Case guesses:

David writes:

Dear Hosts,

It was extremely interesting to hear all of the different diagnoses in the previous podcast. I think you had most of us stumped, but the listeners of TWiP are quite erudite and all of the guesses were well thought out.

In the case of the nurse that Dr. Griffin examined, I believe her foot has been invaded by a hookworm species (most likely Ancylostoma braziliense) which is causing the itchy raised serpiginous rash on her foot. This zoonotic disease occurs when a dog or cat hookworm accidentally parasitizes a human host, which is not the parasite’s definitive host. The worm aimlessly wanders throughout the dermal tissue, leaving a trail of secretions containing hydrolytic enzymes that trigger an inflammatory reaction and producing the “creeping eruption” characteristic of cutaneous larva migrans.

Treatment of this condition are numerous, and include:

  • Oral treatments such as albendazole (1+ dose) and ivermectin (1 dose)
  • Topical applications such as thiabendazole (10-15% three times a day for 5-7 days)
  • Topical freezing agents such as liquid nitrogen (not recommended)

All things considered, I’d like to think the theme revolves around Worms of All Shapes, Sizes, and Species – we have seen an arthropod worm (maggot), and then moved onto a nematode hookworm. I wonder if the next case study will showcase a tapeworm or a flatworm? Perhaps an alternative recurring theme is young professionals travelling and contracting worms (or any illness for that matter)?

Thanks again for the informative podcast


David P.

Peter writes:

Hi TWiP team.

The serpiginous lesion that changes location clearly points to cutaneous larva migrans ‘CLM’.

Described in Parasitic Diseases Sixth Edition under Aberrant Nematode Infections.

This is the result of a zoonnotic hookworm infection from either Ancylostoma braziliense

Uncinaria stenocephala, these nematodes are parasitizes dogs and cats, there are other nematodes that can cause CLM but they do not always produce serpiginous skin lesions. CLM  can be diagnosed from the characteristic skin lesions. Biopsy is not recommended.

Cutaneous Larva Migrans is self-limiting as the larvae are unable to complete their life cycle in humans. According to the CDC migrating larvae usually die after 5–6 weeks.

According to Parasitic Diseases migrating larvae can survive the epidermis for about 10 days

Albendazole and  Ivermectin are both  effective treatments but according to the CDC Ivermectin is not approved for this condition.  

Secondary bacterial skin infection  may need treatment with antibiotics.

Antihistamines and topical corticosteroids can be added to the treatment to help pruritus.

Cutaneous larva migrans was also the parasite in the case study for  TWiP 95, it has also been covered on Monsters Inside Me.


Ruben writes:

Dear prolific podcast-shedding Hosts,

 As one of your many infected recipients  I have to free myself from the itch to share my uneducated guess. It comes straight from the book of Dixon and Daniel (plus other Apostles of parasitism).

 The unfortunate nurse recklessly walking barefoot on the feces of dogs and cats may have a case of cutaneous larva migrans caused by larvae of  the dog and cat hookworms Ancylostoma braziliense, or Uncinaria stenocephala. A.braziliense is appears to be more likely.

  Now the treatment.  Hit the larvae with albendazole and ivermectin, cover the larvae with thiabenazole cream or freeze them if you can guess where they are hiding now.

 In conclusion: sometimes the ignorance, a frequent companion of youth, is bliss but not in this case.  Please put your shoes on.

 With kind regards,


La Jolla, California

  1. This sentence in your online description of “Case Study for TWiP123 need fixing: “.. Easts local food, exposure to dogs, cats, sister.  ..”

Iosif writes:

My main differential for this case would be a worm that is crawling through this young woman’s foot leading to Cutaneous Larva Migrans (AKA “ground itch” or “plumber’s itch”. My most likely guess as to the culprit would be Ancylostoma braziliense. This worm normally parasitizes cats or dogs, but can accidentally get into us. Once in us, they cannot complete their life cycle since they lack a collagenase enzyme necessary to pass through the basement membrane in humans. Thus, they squirm around in a futile attempt to find the correct blood vessel until they die. The immune reaction by the host leaves the serpiginous lesion; however, I’ve been told that the lesion no longer houses the worm, but rather only shows where the worm has been. If she starts to develop pulmonary symptoms, GI symptoms, positive hemoccult, or symptoms of iron deficiency anemia then I would be concerned about other worms that are more successful in humans. Worms such as Ancylostoma duodenale, Necator americanus and Strongyloides stercoralis all have the necessary collagenase enzyme and can travel through the outer layers of skin, make it into a blood vessel, reach a pulmonary capillary, burst through, travel up the trachea and finally be swallowed into the GI tract. I don’t think I would even test this woman for the particular worm since the treatment would be ivermectin in any case. I predict that she got better and I hope that the knowledge of having worms in her body does not deter her from future global health adventures.


Iosif Davidov

Toni writes:

Dear doctors:

I am Toni, the microbiologist from Spain, writing again.

As always, here is another interesting case study.

The main symptom is the presence of itchy papular (elevated) lesions on one foot. So the differential diagnosis could be:

1) A fungal infection. It is usually itchy. The unresponsiveness doesn´t rule out a fungal infection, since there are several highly resistant species, but makes it less likely.

2) Another option could be scabies. It produces an uncontrollable itchy feeling and on inspection we can find the tiny burrows on the skin as one-centimeter-long-whitish lines. The location is not usual for scabies. And given its high transmissibility, we must find more people suffering the same type of symptoms.

3) Another option could be Tungiasis caused by Tunga penetrans. This infection is acquired walking barefoot on humid soils, as is the case in our patient. The dermatological sign is a less than 1 cm wide white patch with a black dot in the center and can be itchy, burning or painful.

4) Lastly, another option, which is my best guess, could be cutaneous larva migrans, a term used to describe several types of parasitic infections that can cause migrating lessons in their immature stages. Several parasites can cause larva migrans: Toxocara canis, Toxocara catis (both acquired by ingesting infective eggs), Fasciola hepatica (ingesting fresh water vegetables like watercress), Strongyloides stercoralis (skin penetration of infective larvae),gnathostomiasis,among others. The most usual aetiology for larva migrans is A. braziliense, A. caninum, Uncinaria stenocephala, collectively known as zoonotic hookworms. In the Americas the most common species is A. braziliense. These are the equivalent in dogs to human hookworm. The immature larvae cannot penetrate the skin so they are not able to finish their life cycle as the do in their definitive hosts. The speed at which the larva moves is also important: in the case of zoonotic hookworms the speed ranges between 1 and 5 cms a day. Strongyloides is much faster, with a 5 to 15 cms per hour!.

Said that, the speed is important. We can measure the speed just by putting a mark on the skin of the moving-front and another mark one hour latter.

P.S. Do you believe in coincidences??. I want to share with you my experience. In 2005, I was working with my wife in Southern Mozambique with an NGO involved in a health project. It happened that my wife begun to feel uncomfortably for several days and someone suggested to do a blood test to check for malaria. It then seemed unlikely since she was taking preventive pills (mefloquine), so finally I did the thin smear. That exactly day was her birthday, the 25th of April. To our surprise, I diagnosed her a (2+) infection by Plasmodium falciparum. And it also results that the 25th of April is the WORLD MALARIA DAY.

Thank you very much and happy christmas for everyone.

I hope many more fantastic episodes for 2017!!.

John writes:

Hi Three Wise Men (well, ’tis the season),

I’ve been listening for a while and this is my first email and first case study guess. My background is in software but my research for this case involved “Parasitic Diseases 6ed” and wikipedia.

My initial guess (mainly because it’s one of the few parasites I knew about) was the ‘Guinea worm’ (Dracunculus medinensis). It affects feet and can be ingested by swallowing infected copepods by swimming in infected water (as this patient did).  However, it is now rare due to significant eradication efforts (including by President Carter) and occurs mainly (maybe even exclusively) in Africa, not Central America. Also, infection with the worm is usually associated with intense pain when the blisters have formed but the patient described it as “itchy”.

I briefly considered “Strongyloides stercoralis” but it didn’t really fit.

My actual guess is “cutaneous larva migrans” caused by the larvae of cat or dog hookworms. It seems to fit for several reasons. It is common in the Caribbean. There is a cat in the house. She walks barefoot. It presents most often in the lower limbs or feet. It is itchy. The lines on her feet are “serpiginous” (thanks Dickson). It moves. There are small fluid filled blisters. For treatment, I would refer you to “Parasitic Diseases 6ed, p313-314”.

BTW, Dickson suggested during the episode that the chemical elements have been around for the 14 billion year history of the universe. This is true for Hydrogen (about 73% of normal matter) and Helium (about 25% of normal matter). A tiny amount of lithium and beryllium and maybe boron were formed during the same period (within 20 minutes of the Big Bang). Of the remaining 2%, most (up to Iron) were formed later in stars (by Stellar nucleosynthesis) or (for elements larger than Iron) in supernovae (by Supernova nucleosynthesis) in processes that are still going on today.

(Listener Pick?) If you’re interested in Stars, Galaxies and the Universe, Professor Pogge of Ohio State University has audio recordings and lecture notes for his  “An Introduction to Solar System Astronomy – Astronomy 161“, “Life in the Universe – Astronomy 141” and “Introduction to Stars, Galaxies, & the Universe – Astronomy 162” courses.

Regards and thanks for all the podcasts,

Best of luck for 2017,




Mike writes:

Hi guys

At first I was thinking it might be “swimmer’s itch” (Schistosomiasis), but now I’m leaning towards “plummer’s itch” ie. Hookworm -Ancylostoma duodenale or Necator americanus. I still remember Dickson telling a wonderful story of hookworm in TWIP #22. People! Remember to make your outhouse hole at least 6ft deep. I used to have a micrograph of hookworm as my desktop image until my wife saw it and freaked out.

Mike in Oregon

Sathish writes:

Dear TWiParasites,

The curious case of the snake-like rashes on the nursing intern sounds like the classical textbook description of “Cutaneous larva migrans” caused by the 3rd stage larvae of Ancylostoma braziliense, which burrows onto the skin. Given her history of barefoot adventures it is easy to imagine the repeated exposure to this parasite abundant in soil. The disease is also known as “Creeping eruption” with most cases appearing on the feet with the serpiginous lesions upto 5 cms long. It can also present in the buttocks, abdomen, legs, arms and face. It is usually self-limiting, but short course oral albendazole or ivermectin can be used.

Sathish K

PS: I am currently working through parasitology as part of my Masters in Infectious Diseases from the London School of hygiene & tropical medicine. I am thankful to TWiP especially your initial 50 episodes which are a great resource to understand the basics of parasitology and helped me bridge the gap between bench to bedside 🙂 In fact, it was a sweet co-incidence that I was just beginning to read hookworm chapter in my textbook when I was wondering about this case. The book chapter had all the keywords, “moving lesion”, “serpiginous”, which were dropped quite smartly, by Dr. Racaniello in the podcast which got me hooked to the chapter. The final giveaway for me was a picture of the classic lesion which was referenced to Despommier et al and Parasitic Diseases, 4th edition. Aha! I never looked elsewhere from that point.

Dr. Griffin, I remember you saying that you visit India frequently. I was wondering if I could get an opportunity to meet you face-to-face when you come here for your talks. I have grown so accustomed to all your voices, jokes and insights. I learn a lot from you all and feel a certain connection, dare I say emotionally, with you all. I guess TWiP is like a boy band and your talk is music to us all. So, please let me know when you come to India next time, so I that I can visit you and get my parasitology books autographed! I live close to Vellore in south India.

I wish you all a happy new year 2017.


Iosif writes:

Dear Twiplets,

Due to the vague nature of the symptoms and lack of “buzzwords” in this case, I have gone with several worms in order of what I think are most to least likely.

My most likely worm would be Strongyloides stercoralis. This worm is absolutely prominent in the DR and can cause a diarrheal illness. The worm may be obtained from the soil and burrows through the foot of the host, it then travels to the lung capillaries, goes up the trachea to finally be swallowed into the nice, moist, warm, comfy GI tract. If the host is immunocompromised, then the worm may disseminate and form a “thumbprint” rash. I believe that Strongyloides could be the appropriate size and so fits the case most well.

Hookworms are also on the differential. Necator americanus or Ancylostoma duodenale infections may lead to diarrhea, but also usually eventually to an iron-deficiency anemia. Heavy infections may also present with respiratory symptoms due to the migration of the worms through the lungs on their way to the GI tract. The patient does admit to walking barefoot, which would provide the right risk factor for this infection. Furthermore, the adult worms may be around 1cm as reported. The reason this diagnosis may not fit is that there doesn’t seem to be any symptoms of iron deficiency anemia to clinch the diagnosis. I would look at the patient’s feet to see if I could see any serpiginous lesions or rashes.

Next is Trichuris trichiura also known as “whipworm.” These worms may cause an inflammatory diarrhea that can be what our patient is experiencing. It is typically tropical, but can be found worldwide. The most disturbing symptoms that may follow are the tenesmus (feeling or inclination that you need to empty your bowel) and eventually rectal prolapse. Neither of these symptoms are things that our patient is presenting with, thankfully. Furthermore, the adult worm is usually 3-5 cm in length and not the 1cm reported within the stool.

Enterobius vermicularis is also around 1cm in length, but the symptomatology does not match. It usually does not cause diarrhea and instead leads to an itchy behind.

While I await ova and parasites analysis on the stool samples, I would start ivermectin as treatment since it should be effective on most of these worms.


Iosif Davidov

P.S. I had heard before that a disseminated worm infection could lead to Strep bovis seeding out of the GI tract and being found in the blood or CSF. I haven’t found any evidence to suggest this, but is this something that you have heard about? And if so, should all patients positive for Strep bovis get both a colonoscopy and an ova&parasites?

P.P.S. Thanks again for the textbooks to our medical school!

Hayley writes:

Dear Twip Doctors,

I work as a food safety & quality specialist at produce company, so your case presentation of the woman with intestinal myiasis from fruit fly larvae was the talk of our office this morning (or rather it was me talking, making everyone else uncomfortable)! Not only do we love mangoes in our office, but as health conscious individuals, we eat the skin for an extra dose of fiber and for its various phenolic compounds. If the urushiol has any effects on us, we are as yet unaware of them; I’d like to think that I’m inducing immunotolerance to the substance by introducing small quantities of it to the lymphocytes in my Peyer’s patches so I might have less of a reaction if I ever encounter poison ivy on a hike (?), but maybe that’s just wishful thinking.

Some of your listeners might be relieved to know that mangoes imported to the United States are subject to various phytosanitary treatments before they’re allowed to enter the US, and many of these are specifically designed to kill fruit fly larvae. Hot water treatments of 115-118 F are common, for different durations depending on fruit weight and cultivar. Ionizing radiation doses are also used, minimum levels differing based on which pests are endemic to the exporting country. Both treatments are done to protect crops in the US from pests of economic significance, of course, but hopefully this may also reduce the pests of clinical significance as well (although I’m not sure what levels would be required to kill larvae of the false stable fly or others capable of causing myiasis). Which treatments are required for which country exporting the fruit is determined by APHIS, the Animal and Plant Health Inspection Service. Anyone interested in this can look at APHIS’s Treatment Manual which you can download online (see link below).

However, since parasites don’t have borders, these treatments wouldn’t affect fruit flies that would begin their infestations after the fruit had been imported. One case study I found online was a 12-month old girl in Washington, DC who had developed myiasis after being fed fly-ridden bananas (link below). Another I found was in two children whose father ran a compost business. It seems to me like the biggest risk in the US is to, sadly, to poor and/or desperate individuals forced to eat food that probably shouldn’t be eaten anyway, or to children whose parents do not keep sanitary households.

I have a question for you gentlemen. My mother watches Hoarders, a show about individuals who suffer from compulsive hoarding, a form of OCD that sometimes causes them to keep things are rotting or unsanitary. Every time I see the show, I think that people with compulsive hoarding must get all sorts of random diseases that your average doctor would not expect. Do you know of any parasitic diseases that compulsive hoarders may be at an increased risk for? Is anyone investigating this? Do you think if a doctor diagnoses a child with myiasis, that the doctor has an obligation to ask about the sanitary condition of the household and should maybe contact a social worker? I’d just like your opinions.

Thanks so much,

Anthony writes:

I don’t think that leeches have been featured on TWiP.

Leeches still are used in medicine:

It appears that leeches can be disease vectors.  (See below.)

Thank you.

Anthony Olszewski

# # #

J Exp Med. 1957 Apr 1;105(4):373-82.

The leech as a potential virus reservoir.


Parasitol Res. 1994;80(4):277-90.

Experiments on the possible role of leeches as vectors of animal and human pathogens: a light and electron microscopy study.

Nehili M1, Ilk C, Mehlhorn H, Ruhnau K, Dick W, Njayou M.

Tick Longicin Implicated in the Arthropod Transmission of Toxoplasma Gondii

I don’t remember arthropod vectors of Toxoplasma gondii having been discussed on TWiP,  It appears that ticks can carry the organism.  

I wonder if cat fleas can transmit Toxoplasma gondii?

Eugene writes:


I heard a review of a book, The Lost City of the Monkey God by Douglas Preston. The book describes the location and exploration of a pre Columbian city in Honduras. Preston was among those involved in the exploration. He described the area around the city as having a particularly high density of dangerous arthropods. Apparently, all of the members of the expedition came down with a form of Leishmaniasis.

I have put the book on my short list and will get to it soon, but I thought that you might be interested in reading it, as the author implies that there was something peculiar to the area which made it far more dangerous than other pre Columbian sites.

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