Monday, February 18, 2019

Case of the Week 532

This week's case was generously donated by Dr. Richard Bradbury and Dr. Sarah Sapp from the Morphology lab at the US Centers for Disease Control and Prevention. The following objects were seen in a wet mount of a concentrated stool specimen. The specimen was obtained from a West African baboon, but this finding may also be seen in human stool specimens. Identification?

Monday, February 11, 2019

Case of the Week 531

This week's case was generously donated by Florida Fan. The following was noted in skin scrapings from an elderly man.

This moving object was still noted 5 days after collection!


Sunday, February 10, 2019

Answer to Case 531

Answer to Parasite Case of the Week 531: Sarcoptes scabei, var. hominis, the human "itch" mite. Seen here are mites, eggs and fecal pellets (scybala).

Old one nicely described the biology and morphology of these arthropods:
Sarcoptes scabei occur in a number of host species. Primarily in swine here in Minnesota but occasionally in humans. The male mites range in size from 213-285 μm long by 162-240 μm wide and the female mites range from 300-504 μm long to 230-420 μm wide. Sarcoptes are round to ovoid when viewed from the back; when viewed from the side they are ventrally flattened and dorsally rounded (similar to a turtle). They possess short stumpy legs, and have no internal or external respiration apparatus (stigmata or tracheae). The ventral surface contains a number of chitinized plates called apodemes, the dorsal surface is partially covered by wide-angled, V-shaped-spines (>). The cuticular surface is sculptured into numerous parallel ridges which superficially resemble human finger prints, and the anus is at the posterior end of the mite (this is the characteristic used to differentiate Sarcoptes from Notoedres which has a dorsal anus and sometimes infests humans) The morphology of the developmental stages of Sarcoptes varies. You can, however, differentiate the adult stages from other mite species using easily recognized characteristics. The last segment (tarsus) of legs 1, 2, and 4 on males and legs 1 and 2 on females have a long, unjointed empodium or stalk with a small sucker-like pad at its end. These stalks are diagnostic for Sarcoptes. You can see these suckered stalks in the wonderful video [in this case].
Here are some images from previous cases that show some of these features:
Mite shown in cross-section within the stratum corneum in a hematoxylin and eosin (H&E) stained tissue:

As noted by Bernardino Rocha, the scabies mite is an efficient miner. That's a neat way to think about this interesting arthropod. Sarcoptes scabei spend their entire lifecycle on or in their human host. The female burrows into the outer most layer of the epidermis (the stratum corneum) to create a short burrow called a molting pouch. The male penetrates this pouch and mates with the female. Interestingly, a female only mates once, and then remains fertile for the rest of her life. She leaves the molting pouch after mating to find another suitable location to create a permanent burrow.  Bernardino further notes that "dispersed along the burrows are eggs, hatched larvae, and excrements."

According to the CDC, "Scabies mites generally do not survive more than 2 to 3 days away from human skin." However, the mite in this case was still 'alive and kicking' 5 days after collection, so clearly there is a range in the survival time away from the host, which may have important implications for scabies prevention and control measures.

I'll leave you all with this lovely poem from Blaine Mathison:
You go to the doctor when your groin starts to itch
so he scraps some of your skin into a petri dish
and after a thorough microscopic examination
he tells you scabies is the cause of your sensation
to which you reply, 'Son of a ...'

Monday, February 4, 2019

Case of the Week 530

It's the first Monday of the month, and time for our case from Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following objects were seen on a wet mount (with iodine) of a concentrated stool specimen (400x original magnification).Size is between 15 and 20 µm in length.

Here is another view on a carbolfuchsine staining according to Heine (1000x). Identification?

Sunday, February 3, 2019

Answer to Case 530

Answer to Case of the Week 530: Sarcocystis sp.; either S. hominis or S. suihominis

Thanks again to Idzi Potters and the Institute of Tropical Medicine, Antwerp, for sharing this case with us. I haven't featured intestinal sarcocystosis on this blog before, and so having these great photographs is a real treat. As Old One, Florida Fan, Blaine and others noted, humans serve as the definitive host for the intestinal form of sarcocystosis and shed sporulated oocysts and sarcocysts in their stool. Both forms are seen in this case:
Oocysts contain 2 sporocysts. Due to their fragile nature, they easily rupture so that free sporocysts are also commonly seen in stool specimens. Humans acquire S. hominis and S. suihominis by ingesting undercooked beef or pork respectively. As a pathology resident, I performed a survey of U.S. beef in collaboration with the USDA and confirmed the results of previous surveys that S. hominis was not present in the U.S. beef supply. Having said that, I still wouldn't recommend eating raw beef! Most cases of intestinal disease are asymptomatic, but infected individuals may experience mild watery diarrhea, fever and chills.

Rarely, humans may also serve as the intermediate host for some Sarcocystis species when ingesting oocysts or sporocysts in contaminated food or water. In this form of disease, sarcocysts form within various muscles in the body, causing transient myalgias, muscle weakness and associated edema. HERE is what a sarcocyst looks like in skeletal muscle (a case of S. cruzi; not a human pathogen).

Monday, January 28, 2019

Case of the Week 529

The following objects were seen in a wet mount of a concentrated stool specimen from a 50-year-old woman. They measure approximately 50-60 micrometers in greatest dimension. No additional history is available. Identification?

Thanks to Emily and Tony from my lab for taking these lovely photos.

Sunday, January 27, 2019

Answer to Case 529

Answer to Parasite Case of the Week 529: Pollen grains
Congratulations to everyone who wrote in with the correct answer. Most of you recognized this as some type of artifact, with only a few suggesting that these might be helminth eggs. As Old One mentioned, "These structures superficially resemble ascarid eggs. Size, and surface texture would help with differentiation. Toxocara canis is 80-85 micrometers in greatest dimension with a golfball pitted surface texture. T. cat is 65-70 micrometers it also has the golfball pitting but smaller and less distinct then that of T. canis. Baylisascaris procyonis is 63-88 u and has a granular surface texture. I will always checkout surface texture by focusing up and down on the focal plane of an eggs surface. It is surprising the things you'll see. This is how we diagnosed a mixed infection of T. canis and B. procyonis in a dog." (!)
Here is a side-by-side comparison of the pollen in our case and a Toxocara sp. egg. Note also the pores which help to differentiate the pollen grain from a true helminth egg.

I didn't provide a size of the pollen in this case, but estimate the grains to be ~40 micrometers long.

Interestingly, Old one and SilvaB suggested that these might be pollen of the cornflower (Psephellus). I don't know much about pollen, but a quick google search revealed THIS manuscript which has some nice photos of several pollen genera that bear a resemblance to the pollen in this case. Enjoy!

Tuesday, January 22, 2019

Case of the Week 528

This week's case was donated by Dr. Lars Westblade. The patient is a middle-aged man who recently returned from Tanzania. He presented with multiple furuncular lesions including the following:
The patient saw a dermatologist who performed a skin biopsy. Here are representative sections (stained with hematoxylin and eosin):

What is the diagnosis?

Sunday, January 20, 2019

Answer to Case 528

Answer to Case 528: Botfly larva; clinical presentation is consistent with furucular myiasis. As Blaine and others have mentioned, "the epidemiology supports this being the 'Tumbu fly', Cordylobia anthropophaga. Cordylobia rodhani is also in Tanzania but less-commonly documented as a source of human myiasis." From a clinical standpoint, the presence of multiple furuncular lesions is also consistent with C. anthropophaga; this fly lays eggs its eggs on soil or damp clothing (e.g. those hanging on a line to dry).  The eggs hatch when they come into contact with the skin of the host, and the larvae burrow into the skin to cause furuncles. This is why clothing should be ironed in endemic areas after being taken off the clothes line; ironing destroys the eggs and prevents infection.

Blaine further mentions that the "morphologic features shown in the cuts include the gut, tracheae, and striated musculature. Unlike with tungiasis, eggs are not present as this is a sexually-immature larva. The yellow spines are indeed the cuticular spices; sclerotized chitin (a carbohydrate in the arthropod exoskeleton) usually stains yellow in H&E)."

Unfortunately we don't have the intact larva to identify. Idzi mentioned that "for differentiation of C. anthropophaga from C. rodhani, I’d like to see the spiracular slits as the ones for rodhaini are sinusoidal. Strong pigmentation of the spines suggests anthropophaga though. Rodhaini also is very exceptional..."

Finally, Bernardino, Nema and others mentioned that excision is not necessary for treatment. Instead, the easiest way to remove the larva is to first occlude the opening of the furuncle (through which the larva breathes) with an occlusive substance like petroleum jelly or soap paste (see Case of the Week 408 for a great example of Dermatobia hominis larva removal). After a short period of time, the larva can be removed by simply squeezing the lesion.

Monday, January 14, 2019

Case of the Week 527

This week's case is a good deal more trickier than the last. It was graciously donated by Florida Fan. The patient is a toddler who passed the following 15-cm long worm.
Despite its suggestive outer appearance, the proboscis could not be seen to allow for definitive diagnosis:
Therefore the specimen was sent for histologic sectioning which revealed the following:
In my mind, this is the best use of histologic sectioning for worms - at the direction of the microbiologist, and AFTER the gross specimen has been adequately examined.