Case guesses:

Kevin writes:

Dear TWitch Doctors,

Case guess for TWiP 188: Sarcoptes scabiei, as suggested by the interdigital distribution and nocturnal timing of the itch, the duration, transmission between partners, possible acquisition in a hotel bed, the diagnosis by skin scraping, and the course of ivermectin treatment. The patient had itching all over, which is often due to spread of allergens rather than the mites themselves. I wondered whether the immune/allergy response to the mites might be different in older individuals. All I found so far was a study of scabies outbreaks in nursing homes that reported fewer hosts reporting symptoms or showing burrows in the typical spots. Perhaps our patients were diagnosed later because physicians were not looking in the right places for burrows?

Unrelatedly, the thought recently struck me that the feats of Toxoplasma gondii are often talked about such as its incredible ability to infect so many hosts and cell types without being eliminated by the immune system. However, this is only one side of a coevolutionary story. Shifting perspective, there could be selective pressure for incidental hosts like ourselves to not react strongly against this ubiquitous, mostly harmless parasite if the immune response would be costly, ineffective, and dangerous. To anthropomorphize, the success of T. gondii could be attributed to our apathy as much as its guile. Perhaps this isn’t such a novel thought, but I was invigorated by it. 

Best regards,


Tim writes:

Greetings TWiP,

The TWiPing is so much nicer when the case study is easily treatable and involves an old guy with senescent immunology vs. the baby with hydrocephaly (TWiP 187. – I didn’t get the prognosis on that … it seems widely variable?)

My searches using Invermectin as keyword and further readings are pointing to Scabies. 

Returning to your textbook – confirms this I think…

“From Chapter 39. Arachnids Human Itch Mite: Sarcoptes Scabiei p. 489.” Parasitic Diseases, by Dickson D. Despommier et al., Parasites Without Borders, 2019. 

Two nice footnotes in your textbook on Invermectin to treat this…

50- Goldust, M., et al., Treatment of scabies: Comparison of permethrin 5% versus ivermectin. J

Dermatol 2012, 39 (6), 545-7.

51 – Romani, L., et al., Mass Drug Administration for Scabies Control in a Population with Endemic

Disease. N Engl J Med 2015, 373 (24), 2305-13.

Nice two minute video on the SHIFT trial exploring Permethrin vs. Invermectin from this last footnote- worth the NEJM account creation to view…

I really liked this tidbit (and the many placed throughout the textbook) as well just north of the Arachnids chapter… I wasn’t aware of Miriam and now I am… many people think and have thought about parasites.  Now I am one of them thanks to TWiP and others like you and Miriam who think and thought harder still.  Carry on

Barbara writes:

The man has scabies. 

I am an ordinary lay person, so I don’t know much. But the increased itchiness at night, the likely spread from his wife (via the hotel bedding or towels) and the eventual diagnosis from skin scrapings indicates this is scabies.  

I don’t know why ivermectin was given rather than scabicide ointments (what a wonderful term!).  Perhaps because of old age, or because previous treatments had failed? I do hope they decontaminated their bedding and clothes.

Scabies is quite common here in South Africa amongst young children in early childhood centres. At least, it was until Covid-19 put most ECD centres out of business. Who knows what children are suffering now? Scabies, lack of stimulation, toxic stress, deepened poverty, hunger?

Thank you for your cheerful, chatty and informative podcasts – the kind that make you interested. 


13C, windy, drought conditions

David writes:

Hello TWiP,

For the case presented during this episode, I will submit a guess of Norwegian or crusted scabies caused by mite infestation.

The patients both fit the profile of individuals that could be at risk due to their age, and presumably their lower immune system responses. With the wife experiencing the symptoms first, possibly from exposure during her trip and stay at a hotel, her return home in an infested state could have easily passed this along to the husband.

Dr. Griffin’s characterization of the brown, scabbed area between the toes seems to fit with a case of crusted scabies. if the sample collected showed mites, eggs, or other signs of the infestation, the prescription of ivermectin would be indicated.  The description of the stronger dosage, and repeated use of ivermectin, also seems to fit with the guess.

Very curious as to what this is, if it is not scabies. I made the assumption that this was a locally sourced infection vs. a more exotic tropical disease.

Thanks for the show and for providing productive brain stimulation while we hunker down waiting for the COVID-19 fall and winter to pass.

Take care,


Abingdon, MD

Jeremy writes:

wife picked up the sarcoptes in the hotel. took them home to him. 

has scabies.

Alexander writes:

Dear TWIPers,

I‘m a regular listener of Twiv since the corona pandemic, not missing a single episode.

Lately I also discovered Twip and the possibility to participate in solving the case. 

In the actual case a lot leads to a diagnosis of scabies.

It is caused by mites and is typically aquired after skin-to-skin contact. Occasionally transmission may occur via fomites (bedding or clothing) like in a hotel.  It leads to a generalized rash which is an immune reaction to the mites. The rash is more severe at night in bed because of increased temperature. I think the rash can be influenced by cortisone although this does not solve the problem as the mites are still there. 

Scabies can be treated by giving ivermectin but you always have to treat the partner, too. Otherwise you get “ping pong” infections. 

After making the diagnosis (finding a lesion between the toes where the skin is thin and an ideal location for the mites to infest) and treating both of the couple led to the resolution of the disease and clearance of the rash.

Looking forward to more interesting parasitic cases …

Best regards from Germany,


Susan writes:

Love your show!!! My guess for 90yr old man & wife: bedbugs.

Thank you,


New Port Richey, FL

Leland writes:

Dear TWIPlets,

When I was in medical school, an old sage once told us that if interaction with a patient left you feeling depressed, then there was a high probability that the patient was suffering from depression.  I have found this to be a useful trigger for further investigations, but I have also been aware that this effect is not limited to psychiatric disorders.  This case in point…  As Daniel began giving the details of the case, I subconsciously began to rub my forearms and the back of my ears, and the more information was given, the itchier I got, until by the end of the presentation, I myself was ready to claw my own skin off.  As anyone who has ever taken care of a patient knows, the mere mention of Scabies is a more potent irritant than poison ivy, and I suspect that I am not the only one still itching to render a diagnosis!  So just like my mentor’s observations on depression, my own pruritis clenched this diagnosis for me!

Yes, this patient has scabies.  His history is classic: gradual progression, nocturnal exacerbations, transient response to steroids only to worsen, and a transient response to ivermectin.  I would also add that, unfortunately, the missed opportunities to diagnose, treat, and cure this common problem is also classic in the presentation.  Often I see these patients only after others have offered antihistamines, steroids (both topical and systemic), and a bewildering variety of pills, potions, and poultices, none of which have treated the problem effectively.  In this case, this man acquired the infection from his wife, and he was ultimately prescribed the proper drug (ivermectin), but he never got a second dose of the drug 2 weeks later to dispatch the eggs which hatched following the eradication of the infestation with the first dose.  Ivermectin does not kill eggs that have already been laid, so the second dose is almost always necessary.  You might say that one dose barely scratches the surface!

Scabies is passed almost exclusively by direct skin-to-skin contact, but fomite transmission can and occasionally does occur.  The mites burrow into the skin causing an intense inflammatory reaction, and the females lay eggs which then hatch and continue to burrow.  Initial infections are usually limited in scope and can often be identified by linear rashes on and between the fingers or in other intertriginous areas, but over time, or with a large initial exposure, the rash can become more generalized.  Patients with compromised immune systems can progress to the most severe form – crusted, or Norwegian, scabies.  In this case, the rash is overwhelming and can be heaped-up and warty appearing.  I do not think the patient in question had the Norwegian variety because he does not really fall into any of the risk groups, and because crusted scabies is often paradoxically not pruritic as his was reported as being.  

Treatment for this patient should be 2 doses of ivermectin separated by two weeks.  If he indeed does have Norwegian scabies, then he should probably receive doses of ivermectin on days 1,3,5,7, and 14, and also simultaneously be treated with topical permethrin.  His wife also needs to be treated at the same time, as do any other close contacts.

In summary, I am itching now… therefore, it must be scabies.

Now, back to the diabetic feet, the endocarditis, the UTI that really isn’t a UTI, and the COVID.  Oh, and the occasional ectoparasite.  Ah, the life of the ID physician!

Leland Allen MD

Tatiana writes:

First time guesser here. I would love to win a book! You don’t even have to sign it for me, just send right away with no delay!

I think the man and his wife have scabies. I caught this when I went to my college orientation week in 1976. It started as a small scaly patch on one shoulder, and because I didn’t get it seen, it grew to cover my whole body. It took months of lotion to get rid of it, along with washing all my clothes and bedclothes in hot water for that whole time. I’m still not 100% sure it’s completely gone, since for years when I would get sick or run down, I would occasionally see the characteristic wavy tracks on my skin. I checked the Mayo clinic site and found that Ivermectin is a current treatment for it. 

Thanks for all you do! I’m crazy about twiv, twievo, twip, twim, and all the twixes! Also Immune!


Sandro writes:

Greetings esteemed doctors!

I’m a medical lab technician in training from Germany. Parasitology was never a priority topic in the apprenticeship and thus was one of the first victims of the retrenchments as a result of the pandemic. This makes me even more thankful to you for helping me to keep my knowledge fresh and my enthusiasm for the field high. 

As for the case, the temporary and later lasting relief thanks to ivermectin rules out a fungal infection and strongly suggests some sort of parasite as the cause of the patient’s rash. The first dose of ivermectin only providing limited alleviation speaks for a more persistent nematode infection rather than scabies, which would be the only ectoparasitic infestation I’m aware of that would result in a similar clinical manifestation, as scabies should be eradicated with a single application of ivermectin. The abnormal patch the primary care doctor discovered betwixt the patient’s toes is likely to be the area where the agent has first entered the host. A number of nematodes are known to cause ground rash, but I’ve found only one of them to both penetrate skin in order to enter the host and respond to ivermectin in the fashion presented here. This last worm standing is Strongyloides, who’s larvae are able to cause a full body rash, enters the host by penetrating their skin, and is ultimately defeated by ivermectin while not admitting defeat after one relatively low dose. While more common in tropical regions, it’s not excluded to get infected in more temperate climatic zones. Thus my final diagnosis is larva currens due to infection with Strongyloides stercoralis. 

Thank for this case which I personally found challenging and I hope to have made the right conclusions. 

Take care and stay healthy. Best regards, 


James writes:

Wonder why my son in law, “Arthropod Bait.” has not gotten THIS one yet? I should shut my mouth.

Sarcoptes scabei, small mite (arachnid not an insect) that burrows in the skin causing intense pruritis, in between digits is a classic clue.

A bit unusual to go “systemic” like you describe although there is this “Norweigan scabies” syndrome with more general symptoms, probably drove the Vikings to pillage the UK.


Creeping Eruption (sounds dramatic) caused by Hookworms, cutaneous larva migrans

Lice of various kinds I guess, probably body lice

Cercarial dermatitis, unlikely unless they did a surreptitious trip to Africa or Global Warming has progressed more rapidly in the Northeast and someone inoculated some snails into the local flyfishing waters.

Ringworm SOUNDS like a parasite but it’s an unfortunate name for a fungus. It can itch pretty badly too.

A jillion dermatitis syndromes of course although I doubt they are highly sensitive to Ivermectin.

Keep up the good work. 

James M. Small, MD, PhD, FCAP
Associate Professor of Pathology and Microbiology
Clinical Career Adviser
Rocky Vista University

Luke writes:

Hi Dickson, Daniel and Vincent. 

Twip 188 case sounds to me like scabies. A few other possible causes but less likely in temperate climates, and the history of the patient’s wife sleeping in a hotel bed makes me think it is the cause. Maybe the brown lesion between the man’s toes was the cardinal sign of the scabies mite and the microscopic triangular trail it leaves on the skin. 

I am starting my medical internship in Alice Springs (in central Australia) in January, where scabies is a big problem – not only because of the primary infection but because of the co-infection with Strep pyogenes causing post-strep syndromes like rheumatic fever, rheumatic heart disease and glomerulonephritis. 

Anyway, I hope my guess was right after going on about scabies. 

Thanks for the always enjoyable show. 



Alexander writes:

Dear Professors,

The elderly couple with the rash that got better on ivermectin probably suffered from an infection with sarcoptes scaibei, i.e. scabies. These mites burrow through the skin and lay their eggs in the outer layers of the epidermis, the symptoms that people experience, mainly an itchy rash, are caused by the local IgE-mediated reaction to the mites, their eggs and their scybala (balls of mite poop). 

Treatment is usually topical permethrin (cream or bath) in conjunction with strict hygiene including daily changing and washing of all clothes and bedsheets, airing out mattresses and textiles and extending this to all household members. Oral ivermectin is usually reserved for second line treatment in combination with permethrin or for people who are unable to follow hygiene guidance. The source of infection here might have been the hotel the wife stayed in a few months back as these mites can survive for hours to days in bedsheets and clothes.

The lesion between the toes of the gentleman might be a form of crusted scabies. While most people suffering from a scabies infection only have a handful of adult mites on (or rather, in) their body, immunocompromised people can develop thick crusts of scabies. There is no evidence of immunosuppression here, but I’ve seen a small number of crusted scabies cases in people in long term care facilities who were unable to scratch themselves due to advanced neurological disease. The inaccessability of the site might provide fertile breeding ground for the mites here.

I hope both of your patients manage to eradicate those nasty little buggers, I know that this can be very challenging. Keep safe, keep healthy and all the best to the TWIP team and all other listeners,


(Vienna, Austria, 17°C/63 F and a breathtaking, golden autumn sunset)

Katy-Jane writes:

Dear all,

I vowed to write sooner, yet somehow it has been almost a year. I have no real excuse for my hiatus, except, well, 2020 happened and I had a baby, and I will admit that raising a neonate in the midst of a pandemic has not been without its challenges – emotional and otherwise. I am finally getting caught up on missed episodes, and listening to Vincent state with such optimism at the beginning of January’s episode that 2020 is going to be a great year brought, with the wisdom of hindsight, an ironic smile to my face. It is interesting to listen to the coronavirus situation evolve through the podcasts, and when I am caught up on TWiP, I will move to TWiV to try to learn more.

I decided to skip ahead to the current episode in the meantime so that I would be able to enter a guess at Daniel’s case study. I’m a little disappointed that I missed the previous episode’s case study, as I guessed Toxo immediately. Alas, such is life. I’m glad that the prognosis for the infant was optimistic.

For this week’s case study – 90 year old man (and wife), severe itching, particularly at night, unlikely to be allergies. My first thought was bed bugs (Cimex lectularius), especially because the wife had stayed in a hotel not too far prior to the symptoms occurring. However, from further reading, it seems as though people eventually become desensitized to the bites, which is clearly not the case here. Also, it is unlikely that treatment with ivermectin would clear the infection, as bed bugs would continue to be present in the environment.

This leads me to the same cause as my previous TWiP guess – another ectoparasite, Sarcoptes scabiei, or scabies. Scabies causes nocturnal itching, generalized body rashes, and is diagnosed by a skin scraping, often from skin between the digits. PD7 states that treatment of all members of the family may be needed to prevent reinfection, which would support the evidence of both husband and wife receiving treatment and the issue being resolved. Systemic treatment with ivermectin has proven particularly efficacious.

So, my guess is scabies. I may be wrong, but I told myself I would submit my guess this evening, and, these days, if I don’t stick to a deadline, things never get done! Thank you again for all that you do to edutain. 


Wausau, WI (where we are having a beautiful fall and the baby is sleeping)

Viki writes:

Dearest Twippers:

It’s 7:10 AM and skies are clear in Duluth, 47 degrees F by the lake and 41 on the hill.

I’m guessing our elderly couple had scabies. The hotel visit and that one gave the rash the the other is the hint. I consulted with my friend Deb, retired hospital microbiologist, and she said that the mites are very hard to get from a scraping; in all her years working, she never saw a single critter.

Our gentleman had a positive scraping from between his toes. The mites are common in the webbing between fingers, so why not toes? Confirming my diagnosis, Ivermectin cured the condition, though two successive doses were necessary.

Avid fan, Viki


Regarding the topic “Of the Death of Expertise,” using Amazon, I’ve sent a copy of the book “Higher Superstition: the Academic Left and its War on Science,” due to arrive at Vincent’s office by Oct. 19. By “the academic left” we don’t mean  people who vote as Democrats, rather the term refers to those with post modernist views, typically in departments with “studies” in the title (sometimes called collectively “grievance studies”, I hope in good humor).

My husband Bruce Henricksen, retired literature professor, was one of those post modernists, but after reading “Higher Superstition,” he saw the light and gave up his post modernist ways.


Owain writes:

Dear TWIP, 

I enjoyed the last episode, as ever, but also noticed that you didn’t get a chance to discuss a paper in the episode despite it being an hour and a half long! Is this because you get so many guesses, or that the letters are too long? I’m sure we as your audience wouldn’t mind making them briefer if that gives you more time to delve into other aspects of parasitology! Maybe it was just something about last week though, in which case please excuse my pearl-clutching panic that we were at risk of losing one of my favourite parts of TWIP! 

I think the patient in Daniel’s last case has “crusted” or “Norwegian” scabies, given the scraping from between the toes yielding the diagnosis – the “interdigital web” is a classic place for scabies mites to live. Ivermectin treatment was successful which further corroborates this. This is usually seen in immunocompromised patients – are his age and diabetes enough to account for it in this case? 

Sorry to hear that you can’t become a millionaire from selling old copies of West Nile Story, Dickson..! Thanks again to you guys for providing my favourite edutainment of all in these strange times!  

Yours sincerely, 


Schuyler writes:

Dear TWiP Team,

My goodness, I can’t believe I forgot to write in for your last episode even after having discussed the case with my med school’s  ID Interest Group. How am I ever to win a book if I keep forgetting to write in? I was happy to introduce the group to your podcast. So far, due to the fully-virtual curriculum, we haven’t been able to do much. I have, however, been enjoying the virtual once-monthly talks on tropical medicine. On to the case then. The full body rash and the multiple different medication attempts remind me of a dermatology joke:

“If it’s dry, wet it;
If it’s wet, dry it.
If it’s on steroids, stop the steroids;
If it’s off steroids, start steroids.
If you know what it is, don’t touch it;
And if you don’t know what it is, for God’s sake, DON’T touch it!”

Itchiness is extraordinarily unpleasant, it’s terrible that the man and his wife had to suffer for so many months before being able to find relief. Extreme itchiness, symptom persistence despite multiple treatments, and the presence of lesions in between the toes all point to scabies as my main guess. Interesting that ivermectin is used to treat scabies even though I think of it as an anthelminthic drug and scabies are mites. However, it appears to be a treatment for various arthropods, including mites, lice, and bedbugs. I also wonder whether there were any lesions in between the man’s fingers, where people tend to look for scabies – good thought on the PCP’s part to do a literal head-to-toe exam and check the toe webbing.

It is a refreshing 57F here in our nation’s capital. Wishing you all continued safety and good health,

Schuyler (pronounced Skyler, she/her)

Andrew writes:

Kia ora from Pongaroa,

Weather: high winds producing a spectacular cloud-scape and 18°C.

No book won yet: I asked a fortune teller to see if I would win and they said I was bound to win if my number came up in the draw. Feeling confident.

Covid-19: Our Prime Minister Jacinda Ardern, who led us to virtual elimination of the virus in New Zealand, has won a resounding vote of confidence and returned to power in a landslide in our recent elections. Perhaps other politicians should take note – following the scientific advice pays off. However, it is probably advisable to schedule one’s pandemics to avoid coinciding with national elections. We are also seeing many doctors moving to the country – mostly from the USA – sorry about that.

My guess: The Human Itch Mite: Sarcoptes scabiei

Like the teacher in TWiP 176 a head-to-toe examination gives the answer. The difference is that the arthropods were nesting between the toes rather than the fingers.   PD7 states, “Currently, scabies has reached pandemic proportions.” I wonder if the measures to deal with Covid-19 will lead to a reduction in the prevalence of this and other infections that rely on close human contact to spread. Also, one has to wonder how something like this would be picked up in a video consultation.

Ng ā mihi,


Peter writes:

Dear Three TWIPeteers

The case study in TWIP 188 is of a man with full body rash, with a wife with similar infection that resolves after a course of ivermectin.

The man in question is in his 90s with diabetes and hypertension and thus can be said to have a suppressed immune system. The description of a parasite affecting two people that live together, one of whom seems to have caught it while staying in a hotel, sounds like it could be scabies, caused by the human itch mite, Sarcoptes scabiei. The description of the rash as “full body” is a little bit unusual, as scabies-associated rash is generally found on the belly, buttocks, upper back and elbows (PD 7th Ed, p. 489). Perhaps the rash is more widespread because of the patient’s weaker immune system.

The ‘abnormal area between the toes’ could be a skin as shown in the first photo on this page: – this is associated with the actual borrows of the mite. Transmission is via skin to skin contact and can include transmission via bedding, although this is apparently somewhat rare.

Ivermectin is an effective treatment (PD 7 p. 491) but the medicine is not without side effects. Treatment of the affected areas with permethrin is another option, but it can lead to a temporary worsening of scabies symptoms.


Writing from a partly cloudy Cape Town, where the temperature is predicted to peak at 19°C (66°F)  today.

Catherine writes:

Hello again to the TWIP team,

Here is my response to the case presented by Dr. Daniel Griffin in TWIP #188. 

Well this one was fun. Based on the clues provided, my guess is the elderly couple unfortunately acquired scabies, caused by an infection of the parasite, Sarcoptes scabiei, a microscopic mite known as the itch mite. Furthermore, the husband contracted a secondary bacterial infection with Streptococcus pyogenes, which can follow scabies and resulted in the presentation of cellulitis on his foot. 

This guess is based on throwing the following clues into the hopper and hoping one parasite would connect them all: age and generally healthy status; the initial infection of the wife; the wife’s trip and hotel stay; the long period of infection of both spouses; the scraping of a brown, scabbed area between the toes of the husband’s foot that led to the diagnosis and his development of a full body rash; the second effective treatment with high doses of ivermectin; and cellulitis on the husband’s foot. 

If this guess is correct, the disease must have been a complete mystery to the couple, as symptoms of scabies can take up to a month or two to develop in persons without a previous infection.  Without knowing more detail about timing and location, it’s difficult to know how the wife acquired the parasite, but her trip and hotel stay offer a possible scenario. If her hotel room had been previously occupied by a guest with scabies, the mites could survive up to 2-3 days without careful cleaning. The CDC suggests decontamination requires careful vacuuming of furniture and carpets, and using the hot cycles to wash and dry bedding and towels. (As an aside, just how comfortable are parasitologists in hotel rooms?)

Prolonged close contact can spread scabies, so it’s likely that mites from the wife infected her husband. A weakening immune system in elderly people may increase their susceptibility to a more serious case of scabies and a rash that extends beyond normal rash sites. This might explain the husband’s full body rash. Scabbing between the toes is a symptom of scabies and a scraping of the scabbed area is used for diagnosis. Serious cases of scabies can require large doses of ivermectin given two weeks apart. The link with cellulitis was suggested by a review article in the BMJ’s Postgraduate Medical Journal (reference below), which indicated that untreated scabies may be associated with a secondary bacterial infection of S. pyogenes and present as cellulitis. This article had a lot of other good information as well. Of course, I may have misinterpreted or overstretched parts of this article and other information gleaned online. But crossed fingers, it all makes sense.

Reference: JS McCarthy, DJ Kemp, SF Walton and BJ Currie. Scabies: more than just an irritation. Postgrad Med J (2004); 80: 382-387.

Whatever the actual parasite was, I wish the couple continued good health.

May all of you stay safe and well,

Masked on the island,


Vancouver Island, British Columbia

Jody writes:

Dear TWiP Docs,

It’s sunny and cold here in Seattle, where I just got back from a masked playdate that ended with both 7-year-olds discussing the delights of tapeworms and slime molds. In your free time you guys should definitely write a book for kids!

In the case of the nocturnally itching nonagenarian, I believe he and his wife have had the honor of playing host to the human itch mite, Saccoptes scabiei. These wee arthropods usually set up shop and make themselves known at first in the webbing and sides of fingers and toes, later spreading to the rest of the body, and often cozying up in other warm dark places like armpits and the nether regions. 

Scabies is usually transmitted from person to person by direct contact, but can also be spread via bedding or clothing. Daniel mentioned a trip and a hotel, and maybe this is where the gentleman’s wife picked these little stowaways up, perhaps from unwashed bedding (shudder). According to PD7, infection begins when a gravid female mite is transferred to the new host; she tunnels in through the upper layers of the epidermis and deposits fertilized eggs. The six-legged larvae hatch and begin wandering the body, re-invading and starting new burrows. They then eat, molt, and move onto their next state as an eight-legged nymph. Young adult female pioneers begin their own new tunnels and the colony grows. The rash that covers the body does not necessarily correspond to where the female mites have set up their homes, but may represent an allergic response. I just looked at an slideshow of 25 burrowing animals, and scabies were somehow not mentioned! Beauty is in the eye of the beholder, but I do think it would be tough for any mite to compete with a Magellanic penguin, a Columbian ground squirrel, or a greater bilby.

As I know from personal experience, the itching is the worst at night, and the diagnosis can be confirmed through scraping an affected area of skin that contains mites or eggs. As a 7-year-old, I had the pleasure of sitting in a dermatologist’s office, having him scrape some skin off of my finger, then pointing me toward a microscope. His “isn’t this cool?!” message to my young self definitely helped me approach my diagnosis (and the vision of the little critters under the lens) with more curiosity and wonder than any shame or worry. I spent WEEKS with my mom covering my whole body with cream, and I also remember being told that I had perhaps caught it “from tall grass,” though as an adult my mom disclosed to me that I had most definitely caught it from the kids next door, who had memorably questionable personal hygiene habits.

Treatment seems to commonly be Permethrin cream or benzyl benzoate lotion, but two doses of Ivermectin given a week apart are often used with patients who don’t respond to the creams, are immunosuppressed, or have crusted scabies.

Thanks as always for your commitment to keeping us educated and entertained. Stay safe!


Jody Rieck   //   L O S T    L A B O R A T O R Y   /

Aanders writes:

Greetings from Ashland, Wisconsin, the sandy South shore of Lake Gichigami, [I’m sorry for my delay in getting this email out to you!]

Shortly before our long season of snow started I was suggested your show by a friend, Viki-from-Duluth (Ep 186). I forget who led our lunchtime chat — me, bragging about man I’d met recently who’d eaten several Amanita virosa mushrooms yet lived (a superman!, as the other name for that mushroom is the Destroying Angel and it’s among the world’s most deadliest) or her, my friend and mother in law, in her excitement to introduce me to TWiP.

Well. I’m hooked. Please, let me explain; then I need your advice as well:

On hearing your last case quiz I immediately had a hunch your parasites might be in my blood, then was quickly convinced. Viki explained to me her suspicions of scabies and I had to agree, mostly. Details of your case prompted me to think of the Ole men around here — men like me, good Norwegians! You must be describing Norwegian scabies? -Aanders, son of Frederik Jarl and Andrea Clare. Father to the wild women of Wisconsin, Freyja Emily and Eostre Katherine

P.S. Ole and Lena jokes are what I grew up on. Here’s one for ya — Ole and Lena’s neighbor Sven had a boy, Sven Junior, who came home one day and asked, “Papa, I have da biggest feet in da turd grade. Is dat becuss I’m Norvegian?” “No,” said Sven, “It’s because you’re NINETEEN.”

PPS. My need for advice: When one is a barefoot runner on the roads and trails of this great north country, and likewise has fourlegged best friend who’s owner happens to be too foolish to remember antihelminthic prophylactics, what does he do when he finds little albino leach-like organisms on the fur of her cute little caboose and later mixed in with her stool? I observed a little worm stretching itself forward for it’s mechanism of motility, then last night gave “dewormer medications”. No testing was done and now I’m wondering if I need to treat myself and/or my human girls for tapeworms, myself for hookworms, or do anything other than peek at our poop.

Take care,

Aanders Jarl Dommer M.D.
Family Physician in Emergency Medicine
Student of life and in living it

PS I sent an earlier email abc in haste forgot to write in that as kids my family got regular scabies – my little sister Annika must have brought it home from school and it at least got me and my sister Kaia too. As kids I’m sure they didn’t tell us it was itchy because of the scat under skin – ha! It was a fun surprise to learn of when as we got older.

I have a more fitting closing Ole and Lena joke for you if you use my email too:

Take care


Wyatt writes:

Hello TWIP trio, 

All the best from finally cooler Loma Linda. It has stopped hitting 100 degrees Fahrenheit every day, and I believe everyone is very relieved. My response is a little bit of a buzzer beater, because we just had our first large cumulative test on Friday. Our next and second block of medical school is Heme and Immunology, and hopefully it will have a few parasitology lectures imbedded. 

I believe that the poor fellow is suffering from Sarcoptes scabies, and given the scabbing and the patients advanced age, it could most likely be classified as norwegian scabies. The treatment can take some work, and involves intensive household cleaning, along with creams for the affected areas of skin. Some of these creams might consist of 5% permethrin cream, 25% benzyl benzoate lotion, 10% sulfer ointment, or 10% crotamiton cream. 

All the best to you all,


Elise writes:

Dear TWiP Trifecta, 

It is newly chilly (for me, at least)  here in lower Manhattan, 52 degrees F (11 degrees C). I hope this finds you all well. I hope very much that my diagnosis attempt this month isn’t finding you too late. I got swept up in election activism and am just now returning to less high tension diversions. 

I am not at all sure about my diagnosis attempt, but I wonder if the patient and his wife were both suffering from scabies. This is an uncomfortable rash brought on by the Sarcoptes scabiei mite as it burrows under the skin. Scabies can cause awful rashes all over the body, and one of a few favorite spots for the mites to burrow is in the webbing between fingers and toes. 

When I first heard about the patient’s wife having visited a hotel, I thought that the couple might be dealing with a severe bedbug allergy. (The patient brought to mind the story of a friend of mine who had an extended nightmare with her child who was allergic to bedbug bites, and who did get a full body rash from them.) The more I poked around, though, I found that  it isn’t usually necessary to use oral medications like Ivermectin to get rid of the symptoms of bedbug bites, whereas, two doses, spaced weeks apart is a treatment  for scabies infections. 

While scabies mites are usually shared through direct, skin to skin contact, a person with a severe case CAN spread them through towels or upholstery. Perhaps the patient’s wife (whose symptoms actually appeared first) brought them home with her. 

This is not a diagnosis with which I feel particularly confident, but I do hope the couple got relief because from all accounts, this is a really uncomfortable infection, and one that tends to be most excruciating at night, making it impossible to sleep. 

As always, thank you all so very much for all that you do. 

Many many best wishes

Elise (in Lower Manhattan)

Davis writes:

Dear TWiP trio, 

I watched your podcast as an assignment for a Medical Microbiology class at Ohio Wesleyan University and I really enjoyed it. I wanted to give my input on the most recent case you guys presented. 

I believe scabies is the culprit. Upon a little research I found that ivermectin is used to treat multiple different kinds of parasitic diseases. One of those such diseases is scabies. Scabies seems to commonly be found around the hands and feet but can attack the entire body, which is consistent with the information given in the case study. The scabies mites are transmitted by skin contact with an infected person or infected clothing, bedding, or towels. It’s likely the wife got the initial infection from the hotel she visited and then infected the husband. 

Ivermectin is also better in repeated doses because it kills the mites but not the eggs. This was also seen in the case study description.

I’m interested to hear your thoughts.

Thank you,


Kevin writes:

Case Study for TWiP 188

Toe Jammin’

A grandpa shouldn’t be an itchy guy. He ain’t no itchy brother (for reference go back to TWiP 177). Big fellas need big pills. The dose of ivermectin (not FDA approved for scabies) is 200 mcg/kg. Our patient is 91 kg. Total dose is 18,181 mcg. Standard pharmacy stock ivermectin is 3mg tablets. Therefore the correct dose for him is SIX tablets (i.e. 18mg). He was likely under-dosed during his first encounter. Scabies was discussed on 11/06/2019 (TWiP 177) and on 05/02/2018 (TWiP 151). 

My Google search string “scabies sanctuary sites” fortuitously produced a reference by scabies enthusiast P R Cohen which contains the phrase “mite sanctuary sites” and is very relevant to our case. Dr Cohen’s email address is He is clearly a devotee. Our case summary mentions ‘cream’, and I will suppose that this refers to permethrin 5% cream (usually supplied in 60 gram tubes). Scrupulous application of this cream is crucial. It is to be applied in a thin layer to the entire cutaneous surface. This means every nook and cranny (see endnotes for discussion of the word cranny). Nooks and crannies will include underneath fingernails and toenails, between all finger and toe web spaces, all intertriginous regions (axilla, popliteal, gluteal fold, every genital crease and furrow…and in one of my favorite medical locutions, “wherever contiguous folds of flesh generate heat and moisture…” This is to give our enemy ‘no quarter’, no sanctuary, scorched earth policy etc. I think that this grandpappy missed his toes when applying the permethrin cream. To quote Dr Cohen: “…chronic mite infestation can result from inadequate topical application of the scabicide. Many older patients cannot reach their toes or their entire back. In addition, many individuals do not apply the medication to ‘mite sanctuary sites’ such as beneath all of their fingernails and toenails, to their umbilicus, and to their perianal area.”

Scabies infection can be divided into several types:

[1] Classic scabies -typical textbook type [2] Norwegian (crusted) scabies (heavy infestations, often seen in immunosuppressed patients), [3] Scabies incognito (misdiagnosed scabies treated with topical steroids where typical signs can be obscured), [4] Scabies surrepticius—refers to every variety of non-classical scabies presentation. Coined by PR Cohen in 2017 and finally [5] Bullous scabies uncommon blistering form that can mimic diseases such as pemphigoid or phemphigus. 

Plausible scenarios of infection here:

* improper initial treatment (discussed above)

* reinfection

* resistance (has been described, see REF)

* delusions of parasitosis

* development of new non-scabetic dermatosis

* the likely source of infection of this afflicted husband and wife are the grandchildren or greatgrandchildren. 

Scabies diagnosis can be classified as follows: 

1. confirmed: visualization of eggs, mites, mite feces 

2. clinical: no egg, mite visualization. Presence of male genital lesions, burrows / classical lesions in typical distribution + 2 historical details– a) pruritus, b) close contact with a person with pruritus and classic distribution of lesions. 

Scabies Treatment:

1 classic scabies—-TWICE treat…CDC states that permethrin is the drug of choice and is given in two (or more) applications, each about a week apart. Regarding the non-FDA approved ivermectin, CDC recommends two doses (200µg/kg/dose) each approximately one week apart. Other treatments that have been used: crotamiton, sulfur in vaseline and lindane. 

2. crusted scabies — Needs both topical and oral therapy. Keratolytics are often added to the treatment (e.g. urea, lactate, salicylic acid…)

After specific treatment has been initiated, topical steroids be co-administered. Severe pruritis may require oral corticosteroids.

A final scare tactic: Uncommonly scabies can result in a staphylococcal or group A strep infection (so called bacterial impetiginization). Group A Strep infection can potentially result in rheumatic fever or post-streptococcal glomerulonephritis, concerns more relevant to tropical pediatrics. 

Looking forward to the halloween/election TWiP podcast. Please don’t scare me too much.

thanking you three


Please consult my ENDNOTES from TWiP 177, A Scabrous Education, for more on basic scabies biology. 

Scabies Surrepticius (Presenting as Crusted—Norwegian—Scabies, Scalp Scabies, and Scabies Incognito) in an Immunocompromised Patient: A Challenging Condition to Diagnose and Treat, Philip R. Cohen, International Journal of Dermatology and Venereology: September 2020 – Volume 3 – Issue 3 – p 184-185 OPEN ACCESS

Philip R. Cohen

Scabies: A clinical update, Hardy, Myra et al AFP, Volume 46, No.5, 2017 Pages 264-268 (The Royal Australian College of General Practitioners 2017)

International alliance for the control of Scabies

First Documentation of In Vivo and In Vitro Ivermectin Resistance in Sarcoptes scabiei Bart J. Currie et al, 

Clinical Infectious Diseases, Volume 39, Issue 1, 1 July 2004, Pages e8–e12, 


Our 90 year old patient, with all due respect, and not to impugn his podo-hygiene, put me in the mind of a somewhat neglected term. It has a MAD magazine flavor, to wit TOE JAM. This man’s mites seem to have found a secure fortress down there, and it is possible that an accumulation of said jam could add a piquancy to a mites evening meal. Much to my surprise, the term ‘toe-jam’ is in the Oxford English Dictionary:

“toe-jam noun. slang dirt which accumulates between the toes.”

1934 R. Campbell Broken Rec. 165 The stale smell of the toe-jam of the shuffling pedestrian Charlot.

Memoir / Anecdote: The Wellcome Museum of Medical Science on the Euston Road in London has an excellent medical museum. I was there in the mid-70s and marveled at the pickled madura foot, a lower leg and foot encrusted with a mycetoma; it looked like a coral reef. There was also a lurid head of a 19th century seaman afflicted with a massive rodent ulcer. These disturbing exhibits are probably in the back room now. 

Annals of nooks and crannies. What is a cranny? According to the OED: “a small narrow opening or hole; a chink, crevice, crack, fissure.” I just don’t hear cranny much anymore. If our patient was a woman I would suggest that episode 188 be named ‘Granny’s cranny’. But that could be a mite provocative.

Mite feces: Please pick up after your mite….(Some literature mentions the fancy name for bug dung: scybala from the Greek σκύβαλον = dung, excrement)

Insect feces has some interesting names. Example: frass = “the excrement of larvae”

Yvonne writes:

Dear TWIP’sters,

Case study 188,

the man with rash for months and his also suffering wife could be scabies caused by Sarcoptes scabiei.

This mites can be transmitted by close contact or even through clothes and sharing of bedding, so it could be transmitted during the hotel stay of the wife and then from her to her husband. The scaping between his toes probably detected some living mites in the lab. Treatment with ivermectin and maybe some special cream against itching. However, what could one do for prevention?

Many thanks to everyone for sharing your passion and knowledge, it’s great!

With greetings


Alax writes:

Hello TWiP, 

My name is Alax, I am a senior at Ohio Wesleyan University. I am in a Medical Microbiology class and our assignment was to listen to Episode 188 and make a diagnosis for the next case. 

My classmates and I were all put into different discussion groups and my group discussed Scabies and Crusted (Norwegian) Scabies, which is common in immunocompromised, elderly, disabeled, or debilitated persons (the patient is in his 90’s, which is why this was discussed). There where a couple of key things that led us down this path, one being the presence and distribution of rash throughout the body and secondly, when the scab was found on his toe and was sent to the lab, the doctor immediately came back and asked who else he had been in contact with, where he said his wife. 

Scabies is very contagious and is usually spread from human-to-human contact and this is most likely how the husband received it from his wife, who had the symptoms initially. 

In terms of medical diagnosis, it could be difficult to determine Scabies is the culprit without seeing burrows in the skin. It was imperative that the primary care doctor noticed that scab on the patient’s toe. A skin scraping could be examined under a microscope where mites, eggs, etc. could have been identified. A person can be infected even if there are no signs of mites. 

Moving on to treatment, the patient found temporary relief with some medications but the itching always returned and this is consistent with the information I found. The CDC says this, “Because the symptoms of scabies are due to a hypersensitivity reaction (allergy) to mites and their feces (scybala), itching still may continue for several weeks after treatment even if all the mites and eggs are killed. If itching still is present more than 2 to 4 weeks after treatment or if new burrows or pimple-like rash lesions continue to appear, retreatment may be necessary.”

The use of Ivermectin in treatment of Crusted Scabies and Classic Scabies is not FDA approved but there is evidence that shows it is a safe and effective treatment. Specifically with crusted scabies, ivermectin should be taken in three (this was the final dosage that the patient received), five, or seven doses, 

I could be totally off but it was worth a shot, I look forward to possibly hearing my response on the next episode! Thank you for the fun and engaging case study! 

All the best, 


Julie writes:

Dear TWIPers,

A friend in NYC sent me a link to TWIV in March and I have been listening to all the Microbe TV podcasts since then.  They have accompanied me and my dogs on many long pandemic walks.  I am not a scientist; I train horses for a living. However, I really have enjoyed listening and have used the information on Microbe TV as the basis of a science class for my now homeschooled daughter.  My 11-year-old can discuss whether or not a virus is alive (Thanks Vincent!).  

My dogs are the reason I am sending in a guess for case study 188.   It is a bit intimidating hearing all the responses in other episodes from people who are clearly far more educated and erudite about medical issues, but I have many years of experience with animals and served as a Peace Corps Volunteer in Mali and believe I have a good guess.  

Several years ago, one of my dogs had an encounter with a coyote.  A few weeks after that encounter she started itching intensely, particularly around her ears and paws.  A couple of different vets believed she had allergies and prescribed various allergy medications, anti-itch creams, and a short course of prednisone.  The treatments helped a little bit, but it always came back.   After a few months, the poor dog looked like a cooked lobster – red and hairless.   Months later, and after a visit to yet another vet she was finally diagnosed with sarcoptic mange.  Two treatments with Ivermectin and it was gone. 

My guess is that this gentleman’s’ wife picked up scabies during her hotel stay.   Scabies in humans is often transferred by close contact such as sleeping in the same bed with someone who is infected.  Scabies mites often infect areas between the toes and fingers and can cause intense itching that gets worse at night. 

I am very happy to hear the gentleman in this case found relief.  


Josie writes:

Dear TWIPmasters,

Thank you for filling my ears with science every morning as I have been working my way through the entire back catalog of the show. I have been saving up questions and comments for months now, but will try to keep it to one per email.

I’d like to start with my guess for the case described in show 188, about the ninety year old man with full body rash and a small brown lesion between his toes. I can easily think of two possibilities.   He and his wife either have been bitten by sand fleas and have cases of tungariasis, or we have yet another case of scabies on our hands. Without a book I’m going to have to limit my guesses and research, but perhaps Santa Claus will have one set aside for me. While it’s true I could easily download the .pdf to my kindle, I currently am not getting along with it very well, not to mention that as a lifelong reader, I really am happier with a real book. It feels right, it smells right, there’s nothing like a book in your hand and a screen, while useful here where I live in Library Hell, just isn’t the same. Anyway, since I am part of the armchair scientist branch of the family and not a real doctor (MD or PhD, we’ve got one of each), do you really want me attempting to treat your patients, even hypothetically?

Anyhow, I do sympathize with the itchy plight of two poor souls. An unlucky allergic run in with itraconazole left me sleepless for several nights due to full body hives.  They even brought in the students to view my textbook example.  Fortunately prednisone and some very powerful antihistamines provided first some sleep and quickly some relief.  I hope this man and his wife were at least able to get some sleep in all the time they were itching. 

This brings me to my question of the day:  soon after Dr Griffin joined the group, I started noticing a pattern. Some of the names of the drugs being discussed sounded suspiciously like antifungals. Then one morning, he said the dread word, itraconazole.  I no longer recall which parasitic infection this was meant to treat, but the question remains:  for those who are allergic to Sporanox/itraconizole, and therefore likely to react similarly to other drugs in that family, what alternative options are there, if any?  Would I just be stuck?  I hope to someday travel as extensively as any of the three of you have, so I would like to know what if there is something I should be more than extra cautious about. 

Thank you greatly from Library Hell, where the weather is unsatisfyingly pleasant in the low seventies. This New Englander missed real fall!