Case of the Week 601

Here is our monthly case by Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following were seen in skin scrapings from a young immigrant male. Identification?

Answer to Case 601

 Answer: Sarcoptes scabei, the 'human itch mite'

As noted by Kosta, Patrik, and Anon, this is a larval mite, as evidenced by the presence of only 6 legs. Mites are arachnids and have 8 legs in their nymphal and adult stages. 

As noted by Old One in a previous post, 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) It's dorsally-located anus makes it appear subterminal. Check out his additional comments in the comments on this case regarding Notoedres cati. This cat parasite can cause transient pruritic lesions in humans that closely resemble scabies.

Florida Fan also notes that S. scabei fluoresce in the traditional mycology calcofluor white preparation. Here are a few photographs he donated to the blog ages ago - simply stunning! 

Also, check out his beautiful photographs from Parasite Case of the Week 503: Demodex folliculorum, another mite found in human skin scrapings

Case of the Week 600

Wow, I can't believe we are up to Case of the Week 600! To celebrate, my awesome technical specialist, Emily Fernholz, made me this lovely composite image. Click on the image to enlarge and see all of the smaller pictures making up the larger image. Can you tell me what it is, and why it is appropriate for this week's case?

Answer to Case 600

Answer to Parasite Case of the Week 600: Lovely ectoparasite collage of a larval tick of Rhipicephalus sp., courtesy of my amazing technical specialist, Emily Fernholz.

Note that the arthropod has 6 legs (to go with my 600th case), indicating that this is a larva rather than nymph or adult. 

One reader queried if the components of the collage were from all of my cases to date. Wow, what a great idea! There are more than 4000 images present, which might have been able to represent all of the images from my various cases. However, that is not the case here - the collage is made up of many different arthropods, including bed bugs, ticks, fleas and lice. There is even a pubic louse and a Tunga penetrans flea in there if you look closely (good catch, Florida Fan!). 

Old One came up with some additional ideas on how this collage was related to my 600th case:

1.) Wikipedia writes of an unengorged tick gaining 200-600 times its weight after feeding.

2.) King Solomon made a shield of 600 golden shekels. Hard ticks have a scutum (which is a word derived from the latin word scuta which is an oblong shield used by Roman soldiers).

3.) Angel number 600 champions the ideals of family, learning and growing together. We have all grown together with the bounty of knowledge shared over the years on this blog. I also believe that creations, like this wonderful collage (Brava Emily) are like a familial act of kindness.

Finally, Nema reminds us that "This collage of several ectoparasites, implicated in various diseases, should remind us that this week, on July 30th 2020, is the week of the 8th annual ISNTD Bites conference, on vector-borne diseases & vector control, an event that will be held all online."

Case of the Week 599

This week's fun case is from Dr. Tess Karre, one of our former clinical microbiology fellows. The following structures were seen in a hematoxylin and eosin stained small bowel biopsy. Identification?

Answer to Case 599

Answer to Parasite Case of the Week 599: Male Enterobius vermicularis

Congratulations to all of you who got this one correct! This was actually an older case that I had posted back in 2014. I had forgotten that I already posted it! This case comes with an explanatory photo and a fun poem from Blaine Mathison:

While the duodenum is an unusual place to find this worm,

the morphologic features shouldn't cause you to squirm

With lateral alae pointing to the sides

and platymyarian musculature low and wide

a diagnosis of pinworm should be relatively firm!

Case of the Week 598

Welcome to the first case of the month provided by Idzi Potters and the Institute of Tropical Medicine, Antwerp. The following object was obtained during colonoscopy from a 35-year-old woman. It measures approximately 4 cm in length. Travel history is unknown. Identification?

Answer to Case 598

Answer to Parasite Case of the Week 598: Trichuris trichiura, the human whipworm. This is a beautiful classic case from Idzi. Notice the whip-like shape. Just don't be fooled by the anatomy - the anterior end is the skinny end!

Case of the Week 597

This week's case is very timely, as we are seeing a lot of these objects in some of our stool specimens submitted for routine ova and parasite exam. They measure approximately 8-10 micrometers in dimension (shown at 500x and 1000x). Identification? What additional stain or study would you like to do?

Answer to Case 597

Answer: Cyclospora cayetanensis oocysts, unsporulated

I figured this was a very timely posting, as we are currently experiencing an outbreak of cyclosporiasis in the Midwestern United States. It's a good reminder to keep an eye out for these round refractile structures in routine stool preparations and follow-up with confirmatory testing (e.g., modified acid fast, modified safranin, examination for autofluorescence, molecular amplification).

I also figured this was a timely case for my United States readers as the confirmatory modified acid fast and safranin stains provide beautiful red, white and blue images for the 4th of July celebrations (American Independence day; my apologies to my British friends)

Here is a gorgeous image from a modified safranin stain of C. cayetanensis oocysts from Florida Fan:
(from Case of the Week 447):