Case guesses:

Anne writes:

Dear TWIP team:

Regarding the Swiss student with swollen left eye, my thought is thelaziasis, perhaps caused by Thelazia callipaeda.  I did consider larval migrans and Onchocerciasis.

I found a comprehensive review paper in:

Interdisciplinary Perspectives on Infectious Diseases

Volume 2012 (2012), Article ID 587402, 12 pages

Ophthalmic Parasitosis: A Review Article

Amal R. Nimir,1 Ahmed Saliem,1 and Ibrahim Abdel Aziz Ibrahim2

They provided an extensive (exhaustive) list of possible ophthalmic parasitoses almost all of which involve internal structures of the eye whereas Thelazia sp infects superficial structures and feeds on tears (seems poetic stated that way.) My only reservation is that Thelazia callipaeda does not seem to be endemic in northern Africa although I found a reference for its occurrence in Europe, including Switzerland. Would also consider the possibility of a zoonotic infection as several Thelazia species occur in animal species in the region she visited.

Putting a plug in for fungal diseases for future case studies, by the way.

Thanks as always for the engaging and illuminating podcasts.

Anne Lewis, DVM, PhD

Beaverton, OR

Jeff writes:

Dear TWIP doctors,

A very interesting case indeed.  When the discussion started I started thinking maybe this was a case of Acanthamoeba castellanii and Daniel was going to say that she wore contact lenses, but as the description continued there was the mention of flies, sheep, and the final mention of the 1mm long parasites being seen trying to get to the lacrimal duct which sealed the diagnosis as Oestus ovis, which is quite common in several areas including the Mediterranean.  Definitely not your typical parasitic case, but quite thought-provoking!

How was this treated?

Keep them coming!


Jeff Fairman, Ph.D.

Vice President, Research

SutroVax, Inc.

South San Francisco, CA

SJ writes:

Hello TWIPtastic trio,

Sorry about the brief differential and probable typos–I’m typing this out in a hurry.


Oncocerciasis–unlikely, as immune response does not commonly occur prior to organism death.

Loiasis-time frame does not match. Unlikely

Dirophilariasis–edema, symptoms of foreign bodies, presence of worm in conjunctiva. Good one to look into.

Ophthalmyasis externa, however, is my most likely guess. The presence of animals nearby, the ‘rustic’ experience of sleeping outdoors, and the patient waking up covered with flies suggests that the presence of fly larvae is likely. In addition, the often tiny number of larvae present can make it difficult to detect, allowing us to forgive the initial ophthamologist’s having missed this one and treating it as standard conjunctivitis. Treatment involves removal of larvae aided by anticholinesterase ointment to paralyze the larvae.

I look forward to the next episode. Thanks as always!

David writes:

Dear professors,

This week’s case does not seem to be a very common parasite, and I don’t have high hopes of getting it right this time.  I did not manage to come up with a differential diagnosis, but will venture  a guess based on my short research: thelazia.  This parasite is transmitted by flies feeding from tears, and the larvae are deposited in or near the eye.  The eyelid seems to be a reasonable target.  The larvae then move to the lacrimal ducts to feed more.

It seems consistent but I could not find conclusive information about geographical range and size of the worm. Thelazia callipaeda seems most common in humans and is found in Italy, which is at least Mediterranean like Morocco.  Thelazia rhodesii is found in Africa and Europe.

Suggested treatment appears to be mechanical removal, which sounds as if there would often be just one worm, while in this case there were several tiny particles, so I am not very convinced of my findings.

If I got this right, I wonder how it would be treated.  Mechanical removal sounds horrible, but I am very squeamish when it comes to anything regarding the eye.  Wiki mentions topical treatment with thiabendazole and cocaine, and I found a veterinary manual referring to ivermectin and the likes (

Many thanks for the relentless transmission of stimulating podcasts; I look forward to hear the formal diagnosis for this case.

Warm regards from Nicaragua where April has started with very atypical showers after a dreadful heat spell.

Jeffrey writes:

Dear TWiP team,

It’s a cloudy -6 C here in Montréal, with no signs of letting up. Regardless of what any groundhogs may have seen, it seems that winter has stuck around for more than six weeks.

As I finish up my U1 (second) undergraduate year of Microbiology and Immunology at McGill University, the TWiX series is only confirming that I picked the perfect major. My friends might find it bizarre, but podcasts on the wee critters of life (and non-life) make for good breaks after working through the CD’s and IL’s and Th’s of the human immune system, where they get put into clinical context.

Though it’s not dedicated to parasitology, my introductory microbiology course (along with pages 1 and 2 of Google) has prodded me towards Thelazia callipaeda as my diagnosis for the Case Study of TWiP 106. T. callipaeda has been described in Mediterranean regions before, and its transmission through flies seems to fit with the accommodations of the Swiss surfer. I’m not entirely clear on what a blood test constitutes (which I should figure out for future TWiP’s), but it seems reasonable that neither blood smears nor serology would give a positive result if the parasite remains localized to the patient’s immuno-privileged eyes as T. callipaeda does. Again from Google M.D., Florian seems to be on the right track with regards to treatment, as physical removal looks to be the accepted therapy.

Loved the interviews with Dr. Libman from the MUHC and loved Dr. Despommier’s 2015 interview in Lucky Peach on vertical farming.

Best wishes, and keep on TWiPing the light fantastic,

Iosif writes:

Dear Twiposomas,

My first guess for this case would be Shistosoma mansoni. 6-8 weeks after initial infection can lead to Katayama fever which can present with dyspnea, rash, and eosinophilia. I would like to see the rash in order to make a more accurate prediction, and also know whether or not the rash was itchy. The parasite is obtained by contact with infected freshwater and the cerceria burrow their way through your skin into your bloodstream. Treatment with praziquantel.

My other guesses are:

Strongyloidiasis. Strongyloides do live in Lake Victoria and can cause all of the symptoms of our patient. I would be more confident if the rash is serpiginous. I am uncertain of the time-frame; however, if the infection was asymptomatic at first and got worse due to auto-infection, then maybe that would explain the late appearance of the symptoms. Treatment with albendozole.

Necator Americanus or Ancylostoma duodenale. Similar reasoning to the strongyloides.

It is also possible that he could have co-infection of two or more of these worms and so may explain his extremely high eosinophilia. I would want to get stool samples to determine exactly what he may have.

Non-parasitic causes:

Churg-Strauss: This is potentially very dangerous and one of the things at the top of my list if he starts to develop granulomas. I would watch out and ensure that the kidney is functioning well. I would just double check the CBC.

Allergic aspergillosis: A history of asthma or cystic fibrosis would be necessary (or another chronic lung condition.) There also shouldn’t be a rash with this diagnosis. An allergic skin test (just like TB) can be used to diagnose.


Iosif Davidov

P.S. You guys pronounce my name fairly well. You can pronounce it the same way as Joseph. Thanks for all your great work!

Anthony writes:

If memory serves me correctly, with identical twins raised in the same household, the chance of one developing schizophrenia if the other does is very high, but not one.  For identical twins raised in different households, the chance of one twin developing schizophrenia if the other does is still high, but considerably lower than for two raised together.  One might argue that schizophrenia has a strong genetic component that’s necessary, but not sufficient.  

Again if memory serves me correctly there are a number of environmental stresses known to be associated with schizophrenia.

For the speculative leap, for someone who has the inherited predisposition for schizophrenia, perhaps a toxoplasmosis infection might serve as the stress trigger.

Just a stray thought.

Anne writes:

Dear TWIP team:

Thanks as always for the wonderful podcasts. I enjoyed the discussion of this week’s paper on social organization in trematodes, in part because of the revelation of the still extant divide between macroscopic field work and our increasingly molecularly based laboratory work (The discussion arose regarding access to a microscope and camera.)  I think Daniel’s observation that the lab strain of snail was the only one to differ in biology from the field isolated species is particularly interesting. Dickson’s interjections regarding integration of general biologic/ecologic perspectives in many of the discussions is an important reminder of the real world pertinence of the topics presented. There are so many things we can only study in the laboratory environment but if we lose the connection with the ‘real world’ then the work can be elegant but may be less useful or even misleading. This comment is not regarding basic science but the use of appropriate models and understanding of their limitations.

Off my soapbox now. I spent several years studying wildlife biology before starting my professional education and still miss it sometimes although I don’t miss it when it is cold, wet, buggy or humid (ie not often).

Anne Lewis, DVM, PhD

Beaverton, OR

Viktor writes:

This is a message from the long gone past concerning TWiP #37 Dracunculiasis. Dickson comments on how Sweden was planing on building a 17 story vertical farm and you, Vincent, asks if Dickson said Norway. Dickson then says that you shouldn’t mix those two since we don’t like each other.

As a Swede this is far from the truth. I imagine it’s similar to USA’s relationship to Canada. Lots of tongue in cheek jokes between the two but it’s more of a sibling thing, at the end of the day you’re really happy you’re neighbors! Besides, Norway has better skiing slopes.

Anyway, I found out about your “This Week In” – suite about 3 weeks ago and my brain is starting to hurt.

I’m a freelancing artist which means I spend hours upon hours at my desk drawing and resting my forehead on the desk trying to summon inspiration. This also means I listen to hours upon hours of podcasts. Your podcast is the perfect mix of learning and humour, without letting the jokes take the front seat which sadly is the case with many podcasts.

I don’t want to ask questions since I have a feeling that my 550 episodes TWi-backlog will answer them… But as someone who likes to draw things from nature do you have any recommendations for parasites (or viruses and bacteria?) ?) that would look good on an illustration? Probably not going to be a big seller but I like to do some personal work for my own enjoyment.

Thanks for taking time out of your lives to share your wealth of knowledge!


John writes:

Vince and Dick,

Love your show! Do you know what effect fasting would have on strongyloides, that is, could strongyloides be starved to death? For example, a 40-day fast?

Thank you for your work!

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