Case guesses:

Iosif writes:

Dear Twip Team,

My guess for this case is Entorobius vermicularis aka pinworm. This parasite is extremely common with greater than 10% of the US population likely being infected. Infections travel via the fecal-oral route with eggs being ingested leading to larvae growth within the small intestine, from there the larvae matures to an adult and sets up a home within the cecum and appendix of the large intestine. The adult females migrate to the rectum and out onto the perianal folds (usually at night) and lay their eggs in that area. The adult worm and eggs can be irritating which leads to the itchy anus plaguing our patient. Scratching the skin allows the eggs to spread to the fingers and other areas and thus the cycle can begin again. Treatment would consist of either albendazole or pyrantel pamoate, with pyrantel pamoate being preferred due to the fact that it is available OTC and is cheaper. The difficulty comes in the likelihood of reinfection. By the time treatment is administered, the whole family is likely infected and the household is swarming in eggs. Adults also appear to often be asymptomatic with infection. Treatment should consist of the entire family taking medication at one time (a single dose of either drug is effective), and then a second dose of treatment roughly 2 weeks later to remove any reinfection caused by remaining eggs. Furthermore, as much of the linen, underwear, curtains and other areas of the house should be washed within this period as possible. Lastly, the children should be taught the importance of washing their hands and having short nails.


Iosif Davidov

P.S. As for the pronunciation of certain medical words; I too find myself unsure of how to pronounce certain things. For example:

  1. Gilbert’s syndrome – I was told that Dr. Gilbert was French and it is actually pronounced as Zhil-Bear rather than with a hard G and t.
  2. Kaposi’s sarcoma – In the hospital everyone pronounces it as Kuh-po-si, but in the NEJM podcast I heard it pronounced as cap-o-shi. Which one is more accurate?
  3. Pneumocystis jirovecci – I’ve heard most people pronounce jirovecci with a hard juh , but I’ve also heard it pronounced with a yi sound instead of juh and a -tsi instead of a -chi.

I’m sorry if what I have above is confusing especially since I am doing this with an e-mail and cannot pronounce these things in person.

David writes:

Dear Hosts,

The case of the young boy and mother with an itchiness in the anal area which becomes more intense at night sounds like a classic case of pinworm infection by Enterobius vermicularis. This parasite is the most common roundworm infection in the developed world, and ~20% of people (particularly children) in the U.S. may develop this disease at some point in their lives. The itching is caused by the pinworms migrating to the anal region at night in order to lay their eggs in the perianal space.

The child likely caught the pinworms from one or more of his 3 cousins who came to visit – the boy showed no symptoms until after this visit (unless the infectious eggs were transferred from a sushi chef, but the three children visiting seems much more likely). Pinworm eggs are hardy and have an adhesive surface, which can allow eggs laid near the anal region to be easily transferred to an itching fingernail and subsequently onto any other items the infected child may touch (bedsheets, toys, clothing, furniture, etc.) which can explain how the mother caught the infection.

To confirm this diagnosis, doctors should employ the “scotch tape test” – applying a piece of clear adhesive tape to the anal region in order to pick up residual eggs to be viewed under a microscope. Treatment includes medication in the benzimidazole family, including albendazole and mebendazole, which inhibit the microtubule function in adult worms.

Thank you once again for the entertaining and informative podcasts


David P.

Trudy writes:

Dear TWiPpers,

In follow-up to Vincent’s question on TWiP 132 about whether or not one can acquire Paragonimiasis in the U.S., I happened to find the following abstract via Mark Crislip’s puscast:

Although I can’t read the actual paper because it’s behind a paywall, if I correctly recall Crislip’s comments, one has a pretty good chance of acquiring Paragonimiasis (from P. kellicotti) by consuming raw crawfish right here in the U.S.  However, to my recollection, there was no mention of crabs.

While I am writing, I might as well take a guess at this week’s case study.  I am pretty sure that the NYC lady from episode 132 is infected with Enterobius vermicularis, also colloquially known as pinworm.  

The life cycle of this parasite begins with the ingestion of the pinworm eggs, which can be found ALL OVER THE PLACE in houses with small children.  The eggs hatch in the duodenum, where the emerging worms grow and then migrate through the small intestine towards the colon.  Somewhere along the way, the female and male worms mate, the males subsequently die, and are passed with the stool.  The gravid females, however, migrate through the colon towards the rectum, and usually emerge from the anus at night to deposit their eggs around the perianal area.  This is usually what causes the itching sensation.  The reason they need to emerge is because the eggs require oxygen to mature, however, this emergence also causes the mother’s death.  

The itching usually causes small children to scratch themselves, trapping the eggs underneath their fingernails, and propagating the cycle when they put their hands in their mouths.  Yuck!!! Adults are less likely to scratch themselves (especially if they know what is causing the itching!), and even if they do scratch themselves, they are MUCH less likely to stick their hands in their mouths afterwards!!! However, the presence of the eggs all over the house, and the likelihood of the children sticking their hands in the parents’ mouths at times, increases the parents’ chance of becoming infected.  

The pinworm life cycle usually occurs over the course of about a month. Treatment with over-the-counter medications such as pyrantel pamoate, or prescription medications such as mebendazole and albendazole is very effective.  However, since these drugs only kill the actual worms and not the eggs, an effective treatment regimen usually requires a second (or third, or FOURTH) dose at two week intervals to prevent reinfection by adult worms that hatch from any eggs not killed by the first treatment.  

According to “a friend” who recently suffered from this affliction, the movement of the worms is probably THE MOST disgusting sensation that “this friend” has ever sensed! One can diagnose this infection by doing the “scotch tape test”, although why one might want to do that is beyond me.  I would think that the itching on its own would be indicative enough to immediately seek treatment.

Lastly, I think that giving an episode summary at the end of each of the TWiX podcasts is a great idea, because even though I am a loyal fan, my mind does tend to wander sometimes when I listen.    

Thank you for your continued diligence!


Bill writes:

Dear Doctors:

Thank you for the entertaining and educational podcast. I have enjoyed listening to them on my commute in the DC region, where it is an Endor-esque 68 degrees Fahrenheit today.

My guess for the diagnosis is pinworms! As far as my thought process goes, upon hearing the words ‘iching’ and ‘perianal region’. I immediately thought of TWIP #19. Relistening to the episode seems to confirm my diagnosis.

To test this, do a sticky-tape test on the perianal region of all suspected hosts at night. NB: Can use dolls as props, but in that case if the patient speaks Spanish and not English, also add this addendum: “Hazlo a la persona, no a la muñeca”.

As far as advice to give to the patient:

1) Don’t panic! Everybody gets this worm at some point. You can quote Dr. D. on this from TWIP 19: “Nobody is dying from this thing, nobody ever did, and nobody ever will.”

2) Some people go overboard and become hyper-clean. Avoid this if possible as it can add a lot of stress and may be counterproductive, as unknowingly spreading the eggs all over the room can continue spreading the infection.

3) Do: bathe after waking up, wash your bedclothes regularly, wash your hands regularly, especially after using the bathroom or changing diapers, change your underwear every day, avoid nail biting, and avoid scratching the anal area

toxacara risk4) Treat with mebendazol until itching goes away. Itching may come back. If it does, come get some more mebendazol. At some point, the infection should clear with this strategy.

As an aside, listening to the TWIP on toxacara canis reminded me of this picture I have attached which my little brother (who is an award-winning photographer) took at one point from a beach in Brazil. Enjoy!



Nita writes:


   Hello again TWIP-tastic peeps! This is Nita again, the silly hopeful neurologist-to-be. I am glad to hear that the castrating barnacle was amusing! For this week, our young NYC woman experiencing anal itching for a few weeks puts pinworm on the top of my differential list. Often contracted by children through fecal-oral contamination, female pinworm crawl out of the anus at night and causes itching with egg-laying. The child then scratches and often ingests the eggs at a later timepoint, thus reinfecting the poor victim. The itch-scratch-itch cycle is perpetuated, and the child can easily pass this on to the rest of the family. In our patient, because of frequent contact with children and a son with similar symptoms, pinworm seems to be the most likely cause. Treatment is usually mebendazole.  Another parasitic culprit includes scabies, though it’s kind of unusual.

   Other causes of anal itching include dryness or irritation to the perianal skin. This can result from eczema or rashes (in which different textures like new underwear types or new soaps should be investigated). Allergic reactions could also cause irritation/itchiness, so maybe the sushi can cause this? Dry skin can be a result of using harsh soaps. Increased liquidy bowel movements, diarrhea, or incontinence can also result in itching/irritation.

   There are also other sources of infection, such as candidiasis, yeast infection, or HIV that should be investigated.

   Thanks again for the amazing podcasts!

Caleb writes:

Hello, doctors of TWIP!

I’m a relatively new listener, (a grand total of two episodes) and this is the first time that I’ve e-mailed the show.  I work in law enforcement, and listen to your show while I’m on patrol.  I really enjoy the case studies and as a total layperson, am glad to be able to understand about 40% at best of the science you talk about in the papers you review. Please, keep up the good and entertaining work.

I’ve noticed that the responses to case studies that I’ve heard in the past generally come from people who seem to have reference works to check for parasites, or some kind of expertise in the subject matter.  I have nothing of the sort.  Despite this handicap, I was able to muster up the courage to search Google for “anal itch parasite,” and I think I may have found an answer.  My guess is that your patient has an infection from Enterobius vermicularis, otherwise known more commonly as the pinworm.  The information that I found online says that a pinworm infection causes itching in the anal area as its main symptom, which matches the complaint by the patient.  In addition, pinworm infections are common among young children, especially when there are many in a confined area.  The patient could have been exposed when she hosted the three young relatives 3 months prior, OR in their frequent volunteer work with children. In addition, this seems to be the direction that Dr. Depommier was leaning, when he asks if the patient observed any white things in their feces.  The worms are small and white and can sometimes be observed in the feces of the host.  The pinworm settles and lays eggs in the anal area of the human host, which causes the itching.  The worms can be easily spread, and symptoms can be relatively mild, so it could well be that her son is also infected, since she believes she sees him scratching himself more often than normal, even if he isn’t openly complaining.

Pinworm infection can be diagnosed by what seems to be rather obviously called the “tape test.” Upon waking, the host can place the adhesive side of transparent tape to the anal area, and should be able to collect pinworm eggs, which can be viewed under a microscope. The information I’ve found says that the most common treatments for pinworm infections are the following three prescriptions: mebendazole, albendazole, and pyrantel pamoate, as well as good hand hygiene, as the eggs are often spread by hosts scratching the itchy area, and collecting eggs under their fingernails.  I’m at the mercy of the internet for all of this, so I hope this information is correct.

It’s a  beautiful day in eastern Nebraska, 70 degrees with a light north breeze, low humidity, and barometric pressure at 30.11.  Thanks again for putting so much time into entertaining and educating me and others.  Between TWIP and TWIV, you’ve inspired me to become interested in science in a way that I haven’t been since college.  Have a great day, and keep up the good work,
Caleb (pronounced Kay-lub)


Anthony writes:

Perhaps a Believe It or Not feature might be of interest on TWiP.  A candidate might be the Candiru:

The article is sceptical and that’s good.  That being said — if memory serves me correctly -in a tropical fish publication on Piranhas Candiru attacks are mentioned.  The story was that the indigenous people living on the Amazon only feared the Candiru and the sting ray — not piranhas, electric eels, big cats, or reptiles.

Burroughs mentions the Candiru, too:

On a separate note, Bradbury seems to have Delusional Parasitosis in mind in the Illustrated Man.  In that book, Ray Bradbury has his protagonist say this about his tattoos:

“Sometimes at night I can feel them, the pictures, like ants, crawling on my skin.”

Anthony writes:

Beware of ticks bearing young?

A search in Google books using the keywords tick, viviparous yields

Melophagus ovinus


Johan writes:

Here is a bit of additional information on the mosquitoes/mosquitos “controversy”.

I came across the diversity in spelling in a tweet by Darren Naish.

As I had Parasitic Diseases 6e open on my computer, I searched for both spellings and was slightly surprised to see both variants, so I went to Google Books Ngram Viewer

mosquito vs mosquitoe

It appears the usage drifted towards ‘mosquitoes’ starting in the early 1820’s but ‘mosquitos’ has never completely disappeared from usage.


As to the pronunciation of my name, there are two answers as I have lived 30 years in California and I gave up a long time ago to make Americans people use the Swedish pronunciation. People just don’t hear what they are not expecting.

So, here is the American version followed by the Swedish version.

Anthony writes:

Deterioration of basic components of the anti-predator behavior in fish harboring eye fluke larvae

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