John writes:

A few comments on TWiP 99.

  1. At 21:50 Dickson described fleas as “occasional predators on humans.”

The standard entomological term for an insect that feeds without killing is “parasite.”

A parasite that normally kills its host is a “parasitoid”.  The larval stage of the star of the movie Alien was a parasitoid.

If it kills several prey, it is a predator.  A flea predatory on humans belongs in a science fiction horror movie or downwind of Fukushima.

  1. At 23:00 you discussed how Ms. Flea finds a mate.

It is possible for a parasitic female insect to mate while all but her “lady parts” (as you called them) are lodged inside a host.  That is how insects of the order Strepsiptera reproduce.  A wingless female of the genus Xenos spends her life in a wasp’s abdomen. A winged male flies past, smells something good in there, and has his way with her.

You can watch:

  1. At 40:20 Dr. Griffin equated a cubic millimeter with a millilter. A cubic millimeter is a microliter.
  1. At 1:15:20 you revealed that you haven’t heard of famous country singer Merle Haggard.  If you had, you would know how to pronounce Muskogee.

Case guesses

Robin writes:

The euboxic LFTs indicate something that ain’t parenchymally invasive or disruptive in spite of the hepatomegaly. So does the minimally elevated white count.

The eosinophilia goes with NAACP, in this case parasites.

Jeff writes:

Dear esteemed TWIP doctors.  I am going to hazard a guess that the 53 year old woman has chronic/obstructive fasciolosis.  The mode of infection isn’t as clear as it could come from aquatic plants or the washing of vegetables with contaminated water.  The incubation period between acute infection and chronic/obstructive phase lines up as well as the liver tenderness and eosinophilia.  Also this is endemic in rural Bolivia (Epidemiol Infect. 2007 May; 135(4): 669–674.).

Love the TWIX podcasts as we regularly discuss them over lunch or in the lab.


Jeff Fairman, Ph.D.

Vice President, Research

SutroVax, Inc.

South San Francisco, CA 94080

Wink writes:

Another great case!

Well, TWIV Trio,

Lacking Dixon’s knowledge base, I had to hit the books again! But I think the Bolivian vegetarian with RUQ discomfort, hepatomegally and peripheral eosinophilia had fascioliasis, or a liver fluke, and I wonder if she had ingested some aquatic vegetation from the Altiplano. I look forward to the case discussion and episode #100 — Congrats!

Wink Weinberg


Tim writes:

Hello my favorite podcasting doctors,

I just finished up listening to your latest episode, conveniently at the same time I finished evening chores so I don’t have to come up with some odd jobs to do to stretch work a little longer to hear the rest of it.

I have no idea what the cause of the case this week is but would venture a guess of Entameoba Histolytic based on liver pain but no animal contact potentially ruling out Fasciola although who knows who or what pooped on her vegetables before she ate them.

As for the pronunciation of Muskogee an old country song by Merle haggard should clear that up. Here’s  a link to a youtube of the song:

It’s currently abnormally warm and muddy for this time of year making farming a bit annoying as I prefer to only slog through the mud in the spring when I know it will end soon and the world will green up. Winter mud is just a depressing reminder Mother Nature rules my life more so than I hers.

Joel writes:


I have been listening to TWiP for a while now but this is my first time writing in.  It is rather warm today in Cincinnati, OH at 55F (13C) and actually mostly sunny for a change.  

I knew practically nothing about parasites before starting to listen to the podcast so I am learning a lot and it’s really sparked an interest.  As a newbie to the field, I may be way off on my guess but after searching around I have come to the conclusion that it is Fasciolosis caused by a liver fluke.  My reasoning being that it is largely endemic in Bolivia, it can be transmitted through ingestion of several types of plants or untreated water, symptoms can include abdominal pain and liver problems, and fecal tests are not always able to detect it.  I look forward to your next post to see if I’m right but if not, then at least it was a learning experience.

Thanks for the very informative podcasts!

P.S. I’m hoping that Santa brings me a copy of Parasitic Diseases for Christmas!


Elise writes:

Dear TWIP Trifecta,

How are you? It is truly unseasonably warm here in lower Manhattan, currently 54 F (12 C). This is weird, but there is a lot of weird going on in the world right now.

I have a guess diagnosis for the Bolivian woman visiting her daughter and suffering from upper right quadrant belly pain. I suspect she has found herself harboring ascaris lumbricoides worms. Often, in people with mild to moderate infestations, there are no symptoms at all, so it makes sense that she would have had no real symptoms until this pain in the vicinity of her liver. I know she avoids animals, but since she is on a raw vegetable diet (how is she getting enough protein?), she could easily have purchased vegetables that were tainted with ascaris lumbricoides eggs from the fecal matter of the local dogs she avoids (among other possible vectors), so if she didn’t wash them well enough she may have found herself some ascaris lumbricoides eggs there. (According to one excerpt of an article I read from a study in Alexandria, arugula is a particularly popular plant for ascaris lumbricoides.)

One interesting note that I found about ascaris lumbricoides in Bolivia is that, apparently, there is some recent research that suggests that infections with a lumbricoides may aid fertility. The worms may lower women’s immune responses and make their bodies more hospitable not only to the worms themselves, but also to the much larger parasite that is the growing baby.

(This information hit the mainstream media rather recently and it could be dramatic puff pieces but I thought it was interesting since the research was done in Bolivia. Here are a couple of links to articles I saw:

Anyway, I am not positive of this diagnosis because, in part, the patient’s symptoms are not gigantic blinking arrows pointing to one parasite, but given her eating habits, and the fact that she lives in semi rural Bolivia and that ascaris lumbricoides infestations often have no symptoms, or minimal ones that resemble hers, I feel comfortable with this guess.

I hope that the holiday season is not getting you all down and that you have adventures and intrigue and more TWIP planned for the rest of 2015 and off course 2016.

Thank you so much as always


Curt writes:

I suspect the patient harbors an unsegmented flatworm known as the Liver Fluke.

My basis is primarily epidemiological. She lives in a rural area with livestock nearby. She ingests raw vegetables, some of which are foraged locally. If she foraged any from a stream in particular, it seems probable that she did not wash the plant, possibly assuming that the stream had done the work already (and we already know she didn’t cook those plants). This is well-known as problematic to savvy foragers who go looking for the likes of watercress.

The elevated liver enzymes and abdominal pain with the CT being the giveaway test all but nail the coffin shut on this case for me. I’m not sure how to treat it, I’ll look that up soon. Thanks for the great work you guys. I always feel a little like Alan Dove when a new TWiP shows up, in that it’s good to be here.

Arthur writes:

Hello TWIP trifecta

This is the first time I have emailed in as I have only recently made the fabulous discovery of your podcast.

As it happens I was listening to TWIP #99 whilst feeding and cleaning the colony of Galba truncatula we keep at work, many of which are host to the intermediate form of the parasite I believe to be responsible for this womans upper right quadrant tenderness; Fasciola hepatica. The clinical presentation of mild hepatomegaly is consistent with Fascioliasis, as is the high eosinophil count. However, the thing that made this diagnosis the most likely is the unusual diet the woman is currently insistent upon. Liver fluke is transmitted by the ingestion of metacercariae which have encysted upon water plants after motile cercariae are shed from the snail intermediate host. The most adequate way to destroy the metacercariae is to either boil them or to dry them out. However since she was not cooking the plant material, she will have been ingesting entirely viable cysts.

The timing is pretty consistent with the life cycle of F. hepatica, as it takes somewhere in the region of 3 months post-ingestion for the liver fluke to reach patency, though they are likely to cause symptoms some time before this due to migrating newly excysted juvenile fluke.

Faecal samples are clear, which is consistent with what we see in veterinary fascioliasis, where a number of tests are required to determine infection, since faecal egg burdens are often low.

It is likely that the endemicity of this parasite is being sustained by the local ruminant population, since she lives in an area of agriculture.

Thank you for your amiable chat and keep up the fantastic work!


Arthur the English Parasitologist

Hans writes:

Hi TWiP team,

Writing from Seattle on a warm July night–walking home from a long evening of transfections and binding assays. Just finished listening to TWiP 73 about E. histolytica trogocytosis. Very excited to hear you covering that paper as I actually started my science career as a high school and then college student in Bill Petri’s lab at UVA. I’m now at the University of Washington working on maternal to infant HIV transmission. Also applying to MSTP programs and enjoyed Vincent’s TWiV interview with the group of MD/PhD students at Vanderbilt.

I’m writing because Dr. Despommier seemed quite convinced that E. histolytica  trophozoites needed to be cultured in the presence of feeder cells. While I can confirm that trophs are quite excited (forgive the anthropomorphizing) to gobble up most anything you feed them, it’s not necessary that they be around in culture. We use a chemically defined media similar to LB but with different components. And of course we grow under anaerobic conditions. These cultures can be xenic or axenic depending on the isolate and application. Just wanted to clarify that point and tell you that I love listening to all of your podcasts in lab. Keep up the good work and thanks for giving E his some attention.



Blaze writes:

Yes yes yes to Colbert’s show…and I have the perfect pitch for the show runner!

Remember how Jim Fowler would always bring animals on the Tonight show?   Always a popular segment.

Dickson and Dan bring LIVE PARASITES on the Colbert Show.  Imagine the screams!  Live Ascaris!  Writhing tapeworms!

Put together a pitch and email that sucker to Colbert today!

Lela writes:

Hi Vincent, Dickson and Daniel,

I am a postdoc and I’ve listened to TWIP off and on for the last five years. It has always been my favorite of the TWIX podcasts, but I have enjoyed it even more with the addition of the case studies. I finally thought I would try a diagnosis to the case study – google was absolutely necessary as my degree is in molecular biology not medicine. I narrowed my guess to tapeworms or roundworms based on symptoms. I think I’m going to go with roundworm – ascariasis – as my final diagnosis since there are descriptions of humans passing these worms through multiple body orifices, as opposed to tapeworms which seem to be primarily restricted to stool.

I also wanted to mention a science fiction book I read a while back – Symbiont by Mira Grant. It is actually the second in a series about tapeworms that were engineered to secrete medicine to treat diabetes, etc. but manage to migrate into the host brain and either become zombies or (in a few cases) integrate into a tapeworm/person. I thought just the idea was pretty awesome and it is good summer reading.

Thanks for the show – I enjoy listening and telling everyone about the cases!


Caleb writes:

Greetings Drs. Racaniello, Despommier, and Griffin,

It is a “chilly” 66 degrees F in sunny Riverside, California today.

I hope all is going well, and you will be TWIPing again soon. I discovered your Podcasts approximately 2 months ago, in the search for something much more entertaining than listening to NPR or other such talk radio on my way to and from my University. I am currently a first year Ph.D. student in Medical and Veterinary Entomology at the University of California, Riverside, and these podcasts have been absolutely amazing! I listen whenever I get the chance. Walking around campus to get coffee, taking care of my flies ( house flies), I am working on looking at the genetic mechanism behind behavioral resistance to insecticides in house flies, and every chance in between. I listened to the most current 10 podcasts or so very quickly, seeing as I can listen to them at 1.5 or 2 speed and cover the information very quickly( picked up this habit from my girlfriend who is in Medical School.) I am quickly making my way through the back log of episodes, I currently am on episode TWiP 53:

Anti-saliva immunity. These podcasts have made my passion for parasitology and vector borne diseases grow exponentially. I got involved in Medical and Veterinary Entomology’s due to a wonderful professor I had in my Undergrad named  Bradley Mullens, who teaches the Medical and Veterinary Entomology course at UCR. I wonder if any of you know of him? I know that he gave a plug for Dr. Despommier’s book, People, Parasites, and Plowshares in one of lectures. But getting down to the real reason I emailed, is that last week I saw a very interesting paper talking about genetically modified mosquitos, who are “resistant to malaria.” I skimmed the paper, and found it fascinating, just having learned the ins and outs of CRISPR CAS9, RNAi, etc, in my Genomics and genetics core class a few weeks back. Then listening to TWiP last night on my way home from school, I listened to the episode from 2 years ago where you had Dr. James on, talking about some of his work. The timing was impeccable. I just wanted to let you all know to keep up the great work, and I am actually considering having my minor for my Ph.D. be in parasitology thanks to the amazing content you all have put out over the last few years!

Thanks again,



Paulette writes: (99 case study)

Hello Dr.’s Racaniello, Despommier. and Griffin,

Dr. Griffin’s case this episode, characterized by an itchy, black centered nodular lesion on the toe of a beach combing tourist recently returned from Brazil, suggests that the “toe bug”, TUNGA PENETRANS, hitched a ride with our innocent victim back to the states.  A tiny sand flea is a small price to pay for enjoying the beautiful beaches of a tropical paradise, but I will stay home myself.


Paulette & Bob

Dennis writes:

Hi Docs,

Here’s a YouTube.  Someone sprays a giant mantis and as it dies out comes a worm that is twice as long as it.  Is it a roundworm?



Peter writes:

Greetings Dickson,  Vincent and Daniel.

Here are a couple of recent papers that I think would be worth some discussion

Researchers at Imperial College London have engineered Anopheles gambiae mosquitoes, using CRISPR Cas 9,  to pass on genes that cause infertility in female offspring. If released the species could become extinct in a few generations.

A CRISPR-Cas9 gene drive system targeting female reproduction in the malaria mosquito vector Anopheles gambiae

The other paper is based on 9 years of longitudinal data from 986 Tsimane forager horticulturist women living in the Amazonian lowlands of Bolivia. This indicates that women infected with Ascaris lumbricoides tended to have an earlier first pregnancy and to have more children than uninfected women or  women infected with hookworm.

Hookworm infection caused a reduction in fertility.

The increased fertility is thought to result from systemic immunological changes caused by  Ascaris lumbricoides.

Helminth Infection, Fecundity, And Age Of First Pregnancy In Women



Jesse writes:

Hello TWiPpers-

I can’t believe I’m writing for the first time. I’ve listened to TWiP, TWiV and TWiM off and on for the past few years. I will say that as an internist first in Seattle and now at LA County Hospital, TWiP is ironically my favorite as it has historically been the most clinical of the three. I say that this is ironic because of course my day to day practice is all virus NOS (not otherwise specified), HIV, HSV, Staph aureus, Strep pneumo, E. coli, Klebsiella, Pseudomonas, etc. I will only occasionally encounter a parasite, usually toxoplasmosis in an immunocompromised host, although I know well that it is possible that many a parasite pass by me unrecognized. I will further add that I think some of the early episodes of TWiP, where Drs. D and R elaborated on the life cycles and clinical aspects of some of the classics — malaria, for example — are some of the greatest podcasts I have ever heard. So good were those episodes I even remember where I was when I listened to them: running up and down beaches in the Dominican Republic, where I was attending a wedding. And this is high praise, because I listen to A LOT of podcasts. Of course, sadly, this is why I can’t listen to every episode of TWiP, which is quite long. If I listened to every episode, and the Slate Political Gabfest, and The World Next Week, and so on and so on, I’d have to quit my job and leave my girlfriend. There are also all the medical podcasts I listen to. I wonder if you all have ever heard Dr. Mark Crislip’s infectious disease podcasts. There’s one called Puscast and another called A Gobbet o’ Pus. Both are fun and interesting.

Okay — I’ve been known to go on and on, and it’s already too late to stop that, but I will try to wrap it up.

First, I am so glad you all talked about the H. nana case. I anxiously awaited this last episode of TWiP with the expectation that you would and the discussion did not disappoint.

Second, I heard that you offered to send a PDF of Dr. D’s Parasitic Diseases to another one of your listeners. I was hoping I could also get a PDF. I have attached a picture to this e-mail. I have actually bought the book, but it is all beat up and highlighted, which I imagine is the case of most of what’s left on Amazon, where I purchased it. It would be great to have a nice, shiny PDF to use. In the picture, I’ve put the book next to a nice painting of a Thompson Gazelle, which I purchased in Tanzania, where, I guess thankfully, the only parasite I managed to acquire was a virus NOS, also known as the common cold. And I know this is not a parasite at all. No worms, no sleeping sickness, none of that, although everyone on my safari kept asking me if I thought I had malaria.

And I almost forgot: the weather here in LA is no weather at all. I think W.H. Auden said that. Being from Chicago, I miss the bitter cold. People think I’m crazy, but I do.

Thank you for your Podcast. And Dr. R, between the Podcasts and your job at Columbia, I have no idea how you do it. You must have infinite energy. I am jealous.


Jesse Abelson

P.S. I’m looking forward to TWiF, This Week in Fungus. I love fungus for some reason. We see it in our most immunocompromised patients, and for whatever reason I am always fascinated. I’ve diagnosed mucor, which is the term we use to refer to a whole host of invasive molds including Mucormycosis itself, a few times. It’s always just terrible, with the patients needing surgery, about 10 different anti-fungals, and prayer (or luck, depending on your belief system). But I think I find it fascinating because it speaks to the fact that without an immune system, we would all just be overrun by fungus, maybe the most successful species (or family or who knows) of them all. I highly recommend you look up “Oncology versus ID” on YouTube. It is a good and hysterical commentary on this.

Bryce writes:

Hello TWIP Team!

    I was first introduced to this podcast by a fellow lab member.  Needless to say, I was hooked by my first episode.  Then, imagine my excitement when I found out that Dr. Depommier was a Notre Dame alumnus (Go Irish)!  Currently I am in a Notre Dame lab investigating the ectoparasite Culex quinquefasciatus. The passion of the TWIP team and guests is “infectious”; however, much to Dr. Racaniello and Dr. Depommier’s disappointment, I will be pursuing an MD in the coming years.  Therefore, Dr. Griffin, do you have any words of guidance for a future MD who wants to remain in tight association with parasites and research?  Thank you for the phenomenal podcast!



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