Case guesses:

Fredrik writes:

Greeting to you all!

Not to worry, Vincent and Daniel, I think you did a good job of balancing the gravitas/levity. I am (the swedish equivalent of) a resident in Pediatrics at the University Hospital of Northern Sweden. Found your podcast family initially via twip in its early ‘parasitology 101’-era, and have since widened the perspective to include twiv and occasionally tvievo. I am not a scientist, but as a practitioner of medicine it is of course valuable to keep a foothold in the basic science of an ever-expanding universe of biomedical knowledge. I also greatly respect your endeavors to apply the ideals of scientific reasoning in the intersection of your own scientific expertise and public opinion. Most obviously perhaps in twiv, exemplified for instance by the two viral epidemics you have covered as they unfolded, adding a depth and complexity it doesn’t seem possible for traditional media to capture, neither scientific media nor news media. The integrity of those ideals is, in fact, the gravitas from which your levity can spring, even if the entertainment that offers can be a bit nerdy at times.

Enjoying as much as everyone else the case-study I have been on the verge of submitting answers previously, but something or other has gotten in the way. Was there a bit of a give-away in the presentation of the answer to last week’s case, or am I mistaken? My guess, based on the symptoms and the geographical distribution of the pathogen, is gnathostomiasis. The disease is usually self-limiting, but apparently on rare occasions there can be migration to non-cutaneous locales (ocular, neurological) which would present more acute indication for treatment. Traditionally surgical excision of accessible larvae is the standard of care, but albendazole or possibly ivermectin seems to be gaining evidence as an adjunct. For non-cutaneous disease radical surgery may not be possible, here repeated treatment courses of anti-helminthics may be required.


Fredrik, Umeå Sweden

David writes:

Dear TWiP Team,

After a brief respite from answering case studies for TWIP (but carefully listening nonetheless), I thought this particular case would be a fortunate opportunity to relapse into the habit of weekly parasitic pontificating. Upon searching the World Wide Web – a search on “migratory facial swelling” was suffice – I found a parasitic nematode that fits the bill quite nicely: Gnathostoma spinigerum.

This organism has an interesting multi-host life cycle: eggs hatch in fresh water and release L1 larvae, which are eaten by copepods or water fleas. These copepods are eaten by small fish, which are eventually consumed by a carnivorous species (such as a dog or cat) as the larvae develop into the L2 and L3 stages. The L3 larvae in the carnivore bore through the stomach, migrate about the body for around 3 months, then (strangely) return to the stomach and attach to the gastric mucosa, where they mature 6 months later. The eggs are carried through the feces into fresh water, where the life cycle begins again.

Humans, however, are an accidental host for this parasite, and the larvae continuously wander throughout the body, stimulating immune response until they die. A human can either drink water infested with infected copepods, or upon consumption of raw fish, introduce the larvae into the human body. This organism is endemic to Southeast Asia (which fits this patient’s geographic range), and has been known to stem from consumption of raw fish dishes that Thailand and other SE Asian countries are known for.

Current treatment for this parasite includes primarily albendazole, and strangely other antihelminthic drugs such as thiabendazole and metronidazole have not been seen to work experimentally – I wonder why this organism is only susceptible (so far) to albendazole?

Currently a chilly 39 degrees F in North Grafton, MA, and as the chills of winter approach, I will quote the inimitable Roald Dahl – “And they’re certainly not showing / Any signs that they are slowing”.

All the best,

David P

PhD Student, Tufts Cummings School of Veterinary Medicine

Molecular Helminthology Laboratory

Christine writes:

The weather today in Brisbane, Australia is currently 23C with expectations of a lovely 30 degree spring day to come. My guess for the diagnosis is that the patient is suffering from Gnathostomiasis.

“Gnathostomiasis is a food-borne parasitic infection that results from the human ingestion of the third-stage larvae of nematodes within the genus Gnathostoma. The most common species that infects humans is G spinigerum. Human infections are also caused by G hispidum, G nipponicum, G procyonis, G binucleatum and G doloresi. Gnathostomiasis is called by other terms in different countries worldwide such as Choko-Fushu Tua chid or chokofishi (Japan), consular disease (Nanjing), Shanghai rheumatism, Tau-cheed (Thailand), Woodbury bug (Australia), and Yangtze River edema. The larvae may be found in raw or undercooked protein food sources (eg, freshwater fish, chicken, snails, snakes, frogs, pigs) or in contaminated water. In rare instances, larvae can directly penetrate the skin of individuals who are exposed to contaminated food sources or freshwater.

Any organ system can be involved, but the most common manifestation of infection is localized, intermittent, migratory swelling in the skin and subcutaneous tissues. Such swelling may be painful, pruritic, and/or erythematous. In addition, Gnathostoma species commonly cause a parasitic eosinophilic meningitis, due to larval migration into the CNS.[1] Systemic infection is typically associated with peripheral eosinophilia, in which the percentage of eosinophils may exceed 50% of the circulating WBCs.

A classic triad that indicates infection is patient complaint of intermittent migratory swelling, predominance of eosinophilia in laboratory tests, and report of travel or residence in gnathostomiasis endemic areas (mainly Southeast Asia).[2]

It is written on medscape that the only definitive treatment is surgical removal of the worm, which is possible only when it is accessible.

However it also state that

“Although surgical removal, when possible, is the treatment of choice in gnathostomiasis, albendazole appears to have an increasing role in complementing surgical intervention.[14] Ivermectin in a single dose is better tolerated than albendazole but may be less effective.[15] Mebendazole, which was formerly used, had variable results and due to significant toxicities should no longer be used. Adjunctive corticosteroid therapy, as an anti-inflammatory, may have a role in the treatment of CNS disease.”

Thanks for your ongoing efforts with twiv , twip, twim, twievo, and urban ag. I look forward to each episode and am looking forward to updating my copy of parasitic diseases.

Christine from Brisbane , Australia.

Dr. Wink writes:

According to the 6th Edition of Parasitic Diseases (Thanks! — I will be sure to donate) both Gnathostoma spinigerum and Paragonimus westermani infect Thais eating raw fish dishes and may cause subcutaneous swelling. My intuition is to say paragonimiasis because it is more common, so I’ll go back to gnathostomiasis for my guess, because my intuition is often wrong.

Wink Weinberg

Mo writes:

Hi TWIPpers!

I’m a junior doctor from the UK and a recent convert to the Microbe World church!

I’m currently undertaking the East African Diploma in Tropical Medicine and Hygiene – a collaboration between the London School, University of Washington and Johns Hopkins – plus the host institutions (Kilimanjaro Christian Medical University College, Tanzania and Makerere University, Uganda). I would highly recommend it to anyone listening – it’s fantastic.

I started listening to TWIP during our parasitology module, on the recommendation of an old friend with whom I was reacquainted on the course, and have really enjoyed your insights and discussions. The cases have also been very helpful in putting the knowledge from class into a real context.

Given your lack of responses last week I feel this is a good time to put what I have learnt to the test and try and come up with a diagnosis. The relatively short history of migratory facial swellings associated with itchiness, possible preceding GI upset, eosinophilia and history of raw fish consumption in Thailand got me thinking about tapeworms and tissue nematodes! Working through the CHINA mnemonic I think we can pretty confident its a helminth, not least because of the name of the podcast.

My differential diagnosis is:

1) Cutaneous Ganthostomiasis, most likely caused by caused by gnathostoma spinigerum. The triad of migratory swellings, eosinophilia and living in an area where this zoonotic infection is endemic makes it the most likely diagnosis for me. Humans usually become infected by eating raw or inadequately cooked freshwater fish or other intermediate hosts such as snakes, frogs, and chickens. With the lesions on the face, this woman would be at risk of CNS or ocular involvement, which could be catastrophic. In a case I learned about recently, the parasite eventually came out of the patients nose! And with some quick thinking and a google check of the composition of normal saline it was kept alive so the diagnosis could be made macroscopically! In this case, diagnosis would be made by serology I think. Treatment will be needed if it doesn’t make its own way out and although surgical removal would have been needed in the past, I believe Albendazole and/or Ivermectin would be effective. She should probably cook her fish in future.

2) Sparganosis, caused by spirometra spp. I think this could cause a similar pattern of disease and, again, comes from consuming undercooked fish, frogs or the infected copepods. However, this seems a less likely diagnosis. Excising the nodule would treat this infection and allow you to make a diagnosis!

Hopefully I’ve got this one right, not least because I have been telling all my classmates to listen to TWIP. If not, I look forward to finding out the diagnosis and hope that my thoughts were not ridiculous.

All the best, and thanks for all the work you do.


p.s. my friend who recommended the podcast has an almost unhealthy affection and idolisation of Dr Griffin, so if he could say a quick hello to Rebecca I’m sure she would be very grateful, and really annoyed at me! thanks!

Jeff writes:

Hello TWIP triumvirate (assuming Dickson is back),

A much easier case this week, although I have to say that I enjoy the more difficult ones since even when I am wrong I end up learning something.  I believe the patient in Thailand is infected with Gnathostoma spinigerum as it is consistent with a firm facial swelling that is migrating and linked to raw/undercooked seafood (especially swamp eel – doesn’t sound appetizing).  I would be interested to hear if surgical excision is still considered primary treatment with Albendazole available.


Jeff Fairman, Ph.D.

Vice President, Research

SutroVax, Inc.

South San Francisco, CA 94080

Mike writes:

OMG, is that a stack of buzz-saws on its head? Oh, hooklets encircling the cephalic bulb. Nevermind. Of course I am referring to the inimitable nematode, Gnathostoma spinigerum, eager to blaze a meandering trail through your body, and in this patient’s case through the face, resulting in non-pitting swelling. Oh, and don’t forget the pruritis and eosinophilia. She most likely picked it up from eating raw freshwater fish or other raw delicacies such as eel, frog, bird and snake. Yum. If there is one thing I have learned from Lord Crislip, who also happens to play a professional chef on the internets, is that all food should be deep fried, or at least, heavily dosed with microwaves.

And I thought this was going to be “a kinder and gentler case”.      

Mike from Oregon

Allan writes:

Dear Drs. TWIP,

Still love following your family of podcasts though I’m disappointed I’ve not finished the last few episodes in time to make a guess of the case study.

I too am a fan of Thai pickled fish sauces: Pla-som and Pla-ra, although most familiar with the Cambodian national institution of Prahok in soups, as a dipinig sauce and on bread, yum.

Always interested in traditional food preservation practices, I had heard that Prahok was safe from parasites after 3 months of fermentation, but know that some like a vintage of 2-3 years. Do you all know how long would be considered safe?  

Might be an interesting study.

We did some similar studies at Tulane in the early 90’s to see if the citrus juice curing of cervice in Chile was sufficient to protect it from Cholera. (It was in our trials.) And we looked at what dipping sauces would be adequate to protect crawfish. (Of course we had no personal interest in the findings…)

I enjoyed your case study on Thai liver flukes Opisthorchis viverrini, a pervasive problem in northern Thailand, but I think one of you commented you were glad we didn’t have them in the US.

We do, at least here in Hawaii: Fasciola gigantica and Stellantchasmus falcatus especially with a growing public interest in organic watercress.

Regarding this week’s case of the Thai patient with facial swelling.

It sounds a lot like Gnathostomiasis, Gnathostoma spinigerum infection.

A larval nematode common in SE Asia, acquired by eating raw or undercooked fish, and in human, non-definitive hosts, causing non-pitting, “creeping eruption” or “wandering swelling.”

If it is G. spinigerum, then to badly quote Alec Guinness, “We are not the carnivores it was looking for.”

  1. spinnigerem is a multi-host parasite whose eggs hatch in fresh water and the larvae are eaton by Cyclops water fleas, which are in turn eaten by fish, which the parasite hopes will be eaten by almost any member of the Canine or Feline families, plus probably pigs. Over some 9 months, the larvae bore through the storage and eventually attach to the gastric mucosa allowing their eggs to be passed back into the environment in the host’s feces starting the cycle over again.

In humans, albendazole seems generally effective as a treatment.

Thanks for your great podcasts!

PS, Last week’s case was great. I wrote you a couple years ago about a case I saw of dientamoeba fragilis and blastocysts hominis in a family cluster I saw here on the Big Island, probably contracted from exposure pig feces as hunters…… and still I didn’t think of it for the case study.

Missed Dickson’s gracious humor and enthusiasm for related factoids last week.

And we haven’t had an article in a while on the fascinating macro-effects of parasites as TWIP has been famous for. Things like parasitic causes of host behavior change and related environmental changes, like stream depth etc.

Best regards,


Kailua-Kona, Hawaii

Brian writes:

Hello team TWIP,

I love the show, and have been listening to all the TWIx series for some time now. I am an undergraduate studying zoology at Southern Illinois University.  I will happily graduate in May of 2017. I only bring that up because I am not on parasitology professionally speaking with any of you, but that’s the great thing about your show, anyone can participate.

My guess for the 25 year old Thai female is Gnathostomiasis.  I don’t remember covering this organism in my parasitology lab so I was initially at a loss. But I have learned the basics of research and with very minimal digging I arrived at Gnathostoma infection. Not exactly sure which species and I am doing this while at work (and on my smart phone, so please forgive grammar).

Keep them coming and as always thanks for great content across all three shows. I truly enjoy them.

Lela writes:

Hello TWIP team,

I’ve listened to your discussions for quite a while, but this is my first foray into the cases. For the young woman with facial swelling, I’m going to venture a guess of gnathostomiasis. The nematode larvae can infect people when they eat raw or undercooked fish or other meat (like chicken), so it matches with her exposure history. The parasite cannot mature in humans, but the larvae burrow around through tissue and cause all sorts of problems. I got most of my information from the CDC page, where it says that people with an infection on their face are at higher risk for serious complications of the central nervous system.

I found myself interested in the various names for gnathostomiasis, like Yangtze edema, but it seems this parasite was relatively rare, so there isn’t much on the history behind the alternative names available on the internet. I also downloaded your book at parasites without borders – I’m a postdoc in molecular biology (RNA secondary structure), so I might be a dead end host, but I really enjoy your podcast. Thank you for all your hard work!

Trudy writes:

Dear TWiPpers,

I have to admit that in my case, Daniel was definitely right in saying that the reason I don’t send in my guesses for your case studies is that I’m ashamed of my profound ignorance and I am definitely afraid of failure.  However, with Stuart Firestein as my inspiration for overcoming these paralyzing obstacles to success, I will finally venture a guess on last week’s case study.  I hypothesize that the lady with the wandering facial swelling is infected with Gnathostoma spinigerum, a parasitic nematode that is acquired by eating raw or undercooked fish and meat.  

Thank you, Google and Wikipedia!

Yours Truly,


Neeraj writes:

Dear Twipologists,

My diagnosis for this latest case presented by Dr griffin is that of “facial gnathostomiasis in the Thai female. Gnathostomiasis is caused by a roundworm, Gnathostoma spinigerum. The symptoms presented closely align with the pathology observed due to this parasite”. I hope I am right in my diagnosis as I am really interested in getting the PDF of the parasitic diseases for my kind reference:)

Overall, I must say I really enjoy these podcasts and sorely missed having Dr despammier’s insightful answers to the questions that were posed. Please continue to do the noble work and I look forward to learning more about the parasites I didn’t even know existed.

Neeraj from SutroVax (a colleague of the almost always right “Jeff”)

Chris B writes:

Hello Professors,

I don’t want you to mistake the lack of emails on the case studies as a lack of interest, so here’s my guess: gnathostomiasis.

After consulting with Parasitic Diseases (6th Edition) (which I downloaded from and checking with the CDC’s web site, an infection with Gnathostoma spinigerum seems to fit the clinical presentation, geographical location, and eating habits described in the most recent case study. Migratory, subcutaneous lesions (which are described as “firm”) that are accompanied by redness, edema, but not necessarily pain, are commonly associated with gnathostomiasis. Humans generally encounter these worms as a result of eating raw or undercooked freshwater fish that are harboring the third-stage larvae.

A biopsy of the facial lesion could potentially isolate the actual parasite, which could then be identified via microscopy. However, an ELISA analysis of the sample seems to be one of the choice methods by which gnathostomiasis can be diagnosed. Both albendazole and ivermectin have been effective treatments.

Thank you all for the fantastic podcast. It keeps getting better and better each time.



(Dietrich Lab, Columbia University)

David writes:

Dear TWIP masters,

Having just listened to the latest twip episode 119, I decided to write in – partly because Eosinophilia cases are a clear delimiter and for that reason make me feel at least reasonably safe regarding my judgement, and also because it is somehow frustrating that on several occasions my guesses turned out to be right and I missed my chance to shine in the parallel TWIP universe because the next episode became available already.

For the lady from Bangkok with the migratory facial swelling my guess is Gnathostoma spinigerum because it causes facial swelling through cutaneous larvae migrans, is endemic in Thailand and is caused by the eating of raw fish.  I gladly refer to page 321 of Parasitic Diseases for further information.

I would like to take this opportunity to thank you so very much for the free online distribution of this work.  Ever since a mention of it was made about 10 episodes ago, I wondered how I would ever be able to lay my hand on the goodie.  Now it has come as an early Christmas present, and it is a great stimulus to stay on top of the cases.  I doubt whether I will read it in the digital format.  Given that  I spent my working days looking at computer screens writing applications, I dislike on-screen reading about as much as I love the full physical experience of a book.

As the hardcopy is also favorably priced for a work of this magnitude and beauty, I would like to buy it but I am not sure you will ship it outside the US (in my case to Nicaragua).  While this may not be a guarantee for reading, at least I know that the presence of the book will inspire me and my daughters to look at the pictures, and after using the digital version to make an estimated guess for case studies, we could use the hardcopy for bedtime stories.

Writing to you from Nicaragua with a midnight temperature of 25 C, I salute you,

Most sincerely,


Um writes:

Dear TWIP Professors,

If you come to Thailand last month, you will see a lot of people with slightly swollen eyes.  This had nothing to do with parasites. People were crying (me included!) because our beloved king passed away on October 13th.  For seventy years, our king  worked so hard helping his people, especially farmers and the poor.   The government will mourn for one year, so everywhere you go – you see people dress in black.   I believe the royal cremation would be held sometimes late next year.

Back to the case, I think the lady with swollen face has  GNATHOSTOMIASIS.   The worm probably crawl under her skin, and result in tissue inflammation.  She probably got it from consuming the raw fish that has third stage larva embedded in the meat.    I believe this parasite is rather difficult to treat.   Surgical removal of the worm can be tricky, and albendazole is not 100% effective.

As a side comment, the life cycle of this worm was discovered by two Thai researcher back in 1950’s.     One of them became the Minister of Public Health around 1960.  The other one became the Dean of Mahidol University Medical school around the same time.  

Keep up the good work.

We missed you Dickson!

Currently it is 30 degree celsius and we are about to have a evening shower.

Mr. Um  Pae-ra-ta-kul

Bangkok, Thailand.

Jarrett writes:

Hello all,

Regarding the case of the Thai woman with a migratory swelling in her face, my best guess is that she is suffering from an infection with the nematode Gnathostoma spinigerum. According to various sources online, these cases are most common in Thailand, and it appears that the first documented case in a human was in a Thai woman in 1889. Humans are not the definitive host for this organism, that dubious honor belongs to cats, dogs and other mammals. The embryonated eggs of G. spinigerum will hatch in water, where their larvae will infect a number of intermediate hosts, including fish. My guess is that this patient acquired her nematode though some fish-based dish in the typical Thai diet that we are learning so much about these days on TWIP. However there is no mention of gastrointestinal distress, which would be expected when the larvae migrate through the intestinal wall into the abdominal cavity. As a differential, I would consider any geographically appropriate organism that could be the cause of cutaneous larva migrans. According to the 6th edition of Parasitic Diseases, treatment is usually a 21 day course of albendazole.

I cannot thank you enough for putting making a PDF available of the new edition of Parasitic Diseases, it is fantastic reading and the color plates are wonderful. I’m looking forward to the strange looks I will get when I ask for a hardbound copy for Christmas. I cannot help where my curiosity takes me.

The weather in Austin is cloudy at 17 C, 64 F with few signs that sweaters will be appropriate in the near future.

Thanks for the good work,

-Jarrett H.

Austin, Texas.

Iosif writes:

Dear Twip Troupe,

I apologize for not writing for the last case, rotations are hard and time consuming and I don’t always have the time to do full research on the case and come up with an answer that is somewhat intelligent.

Because of that, I took Dr. Racaniello’s advice and looked up “migratory facial swelling due to parasites” to see if there were any previous cases.

Lo and behold, I got back an article about gnathostomiasis causing migratory facial swelling in Thai women! I think I’ll go with this as my prime diagnosis.

Gnathostomiasis can be obtained from eating undercooked snakes, frogs, fish or birds. The nematode found within then lives within the GI tract, but also likes to migrate to subcutaneous tissues throughout the body. If the parasite starts to migrate within the face then a reaction would lead to the distressing symptoms that our patient presented with. Treatment would be with albendazole 400mg x 21 days as reported in the 6th edition of Parasitic Diseases.

Other diagnoses that I may be considering is cutaneous larva migrans caused by other parasites like Ancylostoma braziliense. I would ask if the patient sleeps on the ground or for any reason had her face near the floor for prolonged periods of time recently. I would assume that this wouldn’t present as facial swelling as much as serpiginous lesions, but I have yet to see either so I cannot judge.


Iosif Davidov

Luke writes:


I am a long time listener of TWiM and TWiV and have recently ventured into TWiP. I would like to take a swing at the case this week!

My guess would be Gnathostomiasis by G. spinigerum. The reasoning would be based on the migratory facial edema and eosinophilia.

A differential to consider would be Trichinellosis due to the loose stool a few weeks back.

I would confirm the diagnosis with an assay and do a CT to check for hemorrhage.

I would begin treatment with corticosteroids to control inflammation and then begin treating with albendazole or ivermectin.

Thank you!

Bill writes:

TWIP Crew,

Greetings from Western New York.

Vincent sounded dejected at the lack of response to last weeks case.

Truth be told, I think he was missing Dickson and was perhaps a bit emotional.  🙂

Need not worry, you have many attentive listeners.  All the same, I figured it was time to take another shot – I am one for one.

The case is the woman from Thailand with swelling on the face that is moving around.

My guess is gnathostomiasis.  Per the CDC: Human gnathostomiasis is caused by several species of parasitic worms (nematodes) in the genus Gnathostoma. The disease is found and is most commonly diagnosed in Southeast Asia. People become infected primarily by eating undercooked or raw freshwater fish, eels, frogs, birds, and reptiles. The most common manifestations of the infection in humans are migratory swellings under the skin and increased levels of eosinophils in the blood. The symptoms of gnathostomiasis are thought to be related to the movement of the parasite through the body. When someone eats the parasite, it moves through the wall of the stomach or intestine and liver. During this early phase, many people have no symptoms or they may experience fever, excess tiredness, lack of appetite, nausea, vomiting, diarrhea, or abdominal pain. Later, when the parasite moves under the skin, people may experience swellings under the skin that may be painful, red, or itchy. The swellings move around and typically are not pitting, which means that if you push on the swelling with a finger an indentation is not left behind.

Treat with albendazole or ivermectin.

Many Thanks,


Shelby writes:

I’m writing in to briefly guess that the woman is experiencing gnathostomiasis. I have just downloaded the 6th edition of Parasitic Diseases (and intend to read it).

I really enjoy all of the TWIs keep up the good work!


Jonathan writes:

I just heard your podcast on our Nature paper

Thanks guys – great job!


Professor Jonathan Weitzman

Director, UMR Epigenetics and Cell Fate

UMR 7216 CNRS/University Paris-Diderot



Garren writes:

Just a quick comment that may be of timely interest. First the weather from Lebanon, Oregon. I’m trying to make Lebanon popular, I really do live here as well. The weather is rain.

Now the comment. Our friend Marcus over at Omega Tau podcast just did an entire episode on flying the V-22 Osprey. Its episode 219, came out just over one week ago. It is all about the engineering and flying of the V-22. I even saw one fly of Lebanon this summer.


Katreya writes:

Hi TWiP team!

I thought you guys might find this interesting – it’s a new device that can quickly detect malaria in one minute using a combination of magnets and lasers.



Research Assistant III – Scacheri Lab

Case Western Reserve University

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