Species, No. 724, Spermophilus franklinii

[3] Bosma, Nelly J. 1934. The Life History of the Trematode Alaria mustelae, Bosma, 1931. Transactions of the American Microscopical
Society 53(2):116-153 (http://www.jstor.org/stable/3222088)

Sorry, only the second is open access.

Art form photographics writes:

Thank you for your wonderful episode on parasitology #67

David writes:

Vince and Dick,

Really glad I found your TWIP podcast. I have started on episode 1 and am working my way up so I am not at the current episode yet. The information you provide has been a great help in my invertebrate zoology course. I have been able to bring a lot of additional information on the parasites we study in the course due to TWIP. Keep up the great work.


David W. Allard, PhD
Professor of Biology
Texas A&M University-Texarkana

Jim writes:


I wrote TWIV last week about experiment.com but now have reviewed the 140 projects shown and see four are related to parasites (lung fluke, mosquitoes, parasitic zombies, worm cures) in case this approach interests your listeners. If you support a project, you gain access to progress reports, but after the deadline you can't contribute to gain this access. Something for fence-sitters to keep in mind. I contributed to one project, but it may not reach its goal in which case the contribution is returned and I can use it again, elsewhere. I was a little concerned, at first, about the qualifications of the researchers and couldn't find any details, but now see the site provides background on each project. Also, the site has been around for several years, starting out with the name "microryza" which might be of interest to Prof Schachter.


Smithfield, VA

Suzanne writes:

I write too much :) The issue with people being anti-evolution has less to do with a specific religion than with the rise of fundamentalism. Plenty of Christians don't believe the Bible is factual in the same way scientific evidence is. It's just the ones who do who want to try to squeeze creationism into science.

I believe the main fight against Darwin's theory of evolution began a century or so ago as a reaction to so called social Darwinism at a time when eugenics was a somewhat popular idea. I sat through a sermon not too long ago at my parents' church by a preacher who assumed altruism had no place in evolution. I really wanted to stand up and correct him but figured my parents wouldn't forgive me. It's really frustrating down here in Texas where evolution hasn't been taught in a lot of schools for generations to the point that some people don't even understand what they're trying to keep their kids from learning. And really it's just a noisy minority causing the problem. A lot of people who go along with the creationists or just don't think about it enough to care aren't even really creationists. If you mention natural selection they don't bat an eye. They understand that the flu can mutate. It's just the word evolution that conjures thoughts of monkeys and leaving the poor to die or something.

TWiP 68 letters

Tim writes:

I listened to the latest TWIP this morning. Dickson mentioned the herbicide atrazine but thought it was a fungicide. It is actually a herbicide in the photosynthesis inhibitor class. Another bit of trivia about ag chemicals is that old chemicals like atrazine are making a big comeback in usage due to resistance problems emerging in fields. Too many farmers were spraying nothing but glyphosate on fields due to that being the first GM herbicide resistance trait and now weeds have caught up.

On the subject of monarchs having a bad taste so birds leave them alone you seemed dubious of bird memory and the difference one birds experience meant for monarchs on the whole. I think the reason it works out well as defense for monarchs is that the generation interval for insects is much quicker than birds and some birds live quite long lives and would most likely experience the taste of monarch early in life and not forget because they are not only bad tasting but I believe poisonous due to milkweed that they feed on as larvae. I've tasted milkweed and if monarchs taste like that I can see why birds would avoid them.

I found it interesting you have the view of humans as separate from the general ecology of the earth. Full disclosure: I wrote a paper comparing humans to weeds and pathogenic bacteria in college but have since changed my mind on that subject. I've been working on changing people's minds about that on social media because it seems once we view ourselves as separate from the rest of the world we live in it seems to give people license to do things that make no sense from an ecological sustainability standpoint. To put another way stealing a term from economics, theres a risk of moral hazard when one divorces themselves from their surroundings. I'm not saying this to criticize your thoughts on it and I'm sure you have a much more nuanced full view of the subject. Just some thoughts of mine on that topic.

Scott writes:

Hi Vincent and Dickson!

I just finished with ep64 and wanted to drop you guys a note to hopefully fill up your inbox since you only had 4 emails. I am a Hydrogeologist working for an environmental consulting company in Cincinnati OH, which is currently overcast 24F, 79% humidity, winds at 8 mph out of the S/SE. Though hydrogeology has almost nothing to do with biology i love listening to TWIP, TWIV and TWIM while doing my mundane data manipulation and am a lover of anything science. The furthest we tend to dive into biology would be the injection into groundwater of Dehalococcoides for the sequential reductive dechlorination through the daughter products cis-dichloroethene and vinyl chloride to ethene (guess its a little more relevant to TWiM than TWiP). Please keep going off topic! I love hearing the banter back and forth between you guys! Anyway i love the podcast and look forward to every episode. Hopefully, there are many more to come!

John writes:

Hello TWIP!
I just finished listening to episode #67 in which Vincent asks, "Why was a priest doing experiments?"

I'm parasitologist who will be ordained a priest this June and will teach biology at Creighton University. I earned my PhD in evolutionary biology from OSU before entering the Society of Jesus (AKA Jesuits) in 2003. After ten years of studying philosophy and theology, teaching biology and doing research, I could probably devote an entire TWIP podcast to the topics of priests "doing experiments" as well as parasitology and religion, but let me briefly state the following:

Christianity helped develop science because it assumes (unlike some Eastern philosophies) that the world is real and not an illusion.

Christianity also assumes that the world of creation remains distinct from the world of the supernatural Divine. So unlike many pagan religions that believe in nature gods, Christians assume that Nature follows laws that can be studied.

Finally, Christians believe that God created the world good. Thus, Creation reflects the Creator and so learning about Nature teaches us something about God. In other words, investigating the world of nature and is worth doing.

You (and your listeners) can check out some of my on-line articles on this and related topics at The Jesuit Post, https://thejesuitpost.org/author/jsheasj/

Thanks for the great podcasts and keep up the good work. I plan to use some of these podcasts when teaching parasitology.


Alex writes:

Hi Both Vincent and Dick,

Love the podcasts, in every way but for one thing. Vincent is very clear to hear, Dick fades in an out - meaning a volume can never be perfectly set. I thought I'd illustrate as below ;)


Please fix this so I can continue to enjoy stories from the world of Parasitism....



Christophe writes:

Hi Vincent,

Just thought i would pass on this link incase you had not heard about it already.
I have not watched this documentary series yet but i think i will try and track it down. I heard about it on the BBC Science hour podcast today and would like to hear Dickson and your thoughts on it.

ps. I love the TWip/TwiV/TWiM podcasts - i am only a high school graduate and self taught web designer but find all the TWiP/V/M fascinating - keep up the great work.

"Swallowing three cysts which are twitching with tapeworm larvae sounds like the stuff of nightmares.
But for the past two months, BBC presenter Michael Mosley has been taking part in a toe-curling experiment, allowing three worms to live and grow in his gut.

As part of BBC Four’s natural world season Dr Mosley infested himself with some of the world’s most prevalent parasites including leeches, lice and mosquitoes."



Robin writes:


Marianne writes:

Dear Drs. Racaniello and Despommier;

I do enjoy your podcast, as I do all the TWiX. I've written to TWiV previously, but this is my first opportunity to email TWiP. Your request for emails in the last episode sealed the deal.

I couple of episodes ago you bemoaned the lack of ecological based parasitism research. I smiled to myself because my first undergraduate research experience was in this field. I was a summer student on a field project trapping the prey species of the pine marten of Newfoundland (http://en.wikipedia.org/wiki/Newfoundland_pine_marten) and studying their parasites. I learned a lot that summer, including that I was not cut out for field work. Two months in a cabin on the east coast of Newfoundland was enough for me. I happily started my career in the lab studying immunology, virology, cancer and now vaccines.

More recently, I've been thinking more about parasites, due to my increased interaction with rescued cats. After losing two older cats, we decided to adopt a kitten from a local rescue that helps trap, spay/neuter and then adopt or release feral cats. Before we could adopt our chosen kitty, he had to clear a pretty significant coccidia infection. Of course, through my renewed interest in the subject through listening to TWiP, I was interested in what type of infection our little Felix had, but learned that most vets only look for the presences of oocytes in the stool and since the treatment is basically the same for all coccidia, they don't differentiate. We then fostered a stray mother cat who gave birth to 5 kittens about 12 hours after we brought her inside. Those kitties were happy and healthy until 2 of them went to a local pet store who helped out with adoptions. They both became quite ill with coccidia, while the two we kept in our house remained healthy. I suspect that the well meaning pet store was unwittingly spreading some of these pesky parasites to young kittens through previous inhabitants. Luckily, after several antibiotic courses, all are happy and healthy in their adoptive homes.

On a related note, just last week I saw this story, regarding Toxoplasma gondii cropping up in a beluga whale in the Beaufort Sea.


The story also mentions that Sarcocystis pinnipedi may be responsible for a large die off of grey seals off Cape Breton in 2012. They are suggesting that the parasites are being released by ice thaw. What do you think?

Oh as for the obligatory weather report, its a balmy 4oC here in Halifax, Nova Scotia, Canada. However we are expecting a mix of rain, freezing rain and snow overnight and they are anticipating the temperature to dip to -7oC (wind chill of -14oC) by morning! Still a bit of winter left here in Canada!


Oskar writes:

Hello TWiPers!

I'm studying the third and final year of the Biomedical scientist programme at the Gothenburg university, Sweden. I've just spent my work studies at a medical parasitology lab where I introduced the "old timers" to TWiP. Naturally they became hooked immidiately. Listening to you guys really made it easy and fun to learn the theoretical part of working in a parasitology lab, so I just wanted to say thank you!


PS. The temperature here is a chilly 3 degrees C with rain.

TWiP 67 letters

CN writes:

Greetings Profs,

After having listened to your discussions on Plasmodium (TWiP 64), I explored papers on treatment options that are actually available. After having read some papers, I realized that one of the main roadblocks are the hypnozoites. If I have got it right, apart from the fact that it is involved in reactivation of infection, it's dormant nature allows it to evade the antibiotics. My first thought was "Can the hypnozoites activate the immune system, and can it be a vaccine target." Your thoughts on this would be very helpful.

In connection with the search, I found a paper in nature, cited below which i find is a worthwhile discussion topic on malaria.

Host-cell sensors for Plasmodium activate innate immunity against liver-stage infection

Thank you for all the time spent on educating us

TWiX fan

Kim writes:

Hi Vincent and Dickson,

I just want to let you know that I would very much like to attend a Coursera course on ecology lead by Dickson! I really enjoy episodes such as TWiP 65, where ecology, parasitism and various infectious diseases are intertwined and would love to learn more about the ecological aspects. However, as I study purely infectionbiology I don't have the mental strength to start studying ecology on my free time, as I feel it is hard to know from where to start. Here, I think, a web-based course would be a great way for me to learn more and would keep my interests up with Dickson spicing up the potential future lectures with references to both parasitism and vertical farming! I really hope this materializes.

best regards,
Uppsala, Sweden
-7 Celsius

TWiP 66 letters


Andre writes:

Dear Vincent,

To my great delight, I just discovered your podcasts twiv, twim and twip.

The first twip I heard, about Strongyloides stercoralis, although informative and interesting, seemed to have several inaccuracies. I was not able to find the email from Dick Despommier, and therefore I am writing to you.

Dick said that Strongyloides, when it enters into the host, becomes a protrandrous hermaphrodite adult. Actually this is not true. The parasitic stage of Strongyloides is a female that reproduces by parthenogenesis.

He also said that a protrandrous nematode is first male and then becomes female, so that it can self-fertilize. Actually, as I said, Strongyloides is not a hermaphrodite and therefore it cannot be protrandrous. The only nematode parasites that I know to be a protrandrous hermaphrodites are worms of the genus Rhabdias, which usually infect amphibians and reptiles.

C. elegans is a good example for a protrandrous hermaphrodite nematode. The term protrandrous means that the organism first produces male gametes and later shifts to the production of female gametes. The only difference between C. elegans hermaphrodites and females of closely related species is the ability of the hermaphrodites to produce a limited amount of sperm just before becoming adult. These "female-bodied C. elegans with sperm" are not considered males because they cannot transfer their sperm to other individuals. The sperm of these worms are stored in the spermatheca and used for self-fertilizing the oocytes produced during adulthood. C. elegans males are morphologically very different from hermaphrodites, produce only sperm, and have specialized mating structures used to find and fertilize the hermaphrodites.

My field of specialization is actually evolution of modes of reproduction of nematodes. I study a free-living nematode that can produce males, females and hermaphrodites. In many ways, it resembles parasitic nematodes, because larvae that sense the lack of food become "dauers", which is the dispersive stage of free-living nematodes. Dauers are the equivalent larval stage as the infective stage in parasites. Dauers can resist to harsh environmental conditions, crawl in arthropods and be transported to new places. For the species of nematode that I study, the dauers develop into self-reproducing adults once they encounter a habitat with food. This makes sense, because they can then colonize new environments without the need of a mating partner. The larvae that grow in an environment with enough food develop into females and males.

In case you are interested in reading more about it, check the paper Chaudhuri et al in the website http://wweb.uta.edu/faculty/apires/publications.html.




Noah writes:

Dear Prof. Racaniello,
I have been a huge Twiv, Twip, and twim listener for about a year, I love the show.. Twip the most.. I love listening to you and that Deponia guy.. you guys make me laugh but more importantly I have attained a great deal of knowledge from the podcasts can't help but tell my collieges about the amazing things you two talk about from Toxoplasmosis or several parasite epidemics.

I am writing you b/c tommorow night I am going to post you as The American of the Day in my facebook group because of your great
accomplishments and devotion to educate the public about science. If you get time on the 10/23/13 search the Facebook group American of the Day and you will see your photo and bio added to our list of great Americans... it's a small honor..lol and I have a feeling you won't have time but thankyou so much for the podcasts there is nothing like it out there, if it wasn't for you guys I would have to read these journals all by myself and that gets both confusing and lonely. Thanks again-

Noah RN --- Lebanon PA


Devin writes:

Hey guys:

I am from the San Francisco Bay Area and I wanted to extend my appreciation for the show! I listen to both TWIP and TWIV and would be disappointed if you didn't produce the show into the future. The conversations require the listener to pay attention a bit more than the average podcast, I believe. This may, in part, be due to the use of terminology that I often find myself looking up during the podcast or later when I've heard it more than once on the show. As a result I feel like I'm in on a conversation that I normally wouldn't be and this inspires me to try even harder to understand the concepts.

One more thing: While out at a bar the other day I had randomly met someone who had his Phd in the biosciences (I don't remember specifics -- I studied Earth & Planetary Science) and I had mentioned that I listen to TWIV and TWIP and he knew who Vincent was, which led to him to add your podcast to his iTunes at the bar.

Keep up the good work. I looked for your podcast page on Facebook and didn't find it -- did I miss something? If not, you should create one. Its a good way to promote your show.

Remember for every person that writes an email there's probably a bunch more that want to but just don't get to it.

Thanks guys!

John writes:

Dear Professors,

It is 1 degree outside my window as I write three comments about TWiP 63.

1. You wondered how Plasmodium DNA ended up in ape feces. I learned biology when life was made of cells rather than molecules, so I think of the body not as a big amino acid sequence but rather as a series of tubes. With this old-fashioned background, I thought the path dismissed by Dickson was obvious.

The liver recycles old red blood cells to recover iron. It dumps the rest of the cell contents into the intestines. If it recycles an
infected red blood cell, the waste may include Plasmodium DNA.

2. How do merozoites know when to stop producing copies of themselves and make gametocytes instead? I can imagine three mechanisms:

(a) random chance

(b) a molecular clock like telomeres, which allow cells to count generations

(c) environmental cues related to overpopulation, such as oxygen concentration

If you give me a grant and a lab I would be happy to watch a team of grad students investigate.

3. Do I understand correctly that a deadly infection can result from just one Plasmodium sporozoite cell lodging in the liver? (15 minutes in)

Scott writes:


As a resident of Latin America, it was with some interest that I noted this story in Science Daily. I would appreciate your comments:


As I have, on several occasions, discovered the insect vector in my living space, this parasite is of some concern to me.

I would like to know if the parasite is a threat to the two cats who live in the house with me, or my dog who lives in my yard. I have not been able to find any information on the veterinary implications of this parasite.

Regards and thanks for a great podcast,
Cartago, Costa Rica

Neva writes:

Hi Dickson and Vincent,

I guess the tri-caster medical device is almost here. If this is viable, very cool! What's next?

Rice University researchers have developed a noninvasive technology that accurately detects low levels of malaria infection through the skin in seconds with a laser scanner. The "vapor nanobubble" technology requires no dyes or diagnostic chemicals, and there is no need to draw blood.


Never miss your great podcasts!

Neva from Buda

J writes:

I got recommended your podcast from a colleague. I just wanted to know what song by RJ do you play in your intro? I emailed him and he thought it was "Guitar Sounds" but it's not quite right. Do you mind posting the title somewhere ?



TWiP 65 letters


Perry writes:

Greetings Vincent and Dick,

Hooray for finally mentioning G. pulchrum in episode 62, my most favorite parasite and one worthy of further discussion. As a diagnostic veterinary pathologist, I encounter this spirurid in approximately one third of the dairy cows I autopsy. It is much more common than you surmised. I make a big deal out of its frequent occurrence, not because of its pathogenicity (essentially none), but because it is a paradigm organism. It insinuates itself in the esophageal mucosa, wriggling back and forth in the epithelial layer as it advances (that is why it is called the 'ribbon candy' worm) thereby maintaining its hold and evading immune surveillance. The paradigm is that it is a beautiful example of an innocuous host parasite realtionship and the fact that most diagnosticians readily overlook it. Students of pathology all too often 'look' but fail to 'observe'. A south african veterinary pathologist told me that Gongylonemiasis occurs in the mouth of poor ruaral children, presumably due to the ease with which they ingest an infected beetle intermediate. It has been some time since I last reviewed the literature, but I believe the nematode is world-wide and capable of parasitizing innumerable mammalian species. I enjoy your program, biomedical science musings and digressions. Keep up the good work.

Curt writes:

Hello, Vincent and Dickson!

First, let me start with some praise. I thoroughly enjoy all of the TWiXcasts, but I appreciate TWiP in particular for its one-on-one format and the wealth of clinical experience and case studies that Dickson brings to bear in every episode. I finished Vincent's outstanding Coursera course recently- looking forward to part two, on that note- and it set me to wondering when Dickson is planning on doing a Coursera class on parasitism.

I'm writing because I'm curious if the military has ever tried to weaponize helminths. I'm aware of past efforts by the military to weaponize practically everything, especially in the realm of pathogens- running the spectrum from from Y. Pestis and Smallpox to Coccidiodes fungi. I wouldn't imagine that an attempt to weaponize helminths would be very successful, though, and attempts to imagine such a program are baffling at best.

Keep up the outstanding work, gentlemen, and thanks again for your time and effort.

Cathy writes:

Dear Professors Despommier and Racaniello,

I wanted to write to you to thank you for taking the time to do these fantastic podcasts. TWiP was recommended to me by a former colleague with whom I worked in Professor Paul Duprex's virology lab at Queen's University Belfast, before he moved to Boston University. Since working with Prof. Duprex I got my PhD in molecular parasitology, and now I work in St. George's University of London on the nanomal project (the link for which I've included) which you may find interesting:


We're developing a hand-held point-of-care diagnostic device for malaria that can give a diagnosis in under 20 minutes, but the really exciting part is it will be able to speciate and detect drug resistance-conferring mutations so an informed treatment choice can be made.

Being a malariologist I particularly enjoyed TWiP#35 with David Fidock, and my interest was especially piqued when the contentious subject of artemisinins' mode of action was brought up. I thought this was about to be explored but alas, it was not. Of course, there are not enough hours in the day to debate that subject. If you are interested, however, we recently published an opinion article in Trends in Pharmacological Sciences on the subject which I have attached. Professor Fidock mentioned the haem hypothesis, but I am more in favour of the SERCA hypothesis, which postulates that artemisinins specifically inhibit the sarco/endoplasmic reticulum calcium ATPase (SERCA) of the plasmodia parasites. People may feel that knowing the mode of action of a drug is purely academic, but as you are well aware drug resistance is a serious problem for controlling malaria, and knowing how a drug works can help identify any mutations responsible and hopefully overcome resistance.

Thank you again for all the time and effort you put in to these podcasts. I have thoroughly enjoyed learning about different parasites, not to mention american history and piscatorial pursuits, and constantly recommend TWiP to my fellow parasitologists. I plan to start listening to TWiV but it's been quite a while since my virology days. I hope I can keep up!

Yours sincerely,

Lisa writes:

Hello to Vincent and Dickson, TWIP

First may I say, that it's great you are putting such in-depth content out in the public domain, People such as yourselves, with vast amounts of knowledge and years of experiences giving your knowledge freely is fantastic and I apualde your for it. And not to mention your presentation style is superb and funny.

The Microbe world fascinating to me, I bought a decent Amscope microscope last year, I have always wanted one but after getting into TWIV /TWIP /TWIM, I finally bought one. I've used it many times looking at pond life/mouth bactria/poo from my dog "Bella" who is female and very coprophagic towards next doors cat :( I basically put anything i dare put on a slide to the horror of my fella, Our daughter loves it too, with all the "yucks" and "Errrs".

Anyway to cut a long story short, Not that I have been waiting for a decent infection but last week I contracted what I thought could only be described as food poisoning, after 24 hours of (diarrhea/vomiting/burping/feeling bloated/major cramps) I thought the best thing to to is check a stool sample, naturally..... As I had never been so ill
My thoughts were that it could be Food poisoning but i wasn't convinced, after going back and hearing TWIP #16 Giardia Lamblia it rang a few bells.

On investigation all could see no Giardia Cysts but I could see many uniform tubes with constrictions at the end, Being uniform and tube like my first thought was Dog Tapeworms? Or could it just simply be something I ate as it looks like plant matter, I'm sure if it is parasite debris then Dickson can identify it in a jiffy.

After searching Google to no avail, I feel I may need a copy of "People, Parasites, and Plowshares" for future use?

Here are a few pictures of the tube like forms? Seeing as though Dickson has seen many stool samples in his time, I thought it to be great opportunity to write in and express my gratitude for all the great work you are doing plus a token of that appreciation.

Keep up the good work and thank you so much for bringing science to the rabble.


TWiP 64 letters

Richard writes:

Good morning, day, evening (depending on your time of day). Esteemed professors!

Firstly my weather report, for Weston super Mare, uk.

It is currently 3 centigrade (feels like 2C), dew point 4C, humidity 78%, there has been 1mm of rain/sleet, with a 50% chance of further precipitation, and the wind is 16 km/h from the WNW. It is currently dark so no visibility, but this is estimated as 2 miles, as it is cloudy with light rain.

The predicted high for the day (2PM) 9C, with humidity of 68%, and dew point of 4C, with predicted wind of 21km/h, a 40% chance of precipitation (rain or sleet), to is expected to be partly sunny, with good visibility >10 miles predicted.

I hope the weather report meets your increasingly exacting requirements :)

My question is actually fairly simple; Giardia lamblia and a number of other eukaryotes lack mitochondria. Most of them appear to be anaerobic, and I can see the point that the mitochondria and electron transport mechanism might well be selected against.

However, no where can I find if it is clear that mitochondria where selected against, and lost. Or if these bugs are a branch, that where started before eukaryotes adopted mitochondria.

I'm not scientist, but simply an interested party. I actually work as an engineer, on sewage treatment plants. So I do get to see a lot of bacteria, since they do all the work, treating the sewage. Given plenty of oxygen, and the correct nutrients, they do a fine job of this, and then happily settle out, leaving clean enough water that it can be returned to the environment (or with minimal treatment, and filtration, to the drinking water supply, as is becoming more popular).

However it is my personal theory, that apoptosis in eukariotic cells derives from the incorporation of a once parasitic bacterium. Such a parasite requiring a method to kill the host cell, in order to proliferate into the medium, to infect other cells. I hypothesise that this was co-opted by eukaryotes, in order to allow for apoptosis (or programmed cell death).

Knowing if apoptosis odours in eukaryotes, that lack mitochondria, and if they are a pre mitochondria branch, would answer my question. However I have been unable to find the required information.

I wonder if you can point me in the right direction, and also thought the subject might lead to an interesting conversation on the podcast.

Many thanks for your ongoing series of podcasts.

I have emailed this to both TWIP, and TWIM. I suspect it is better suited to TWIM, but my research has been on parasites, since these seem better studied, so have included TWIP.

Thanks in advance for any insights you may be able to provide, or simply interesting conversation.



Dave writes:


Hiya! Entering mid-dialogue, so sorry for out-of-touch points hereafter. Trivial anyhow.

As to fuel powered machines and discovery of oil deposits (identified as refineable fuel, since deposits were mined for minor purposes in antiquity), um, as I recall, Henry Ford intended his internal combustion engines to run on ethanol at the outset. I have no idea how far earlier the engine-makers planned ethanol, but.... Anyway, Rockefeller et al came along shortly to amend all that. Besides, obviously y'all were perfectly accurate about all that machinery thing and slavery.

More to the point of parasitology, another trivial emendation may be that the first hookworms didn't necessarily enter N. America on African feet after 1600. West Africans had been transported to Caribbean islands for labor by mid 1500s. They may have inoculated soil there with hookworms, which may have been picked up by sojourning barefoot non-Africans, and transported to N. America first by those people after 1600. Maybe. (If I haven't misremembered the true mid-century. Got it from "Diary of an Irish Slave Girl," a novel about a kidnapped child who was taken to a British sugar plantation and ended up marrying an Ashanti man. Therefore my historiography may be off. But I do think those island plantations were started up in the 1550s or so -- and, from other sources, European population growth began to explode, apparently correlated with sudden availability of enough extra calories to delay starvation, preserving more children, etc.)

So anyway. Hope It's not wasted your time. Entertained me, but not enough to edit it down.


Benedict writes:

I love your show, I hear it on the way to work and home again each day. Would love to hear during work as well but my coworkers would complain I guess. I have a question regarding the theme song at the beginning of twip63. What song/remix is that?
Kind regards and all the best!

John writes:

Dear Professors,

I have listened to you discuss parasitic diseases in mice, fish, mosquitoes, ladybugs, cats, and even humans, and feel you have paid relatively little attention to squirrels. A recent paper in BMC Veterinary Research could help cure that deficiency.


British veterinarians studied 163 dead red squirrels. The squirrels were mostly found near houses and roads, and half of them were killed by cars or pets.

The dead squirrels were examined to determine cause of death and inventory parasites and other disease causing agents.

I spotted at least four eukaryotic parasites -- three Apicomplexa and a nematode -- only one of which I recall hearing about on TWiP.

Toxoplasmosis was blamed for one sixth of squirrel deaths on the Isle of Wight. It was considered a direct cause of death rather than a contributing factor like when it prevents mice from avoiding cats.

Hepatozoon infections were common in lungs and heart muscles, and Eimeria in gut contents, but neither seemed to be a primary cause of poor health.

The last parasite is so obscure it does not even have a Wikipedia page. It is related to pinworm, which you have discussed. Quoting the paper:

"Nematodes were sometimes observed during gross and histological examination of intestine. Morphologically they resembled pin worms (Enterobius sp.) but, apart from one case where they were identified as Rodentoxyuris sciuri, none were submitted for species identification. Typically there was no apparent associated pathology but one juvenile with a heavy nematode infection died due to an intestinal intussusception. However, in a second case of intussusception involving an adult there was no significant worm burden and the aetiology was obscure."

The squirrels also had viruses and bacteria, in case you want to have a squirrel week across all three "this week in" podcasts, end ectoparasites and fungus if you want to expand to five podcasts.

Suzanne writes: 

I couldn't remember being tested for Toxoplasmosis with any of my pregnancies while listening to your most recent podcast so I looked it up. According to MayoClinic.com most women aren't tested automatically these days. I didn't find any specific recommendations anywhere, though, so maybe it's something that depends on the doctor.
I do remember tests for AIDS and Hepatitis. Especially since with the most recent one the lab gave me someone else's positive Hepatitis result and missed my anemia :p
These days they just tell every pregnant woman to avoid under cooked meats and litter boxes.


PS It's cold down here in central Texas! I can translate easily from Fahrenheit to Celsius because it's been hovering just above 32F/0C for the last few days. We may even get what passes for snow around here... a few flakes mixed with the rain. I expect by next week it'll be shorts weather again, though.

Maybe that would make more sense as While listening to your most recent podcast, I couldn't remember being tested for Toxoplasmosis during any of my pregnancies...

Sam writes:

Hello TWIP! I write to you again from Tucson, where we are having quite a warm December. Today was a beautiful day, 75F, with sunshine and scattered clouds.

I was listening to Dickson explain the difference between Plasmodium vivax and P. falciparum on a historical TWIP whose number I don't recall, when later that day what should I read but the links below, reporting P. vivax infections in Duffy negative humans. The articles report that duplication of the Duffy binding genes seems to enable infection even without the Duffy receptor (per http://www.eurekalert.org/pub_releases/2013-11/cwru-vmm111413.php another report is expected 12/5, in just a few days).

It seems odd to me that duplicating this gene would have this effect - after all, wouldn't this be like having multiple keys to a door with no lock? It must be using a receptor of some kind, right? If it's not using Duffy, then it must be using another one - is Duffy part of a family of related receptors, or has the gene duplication produced a match for some other receptor altogether? I also wonder how this mutated parasite will fare in ordinary Duffy positive humans. I'd love it if you all could revisit this topic on the show.

On an unrelated note, I must say that the presentation of this open access paper (link below) is really great. No truncated article, clear navigation and organization, and it even includes a twitter interface. Three cheers for PLOS!

Thanks again, Victor and Dickson, for the podcast - Sam









TWiP 63 letters


Helen writes:


As a new listener, I don't know whether you've later corrected this or not, but you got several important things wrong in describing the antebellum South in the first episode on Hookworm. They did have machines, and they made good use of them. What they did not have was factories, because they were making plenty of money farming on the backs of unpaid slaves.

The first Africans arrived in Jamestown in the early 1600's, not long after the European settlers arrived. (You said the 1830's.) The cotton gin was invented in 1793. It made cotton farming *far* more profitable, greatly increasing the slave trade until the international slave trade was banned in 1808. Internal slave trading continued, and the slave population continued to grow dramatically because the slave women were forced to have as many children as possible. Children born to female slaves became slaves, whether their fathers were slave or free. "Due to its inadvertent effect on American slavery, the invention of the cotton gin is frequently cited as one of the ultimate causes of the Civil War." The American South provided two thirds of the world supply of cotton by the start of the Civil War.


So hookworm must have been endemic long before the Civil War. There wasn't much more introduction after 1808. However, substantial parts of the South were still under Native American control, and thus perhaps free of hookworm, until the Trail of Tears forced relocation in 1830, and the land was sold for agricultural use.


Also, there was slavery in the north, though certainly not as much. There were still slaves in New Hampshire and New Jersey until the emancipation proclamation in 1865. Other northern states had banned it earlier. Southerners brought their slaves with them when they came north. You can see George Washington's slave quarters in Philadelphia across the street from the Liberty Bell. Slaves who got their freedom in various ways migrated north.


The American history mistakes start about 10 minutes into the episode.

Thanks for a great podcast!

Anna writes:

Hi Dickson and Vincent,

I recently started listening to TWIP and TWIV, and I love them both! It's been hard trying to catch up and listen to them all (needless to say, I'm not even close).

I'm wondering if you guys know of any neotropical parasites (or viruses for that matter, I just thought parasites might be more likely) that live some part of their lives in both snails and bats.

I'd appreciate any thoughts you may have :)

Thanks so much!!

Neva writes:

Hi TWIP Twosome,


A story about how the US planned to weaponize bats during WWII.
Ed Yong tweeted this. What a batty tale.
You guys are da bomb,

Neva in Buda TX

Shane writes:

Hi Dickson and Vincent,

I listen to every episode of Twiv, Twip and Twim and often follow along with Wikipedia to help me understand terms i am not familiar with and also check out most of your picks.

I also watch Monsters Inside Me with my 12 year old daughters. I am up to Season 2, Episode 3 and was just wondering if you (Dickson) were still advising on this show?

In this episode a man got very ill and his spleen swelled to 5 times it's normal size, after a battery of tests finally a test for leishmaniasis came back positive, would this be visceral leishmaniasis?

I didn't pick this as I would expect some sort of skin lesion. Also they treated him with anti-biotics and he recovered, I am only a computer programmer but I would not think anti biotics would be the recommended treatment for leishmaniasis

Thanks for the awesome work of the entire TWIx crew puts into producing these podcasts

Shane from Australia
P.S. It's a balmy 20 degrees C at 11pm

Bernadeta writes:

Dear TwiP'ers,

I recently found out that when my mum was pregnant with me she was tested for toxoplasmosis, and it turned out that she had very high titres of IgG against toxoplasma. However, she took no treatment, and had absolutely no symptoms of disease. I turned out ok, I think, so it doesn't seem to have done anything bad. So I was wondering, are all pregnant women tested for toxoplasmosis and if so why? My mum was pregnant in 1992 and it was in Lithuania, so I wouldn't be surprised if things have changed from that time or have always been different in US. Does carriage of toxoplasma pose any threats for pregnant women and their foetuses? Also, Is it likely that I now have antibodies against toxoplasma because my mother was infected while pregnant?

Best wishes,



TWiP 62 letters


Blaine writes:

Hi Twippies,

I saw today in the New York Times that a hookworm vaccine will be tested in Gabon. I found this very intriguing as your discussions of parasitic worms have rarely included the possibility of vaccines. Can you please comment on this. Are there certain biological challenges to making vaccines against worms? Or is there simply no money in making these vaccines since they are not needed in rich developed countries? It seems to me that it would be much simpler (and cheaper) to just educate people on how to avoid most of these parasites than to produce a vaccine. Simple practises, such as digging your outhouse six feet deep, or curing your feces before using it as fertilizer would eliminate many of these parasites. I would love to hear your comments on this matter.

Fort McMurray, AB, Canada

PS. The Link to the NYTimes article is here:

John writes:

In a local newspaper:

"Zoonotic research taking Framingham man to Peru"


Robin writes:

Parasites may be sneakier than we surmise:

Transformation of malaria parasites by the spontaneous uptake and expression of DNA from human erythrocytes


We may have more baggage than we know:

Invasive Genes: Humans incorporate DNA from parasite


Jim writes:


A pdf made from a local newspaper article is attached concerning a biologist who found a nematode embedded in his mouth. The article is available online from The Daily Press, but you have to subscribe to read it. I assume it's ok to make the pdf available to your listeners, if you desire.


Smithfield, VA

Mike writes:

Hi Guys,

I know that insect larvae are much bigger than your usual fortey, but I find the bot-fly life-cycle fascinating. I don't think it can be defined as an ecto-parasite, as it actually develops inside the skin, not on top of it. Care to discuss it a little? I would love to hear your take Dick.


Jim writes:

Here's another one, and I quote,

"A scientific discovery falls out of this epidemiologist's nose
Tuesday, October 15, 2013 1:28 PM

Imagine finding a tick up your nose — and being happy about it.

Epidemiologist Tony Goldberg was working with primates in Kibale National Park in Uganda. But, when he returned to his lab at the University of Wisconsin, he began feeling some pain in his nose.

That's when Goldberg discovered a tick inside his right nostril. Definitely not something that's cause for celebration, usually.

"I made use of a mirror, a flashlight and some forceps to remove it," Goldberg said. "I was fortunate to grasp it firmly by the mouth parts and I got the tick in its entirety out of my nose, sparing the surrounding nose hairs."

But, being a man of science, after he removed the tick, Goldberg analyzed its DNA.

The nostril tick belonged to the genus Amblyomma. But it didn't match any known bugs in various databases.

That means it could be a tick that hasn't been genetically characterized yet — or a completely new species.

"We're still learning the pathways that diseases can use to move between wildlife and people. And this nose tick is a slightly amusing and particularly gross example of how diseases move in nature," Goldberg said.

Smithfield, VA

Raihan writes:

Dear esteemed and honoured Professors,

I'm writing in response to TWIP 57 where in the intro Prof Despommier mentioned that he had just returned from Singapore. The question was asked if water is spins clockwise or anticlockwise down the toilet since Singapore lies 1 degree north of the equator and I am pleased to announce, as a Singaporean, that water spins anticlockwise in Singapore.
I just did this experiment in my lab sink and toilet. Finally, I've produced some research worth noting.

Apparently the fact that it does not spin clockwise here has been noted before (check out the last paragraph). But i'm still searching as to why this is so. I do know that the coriolis effect is strongest away form the poles and that it does not have much of an effect on small sinks, ie, you can easily push water in the opposite direction and the water would willingly change its course, but none of these explains why the water rotates anti clockwise.

A student in virology, not so much in the coriolis effect.

Jim writes:

Just got this link to an Australian Video via Digg in case it's of interest.

Smithfield, VA


TWiP 61 letters

Ian writes:

Dear TWiPers,

I just finished listening to the superb Twip #56 and I am thrilled because I am a huge fish nerd. In fact I spent much of my youth catching and chasing fish on the same lovely New Jersey barrier island mentioned in that episode. In my enthusiasm, I wanted to write in with a few thoughts.

The first is nit-picking, but the gar discussed around the 13:00 minute mark is more likely a specimen of Atlantic Needlefish, Strongylura marina, than a member of the “true gar” family Lepisosteidae. Like members of Lepisosteidae, needlefish have elongated, tubular body plans, and are sometimes referred to in common usage as gar. Needlefish often spend time at the surface, but do not gulp air in the cool way fish such as the Florida Gar do. This mix-up might explain Dickson’s surprise at hearing about gar so far north.

As an aside, I might add that I have heard that --if presented with a fly small enough to fit in their diminutive mouth--needlefish make for wonderful sport fish. I myself have caught a needlefish on Barnegat Bay, although not in the manner one might think. I spend my free time sailing a catamaran around the bay. On one windy day I had the rude surprise of a large needlefish jumping out of the water and landing in my boat! My crew and I were as shocked as the fish! It was a memorable experience; particularly because, like many angry fish, the needlefish displayed a heightened, more vibrant coloration than I usually get to see. The fish was promptly returned to the water and I was left relieved that I hadn’t been added to the list of people who have been impaled by needlefish (http://the.honoluluadvertiser.com/article/2005/Jul/30/ln/507300340.html).

In the spirit of “This Week in Fish” I would like to suggest “The Founding Fish” by John McPhee as a pick of the week. The book is a wonderful examination of everything Shad, written by a wonderfully gifted writer. I’m picking it because Twip #56 included a question about shad’s tastiness. As the book points out, the species name of the American Shad, Alosa sapidissima translates to “most delicious”. I am salivating just thinking about a meal of baked shad, perhaps with a side of Atlantic blue crab, whose species name also derives from sapidus the Latin word for savory.

As always, much thanks for all the work that goes into the TWiX podcasts. I am about to leave on a road trip across the US in order to start grad school for biology, and I am looking forward to having tales of viruses, microbes, and parasites keep me company along the way.



Howell writes:

Dear Professors,

First of all, thank you for producing such fascinating podcasts! I got interested in parasites when I read Carl Zimmer's book - I've just discovered TWiP, through Professor Racaniello's course on Coursera, and I intend to try and listen to them all!

I've just got one question so far: is the cover photo for the page of Trichinella?


Andy writes:

Dr. Despommier,

I enjoy your show although parasites are not related in any way to what I do for a living.

You have mentioned the death of the S. A. Andrée's Arctic Balloon Expedition of 1897 crew in a couple of TWIPs including in episode 60 and how they probably died of Trichinosis from eating polar bear.


I was fascinated by this and repeated it a couple of times to friends, but when I was looking for details I came across this entry in Wikipedia which says this theory was "discredited in 2010." The cited links are in Swedish and one appears to be broken at this time. The other one is very brief but using google translate it says they think it was polar bears instead. Obviously anyone can put whatever they want on the internet, but I wonder what your thoughts are on this?


Tommy writes:

Dear Vincent and Dickson,

Just a note about something that Dickson mentioned in TWiP 60, I am sure Dickson realised that he simply misspoke after it went on air, but the digenean responsible for the "Barber Pole Effect" - Leucochloridium paradoxum - is not a schistosome but belongs to the Leucochloriidae family which is on an entirely different branch of the digenean/fluke tree to the schistomes.

There are many different species of Leucochloridium and they come in different colours. For example Leucochloridium paradoxum have green bands or red-brown bands on its sporocyst brood sac (the structure which invades the tentacles of the infected snail) whereas Leucochloridium millsi has yellow or orange-yellow bands. A good paper on this topic can be found below.

Kagan, I. G. (1951). Aspects in the life history of Neoleucochloridium problematicum (Magath, 1920) new comb. and Leucochloridium cyanocittae McIntosh, 1932 (Trematoda: Brachylaemidae). Transactions of the American Microscopical Society, 70(4), 281-318.

Additionally, there is some indication that the behaviour of the snail is altered, as noted by Carl Wesenberg-Lund in this paper below.

Wesenburg-Lund, C. (1931). Contributions to the development of the Trematoda Digenea. I. The biology of  Leucochloridium paradoxum. Memoires de l'Academie Royale des Sciences et des Lettres de Danemark, Copenhague, section des sciences 4, 90-142.

It was cited in Janice Moore's 2002 book "Parasites and the behaviour of animals". Wesenburg-Lund noted that "It seems as if the infested snail seek the light; they are very often see balancing on the borders of the leaves, or sitting on the underside of the leaves with only the antenna infested with the Leucochloridium protruding from the border
of the leaves..."

Now compare this with the behaviour of most terrestrial snails which prefer more damp and secluded surrounding. Such altered behaviour would expose the snail (and it brightly coloured parasite) to predation by the potential bird host.

As a side note, here is a link to a cartoon I drew about Leucochloridium a few years ago
It contains a pop culture reference, which might not be obvious to everyone, though most people below a certain age would immediately recognise it. For the listener who cannot see the imagine, it is a reference to the 2003 song "Milkshake" by Kelis.

Keep up the good work Vincent and Dickson, I look forward to more parasite tales from you in the future.

Robin writes:

Toxoplasmic humans

'Tain't just mice that have adverse behavioural outcomes with Toxoplasma.





Should humans attacked or killed by big cats be checked for Toxoplasmosis?

Suzanne writes:

Thank you for the Bt and mosquito info. I had a feeling there had to be a catch. Since there's always plenty of other water that isn't treated I expect Bt wouldn't become completely useless but it's good to know it's not a wonder fix, either. Ah, well.

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