Case guesses:

David writes:

Dear Hosts,

I will venture a guess that the Panamanian mother with a painful, bloated abdomen and steatorrhea is suffering from giardiasis caused by Giardia lamblia, a parasite which is reported to survive in roof water runoff contaminated by fecal matter of birds, reptiles, or mammals containing infective cysts. Giardia has also been reported to show resistance to albendazole, which may explain the ineffectiveness of the drug in this case.

The ovarian cyst might be presented in this case as a red herring, although there have been examples of parasitic cysts caused by multiple types of organisms, including Schistosoma mansoni and  Enterobius vermicularis, but searching also brought me to parasitic dermoid cysts, which might not be out of the realm of possibility.

Thank you again for the informative and educational podcast.


David P.

Kevin writes:


Chicago IL

Friday, May 4, 2018

Weather here: just weather. I remember a Kenyan at the Liverpool School of Tropical Medicine who was always amused by the English preoccupation with the weather. He said that in Kenya, it was just sunny everyday and nobody talked about it.

The human side of this clinical case begs for the speedy resolution of a mother’s chronic misery. Thanks to the volunteer doctors who undertake this work. Years of bloating, abdominal discomfort, and the frequent passage of bulky, greasy stools in the tropics cannot be enjoyable (the mother in the case not the volunteers). Add to this the frustration of nurturing several children with intractable nocturnal scabetic pruritis. It is small wonder that the patient’s sex drive is less than maximal. It is also very instructive to learn that inappropriate surgery is a hazard even in impoverished tropical locations.

(Feel free to edit out this possibly pedantic aside):

This patient has a combination of symptoms, i.e. a syndrome, here the malabsorption syndrome. Initially we can apply the law of parsimony (Occam’s razor) to lump all of our patient’s symptoms to a single cause. Many diseases can have a final common pathway of the malabsorption syndrome. The nosology (systematic classification of diseases) in this case would fatigue the most diligent intestinal scholar. A quick mental checklist can give anyone the ability to construct a reasonable answer to the patient lament, “Doc, what could it BE?” The mnemonic I use is M M M I I I I C T:    a illness or clinical observation can be laid at the feet of these causes:

Mechanical (something blocked)

Mitotic (cancer)

Metabolic (glands, electrolytes, etc)

Inflammatory (rheumatoid arthritis etc. )


Iatrogenic (the doctors did it)

Idiopathic (who knows what it is?)



I have left out psychological, since this should almost always be last in order to avoid overlooking physical etiologies.

Since this is a parasitology focussed case, noninfectious causes of the malabsorption can be dispensed with, e.g. celiac disease, tropical sprue, inflammatory bowel disease, bacterial overgrowth, chronic pancreatitis, intestinal lymphoma etc, etc.

This leaves infectious causes of malabsorption. Viral disease doesn’t fit this case. Bacterial infections likewise do not explain the chronicity of this patient’s symptoms. We’re now up the evolutionary ladder to protozoa and the likely culprit in this case is Giardia intestinalis (known to me from olden times as Giardia lamblia, or Giardia duodenalis). I have supplied a reference that reports a 42% seroprevalence of IgG to Giardia in a cohort from Panama. We shouldn’t adopt a premature closure however, and give some consideration to other bad actors such as Isospora, Cryptosporidium, Enterocytozoon, and Cyclospora -though these more commonly afflict the immunocompromised host. Since dermoscopy has figured prominently in the last two TWiP episodes, I hope that our moderator can discuss portable microscopy, especially the CellScope, a smartphone based microscope developed at UC Berkeley. I learned about it in a recent New England Journal of Medicine article on onchocerciasis (see ref). In the field, if the diagnosis is not achievable by microscopy one is probably left with ’empiric therapy’, which is treating for the most likely diagnosis, always keeping in mind the harm/benefit ratio. (which would be quite high if ovarian cyst removal was performed). In this case empiric therapy might consist of metronidazole (or nitazoxinide) and cotrimoxazole.

Not to be overlooked are the helminthic infections, the leading candidate being Strongyloides, which should be relatively amenable to field diagnosis with a CellScope or other field microscope such as the Nm1 Newton microscope. The treatment here would be albendazole or ivermectin.

Finally, the other ‘great imitator’ (now that syphilis is slightly out of fashion), tuberculosis, must always be mentioned in an insidious clinical case with relatively non-specific symptoms. The diagnosis and treatment of this malady must be left to the lucubrations of the listeners.

Thanking you all again for a very stimulating podcast.


Tropical malabsorption

B S Ramakrishna, S Venkataraman, and A Mukhopadhya

Postgrad Med J. 2006 Dec; 82(974): 779–787.

This is a fantastic review and very non-technical

Extra-intestinal and long term consequences of Giardia duodenalis infections

Marie CM Halliez and André G Buret

World J Gastroenterol. 2013 Dec 21; 19(47): 8974–8985.

Everything you ever wanted to know about Giardia, and then some.

Malabsorption Syndrome Marvin H. Sleisenger, M.D.November 13, 1969 N Engl J Med 1969; 281:1111-1117

Strangely, this is the most recent NEJM review of the malabsorption syndrome I could find. It’s old fashioned, one might say ‘classic’.

Accuracy of Mobile Phone and Handheld Light Microscopy for the Diagnosis of Schistosomiasis and Intestinal Protozoa Infections in Côte d’Ivoire. Coulibaly JT,  PLoS Negl Trop Dis. 2016 Jun 27;10(6)

Age-related rate of seropositivity of antibody to Giardia lamblia in four diverse populations. Miotti PG, Gilman RH, Santosham M, Ryder RW, Yolken RH:  J Clin Microbiol 1986, 24(6):972-975.

Giardia IgG seropositivity is common in Panama (46%  of patients examined in this survey)

A Test-and-Not-Treat Strategy for Onchocerciasis in Loa loa–Endemic Areas  Joseph Kamgno, M.D., Ph.D.,et al. November 23, 2017

N Engl J Med 2017; 377:2044-2052

This study used the CellScope cell phone microscope to determine filaria counts in blood samples.

Cecelia writes:

Dear Drs. Racaniello,Despommier,and Griffin,

 I discovered your podcast while listening to the quiz show podcast, “Ask Me Another”.

 The topic was, are these real or fake podcasts!

  I am a medical technologist employed in the microbiology lab at a children’s hospital in St. Petersburg, Fl. I have had the privilege of working in Washington DC at Children’s

National Medical Center, with Joe Campos as the Microbiology Lab Director, and Judy Sneed as the Supervisor.

  They were a wealth of knowledge in all areas of microbiology, and parasitology. My current Supervisor, Si Intravichit, has also been a great resource for my coworkers and me.

  In regards to case study 151, I think she has chronic Giardiasis.  The biggest clue is steatorrhea, as well as the other symptoms you listed.

 Although she was given the antiparasitic drug, allbendazole, it would not be effective against Giardia. Occasional diarrhea, and the prevalence of Giardiasis in Central America would also be consistent with chronic Giardiasis.

  Big shout out to my coworkers as well. They are the best at teamwork and getting the job done.



Cullen writes:

Hey TWiP peeps,

I know I’m probably too late, but I thought I’d give this week’s case a try. Due to the nature of the stool, I would presume there is mucus in the stool caused by Giardiasis. Because of the lack of sanitation and their proximity to animals (dogs and pigs), it could be possible for a member of this population to acquire Giardia lamblia through the fecal-oral route. There could be many other possible diagnoses, so I would suggest testing the stool microscopically over the course of a few days to see if there are any characteristic trophozoites or cysts in the stool.



Molecular Microbiology Tech

Atlanta, GA

Peter writes:

A cháirde (ah khawr-djeh) TWIP,

Rushed and hopefully not late guess for the last TWIP case. Some of us were presenting at a joint parasitology meeting (ISP/BSPP/BAVP/EVPC) in Belgium when the last podcast came out. Of course getting back from being away there were lots of larvae to be counted and small mammals to be surveyed, but I had a quick listen with parasitology lab mates (rhymes with TWIPER it’s) Gwen Deslyper and new excellent visiting student from University of Toulouse, Manon Dafau Sargousse.

The difficulty in cleaning themselves after passing stools made us immediately think of Giardia and we believe none of the drugs she has been given would affect Giardia. The length of the infection seems unusual but if the water storage is contaminated perhaps there is the possibility of repeat infections. The long period over which the woman has suffered these symptoms suggests also the possibility of infection with Entamoeba histolytica, which may also have contaminated the water storage and can also cause mucousy stools. Similarly we also do not think the drugs administered would have cured E. histolytica infection. One problem with this line of thinking is everyone else using the water source should also be infected, but they may be asymptomatic.

On the way to the airport, after the parasitology meeting, I mentioned the case study to a friend who may also now become a TWIP devotee. She mentioned Tritrichomonas, a parasite more associated with cattle, but with rare opportunistic human infections. Although unlikely, due to the rarity of cases, I thought I would bring it up as I found it very interesting and I am not sure if has been mentioned on TWIP before. She also mentioned the possibility of celiac disease, which would match the symptoms. In reading up more on gluten intolerance we did read of the possibility of lactose intolerance developing from giardia infection so that is another possibility.

So our next step would be to examine stool for evidence of the presence of the parasites and possibly some allergy tests. If parasites were found it would also be good to examine where the water is stored to see if it is contaminated.

Slán (slawn),

Peter Stuart,


William writes:

Greetings Twiptologists,

As a long-time listener of TWIV while studying as a Biology major at the College of William and Mary, I was delighted to latch on to TWIP this year as an outstanding educational resource and way to pass the time during my long commutes. I have had a run of correct guesses the last few episodes so I figured I may as well throw my hat into the ring for this case differential.

As was remarked on the podcast by Dr. Despommier and Dr. Griffin, the symptoms described seem to point to a number of possible parasitic infections. My first thought was Giardiasis with the bloating, steatorrhea, and diffuse abdominal pain, but the likelihood of this continuing unabated for 3 years without diagnosis seems low to me. Additionally, treatment with Albendazol having no effect (listed as an alternative treatment for G. lamblia infections in the 6th edition of Parasitic Diseases) seems to make this more unlikely.

The lack of Albendazol efficacy might not be the ideal way to narrow down the list of possibilities, as some infections (such as trichiura) can require multiple doses over time to cure, but as I don’t know the course of Albendazol treatment given, I am still going to use it. This would dissuade me from citing hookworm or similar infections generally treatable with Albendazol.

While Trichinella can present in ways that point to a number of possible diseases, I do not think that it fits the bill here, as the timeline does not add up. According to 6th edition (my main source for all these guesses), the abdominal pain should be closely associated with the early gastrointestinal phase after ingesting infected tissue, and different symptoms would have presented long before now. This extended affliction (as well as the non-watery stool) also seems to rule out something like Cryptosporidiosis.

Currently my best guess for the culprit of this infection, given the duration of the noted gastrointestinal symptoms (diffuse abdominal pain, bloating, and loose or slimy stools), would be a long-term mild case of Entamoeba histolytica which if left untreated can persist for months or years. My hesitation with this is the lack of blood in the stool, as untreated infections will often lead to some form of dysentery. I don’t think in the podcast there was a specific mention of heme testing for the stool, so maybe it just wasn’t immediately apparent? (this is my lack of clinical experience showing here) If this is the case, the recommended treatment would be Metronidazole either orally or intravenously.

Thanks for the excellent podcast, this is such a great program for aspiring scientists and health professionals.



(P.S. it is currently 21 degrees Celsius and raining, here in the Washington D.C. metropolitan area)

Chris writes:

Hello, TWIPsters!

The symptoms presented by this patient seem to suggest chronic Giardia infection. Steatorrhea and abdominal pain are particularly telling. But the primary water source of this household doesn’t seem especially susceptible to contamination, that being rainwater collected from the tin roof. The source of infection would likely be elsewhere. The evidence for this parasite isn’t overwhelming, but its sheer ubiquity is enough to warrant some consideration.

Molecular diagnosis is preferred because of the intermittent shedding of parasite cysts, which can make them difficult to detect in a single fecal sample. Treatment with metronidazole is common.


in Athens, GA