Case guesses:

Lucian writes:

Dear TWiP-masters,

Which parasite is it? Based on the morphology, I believe the patient had whipworm. The narrow end followed by a larger, coiled end is indicative of whipworm, and the length is within the normal range. In addition, the adults live in the large intestine, where a colonoscopy could discover them.

Is it normally associated with eosinophilia? Severe cases can induce eosinophilia (doi: 10.1016/j.iac.2015.05.003), along with intestinal bleeding and anemia.

Is it normally associated with anemia? If the patient had a severe infection, the CDC reports that this can cause bloody stool. Perhaps if she was losing enough blood, this could lead to anemia. A case reported in Gastrointestinal Endoscopy also found eosinophilic gastroenteritis and borderline anemia in trichuriasis (PMID 17141232).

Could it have come from a rural area in the US? The CDC also reports that though whipworm is relatively rare in the US, that it is primarily a tropical disease, there are cases in the rural Southeast. It is spread when humans ingest eggs found in human feces, and is associated with warmer climes. The rural SE United States certainly has very poor and subtropical regions.

I shall now return to counting CFUs at the Listeria lab I work in. Many thanks for the podcast! It makes time pass much more quickly and pleasantly.

Lucian DiPeso

Molecular & Cell Biology Program

University of Washington

Todd writes:

Dear TWIP trichotomy,

I have been listening to TWIP, TWIM, and TWIV for two years and this is my first correspondence.  I really love your interesting podcasts and often listen during my long runs as I train for half and full marathons.  I am a Med Tech who is a Research Scientist at a pharmaceutical company in the Philadelphia, PA area. It is a typical fall day, partly cloudy and windy with a temp of 8 degrees C.  The worm in TWIP 142 found by colonoscopy is a male adult whipworm, Trichuris trichiura.  Adult male whipworms have a coiled posterior and females have blunt ended posteriors.  Trichuriasis is caused by ingesting embryonic eggs or ova from the environment.  Ingested ova hatch in the small intestine and burrow into the crypts as larvae.  After 1-3 months of maturation, the larvae migrate to the large intestine (cecum and ascending colon) where the thin, threadlike anterior end of the worm penetrates the mucosal epithelial cells and feeds on tissue secretions.  Histology exam of the mucosa can reveal localized eosinophilic infiltration in the lamina propria.  Eosinophilia in the peripheral blood is rarely seen in T. trichiura infections. The posterior of the adult worm ruptures the cell membrane, matures, mates with nearby worms, and lay ova.  In endemic areas most mild infections lack symptoms and only patients with severe infections are symptomatic.   Symptoms may include abdominal pain, diarrhea, anemia, malnutrition, weight loss, appendicitis, intestinal bleeding, colonic obstruction, perforation, finger clubbing, abdominal tenderness, and anemia.  Rectal prolapse can occur in children with large numbers of worms.  Diagnosis can be made by identifying the ova in feces.  This can be done with an ova and parasite screen (O&P).  Multiple samples may be necessary to see the ova,  with some infections never resulting in a positive O&P.  Mebendazole or Albendazole daily for 3 days is the standard treatment.   Discontinued use of pesticides and the use of organic fertilizers causes the spread of this helminth.  Humans are the principal host with infections also seen in lemurs, pigs and monkeys.  The 5-15 year age group has the most clinically significant cases because of their higher risk of eating soil.  Interestingly, young boys are more likely to become infected as they tend to ingest more soil than girls.  Infections are most common in warm moist, tropical and subtropical climates.  In the US, the most common areas are the southern Appalachian range and Gulf coast states.

Keep the informative TWIX content coming!  Also, I would be very interested in seeing the three of you at a “live” podcast in NYC!


Anthony writes:

Recently, I noticed on the shelf of an enclosure of one of the rescue kittens approximately a tablespoon of what appeared to be mucus with lumps.  After wiping it up into a paper towel, I inspected the material.  Without my glasses, I spotted 3 or so worms.  Because of the watch spring position, I at first thought that they were ascaris.  On closer scrutiny, even with diminished vision, I noticed discrepancies: the worms were much smaller and the width was much less than that of the usual roundworms.  After finally fetching a pair of reading glasses, I was able to see that there was an additional striking difference.  These worms were non-symmetrical.  One end was much finer that the other.  Reasoning that probably the only common feline worm that I’d not seen before my eyes was the whipworm, I did a Google image search for that.  Google confirmed that the feral kitten indeed was afflicted with whipworms — Trichuris serrata.

The case study for TWiP 142 conjured up a mental vision of the little demons that I’d found.  It struck me that I’d not taken the most obvious precaution — to check if the cat parasites were transmissible to humans.  I was relieved to be assured by the crystal ball of Google that though people can catch whipworms, it’s usually a different species — Trichuris trichiura.

The article at the URL above states “FBC: often shows eosinophilia and, rarely, anaemia.”  I’m not certain about the question concerning severity of anemia.  The CDC says “Children with heavy infections can become severely anemic”.

Does that mean that adults will only be mildly anemic?

Trichuris trichiura enjoys worldwide distribution and so can be caught anywhere that people and soil are found.  Though the eggs are passed in feces and there’s no vector/intermediate host, transmission is not directly oral-fecal.  The eggs need time in the earth — days or weeks — to mature.  This certainly is much more likely for those living under primitive conditions in rural areas — both in and outside of the US.  Even so, city dwellers need to be concerned, too.  Patrons of New York City fine restaurants dining on salad or fruit not well washed might get a little something not mentioned in the menu.

Thank you.

David writes:

Dear Hosts,

It has been a while since I emailed in a case guess, but after hearing the details presented in episode 142, I could not resist the temptation to answer: especially with a free signed book on the line!

I suspect the woman from a rural area with limited resources has been infected with whipworm, or Trichuris trichuria. The worm recovered nicely fits the description of a male whipworm: 45 mm in length, and having both a long, slender end and a thicker, curled and blunt end. The larvae of this worm penetrate the mucosa of the large intestine and grow into adults in the colon. According to the Sixth Edition of Parasitic Diseases, the resulting capillary damage and erosion caused by the worm may lead to iron-deficiency anemia and inflammation, which fits the description of the patient’s anemia.

Trichuris has also been reported in causing marked peripheral eosinophilia in cases where anemia and dysentery are present, but still other sources claim that whipworm does not typically induce eosinophilia. It is possible she has another infection which is causing the eosinophilia, and the anemia – caused by the whipworm – are what brought her into the hospital.

Whipworm infection is worldwide, but occurs most frequently in areas with poor public hygiene conducive to soil pollution, a warm climate, heavy rainfall, and dense shade. This includes several countries in Africa, Asia, and even has been widely reported in the Southeast United States, where it is the 2nd most common nematode infection following Enterobius. It is possible this woman is an immigrant from another “tropical” country where whipworm is endemic, or she is from an area in the southern United States with poor sanitary conditions.

Thank you once again for the informative and entertaining podcasts.


David P.

Molecular Helminthology Lab

Tufts Cummings School of Veterinary Medicine

Dr. Wink writes:

Dear TWIP Team,

My guess for the 4.5 cm motile worm in the large bowel is Trichuris trichiura. The size and shape and location are all right and it was motile, suggested by the name “whipworm.” The textbook says it can cause anemia. Thanks for everything. If I win the textbook I want to donate it to somewhere like Haiti.

Wink Weinberg


Melissa writes: winner

Hi TWIPians,

After sniffing around and following the clues for the last case study, I’m finding this quite fun.  I wonder if this is what my dog feels like when I do nose work with him.

Here is my guess for this TWIP:

I think Trichuris trichiura fits the description of the worm. I looked through the photos (and descriptions of size) in Parasitic Diseases to figure out what it could possibly be.  Once I got to Trichuris, I thought, “Wow, so this is what Daniel meant by one end is slender and the other is large and curled.”  After reading through the section, it doesn’t seem like Trichuris trichiura is associated with eosinophilia.  As far as the anemia part, Trichuris doesn’t ingest blood, but  it can cause capillary damage and erosion which will lead to blood loss and anemia, so I’m guessing mild anemia?  It doesn’t look like there are cases in southeast United States anymore, but it could just be super rare now in that area.  I think this female patient most likely picked this up from outside of the US in a developing country with poor sanitation since the eggs of the worm are excreted in human feces.

Hopefully, my guess is correct.

Moving on to your question if anyone will come to a TWIP in NYC for a book signing, I’d love to go, but alas it is too far.  If you have it in San Diego (at UCSD), I would definitely come by.

Please keep the case studies coming, I’m having a blast searching around for the answers.



Melissa Ly

Associate Biosafety Officer

University of California, San Diego

Melissa writes:

Dear TWiPozoites,

I just discovered this podcast and I am hooked! I have a PhD in Neurobiology, but no medical background. I am fascinated by parasites though, especially the weird eukaryotes, and I thought I’d take a stab at your case this week.

This case seemed like a good one to start with because they actually found a worm! or “long slender serpiginous motile object” as you described it.

My first thought was a Taenia tapeworm, as there is a width differential between the head or scolex, and the mature proglottids at the tail. However, the worm described was only 4.5cm long, which would be tiny for a tapeworm, and furthermore one end of the extracted worm was “large and curled but not blunt”. The size and morphology therefore rule out tapeworm.

My next idea was an intestinal fluke. I could find only one fluke that attains this size, Fasciolopsis buski. Eosinophilia and anemia would fit with F. buski infection. However, the shape described doesn’t match a fluke, so I ruled this out as well.

After two strikes, I moved on from Phylum Platyhelminthes to Phylum Nematoda. I found a nematode that matches the size and shape almost immediately, and this is my official guess: human whipworm, Trichuris trichiura.

Whipworm is widespread worldwide, and is most prevalent in tropical areas. UpToDate suggests that up to a quarter of the world’s population is infected with whipworm. However, although the patient was an immigrant, she could have acquired this infection in the United States, as whipworm is endemic here, particularly in the southeastern US, where perhaps 2-3 million people are infected. She could have been infected by fecal-oral transmission of embryonated eggs either in her home country or in the US.

Whipworm infection is usually asymptomatic, so I surmise the patient has a moderate to heavy infection based on the anemia — more than 50 worms. Eosinophilia is not present in all patients. Paniker’s Textbook of Medical Parasitology states that eosinophilia may be present in early stages of the infection. A paper from 2014 suggests about half of patients with T. trichiura infection display eosinophilia, although this paper studied indigenous Australians in remote communities, and I don’t know how far I can generalize this result (Crowe et al. 2014. Decreasing prevalence of Trichuris trichiura (whipworm) in the Northern Territory from 2002 to 2012. Med J. Aust)

Anemia is not normally a symptom of light infection, but can be associated with heavy infection. A cursory PubMed search turned up a few studies of anemia in children or pregnant women with trichuriasis, but I couldn’t find a good reference for levels of hemoglobin in infected nonpregnant women. So I’m not sure, but I’m going to go with mild anemia, as anemia in pregnant women seems to be mild even with a heavy worm burden (Gyorkos et al. (2012) Re-Visiting Trichuris trichiura Intensity Thresholds Based on Anemia during Pregnancy. PLoS Neglected Tropical Diseases)

The treatment is mebendazole. I was fascinated to read that this probably works by inhibiting tubulin polymerization. She should also receive iron supplements for the anemia.

I would love to hear your thoughts on deliberate infection with T. trichiura for diseases such as inflammatory bowel disease.

Thanks and keep up the awesome work!

Alijah writes:

Hey TWiP team!

Long-time listener, first-time answerer here.  I just want to thank you all for all your hard work reaching out to and enlightening thousands of listeners like me.  Based on the information Daniel has given, I would suspect that this is a case of Trichuriasis, the infection of the body by the whipworm Trichuris trichiura.  

These roundworms, when found in the body, localize in the caecum after reaching adulthood and can grow to the listed length of 4.5cm.  Interestingly, the worm recovered from this patient would have likely been a male, as the posterior end was described as ‘curled’ (in contrast to the female’s typical blunt end).  Eosinophilia is a common phenomenon in Trichuriasis and other helminthic infections, so this is also a match.  As for the reported anemia, I suspect that it could be related, as the infection can elicit bloody diarrhea in affected individuals.  However, I would guess that the anemia would be rather mild (unless, of course, this individual had been experiencing bloody diarrhea for an extended period of time—info not given).

Finally, are these infections only found in immigrants?  Well, epidemiologically, Trichuriasis is most common in more undeveloped areas of the world, where it is contacted via the ingestion of eggs in contaminated food, water, or fecal matter.  It should be noted, however, that there are cases of whipworm that are reported in the southeastern portion of the states (this according to the CDC website).  As mentioned in earlier TWiPs, this region still lags behind the rest of the country in terms of technological and societal advances, leading to the perpetuation of some of these infections and ailments.

Keep up the great work!  It’s always a pleasure to listen to you guys.


Alijah (pronounced Uh-Lie-Uh)

Ithaca, NY

p.s.  I was wondering if I could suggest an episode (either TWiM or TWiP) dedicated to Borrelia burgdorferi, the etiological agent of Lyme Disease.  I have personally been affected by the disease and subsequent illness (now termed Post-Treatment Lyme Disease Disorder).  But, the Lyme Disease realm is rife with controversy—societally, scientifically, and now legally (see article below)—so it would be really interesting to hear you guys talking about it.  There is even a world-renowned Lyme Disease Center at Columbia run by Brian Fallon.  Regardless, thanks again for everything.

Insurers Accused of Conspiring to Deny Lyme Disease Coverage

Gavin writes:

Dear Hosts vivax,

My case guess for the ~50 year old woman is the Whipworm Trichuris trichiura. When I first heard “worm” and “iron deficiency anemia” I jumped to Hookworm, but that didn’t check out for a number of reasons. Hookworms are smaller (females are 7-13 mm), and are typically found in the small intestine. I don’t know how particular Hookworms are to the small intestine, but I was able to find video of Hookworms on endoscopy but not colonoscopy.

Whipworm fits the size and morphological description given, and are frequently found on colonoscopy. Ascaris, pinworm, and Anisakis are also commonly found on colonoscopy (at least in Korea), but don’t match the description as well. Treat with mebendazole or  albendazole.\

Trichuria occasionally presents with Eosinophilia. I think this may be due to immune modulation and the limited degree of tissue penetration. Anemia is normally only seen in severe cases, but is generally less severe than hookworm. This person could have acquired this in the American South, especially given the recent news regarding hookworm.

Thanks for the fantastic case! We covered causes of anemia before the break, so this topic has been on my mind. If I win the book, I’ll leave it in the student lounge for my peers.


Gavin Sowa

UCSF School of Medicine

Class of 2021

Adam writes:


I’m writing this on the go so take it for what it is…:)

To me the case in episode 142 sounds like whipworm, Trichurius trichiura. I cannot find that it’s usually associated with eosinophilia. The anemia is usually mild. It seems doubtful the the whipworm infection alone can explain this patients findings, and further investigation might be needed. The infection might have been acquired in the USA.

A few weeks ago a listener suggested a “This Week in Global Health”. I know you guys are busy, but I think that is a great idea! Also, some time ago you introduced an executive summary, summarising the article you had discussed and the implications of its findings. I really appreciated this, but lately you seem to have forgotten about it… Just a friendly reminder.

Finally I must say that I’m really looking forward to the video series! It’s gonna be awesome!

Best regards,

Adam Oscarson, Medical Intern

Halmstad, Sweden


Melissa writes:

Hi TWIP team,

I very much enjoy listening to your case studies.  I’ve never written into TWIP before, but there is a first time for everything! (I’ve only written into TWIM. I used to work in Dr. Pride’s lab with his virome projects, but I’ve moved onto the dreaded EH&S department that researchers fear working with.  I over exaggerate, I hope.  My time in the lab has definitely proved useful when working with labs.)

Here is my thought process:

For the O&P results, when I heard entamoeba coli, I imagined an amoeba in the intestines.  A quick search on CDC showed that entamoeba coli is generally considered a harmless, and non-pathogenic resident of the human large intestine.

I wasn’t sure what endolimax nana was, but it also showed up on the same CDC page that said the entamoeba coli was generally non-pathogenic.

I had to search on CDC again about the blastocystis hominis, which said whether this can cause infection with symptoms is up for debate right now.  This is now getting bookmarked in my mind.

Since Daniel is already addressing the salmonella and she is getting better enough to get discharged, I don’t think the blastocystis hominis is giving her any problems.  (Some people can carry blastocystis hominis in their intestines without having any problems.)

In two weeks, when she comes back into the clinic, I would just make sure she isn’t still constipated or having diarrhea or any other intestinal problems (since blastocystis hominis symptoms range from diarrhea to excessive flatulence).  If she isn’t having any problems, I would imagine she is good to go.  (If I’m completely out in left field on my response, that’s the reason why I’m not a doctor. Haha!)

Thanks for keeping my days fun!  I look forward to listening to many more TWIP episodes.



Melissa Ly

Associate Biosafety Officer

University of California, San Diego

Anthony writes:



“We have found dozens of fully grown parasitic worms in his damaged intestines,’’ said Dr. Lee Cook-jong, a lead surgeon. “It was a serious parasitic infection.”

During a news briefing this week, Dr. Lee showed photographs of worms as long as 10 or 11 inches.

Experts in parasitic worms were not surprised, however. They said that the finding was consistent with the broad sense of conditions in the isolated, impoverished North.

Defectors to the South have cited the existence of parasites and abysmal nutrition. Because it lacks chemical fertilizers, North Korea still relies on human excrement to fertilize its fields, helping parasites to spread, the experts said.


Anthony writes:

I found fascinating that from Tropical Medicine to Neglected Tropical Diseases we’re now at Global Medicine.  This new normal clearly is a facet of the Global Village.  It’s also a harsh reminder that McLuhan’s prediction of a tsunami of primitivism enabled by technology was not a promise of perfection, but a prophecy of doom.


Bill writes:


I’m even further behind on listening to TWiP than I am on TWiV (but perhaps now that the baseball and college football seasons are about over I will catch up).

A friend just shared this Navy Times article. Ever heard of this before? The VA continues to get lots of bad press, but perhaps they can figure this out. As a Navy veteran who spent time in Southeast Asia (well, I was stationed in Bangkok and living in a downtown hotel in 1975) I am concerned.



Bill Spindler’s Antarctica

Anthony writes:

For who knows what reason, Accuweather decided that I needed to see this ad.

Fungal parasites don’t seem to be discussed much.  They are eukaryotes, too.