Anthony writes:

I had made a slight mistake in my last guess – Hookworms are not treated normally with ivermectin – albendazole is the drug of choice for them! 

On to the man with an ectoparasite – I believe it is either lice or scabies mites, treatment is normally topical pyrethrin

I am quite awful when it comes to insects and arachnids – however I do quite enjoy the arthro-pod podcast  – Jody Greene (one of the hosts of the show) has specialized in human ectoparasites  – perhaps could make for an interesting crossover event? 


 Andrew writes:

Kia ora from Pongaroa,

I am crestfallen at having forgotten to send my guess in for Case 194. It is still sitting in my draft folder. Would I have won? Probably not and winning is not the point but I am annoyed at myself and feel absolutely lousy (see below).

My guess, for the homeless man in his 60s is Pediculus humanus humanus the body louse. PD7 tells me that, unlike the species that specialize on hairy parts of the body, this arthropod lives in clothing and only goes onto the body for blood meals. 

Sending this straight away to make sure I am in the next TwiPisode and book draw.



Gabriel writes:

Hello to everyone.

I am a biologist, and I studied animal parasitology in school. I also have experience having grown up in a farm in Rosarito, Baja California, Mexico and have learned firsthand about both animal and plant parasites.

The fact that the inspection of the patient did not show the cause or culprit of the symptoms, and the heavy coat did, leads me to think of a parasite like bed bugs (Cimex lectularius), which do not actually live on their hosts, but on their bedding, or in this case clothing. The size of the red skin marks of 1 cm is within the range of possible reactions of the skin when bitten by this insect. The itching goes well with this diagnosis, including the persistent itching as to cause breakage of the skin and scabbing.

Thank you    


PS I am new to microbe tv and have started spreading the news to my fellow biologists and teachers. Thank you for the knowledge and discussions.

Annie writes:

Hello again from Baltimore! It sounds like the patient is infested with body lice, which like to hide and reproduce within the folds of heavy clothing. 



Sophia writes:

Happy month everyone! Happy summer and if I remember this correctly happy B-day to Dickson!

my guess for this case is : scabies

Speaking of homeless people, did the homeless in NY get vaccinated just like the homeless in Massachusetts did? if they did, then along with vaccination they could be checked and treated for scabies or other things? The Red Cross in Serbia did a good job with vaccinating the homeless by setting up shelters where they offered food and vaccine info and most of the homeless said “yes, vaccinating sounds like a good idea”

all the best


Elise writes:

Dear TWiP Trifecta, 

I do hope this finds you all well. It is 70 Degrees F (21 C) here in Lower Manhattan. I had occasion to think of all of you yesterday because I brought my family to the Bronx Zoo where we spent some time admiring the penguins and Arctic Terns that you visited for TWiP 110. As you can see, I am not afraid to travel and I do love the Staten Island Ferry, but getting a sluggish teenager out to a part of the island that was far from public transportation was trickier than it sounds on the face of it. 

I have a guess diagnosis for TWiP 195, the gentleman with extremely itchy skin, but I am unsure. I am wondering if the patient has bedbugs that are living in his clothing that he doesn’t have the opportunity to change often. While some people manage not to notice bedbug bites, many do have an itchy, hive-like reaction to them. Dr. Griffin said that the diagnosis was made by examining the patient’s clothing, which could suggest that the parasite itself was not inside his body. Bedbugs live in places where they can have access to their blood meals (which is why beds, with their sleepers on top of them are such common habitats for them), but don’t actually reside within the human body. I considered the possibility that the patient might have had scabies, because those mites cause people to be tremendously itchy, but scabies mites are so hard to see without magnification, I am leaning towards thinking that the patient’s problem is bedbugs. You can see them, they hang onto fabric between blood meals, their bites can cause those small red patches with substantial itching, and the case was solved by finding something on the gentleman’s clothing. Treatment would involve de-infesting the patient’s clothing and belongings and then providing topical ointments and an antihistamine to reduce the itching, and taking care of any area where the skin is broken to avoid infection or cellulitis. 

This was a sad case, whether or not I guessed correctly and I hope that the patient could get relief. Perhaps some success with the itching can provide him with a degree of trust and he can begin to seek help for some of the other issues he struggles with. 

As always thank you so much for everything you do. 

Many, many best wishes, 

Elise (Mac Adam – in Lower Manhattan)


Here is a snapshot of some of your Bronx Zoo penguin friends relaxing on the holiday weekend. 

Byron writes:

Distinguished TWiP hosts,

My guess for the case study for TWiP 195, the gentlemen suffered from bed bug bites, aka Cimex lectularius and Cimex hemipterus. Thanks for all the podcasts as I have learned a great deal. 

All the best,


Sherrill writes:

Hi Vincent, Daniel & Dickson!

The case  presented for diagnosis is a homeless Gentleman in his 60s, wearing a heavy coat

and an unwashed polyester shirt. 

This gentleman’s malady includes pruritis, 1 cm diameter skin patches, and open erythematous areas covering much of his torso. 

The clue to the solution involves examining the patient’s clothes.  

My diagnosis is body lice (Pediculus humanus humanus, also known as Pediculus humanus corporis).

In the You Tube Vid “Parasites Without Borders”, Chapter 21,

Medical Handbook for Limited Resources, D & D (Daniel & Dickson) discuss head, body & pubic lice.   Dickson cites a book called “Rats, Lice and History” and mentions that body lice are dangerous because they can spread epidemic Typhus.  He notes that such lice decimated Napoleon’s army. 

WHO’s website states that “louse borne typhus fever is the only rickettsial disease that can cause explosive epidemics”.

The clincher on this case is the clue about the clothes. Body lice aka called ”clothes lice” live and lay nits (lice eggs) on clothing. They usually only move to the skin to take a blood meal. 

Ok that does it —though there is lot more fascinating detail online. 

 I am an attorney with JD from UCLA and also a broker here in Hawaii. I love nature and science.  Have listened to all Twiv, Twim, Twip, Twievo,Twimune, since stumbling on Vincent’s Twip voice in March 2020. I am a huge admirer of the podcasts and the video lectures.

Hope to win an actual book -though books are obsolete. I read with my phone now. I do still love the scent of fresh pages and cracking that spine open. 

Aloha! You guys are awesome. Happy Birthday Dickson!


Alexander writes:


it’s body lice. Regards,


Erika writes:

Hi TWiP,

Sounds like the gentleman from episode 195 was suffering from body lice (Pediculus humanus humanus/corporis). 

Fortunately, it’s easy enough cure, although the same can’t be said for the socioeconomic conditions that are conducive to infection. 

I’m happy to say that I’ve finally become a subscribing member to! The knowledge and company I’ve gained from you guys has been invaluable and I’m looking forward to lots more of good times even after the pandemic.

Keep up the excellent work,


21°C and partly cloudy

Toronto, Canada

David writes:

Dear wise men of TWiP,

I am going to go ahead and say that the patient with pruritus is suffering from an infestation of Pediculus humanus humanus or body lice. 

Treatments include a battery of ointments (an example list in, PD 7th edition recommending permethrin.  However, the real challenge is personal hygiene I presume.  I do not think it is plausible for a homeless person to change underwear and clothes regularly, and I can’t but feel for them.  

Thanks for bringing the plights of the less fortunate to general attention, my deepest respect to you all, 

David, from a Nicaragua where the rainy season finally seems to have arrived

PS I finally won THE book last episode and will try to bring this to attention in my following responses so I am excluded of the lottery

PPS I was glad that it was mentioned that there is a new parasite course available.  Having started with TWiP around episode 70, just before the arrival of Dr Griffin, I did take the dr Despommiers’ lectures as were mentioned during earlier episodes, and went through the first 35 or so episodes as a parasitism 101, but by then this latest course had not been uploaded yet.  I also noted that there are certification exams now, which is great to monitor progress in understanding and hands-on knowledge.

Caroline writes:

Hi everyone!

For this case, I suspect the patient is suffering from pediculosis corporis caused by body lice.

Bites from the louse produce skin lesions and severe pruritus, due to an allergic and/or inflammatory reaction to the louse saliva. Intense scratching of bites can lead to skin excoriation. These were observed in the patient.

Diagnosis is usually confirmed by finding eggs and lice in the seams of clothing, as I suspect happened in this case.

In the US, cases of body lice infestations most commonly occur in the homeless population; infestations are strongly correlated with poor body hygiene and lack of access to clean clothing.

Treatment is usually to improve the patient’s hygiene and wash their clothes. However with a homeless patient this would seem to be a short term solution; without access to regular clean clothes, it is likely that this will re-occur.

Thanks again and stay safe

Caroline L., in Canada

Katy-Jane writes:

Hi all,

61F and cloudy here in north central Wisconsin. Our first cooler day in a while.

For the case study, my differential: Anything bitey and itchy! Fleas, lice, mites…sadly these are all common problems in homeless populations.

My first thought was scabies, but from memory that tends to manifest between the digits and is diagnosed by a skin scraping, not the person’s clothes.

Fleas seem more plausible. Even though the patient doesn’t have a dog, it’s highly likely that he associates with people who do. However, according to PD7, fleas tend to cause more itching on the arms, legs, face, and neck, not the main trunk of the body. 

Head lice and pubic lice are usually found on the body in regions where there is hair, whereas body lice (Pediculus humanus humanus) are usually found on clothing. The fact that there is a disease called Vagabond’s Disease caused by body lice shows the common occurrence of body lice infestations of people without a fixed abode. This disease results in a darkening of the skin due to extreme pruritis, which fits with the description given. My guess is human body lice.

Thanks again – as always, I will be looking forward to the next episode!

Katy-Jane Shanak
Adjunct Faculty in Veterinary & Dairy Sciences
Northcentral Technical College
Wausau, WI

Caton writes:

Hello TWIPers,

The poor fellow was suffering from body lice. The body louse (Pediculus humanus humanus, also known as Pediculus humanus corporis) is a blood-sucking insect that infests humans.  Besides making a person extremely itchy, body lice can also act as vectors of disease for Rickettsia prowazekii (causes epidemic typhus), Borrelia recurrentis (causes relapsing fever), and Bartonella quintana (causes trench fever). Excessive scratching can also cause infection.

 When the gentleman’s clothing was examined, the lice could be found in the crevices and seams of the garments.  During the winter, street people may huddle together to share body heat, and they also end up sharing these critters as well.  Lacking access to daily changes of clothes, laundry facilities, and bathtubs, their clothing becomes infested with the lice.  See link for images.

The question is: how can this problem be realistically treated?  Homelessness is often accompanied by mental health issues, alcoholism, drug addiction, as well as poverty.  Do you just give the guy a shower, incinerate his clothing, issue a new suit and send him on his way?  If so, when do you expect him back for a follow-up treatment?   I am hoping there is a better ending to this story than my sarcastic remarks suggest.  But I see this as a societal issue rather than one that can be corrected medically in the case of homelessness.  

After writing up my guess, I am beginning to appreciate the deer flies that endlessly pursue me every time I set foot outdoors during the summer.  They are flying blood suckers that give me giant welts, but at least I have the ability to escape them.  

S&C Nelson Farm
Iron River, Michigan

Owain writes:

Dear TWIP team,

My guess this month is that this gentleman has human body lice (Pediculus humanus), based on the fact that looking at his clothes gave the answer. I imagine that what were seen were egg casings and/or live lice! Very unpleasant… A differential would be scabies based on his potential risk factors and symptoms, but I’m not sure what would be visible on the clothes to confirm that diagnosis.

Thanks, as ever – keep doing what you do!


Martha writes: <= winner

Dear TWiP team: I’ll try to keep this short since I’m sure you will get many responses to this case. I enjoy Dr. Griffin’s case presentations. I am  sure that enigmatic smile is due to the pleasure of educating his fellow humans and not due to the joy of obfuscating. The fact that the diagnosis was made by looking at the clothing makes me think of ectoparasites, since this podcast is not: This Week in Contact Dermatitis. Now, the detail of the polyester shirt and the heavy coat, what are we to make of that? Is it hinting that the parasite is something found in a warmer climate that has found a suitable local environment. Is it hinting that the shirt is occlusive, preventing the exit of a parasite that would usually not stay with the host. Is the discussion of the sleeping arrangements meant to make us wonder if some bedbugs are adapting to the coat as a hiding place. I am sure that Dr. Griffin is an expert naked eye entomologist who could identify a multitude of parasitic creatures.

However, I think that I am overthinking this. (And not keeping this short.) I will go with the human body louse, Pediculus humanus corporis. The man’s living conditions are consistent with this diagnosis. Lice are known to hide in the seams of clothing, their bites cause pruritus and chronic infestation can lead to discoloration and thickening of the skin.

Hoping to win the book.

Best wishes to you all


Dhruti writes:

I guess for TWiP 195 a man with no stable home presenting with pruritus might be suffering from body louse infection. 

Thank you 


The Parasitology Club of The University of Central Lancashire writes:

Dear TWIP Professors,

A warm welcome from the University of Central Lancashire. We are based in the largest region of the United Kingdom in the city of Preston, this is near to Manchester City.

We are basking in the hot sunny weather at an amazing 23 degrees Celsius as we write.

We love hearing your amazing podcasts and we have come to a conclusion about the Twip 195 case as follows.

The destitute male patient presented in hospital with an excoriating itchy rash mainly on the trunk.  

We determined that the gentleman has a body louse infestation and the clue regarding examination of the overcoat suggests that ectoparasites were visible on the garment.

This could be the body louse (lice) Pediculus humanus humanus. The body louse is an ectoparasite whose only host is humans (, 2018). The lice need the host and sits near the body for blood meals and comfortable temperature.  Body lice area 1-3mm in length and would be easily seen by the naked eye on clothing. 

We discarded the head louse Pediculus humanus capitis as there was no mention on infestation of the hair and scalp

We also discarded the alternative diagnosis of Sarcoptes scabiei var. hominis) as this parasite is too small to be seen with the naked eye and generally burrows through the epidermis so would be less likely to be seen on clothing (CDC, 2019).

We concluded that the size was the important diagnostic feature of this parasitic infection, and this is quite common in persons that are living in destitute situations as well as war refugees, people displaced by natural disasters can cause other complications of this nature.

Treatments include shampoo’s lotions, or creams are available followed by a second treatment after 7 days, reapplying the treatment after 7 days will ensure that any lice are killed before they are old enough to lay more eggs (NHS Choices, 2019).

Preventative measures include washing clothing, towels, and bedding in a washing machine. This should be on a hot cycle (50 0C / 130 0 F) or higher) to ensure the lice are killed and to prevent reinfection.

As this patient is homeless, he will need further support and is at higher risk to reinfection as to the places that he visits or sleeps in areas that other homeless people visit are most likely infected also.


A new variant of head lice has appeared, and they are resistant to all conventional treatments.

This has left scientists scratching their heads.

(Charlesworth et al., 1986)

We look forward to your next Twip case, all the best, from a very warm sunny place in Preston, United Kingdom.

Neal Vickers 
The Parasitology Club 
The University of Central Lancashire