Tuesday, October 26, 2021
Tuesday, October 19, 2021
Sunday, October 17, 2021
Answer to the Parasite Case of the Week 657: Plasmodium vivax
Thanks to all of the great comments on this case! There are so many classic features of P. vivax here, that it makes for a fabulous teaching slide. Florida Fan very nicely outlined all of the diagnostic features along with his thought process for coming to the final identification:
1/ The ring is fairly large, and the infected red cell is larger than the not infected. As such, there is a predilection for reticulocytes. Either P. vivax or P. ovale.
2/ The mature trophozoites are ameboid form, showing them to be highly Vivacious. More than likely P. vivax.
3/ The schizont in the third picture demonstrates more than twelve merozoites, P. ovale does not usually have that many. (on average, 8)
4/ The gametocyte in the fourth picture is not Falciform, it occupies almost the entire red cell. Though there is a little bit of fimbriation, all evidence gathered so far including the geographic area are consistent with an identification of P. vivax.
Here is a composite image of the 4 forms shown in this case:
Tuesday, October 5, 2021
It's time for our monthly case with Idzi Potters and the Institute of Tropical Medicine, Antwerp:
The following was seen in a urine sediment from a backpacker returning to Belgium following a 2-month's trip in Northern Senegal. During his travels, he reports being bitten by insects, drinking and eating local foods, and swimming in fresh water lakes. He is asymptomatic, but is concerned that he may has picked up a parasite along the way.
How would you interpret this finding?
Monday, October 4, 2021
Answer to the Parasite Case of the Week 656: mite, probable contaminant from the environment. Not likely of human medical significance.
As several readers noted, this mite is not one of the 2 human pathogenic mites, Sarcoptes scabei or Demodex. Instead, it is likely a mite from the environment, such as Dermatophagoides, the dust mite. The presence of many squamous epithelial cells in the background would support this idea:
You can read the following posts for more information for how to differentiate the various mites found in human specimens:
Case of the Week 634: Free-living mite found in stool
Case of the Week 196: Differentiating Sarcoptes scabei from other mites
Case of the Week 601: Key identifying features of Sarcoptes scabei
Monday, September 27, 2021
Sunday, September 26, 2021
Answer to the Parasite Case of the Week 655: Microsporidia spores. Nucleic acid amplification/sequencing and/or electron microscopy is required for genus and species level identification.
Microsporidia that are commonly implicated in corneal infection include Vittaforma corneae and Encephalitozoon hellem.
As noted by Dr. Harsha Sheorey, the Ryan’s modified Trichrome stain was created by his friend and colleague, Dr Norbert Ryan. This stain has now become a standard staining technique for these organisms, and what was used in this case. The microsporidia spores stain bright red against a blue background.
Monday, September 20, 2021
This week's case is of a middle-aged man with a painful lesion on the dorsum of his foot. He recently returned from Brazil, during which he swam in the ocean, walked barefoot on the beach, and ate local foods. An excisional biopsy was performed and submitted to the clinical microbiology lab to rule out a possible parasite. The specimen received was an excised ellipse of skin on which there was a central defect measuring ~ 5 mm in diameter:
Sunday, September 19, 2021
Answer to the Parasite Case of the Week 654: Tunga sp. flea
I encourage you to check out the posts in the Comments section by Kosta and Florida Fan who give us an excellent description of the taxonomy, morphology, epidemiology, and clinical presentation of this parasitic flea.
Here are some of the diagnostic features from this case:
Tunga sp. eggs measuring ~0.6 mm long:
Monday, September 13, 2021
This week's case was generously donated by Drs. Alex Fenwick and Julie Ribes at the University of Kentucky. The following structure was retrieved from bronchial washings of a patient with end-stage lung disease due to cystic fibrosis.