Case guesses:

Carl writes:

Dear TWIPniks,

It is a beautiful sunny crisp New England fall day here in Lexington Massachusetts.

Thank you for releasing your book as a free PDF.  I have been reading it with great interest and some horror.  Unlike most of your correspondents, I have no medical or biological experience whatsoever.  My degree is in electrical engineering, and I now write statistical software for a living.  However, having read your book, and, with the help of Google, I will now attempt a diagnosis of the case of the week.

The Peruvian woman with bloody nasal discharge is suffering from mucocutaneous Leishmaniasis.  The hypopigmented scars on her exposed areas are healed cases of cutaneous Leishmaniasis, one of which is the original entry point of the parasites now afflicting her nasal mucosa.

The first stage treatment is sodium stibogluconate or other pentavalent antimony compound.  This is much more effective against Leishmania Brasiliensis than against L. Mexicana, and I don’t know which one she has.  It is also possibly a resistant strain, although this is usually only found in India or in a patient that has already received a course of antimonials.  If a course of antimonials doesn’t work, it is time to try a more expensive drug like Amphotericin B.

If I am right in my diagnosis, you may wish to reconsider giving away your book.  By writing such a clear and compendious tome, you have given away the secrets of parasitology to the entire world.  This may negatively affect your future employment prospects, now that any shmoe such as myself can do some of your job.  However, employment is always available in the burgeoning field of statistical software.  Contact me if you need a job; we offer training to people with doctorates in other fields.

Parasitically yours,


Iosif writes:

Dear Twip Team,

   My primary diagnosis for this case is mucocutaneous leishmaniasis, most likely from an infection with Leishmania braziliensis. The infection can be acquired from the bite of an infected sand-fly where the promastigotes are released and infect nearby dendritic cells and macrophages. While the initial infection may show up as an ulcer of the area, some of the amastigotes find their way to mucous membranes and start another reaction there. While the cutaneous lesions may heal (leading to the hypopigmented scars of our patient) the mucocutaneous lesions do not and a chronic ulcer would form. Diagnosis would be by PCR. Treatment would differ depending on where she was; most countries would use sodium stibogluconate due to its availability and low cost, amphotericin could be used if sodium stibogluconate fails. I hope that this wasn’t an arsenic resistant strain. Alternatively, maybe you could call a lab and get some kinetoplastid proteasome inhibitor mentioned in TWiP 116 for an experimental try if nothing else works.


Iosif Davidov

Hofstra SOM Class of 2018

P.S. Yes, we have a parasite lecture at the school; no plural. I would love more, but I understand that there are a lot of other topics that need to be covered as well.

Wink writes:

I am hoping sincerely that Daniel saved the lady from Cuzco from the likes of Figure 4.2 of the 6th Edition, but my guess is mucocutaneous leishmaniasis.

Wink Weinberg

Shelby writes:

Greetings from Nashville,

Tonight it’s a (very welcome) rainy 16°C.

My guess this week is muco-cutaneous leishmaniasis. A simple test was mentioned and I found that leishmaniasis could be diagnosed by taking a tissue samples and examining it for amastigotes of Leishmania spp.

MPU writes:

Dear tri-trypers,

I have been to Peru and visited the Leishmania clinical unit at UPCH in Lima, and I worked on Leishmania don, and also L bra and L per parasite genomes, and I’ve been listening since ~2009.

Diagnostic: MCL metastatic muco-cutaneous Leishmaniasis or muco-cutaneous Leishmaniasis

Parasite: caused by L brasiliensis

diagnostic method: use lateral flow (LF) immunochromatographic strip

treatment: Amphotericin B (that was what a doctor told me at a clinic.)

      For CL: heat-treatment of a few minutes.

I enjoy twip most among other twixes. You have twipped a few papers from our institute on Tryp. You said ‘We probably are mis-pronouncing names’

Also the sleeping sickness diagnostic tool mentioned came from us. I am a theoretical physicist ended up in computational biology.



Antwerp, Belgium.

Dan writes:

Dear TWiProfessors

Both TWiP and TWiV have been unmissable since I discovered them 6 months ago. I’m working through the back catalog. I am a UK-based travel doc with more than a passing interest in parasites. Today it’s a windy 6 degrees C in London.

For the 55-year-old Peruvian lady from the highlands around Cusco, the word ‘mucocutaneous’ in Dr Griffin’s description was a big clue. Or was it a red herring?

I’d still go for mucocutaneous leishmaniasis or espundia as first choice. It can be a complication of L. (V.) braziliensis cutaneous leishmaniasis, endemic in parts of south America. This parasite is transmitted from animal hosts by phlebotomine sand flies. It can be detected by PCR or possibly microscopy and culture.

MCL can cause major tissue destruction and usually needs systemic treatment with pentavalent antimonials or amphotericin.

There is not a clear history of cutaneous leishmaniasis although the hypopigmented scars on exposed extremities could be long-healed previous lesions.

For a non-parasitic differential I’d consider Wegener’s granulomatosis or malignancy.

Looking forward to hearing the right answer.

Keep up the good work!


David writes:

Dear Twippers,

   I believe the woman from Peru has contracted a case of mucocutaneous leishmaniasis, which occurs frequently in South American countries such as Brazil, Bolivia, and Peru.

   The culprit organism is most likely Leishmania braziliensis or Leishmania donovani. The organism is spread by the bite of a female phlebotomine sandfly during a bloodmeal, and metacyclic promastigotes are transferred to the bloodstream. These invade host macrophages or granulocytes, transform into amastigotes, and multiply within the infected leukocyte before escaping into the bloodstream to be taken up by the next blood meal.

   Invasion of this parasite can form a disfiguring lesion in the mucosal regions of the face called a “chiclero ulcer”. These can lead to social ostracization – quite unfortunate for those who suffer.

   Once more, thank you very much for the informative podcasts.


David P

Lela writes:

Hello to everyone,

I was somewhat slow to finish the last episode, but since I don’t believe a new case has come out, I thought I would write in with my guess for TWIP 121. I think this woman has cutaneous leishmaniasis. The lesion in her nose may be a mucocutaneous development from an original untreated lesion. I am a little hesitant in my guess because it seems like this a relatively well known endemic disease and so I’m surprised she wasn’t able to get a diagnosis earlier or closer to home. I look forward to your next episode!

Emily writes:

Greetings esteemed doctors,

I am writing to venture a guess as to the cause of the chronic epistaxis suffered by the woman in episode 121. I began listening to your podcast a little over a year ago when it was recommended to me during an undergraduate parasitology course taught by Dr. Steven Nadler at UC Davis. I have since completed my B.S. and am enjoying my first year of veterinary school at the same fine institution.

I suspect that the Peruvian woman is suffering from cutaneous leishmaniasis. Both cutaneous and mucocutaneous leishmaniasis are seen in Peru, but I believe the cutaneous form is found near Cuzco. Also consistent with the diagnosis is the presence of dogs and rodents in her vicinity as they can serve as a reservoir host for the protozoan. While the majority of her lesions resemble healed cutaneous ulcers, it is possible she is infected w/ a species also capable of producing mucocutaneous lesions. This would explain the scarring and concurrent nonhealing nasal lesion.

Thank you for the fantastic podcasts. I look forward to hearing the diagnosis.



P.s. Perhaps I am biased, but I would be interested to hear more veterinary cases!


Peter writes:

Dear TWiP team

After a very busy few weeks I have at last had time to catch up with the Microbe TV podcasts.

I am currently residing in Mersin on the Mediterranean coast of Turkey, where it is very dry with mid November daytime temperatures of 23°C dropping to 12°C at night.

To get back the TWiP 120 case study

The prognosis really does not look good for this patient.

Fungating lesions are associated with advanced cancer, in this patient the cancer is most likely the result of immune suppression.

A small proportion of patients with fungating lesions may achieve healing following surgical excision, but treatment is usually palliative.

The patient is infected with HIV1 clade B  with a T cells <100.  

A normal T cell count is from 500 to 1,500 cells per cubic millimetre of blood.  A T cell count below 200 and the presence of HIV virus is diagnostic of AIDS.

His T cell  count of <100 indicates advanced HIV / AIDS.

HIV  is common in Mali, a country in the heart of West Africa but it does not have a high incidence of HIV 1 clade B, which is the predominant strain in  America and Europe.  This indicates that he most likely did not become infected in Mali.

From my readings I find that Cryptosporidiosis infection is a common cause of watery diarrhoea, particularly in people with untreated AIDS.. There are possible differential diagnoses (microsporidia, cytomegalovirus (CMV), and Mycobacterium avium complex (MAC)) but I am assuming we are looking for parasitic rather than fungal, bacterial or viral causes.  Isosporiasis caused by the protozoan parasite Cystoisospora belli is a possibility, but I don’t think it is such a good match for the symptoms, it could be confirmed or ruled out by  microscope examination of a stool sample.

Cryptosporidium is a genus of apicomplexan parasitic protozoa that can cause both  respiratory and gastrointestinal illness.  They are ubiquitous and a common cause of watery diarrhoea throughout the world.  In immune-competent persons Cryptosporidium is usually a mild, self limiting infection, however in patients with AIDS it can become a chronic condition, causing malabsorption and gradual debilitation through dehydration, and metabolic abnormalities.

Diagnostic tests for Cryptosporidium include microscopy, staining, and detection of antibodies, antigens and DNA by Polymerase chain reaction

Assuming that I am correct the patients weight loss and wasted, cachectic appearance  may be due to malabsorption caused by Intestinal cryptosporidiosis though his cancer may also be contributing to this.

Low-grade fever could be due to both cryptosporidiosis and the fungating lesion becoming infected with bacteria.

Fast breathing and rapid heart rate could both be due to cancer or Cryptosporidiosis.

Low blood pressure is probably due to severe dehydration from diarrhoea.

The most immediate action should be rehydration treatment for the patient using oral or IV hydration

Anti diarrhoea medication should be given.

He should be started on highly active antiretroviral therapy..

Nitazoxanide is approved for treatment of diarrhoea caused by Cryptosporidium parvum, the most common strain of Cryptosporidium. I HIV patients it should be given in combination with antiretroviral therapy

Jonathan writes:

Hello Vincent, Dickson & Daniel!

I found TWiP 111 fun and informative. I believe Dickson had mentioned some research that had been done to see if HCV could be transmitted by bed bugs.  I recall an article that came out in 2015 that discussed Cimex lectularius as a vector of Trypanosoma cruzi.

Being new to the TWiP, TWiV and TWiM podcasts, I didn’t know if this topic had already been discussed.  Since it wasn’t mentioned in TWiP 111 I felt like throwing it out there for anyone interested.

Also, as a public health professional I have found all your podcasts extremely interesting and enlightening.  I have noticed that your discussions often times wander over into public health.

Have you had many podcasts with epidemiologists or other public health professionals as guest speakers?  I’d be interested in listening to those if you have. Perhaps some day there could be another Vincent Racaniello podcast: This Week in Public Health (TWiPH)

*pronounced ‘twif’

And if it helps, I’ll wave all creative licensing rights 😛

Thanks again for all the great work!

Neeraj writes:

Dear Doctors,

This is Neeraj and am mailing from the biotech hub in California, South San Francisco (am currently working at SutroVax, Inc). In the past, I have written on and off about cases that get discussed on the podcast but I won’t make a failed attempt to guess the most recent case (I don’t think I am confident about the diagnosis, so I will let the more informed enlighten us all). But let me assure you that this will never be a reason sufficient, to not eagerly wait to listen to the next episode as and when it gets released!

On a separate note, I am mailing more for the immense wealth of knowledge this podcast is. Having personally benefitted from it, I can vouch to say that the cases, the facts and the depth of science that gets discussed on this podcast, is simply outstanding. I wish I knew about a resource like this when I was a lowly graduate student in biomedical sciences at the Rockefeller University (although I doubt having the knowledge back then, I would have still used the NYC subway system so much) . In a weird way, I am always fascinated by the remarkably complex and beautiful world of parasites around us.

Speaking from personal experience, recently when I wanted to gain insights into the complex world of malaria and how the parasite evades the immune system to do such an amazing job of infecting us, I listened to all the initial podcasts that Dr Despommier and Dr Racaniello had recorded on the subject. Having listened / re-listened to quite a few of those, I must say that those are probably the best sources of Malaria related information that I have encountered (certainly found it better than CDC). The detail with which the lifecycle of the parasite was discussed along with how disease progression relates to the clinical symptoms, was particularly pleasing. And for this, I want to personally thank and applaud you for this generous labor (certainly won’t be the same without the outstanding narrative of Dr Despommier). Sir, your knack of telling stories is just uncanny and penetrative and if TwiP weren’t about parasites, I would have very much started sharing it with my 2 year old son (I am sure in time he will appreciate all the needle pricks that he had to suffer through to get vaccinated). But overall, I must say I appreciate / learn / learn-more from your kind contributions and please continue to produce this amazing content and resource. And if you ever stop by sunny California to organize an event, I would very much be interested in being in attendance or have an opportunity to meet. So hopefully someday TWiP will make a trip to the biotech hub of California.

Thanks for the knowledge,


P.S: Talking of Malaria, please find attached a recent article published in science where in the authors show the efficacy of counteracting Malaria by Oral, ultra-long lasting drug delivery mechanisms. Would be interested to hear the thoughts of the TWiP team on this (Dr Griffin I apologize for only praising the other docs on the podcast but without your case studies, the present production would be very lean and far less outreaching. So please keep bringing in the case studies as they always present clinical manifestations that at times are bizarre yet very enlightening).

Neeraj Kapoor, Ph.D.

Scientist, SutroVax

400 E Jamie Ct

Suite # 205

South San Francisco

Anthony writes:

Concerning TWiP 121

I don’t know if it’s central or tangential, but bats maintain a high body temperature only during flight.  When resting, bats go into a torpor with a lower body temperature.  Mother bats are an exception.

Bats have their own subspecies of the Chagas disease organism — T. c. marinkellei.  It appears that T. cruzi emerged from bats.

Opossums are both reservoirs and vectors of Trypanosoma cruzi. Opossums survive the infection.

Are there echoes here of Hendra and Rabies?  Hendra is carried by bats.  The native marsupials were not affected, but people and horses died.  In NJ, there are many reported cases of Rabies in raccoons, skunks and other animals — but extremely few for opossums.


Adam writes:


I started to listen to TWIP about a year and a half ago and since then it’s been (almost) the only podcast I’ve listen to. Now I’ve finally worked my way through the past episodes and recently listened to the latest one. Not without a sense of accomplishment I might add, but also with a slight feeling of emptiness. Now I must wait for the new episodes!

I’m a junior doctor in Sweden interested in infectious diseases. I’ve been working in two different Departments of Infectious Diseases – currently in Halmstad, south of Gothenburg on the west coast of Sweden. Later on I wish to specialise in infectious diseases. Parasites aren’t exactly common in Sweden and hence this podcast not particularly clinically relevant for me and I could probably have spent all those hours on something more useful:) But I find them fascinating, and this podcast interesting and entertaining. However, if I could make a request, it would be to include more clinically relevant papers in the podcast. Most papers you discuss are basic science – often about genetics or molecular science – and I find that not as interesting and sometimes hard to understand and hence I sometimes struggle to stay focused throughout the discussion… Also, a short summary about the article and its implications would be very useful, as would a short summary of the main facts of the parasite involved in last episode’s case.

From January to September this year me and my girlfriend travelled through Asia – Sri Lanka, Nepal, Brunei, Malaysian- and Indonesian Borneo (Sabah and North- and East Kalimantan), Singapore, Taiwan and Japan. We had a fantastic journey and apart from two episodes of giardiasis in Nepal we didn’t catch any parasites, at least that we know of… At the end of our trip we visited Tokyo and the Meguro Parasitological Museum, and we had a great time! I can really recommend it to anyone interested in parasites, and you can buy a lot of souvenirs and stuff. I’m attaching a few photos from the museum, maybe you’ll enjoy them.

Many thanks, and keep up the good work!

Adam Oscarson, Halmstad, Sweden – where it’s 8 degrees, raining and a storm approaching.


Rachel writes:


 Thought you all would be interested in this.

Brandon writes:

Dear Dr. Racaniello and Dr. Despommier,

I am a scientist for a large animal health company in the R&D division developing vaccines.  I have recently discovered your podcast “TWIP” and  have developed a high affinity for the robust information delivered in a fantastic manner.  I have decided to start on TWIP 1 and work my way through the podcast’s to date, thus this question may seem outdated however relevant to me in my time of reference.  During my undergraduate studies, I worked for an animal emergency clinic in Iowa as a veterinary technician  because I could work full time on off hours while attending school.  There were 5 or 6 patients throughout my 5 years of working there where dogs had come in for various other issues and while taking a stool sample or without stool (proglottiding out on it’s own) we discovered tapeworm proglottids and once I recall finding a tapeworm eggs on a fecal float.  After listening through the first 7 TWIPs, I cannot determine based on listening to the life cycles of each, what species it would have been because the Dog tapeworm just does not seem to fit the description based on the phenotypic nature of dog tapeworm and the dogs lifestyles, e.g. urban vs rural.  Could these cases be from beef tapeworm or something entirely different?  Pardon the seemingly simplistic question as my parasitic foundation is quite weak, however am leveraging my knowledge in immunology to strengthen my parasitic knowledge response.  I look forward to getting caught up in the next month or two and greatly enjoy the case study aspects of the more recent ones!


Brandon Russell

Lincoln, NE

PS:  I have requested Parasitic Diseases 6th Edition as a Christmas gift and could not be more excited to start reading through it!

Richard writes:


My hero growing up was my Grandfather Dr. Paul C. Beaver. He was one of the reasons I became a Wildlife Biologist. He died in 1993, but wondered how you might characterize his scientific contributions to the study of parasites and if either of you ever worked with him?

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