Case of the Week 572

This week's cool case is from Dr. Marta Maia. The specimen is skin currettings, and the object below was viewed using a dissecting microscope. The patient had developed a firm, painful 3 mm-diameter lesion on the sole of his foot after a recent vacation in Brazil. During his vacation, we swam in the ocean and walked barefoot on the beach. Identification?

Answer to Case 572

Answer to Parasite Case of the Week 572: Tungiasis, due to the parasitic female sand flea. As Blaine mentioned, it is most likely Tunga penetrans, but in Brazil, Ecuador and Peru, there is a second species infesting humans: T. trimamillata. It's not possible to tell the two species apart from this image alone.

What we can see from this beautiful image by Dr. Maia is an anterior portion of the female Tunga flea that had been curretted from the patient's foot lesion.

Infestation with the Tunga flea is called tungiasis. From anonymous: Tungiasis "is one of our favorite words as sounds very nasty and rolls off the tongue very nicely." Indeed, tungiasis is a particularly nasty, painful, and potentially debilitating condition where the female flea burrows head first into exposed skin - often between the toes and under nail beds. Santiago reminds us that medical treatment is ineffective, and "prevention is thus the best way of controlling the disease, preventing the parasite from penetrating the intact skin. But who wants to wear shoes at the beach?"

Thanks again to Dr. Maia for sharing this case!

Case of the Week 571

Welcome to the first case of the month, a regular feature by Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following objects were seen in an unstained duodenal aspirate specimen. Identification?

Answer to Case 571

Answer: Giardia duodenalis (a.k.a. G. lamblia, G. intestinalis) trophozoites with "falling leaf" or "tumbling" motility. Note that this is quite different than the "spiraling" motility of Chilomastix mesnili and the "jerky" motility of Pentatrichomonas hominis - two other flagellates - both non-pathogns - that may be seen in human stool specimens. As pointed out by Florida Fan, the motility is further enhanced by dark field videography, which makes everything more interesting. Thanks again to Idzi for the very cool videos!

Santiago gave us further information on how Giardia trophozoites move in the intestine to attach to the duodenal intestinal mucosa:
After excystation in the small intestine, the trophozoites quickly swim towards the epithelium and attach forming a monolayer; this contributes to the pathology and allows the parasite to escape the turbulent flow of the small intestine and continue the life cycle in the human host.
To achieve this, it uses a combination of movements involving its four pairs of flagella as well as its caudal region, and it is able to switch its motility from "free swimming" in the intestinal lumen, which is more rapid, to a "pre-attachment" pace which is slower and more stable, facilitating effective attachment to the intestinal epithelium in the desired location to form a monolayer.

Lastly, Old One reminds us how
Antonie van Leeuwenhoek was delighted when he took a look
at his own watery stool
Seeing For the very first time
Animalcules

“Bellies flatlike with bodies furnisht with sundry little paws. making quick motion with these paws, yet for all that, they made but slow progress yet a-moving very prettily.”

What a neat parasite!

Case of the Week 570

This week's case was generously donated by Dave Neitzel at the Minnesota Department of Health. A mutant headless tick! Wouldn't it be great if they were all this way?

Can anyone identify the genus of this tick?

Answer to Case 570

Answer to Parasite Case of the Week 570: Ixodes scapularis adult female with a missing external capitulum and mouthparts. Or as Blaine noted, "A headless tick:  Ichabod scapularis!"

The image below shows these parts where they are normally located on the accompanying female tick (white oval):

Examination of the ventral aspect shows an "inverted-U" shaped anal groove, allowing this tick to be identified to the Ixodes genus. One reader had queried if the genital pore was also absent on our mutant tick, but re-examination by Dave Neitzel indicated that it IS there; it is just obscured by the glare of the light.

So how did this happen? Well, Dave and some of our readers rightly indicated that the tick must have taken 2 prior blood meals in order to molt from larva to nymph, and then nymph to adult; thus it must have had functional mouthparts during those previous stages. However, as Dave noted, "something went horribly wrong during the last mold from nymph to adult. Given the radical changes that occur during a molt, I am surprised that we don't see more obvious mutations!" He also shared that he has seen several 7-legged ticks from his regular field collections in Minnesota, but surprisingly, no other mutants. He hypothesized that the capitulum and mouthparts are still present, but that they are inverted and therefore not externally-facing. The lack of of the visible capitulum and mouthparts has shifted the position of the legs, thus making them look longer. Finally, he commented on the "sclerotic structure" noted between the first pair of the legs by Makrone.  He also had seen this and speculated that it might be some of the residual tissue from the inverted mouthparts/capitulum.

Thanks to Dave for the fascinating case! As Sam mentioned, Ixodes scapularis is the vector for Babesia microti, as well as several bacterial pathogens and Powassan virus. Wouldn't it be great if they were all 'headless'?

Case of the Week 569

This week's case was captured by my awesome Parasitology Education Specialist, Felicity Norrie, MLS(ASCP). The following were identified from skin scrapings from a resident of a skilled nursing facility. Identification?

Answer to Case 569

Answer to Parasite Case of the Week 569: Sarcoptes scabei eggs, larva and adult. Fecal pellets (scybala) are also seen. I love how you can see the larval mite emerging from the egg in this photo:

As several readers mention, scabies is infectious to others, and thus the residents and health care workers in this skilled nursing facility must be evaluated for infection and treated if need be. Anonymous also mentioned that "scabies is not a problem of lack of hygiene but of overcrowding and wherever close person-to person contact is common. Scabies spreads quickly especially in nursing/care homes if no skilled GP or dermatologist is available to diagnose the index Patient, even in highly developed countries." This comments brings up the important point that infection does NOT reflect poor hygiene of the infected individuals. The mite infects all ages, ethnicities and social strata.

Case of the Week 568

This week's case is from Old One - illustrated by him and animated by his son. It features an arthropod that measures a few millimeters in length.

See it in action HERE!
Identification?

Answer to Case 568

Answer to Parasite Case of the Week 568: Pseudoscorpion or false scorporion, not a human parasite.

This fun little arthropod is occasionally submitted to the clinical laboratory for identification, and may be mistaken as a true scorpion. While both scorpions and pseudoscorpions are arachnids, pseudoscorpions are very small (1 cm or less in length) and lack a tail with a stinger. As sylvie g and Santiago note, pseudoscorpions can occasionally be found in the house, but they don't bite or sting humans, and instead feed on other small arthropods such as booklice.

Thanks again to Old One and his son for the donation of the cool animated illustration.