Case of the Week 374

This lovely little family was found on a 20 year old male. Thanks to Florida Fan for donating this case!  Identification?

Answer to Case 374

Answer: Pthirus pubis ('crab' lice)

As noted by Arthur, "two females are apparent by the presence of a bifurcate posterior, whereas the male has a rounded posterior."

Note that the claws on first pair of legs are slender, compared to the larger claws on the 2nd and 3rd pairs of legs.

To answer MicrOlivier Biologist's question about this species being endangered due to modern practices of pubic hair removal, I have to say to say that it still seems to turn up with some regularity in the routine clinical microbiology lab, so clearly there are a population of 'adequately' hairy individuals out there!

Thanks again to Florida Fan for donating this case, and also to all of my readers for their excellent comments and questions.

Case of the Week 373

The following structures were found in stool.  They measure approximately 60 micrometers in greatest dimension. Identification?

Answer to Case 373

Answer: pinworm eggs - with a newly emerging larva. Kudos to Felicity in my lab for catching this worm in action!

Note the range of eggs seen here, including a classic oval/elliptical eggs with flattened side, an egg containing a larva, and lastly, the emerging larva.

And here's a poem from Blaine!

So many nematodes in the gut, it’s hard to tell which is which

But Enterobius vermicularis fulfills a particular niche

For she likes to come out at night

And oviposit at the site

That is sure to make your booty itch!

Case of the Week 372

Several objects were removed from a foot wound of a 70 year old woman. Representative photos of one of these objects is shown below. Identification?

Answer to Case 372

Answer: Musca domestica (common housefly) larva

Unlike obligate parasites such as Dermatobia hominis, Musca domestica is a cause of accidental myiasis. While M. domestica larvae are usually found in nutrient rich organic material such as compost and manure, they can occasionally infest human tissues. The adult flies can also serve as a mechanical vector for infectious agents including bacteria, viruses and parasites.

The CDC has an excellent online reference for identifying medically important flies that you can access HERE. As you can see from the identification key, fly larvae are identified by a number of features including their overall shape and characteristics of their posterior spiracles. The line drawing of the M. domestica spiracles is shown below, next to the photograph from this case for this comparison.

Case of the Week 371

This week's case was generously donated by Dr. Zhenwen Zhou, MD, from the Department of Laboratory Medicine at Guangzhou Women and Children's Medical Center, Guangzhou Medical College, in Guangzhou, People's Republic of China.

The patient is a middle-aged man who found the object below in his stool. He reports eating rare beef approximately 2 months earlier.

Identification?

Answer to Case 371

Answer: Taenia species tapeworm segment.

The segment shown is notable for the fact that it is still moving (!) as well as the fact that the proglottids are longer than they are wide. The latter feature, in addition to the large size of the worm, supports an identification of Taenia species (as compared to Diphyllobothrium spp., Dipylidium caninum, and Hymenolepis spp. Unfortunately, we are not given any additional morphologic features that would allow us to determine which Taenia species is shown (such as the uterine branching pattern or scolex). However, Florida Fan and other readers correctly note, that the history of eating undercooked beef supports the supposition that this is T. saginata. In comparison, Taenia solium and Taenia asciatica are acquired by ingesting undercooked pig (muscle, or in the case of T. asciatica, liver and possibly other organs).

Case of the Week 370

Happy Halloween dear readers!

Like last year, this week's case highlights some of the costumes and goodies from my annual Halloween Party. 

First - the costumes! Here are the amebae ladies. Can you guess which is which? I'll give you a hint in that they are all morphologically identical, but one is slightly smaller than the others.

Here are 2 of our Clinical Microbiology Fellows - the "FakeArray" and the baker (scroll down further to see photos of her goodies) 

Close up of the "FakeArray" Sugar Overload Panel, which detects 24 sweet targets. (The actual FilmArray(R) detects multiple enteric pathogens, including 4 parasites)

And here is the party's hostess, parasite gal in a Peromyscus leucopus costume. Note my Ixodes scapularis accessories.

And last, but not least, the gory baker's cupcakes. Can you tell which parasite is shown on the cupcake with the pretzel stick?