Blaine's Professional Curiosities

[bmathison1972]

Got something cool in the lab yesterday so I thought I would showcase cool REAL critters I get to see as part of my job as a professional parasitologist. Not sure how often I will post here, but I will every now and then as interesting things come in!

This is a larva of the bot fly, Dermatobia hominis. Don't have any info on the patient specifically, but the epidemiology and life cycle of the parasites suggests it was extracted from their skin and that the patient had recent travel to Latin America or the Caribbean where the fly is endemic.

Dermatobia hominis has one of the most interesting life cycles as it's the only arthropod transmitted by another arthropod. Female flies lay their eggs on the head of a mosquito. When the mosquito takes a blood meal, the warmth of the host's skin causes the egg to hatch. The larva falls to the skin of the host and enters the bite site of the mosquito. There is develops under the skin ('furuncular myiasis'). After the larva is mature, it leaves the skin and finds a secluded place to pupate.

[Gwangi]

Fascinating, thanks for sharing. Not too many animals creep me out but bot flies are definitely on the list. I still find them interesting though!

[bmathison1972]

This was found in a patient's stool, proglottids (segments) of one of the fish tapeworms. If acquired in the United States, it was probably caused by Dibothriocephalus latus, which is usually acquired from eating undercooked pike, walleye, and other freshwater fish in the Upper Midwest/Great Lakes area, or D. nihonkaiensis, which is acquired from eating undercooked salmon in the Pacific Northwest. However, there are a dozen or species in three genera that infect humans and can look like this. The most common clinical presentation is vitamin B12 deficiency.



Microscopic exam of the patient's stool also revealed the tapeworm's eggs:

[bmathison1972]

Saw this today in the lab. This is a stool smear stained with trichrome. The arrows are pointing to the trophozoites stage of Dientamoeba fragilis, a flagellate that lacks flagella, well external ones at least. It is related to things like Giardia and Trichomonas but moves and feeds like an ameba. They have an interesting life cycle in that there is no defined cyst stage (in 2014, a 'cyst' stage was described, but I find issues with some of the data and remain unconvinced).
Dientamoeba fragilis is also unusual in that it is not a confirmed pathogen, although most of us feel that at least some people are susceptible and experience GI distress from it. We just don't know what it's doing to cause distress.

[bmathison1972]

got this in the lab today, an adult Ascaris lumbricoides. In the USA, where infrastructure, sewage management, and hygiene have reduced the burden of parasitic infections, A. lumbricoides is mostly a zoonotic disease associated with pigs. People get infected ingesting the worm's eggs on produce or fomites contaminated with soil that has been contaminated with pig feces. Veterinarians will say the pig isolates are Ascaris suum but the morphology, biology, epidemiology, ecology, and even molecular studies do not justify recognition of A. suum as a valid species.

This specimen is about 13-15 cm long!

[Lanthanotus]

I have to say, in all scientific objectivity I can muster and with all my love and fascination for life and its weird evolution, your professional field is sincerely disgusting Thanks for those looks behind the scenes.

[bmathison1972]

I have to say, in all scientific objectivity I can muster and with all my love and fascination for life and its weird evolution, your professional field is sincerely disgusting Thanks for those looks behind the scenes.

Hahahahaha :-D

[Lanthanotus]

On a serious note...when we were in Australia for the second time, I had a very small land bound leech on my index finger and let it suck there for I was curious how long it would take and how thick it would fill itself. And as I dissected dozens of goannas and other reptiles to learn about their diet and feeding behaviour, I have seen my share of internal parasites. It is a fascinating field and the evolution of many of those animals so strange and impropable, that it blows my mind.

[bmathison1972]

Found these characters in a stool specimen today! Trophozoites of Giardia duodenalis. Many people who are not professionally trained in microbiology or parasitology are familiar with this protozoan, as it's an agent of one of the most common parasitic diseases worldwide.

[bmathison1972]

Saw this in a stool specimen today, eggs of pinworm (Enterobius vermicularis). Normally stool isn't examined for this parasite, but sometimes eggs can be found. Instead, the 'Scotch tape' prep method is used! This is a very common parasites and one of the few 'contagious' worm infections. If any of you have kids, you may have had to, or might some day have to, deal with critter

[bmathison1972]

Been a while since I posted here, but I came across these in a stool specimen today, eggs of the dwarf tapeworm, Rodentolepis nana (formerly Hymenolepis nana). Most tapeworms require two hosts, and humans get infected by eating the larval stage in an intermediate host. While humans can get R. nana from eating the natural intermediate host (insects, especially beetles), R. nana is unique in that it can bypass the intermediate host and cause patent infections (infections with adult tapeworms) after eating only the eggs! That's one reason it's considered the most common intestinal tapeworm of humans (although I am not sure there is hard data to back that claim).

[bmathison1972]

The spinose ear tick, Otobius megnini! While this specimen came from a dog (owned by the brother of a co-worker), I have seen one case from a person. The nymphs and larvae are parasitic in the ears of mammals, especially ungulates and dogs. Adults are not parasitic. Excuse the poor quality; I haven't mastered holding a cell phone up to the eyepiece of a microscope

[Gwangi]

That's a pretty great picture considering how you took it and how small the tick is.