Alexander writes:

Hello all,

I think I should clarify that the tool I mentioned in my previous email is a cruisers stick, which uses the law of similar triangles and your arm length to be able to measure heights and diameters. They have two parts, sometimes a third being a yard stick, a hypsometer and a Biltmore stick. To determine the heights, you can walk back a set distance and see the height as the top of the tree should fall between lines marked on the stick. It isn’t considered accurate, but when you are 66 ft away from a tree and guessing where the top of it is among the forest it doesn’t really seem to matter if you are a few feet off. Then again, it does have it’s limitations, it doesn’t really work on slopes and shouldn’t be used for cruising high value timber.

On to the case, I had initially thought that it might be scabies, with the nocturnal itching, but the primary infection are delayed by several weeks and the rash doesn’t really sound right. Next, I thought of bed bugs (Cimex hemipterus), but after further reading I saw “paired bitemarks” and recalling the unused mattresses mentioned in the case, I didn’t want to get stuck on it. Looking further at Parasitic Diseases 6th edition, I went to fleas which I thought about because of the rat nests present and how they moved in recently. This is going to be a guess, but I think that when the family moved in, they might have scared the rats away and without food, fleas might have taken the opportunity to feed on the family. I’m going to stop there and say that my diagnosis is going to be that they might have some fleas which may have given the woman a secondary bacterial infection.

Might I be so bold to request that in the next edition of Parasitic Diseases, you make a diagram of differences in bites and throw a few drawing on it, as while looking for a description of the bites, I only found one website that said that they had a single central puncture which is mostly all of what I am basing my diagnosis on.

Thank you,


Chris writes:

Hello professors,

It is a cloudy 70F here in Stony Brook long island. For this weeks case study I believe the woman and her family are suffering from bed bugs. This was a much easier one than the last two or three cases so I feel pretty good about this. One hold up I have is that Daniel said that the way they solved this case was to do a skin scrape, I was under the impression that bed bugs stay on the bed. So why would a skin scrape work, do a few of the bed bugs not jump ship when the woman got out of bed? Another possibility is that she could have scabies or even fleas,  but i don’t think these two options are as viable. Again please don’t put me in the running for the book as I already have one.

Also, you mention how you found the paper about ant parasites (one of your listeners sent in) interesting so I figured I would send in relevant work. This work focuses on a Trematode that also has host manipulation behavior that vary depending on the temperature and humidity , and being that this is this week in parasitism thought you would all enjoy it in addition to the paper sent in last week.  I think it is a really, really cool and classic example of host behavior manipulation that is commonly observed in the animal world, and that it would pair well with the paper sent in last week.

Lastly I have a question for Daniel, how do you deal with the ticks on long island!? As I have previously mentioned I recently moved to Long island and I knew there were going to be a lot of ticks but last week I found over 60+ ticks on me, I lost count after 60 it was probably closer to 100 though. I acquired  all of these ticks after about 10 min walk through a nature preserve. the ticks seems to get stuck in my shoes and socks so I ended up putting my shoes in the freezer for ~30min and then I went to my lab and had to spray my legs with 95% ethanol to try to wash off the ones renaming on my legs. is this an effective strategy for when I inevitably get swarmed again?

Once again thanks for everything, I recently started riding my bike to school every day and twip and twiv make my 40min ride a very pleasurable time.

Warm regards,


Delbert writes:

Hello Twipsters,

My guess for the case presented in TWIP 157 is that the offending parasite is bed bugs insects. The two most common species implicated in human infestations are Cimex lectularius or Cimex hemipterus; the former of which is cosmopolitan and the latter being found mostly in the tropics or sub-tropics. Like other members of the Hemiptera order, they contain piercing-sucking mouthparts. It sounds from the evidence presented by Dr. Griffin that these little parasites have infested the coconut husk mattresses or have taken up residence somewhere else in the patient’s new home. The fact that the rest of the family is also suffering similar symptoms points to bed bugs as well. While a nuisance to have in a home or dwelling, they are not usually of any severe medical importance. Their primary medical importance is inflammation associated with their bites. While some Cimex spp. have been found to harbor blood-borne pathogens, they are not effective vectors of disease. Treatment includes over-the-counter medication to relieve itching (cortisone creams and antihistamines). Excessive itching/scratching can lead to secondary infection. Treating the house to rid it of the infestation is also possible, however expensive and probably not within the means of the family.

Please keep up the good work with the podcasts. I am long time listener of TWIP, I started listening in grad school while I was still a PhD student. I have listened to every TWIP episode and I am now an avid listener of every other TWIX series. I listen to all of them all the time. I subscribe to all and never miss an episode. Do not stop doing these – they are immensely useful and helpful. As a matter of fact, early TWIP episodes that cover the basics of parasites are required listening for my parasitology course. Also, recently I have switched over my course book to parasitic diseases (particularly now that it is free) and will not use any other textbook. Thank you immensely for making that book free and accessible. There are a lot of colleges/universities out there where students can not afford textbooks. You are doing a great educational service – fantastic work!

Thank you,


Adil writes:

Dear Doctors,

Firstly thank you for your TWIP smart banter and utterly engaging podcast. After multiple weeks of being right and yet reticent to take my shot I will hazard a guess. Initially I thought scabies because the itching was noted to be worse at night. The punctuation and explicit reference to unused bedding made me think of body lice however. The regions impacted seemed to align with this as well. Unlike with last episodes diagnosis of Babesia I am not at all confident but there it is. Hope all is well wiith you and that I can send forth future response with a bit conviction in my diagnosis.


Kevin writes:

Cool, like Autumn.

Our case involves a woman (and her family) with an unfortunate dermatologic affliction. The itch, rash, scurf, pruritis, cooties, dermatitis, eczema, prurigo, lichen simplex, the eruption, the crust….however described– a widespread pruritic rash can result in anguish of an almost biblical magnitude.

It was often taught that the skin was “the largest organ in the body.” Is that still true?  Now there is the immune system, the biome —gastrointestinal and otherwise. Nevertheless, considering weight and surface area, the skin is still a contender. It is very sensitive, full of nerves and raises the alarm when invaders are about.

Acute cutaneous eruptions or symptoms may be due to a primary dermatological condition or a an external manifestation of an internal condition. The tropical location, presence of a known substrate for arthropod pests, acute onset, cohabitation with rodent pests and multiple afflicted family members strongly argues against a systemic disease (e.g. chronic renal failure, cutaneous lymphoma, cholestatic pruritis, rickettsial infection, scrub typhus etc). The papular nature of her diffuse rash, along with a central punctum, argues against bacterial or viral skin eruptions such as erysipelas, impetigo, herpes, furunculosis etc. This leaves us with “whatsoever hath more feet among all creeping things that creep upon the earth.”

I will discount helminth infections such as toxocara, strongyloides, hookworm etc as inconsistent with our case. Likewise we may forego consideration of biting flies and myiasis (cutaneous maggot infestation).  Infestation with Cimex lectularis (bedbugs) is a possibility, but the widespread nature of the rash and intensity of itching argues against this. The fact that the home was vacant for several weeks prior to the patients’ occupancy raises the possibility of a flea infestation; to quote the Gordon and Lavoipierre textbook: “this (vibration induced hatching) probably accounts for the many instances of persons who having entered deserted dwellings, are later attacked by large numbers of fleas seeking their first blood meal.”  Flea bites are less likely to produce such widespread rash, and the patients would probably report seeing these fairly visible insects. Smith’s Medical Entomology text (1973) in a flight of terminological excess states: “a flea-puncture is characterized by a tiny dark spot (purpura pulicose)…surrounded by a patch of swollen and reddish skin (roseola pulicose).”

The presence of rat nests, besides being a risk for flea infestation, prompts discussion of Ornithonyssus bacoti, the tropical rat mite, a hematophagous arachnid that can cause dermatitis in humans. These mites have been found in gerbils and other rodent pets in Europe (see Refs). Diagnosis requires a microscopic examination of the mites. Of course, scabies should be mentioned, though the abrupt onset of the dermatitis coincident with moving into an environment conducive to other mite pests allows me to dismiss this idea.

Coir, a fiber obtained from the coconut husk is used in a variety of manufacturing. Coir mattresses are very popular in India (ref) and the tropical world (they are also widely available in the US, with one king-sized coir mattress retailing at $4,500). Our patients moved into a home that was presumably a component of a cottage industry producing coir mattresses. The large quantities of coir fibres in the home makes the diagnosis of Copra Itch very compelling. (note: copra is the dried meat or kernel of the coconut). The  PD6 text does mention skin irritation due to mites “associated with straw, flour, grain, dried fruits, vanilla, copra, and cheese”, these conditions often are colloquially referred to as ‘grain itch’ or ‘grocer’s itch’. A case report (almost identical to TWiP 157) from the Mueang area of southern Thailand, is beautifully described by Sarathep in the journal IDCases (2018, open access, ref below). The mite Tyrophagus longior causes Copra Itch, an intensely pruritic dermatitis that results in widespread erythematous papules and can cause systemic symptoms such as myalgias, fever, shortness of breath and fatigue. Sarathep also provides a clear photograph of a papule with a central punctum. These mites do not tunnel under the skin like Sarcoptes, but do bite and attach, as evidenced by Sarathep’s photo of Tyrophagus recovered from a papule. Treatment with 5% permethrin cream is advised. Adjunctive topical steroids for the most pruritic areas and oral antihistamines for generalized pruritis may help. The entire environment must be thoroughly decontaminated and all of the debris and rodent habitats removed.

Thanks to TWiP team for stimuli as piquant as the bite of a mite.

References and notes

India Mattress Market Outlook 2022

The organized mattress market encompasses of three types of mattresses namely Coir, PU foam and spring mattress. Indian consumers usually prefer a coir mattress or a foam mattress but the demand is now changing towards spring mattresses.

British Journal of Industrial Medicine 1975, 32, 66-71A clinical and radiographic study of coir

workers, C. G. URAGODA Central Chest Clinic, Deans Road, Colombo 10, Sri Lanka

A study of 779 workers. The author concluded that there was no occupational lung disease in coir processing workers

Laboratory Identification of Arthropod Ectoparasites, Blaine A. Mathison,a Bobbi S. Prittb

Mayo Clinic, Rochester, Minnesota, USAb  Clin Microbiol Rev. 2014 Jan; 27(1): 48–67.

Really excellent and beautifully illustrated review of hands-on laboratory based medical entomology.

The Epidemiology, Diagnosis, Management, and Prevention of Ectoparasitic Diseases in Travelers

James H. Diaz, MD, Dr PH Journal of Travel Medicine, Volume 13, Issue 2, 1 March 2006, Pages 100–111,16 March 2006   Open access

A lost world disease: Copra itch outbreak caused by Tyrophagus longior mite Prakit Sarathep, Worayot Phonkaew, IDCases 12 (2018) 58–63  

This review outlines a very similar case to TWiP 157. It is open access.

the treatment: Only one confirmed case and two probable cases with severe clinical manifestations were treated by dermatologist with antimicrobial and supportive drugs including doxycycline 100 mgÅ~2 tablets 5 days, gamma benzene hexachloride (0.1%), hydroxyzine 10 mg, cetirizine 10 mg, 3% vioform in 0.02% triamcinilone acetonide cream 5 g, tar shampoo.  seed mite=Tyrophagus longior  Tyrophagus longior (Gervais, 1844)  –excellent morphology/detailed photographs

Occurrence of a house-infesting Tropical rat mite (Ornithonyssus bacoti) on murides and human beings. Beck Travel Medicine and Infectious Disease (2008) 6, 245–249

Entomology for Students of Medicine, RM Gordon, MMJ Lavoipierre,  Oxford: Blackwell, 1978

Insects and other Arthropods of Medical Importance. K G V Smith ed. London: Trustees of the British Museum (Natural History), 1973

Note on Copra Itch. ALDO CASTELLANI, M.D. 1913, Trustees of the British Museum   free download

Andrews’ Diseases of the Skin E-Book: Clinical Dermatology By William D. James, Dirk Elston, Timothy Berger, Isaac Neuhaus, Elsevier, 2015 –very good section on mite associated dermatidites. Sections free on googlebooks

Pediatric Dermatology E-Book By Lawrence A. Schachner, Ronald C. Hanse, Elsevier 2011. –extensive treatment of mite infestations  some sections free on googlebooks…

Report on the Mite causing the Copra Itch, Proc R Soc Med. 1913; 6(Dermatol Sect): 29–31. Stanley Hirst

Coir is the fibre obtained from the husk of the coconut. It has a wide variety of uses depending on the colour, length, and thickness of the fibres. The thick long variety or bristle is used for the manufacture of brushes. The short thin fibres are in demand for use in mattresses.

Hannah writes:

Dear TWiP hosts,

This just came across my news feed: a recent paper in Scientific Reports in which researchers managed to image lancet liver fluke “brain worms” in situ in an ant’s brain, showing the physical connection between the parasite and the intermediate host’s brain tissue.

Here’s an article/press release from the Natural History Museum in London, where this work was done:

Love your show: keep up the good work!