Case guesses:

Suellen writes:

Time for me to take another semi-educated guess, this time on what’s ailing the 30-something HIV patient who has presented complaining of diarrhea, vomiting, weight loss, and dehydration. This guy has a lot going on, so it was difficult for an amateur like me to separate what symptoms resulted from his parasitic infection, and which ones from his untreated HIV infection.

After some research, I’m ready to guess that our patient has Cryptosporidium in his intestines, and those little guys are living it up and making his life hell. Crypto commonly causes vomiting, diarrhea, and weight loss, and I even found some special recommendations on the CDC’s web site regarding the elevated risk of this parasite in HIV patients and others with compromised immune systems, who are at higher risk for this parasitic infection.

How did he acquire the parasite? That is much harder for me to say, but I did read that the infection can be passed sexually, so I would suggest that further examination include the man’s partner. How did the partner acquire Crypto? Can’t say.

Keep up the great work, doctors! Love the show, love the cases!

Suellen in Roswell, GA

Wink writes:

Dear TWIP Professors,

I was a small boy in New York City in the 1950s, so one of my heroes was Mickey Mantle. I am proud to have approximately Mantle’s batting average for my TWIP diagnoses! My swing at the man with AIDS wasting and eosinophilia is Cystoisospora belli, previously known as Isospora belli. My diagnostic test of choice is to send a stool sample to Dixon.

Wink Weinberg


Iosif writes:

Dear Twip team,

For my differential I’m finding it difficult as I can’t narrow down my differential to a single diagnosis. So here are my thoughts.

Unlikely Diagnoses: Cyclospora cayetanensis, Cryptosporidium parvum and Giardia lamblia. None of these present with a significant eosinophilia as far as I can tell and I don’t see any risk factors that could lead to them such as consumption of raspberries or contaminated water; however, I am assuming that this infectious agent was either brought in by the patient’s partner or acquired from the nearby area.

More Likely Diagnoses: Cystoisospora Belli, Trichuris trichiura, Strongyloides, Capillaria phillipinensis, Hymenolepis Nana, Paragonimus westermani,

Cystoisospora belli – One of the few protozoans that can lead to eosinophilia and so is on my list. It is transmitted by fecal contaminated food or water.

Trichuris trichiura – Not too high on my list due to the patient not exhibiting many of the classic symptoms like tenesmus. I can’t rule it out completely though.

Strongyloides – I was hoping for some type of rash or cough to help identify this worm. Furthermore, I’d be worried about dissemination in someone as immunocompromised as our patient.

Capillaria phillipinensis – Unlikely because our patient is not in the Philippines.

Hymenolepis Nana – Popularized because of the Colombian patient with the nests of neoplastic cells that were thought to have been derived by this infection. Our patient in not in the Mediterranean so this is again unlikely.

Paragonimus Westermani – Obtained from cray and crabs, neither of which were mentioned in the case. Furthermore, I would expect some type of pulmonary complication.

Overall, I don’t have enough information to say that any of these are definitive. For our patient, the first thing that I would want to do is start some form of IV fluids. He seems to be extremely dehydrated and treating an infection is pointless if he dies before it can be cleared. I would then want to order a stool ova and parasites to see if I could get any information on which parasite is likely and to what medications may be started. Despite all of the parasites listed above, I would still not want to rule out a concurring viral or bacterial infection. I don’t think I would wait for the results before starting antibiotics and antiparasite medications. I think I would start off with albendazole, ivermectin, TMP-SMX, and azithromycin (for MAI). If none of these work, then I would be worried about a fungal disease (maybe GI candidiasis?) Please let me know if my reasoning is flawed.


Iosif Davidov

P.S. When discussing Onchocerca volvulus in the last episode, I remembered that there was a paper that you guys discussed about using imatinib to target filarial ABL like kinases and this could treat the adult filarial worms and thus bypass the 20 year ivermectin treatment. Do you think there is any chance that this could one day be a possibility, or is imatinib just way too profitable/expensive for this to be done?

P.P.S. This case reminds me of a play we recently performed at our school called A Question of Mercy by David Rabe. I don’t know if I am allowed to attach the play because it is supposed to be distributed solely for educational purposes, but if you want to see our performance it is here: School of Medicine Presentation. The play is about a terminally ill AIDS patient in NYC during 1990, suffering terribly (also from diarrhea) and his wish to end his life.

Peter writes:

Greetings TWiP team.

I am currently in Mersin, Turkey, where at time of writing it is dry and sunny with a temperature of 22°C.

The patient in this case study has untreated HIV/AIDS so will be susceptible to numerous opportunistic infections and possible reactivation of latent infections.  The described gastrointestinal symptoms of diarrhoea, vomiting, abdominal pain, weight loss, and dehydration were common in AIDS patients before the widespread use of HAART.

I think that the symptoms indicate a protozoan parasitic infection of the intestines rather than a helminth, though I suppose that co infection is a possibility.

I presume you would want to start the patient on HAART before continuing with the diagnostic testing?

Having done a literature search for ‘Opportunistic parasitic infections in HIV/AIDS patients‘ and listened again to some early episodes of TWiV, I will stick with  protozoan parasites. The most likely. parasites will include Cystoisospora belli, Giardia lamblia, Cryptosporidium parvum, Amoeba, and Microsporidia

Given the lack of pet ownership zoonotic infections are less likely. A lack of foreign travel further limits the likely parasites. I would make a guess at this being a food or water transmitted parasite, further analysis of stool samples, colonoscopy and biopsy will be required to clearly identify the parasite or parasite.

I strongly suspect that the patient is suffering from Cryptosporidiosis due to Cryptosporidium parvum infection.

The CDC has this to say about Cryptosporidiosis:

Nitazoxanide has been FDA-approved for treatment of diarrhea caused by Cryptosporidium in people with healthy immune systems and is available by prescription. However, the effectiveness of nitazoxanide in immunosuppressed individuals is unclear…

For those persons with AIDS, anti-retroviral therapy that improves the immune status will also decrease or eliminate symptoms of cryptosporidiosis. However, even if symptoms disappear, cryptosporidiosis is often not curable and the symptoms may return if the immune status worsens.”

Without antiretroviral treatment cryptosporidiosis has a high mortality rate for AIDS patients and even with antiretroviral treatment total elimination if the infection is unlikely.



Michelle writes:

Dear TWIP Team,

For the case of the HIV positive man with chronic diarrhea and eosinophilia.

If the diarrhea is of infectious origin, it appears that it is due to an opportunistic pathogen which the man is susceptible to due to HIV infection. Although I don’t recall any CD4 cell counts given, I am presuming they are low because the man is not on therapy, has oral thrush, and his partner who is HIV positive remains unaffected.

The more common opportunistic pathogens in the HIV/AIDS patient population in the U.S. that cause diarrhea include Cryptosporidium parvum, Cyclospora sp., Cystoisospora sp., microsporidia, Blastocystis hominis, disseminated MAC, and Cytomegalovirus. There are many other viruses and bacteria that could be involved, the HIV virus itself can also cause enteropathy, and there are possible noninfectious origins like inflammatory bowel disease, but I am guessing there is a parasite involved.

The clue of eosinophilia suggests Cystoisospora belli (in Parasitic diseases: Cytoisospora belli), Dientamoeba fragilis, or Sarcocystis sp, which can all cause diarrhea in AIDS patients. The patient’s symptoms are textbook for C. belli, which is an apicomplexan parasite that infects the intestinal epithelial cells. A person becomes infected by ingesting oocysts typically through ingestion of fecally contaminated water or food. Symptoms in the immunocompromised population include chronic diarrhea that can be extreme, weight loss, weakness and fever. Just as described for this patient.  Diagnosis: The oocysts can be found in stool and are acid fast. Treatment: long course of  trimethoprimsulfamethoxazole.

Dientamoeba fragilis is an intestinal amoeba that is obtained through ingesting cysts that are passed out in human feces. This pathogen can be diagnosed in stained fecal smears, fecal cultures, and PCR diagnostics.  

Sarcocystitis is not strongly associated with HIV patients and thus it is down further on my list. It is another apicomplexan that is obtained by eating undercooked meat. Its life cycle involves an intermediate host. Oocysts are passed in feces of the definitive host and ingested by an intermediate host (often cow or pig). The sporozoites invade tissues undergoing several rounds of reproduction ending their final round in the muscles. Thus, eating the undercooked muscles transmits the parasite to the definitive host.

Thanks for the edutainment,


Carl writes:

Dear TWIPniks,

You mentioned that the ill man in TWIP 129 had a diagnosis that was in “Parasitic Diseases Sixth Edition”.  I figured that meant I had a chance of figuring it out despite my complete lack of medical and biological training.  So last night, I decided to lull myself to sleep by reading all the paragraphs in your book containing the word “diarrhea”.  Fascinating as this was, it was also time-consuming, and I nodded off between the section on Protozoa and the section on Nematodes.  But I think I found a good protozoan diagnosis, so I feel confident in saying that this is a case of Cytoisospora Belli.  (Or it’s some worm from the 400 pages of the book I didn’t read, in which case you can all have a good laugh.)  This is one of three protozoa that cause eosiniphilia, and of those, one of two that causes diarrhea, and of those, the only one found in New York, the only one prominent in immunocompromised patients, and the only one where the diarrhea is bloodless.   

Googling around, it seems like the usual treatment for this would involve, in addition to an antiprotozoal, starting antiretroviral therapy so the patient’s immune system can clean up the mess.  I wonder how this will affect the patient’s decision to forsake such drugs?  I look forward to finding out in your next thrilling episode.

It is a gloomy 40 degrees Fahrenheit here in Lexington Massachusetts as the rain erodes the last piles of winter’s snow.


Gavin writes:

Dear TWIP team,

I’m running way behind on my podcasts, so I need to submit my guess for TWIP 129 ASAP! Could you give us some guidelines on when we should have our guesses in? I work so much better when I have a deadline.

There are a lot of great review articles on diarrheal diseases in HIV-infected patients. It seems that CMV, Cryptosporidium, E. histolytica, etc… are all on the list of usual suspects. However, I’m beginning to suspect that we evolved eosinophils to aid in our differential diagnosis. Cytoisospora belli, Dientamoeba fragilis and Sarcocystis are among the few pathogens which cause diarrhea and eosinophilia.

Sarcocystis seems to be uncommon in the United States, and our patient does not report eating undercooked meat or travel to Asia. D. fragilis is an interesting possibility, but my guess is Cytoisospora belli. As is often the case on TWIP, the proof is in the pudding. Cytoisospora Oocysts can be detected in the stool via autofluorescence. Treatment is with trimethoprim (160 mg) and sulfamethoxazole (800 mg) two to four times a day for 10-14 days. The patient should be started on HAART, with caution given to IRIS. I wouldn’t be surprised if there was a coinfection as well.

Thanks again for such a wonderful podcast! I appreciated Dr. Griffin’s medical school advice, and I’ll keep you posted on where I end up after April 30th.




Elise writes:

Dear TWIP Trifecta,

I am not even close to being caught up on TWIP episodes but I did listen to TWIP 127 and was quite abashed to hear my name mentioned for being truant. I did indeed fall way behind on my listening and researching and writing. I can’t offer any excuses beyond the obvious: “Life gets in the way” one that just feels rather shabby.

I’m now in the process of getting my act together and I promise to write again with diagnoses pronto.

Excuses aside, I have missed very much this parasitic detective work (even though I am prone to diagnostic stumbles).

More soon, soon, very soon.

Best wishes to all

Elise (in lower Manhattan)

Steve writes:

Thought you might like this stop motion public info cartoon of the life cycle, out NHM posted for World Water Day.

All the best,





Steve writes:

Hi Vincent et al,

Just come across this piece on the gruesome-sounding

‘brainworm’. Whether or not the unfortunate moose–executed for ‘blocking a snowmobile trail’ 🙁 — actually was infected remains to be seen, but this would appear to be another example of a parasite that causes little harm in one species, effecting behavioural changes in another.

Might make an interesting topic for TWiP–maybe even a case history to stump the chumps…

‎”The life cycle of _P. tenuis_ is complex and multi-staged. Adults will lay eggs on the dura mater (the outer layer of the meninges) of the brain or directly into the blood stream of an infected host. The eggs hatch into 1st stage larvae, which travel in the bloodstream to the lungs where they travel up the respiratory tract, are swallowed, and then pass out of the body in the mucus coating of fecal pellets. Gastropods feed on this mucus and ingest the larvae, where they develop into a 2nd and 3rd stage. Infected gastropods may then be accidentally ingested by an herbivore, and the larvae moves from the gastrointestinal tract to the bloodstream, reaching the central nervous system, where they develop to adults and the cycle begins over again. – Mod.PMB”

Amazing we have any wild animals at all really!

All the best,





Leave a Reply

Your email address will not be published. Required fields are marked *

One comment on “TWiP 130 letters