Monday, August 3, 2020
Sunday, August 2, 2020
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
Monday, July 27, 2020
Sunday, July 26, 2020
Monday, July 13, 2020
Sunday, July 12, 2020
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:
Monday, July 6, 2020
Sunday, July 5, 2020
Monday, June 29, 2020
Sunday, June 28, 2020
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):