Monday, July 31, 2023

Answer to Case 723

Answer to the Parasite Case of the Week 723: mite, not scabies. Given that this mite was found in a fungal culture from skin scrapings, it could very well be a dust mite (Dermatophagoides sp.) as many of you suggested. However, mites are challenging to identify, so genus/species level identification is best left to the acarologists (people who study mites and ticks). 

The biggest concern here is its location - on a fungal culture in the mycology laboratory. Mites are a terror in the mycology lab. They crawl from plate to plate, contaminating and destroying cultures from patient samples. In most cases, the culture plates need to be destroyed and the lab decontaminated. This is the reason why my colleague, Dr. Wengenack, was so upset to find these! However, she knew of my interest in mites and was kind enough to donate this case to the blog.

Some readers questioned if these were scabies mites. Fortunately scabies mites (Sarcoptes scabei) can be easily differentiated from most zoonotic and environmental mites by their rounded bodies and short legs:


Anonymous said...

Can these be found in contaminated compost which contains human waste

Bernardino Rocha said...

Again, great explanation. Thank Tou.

ParasiteGal said...

To Anon - mites are found all over our environment - even though we can't see most of them without a microscope. Dust mites, for example, live in our homes and feed on dead human skin cells. Most of the time these mites cause no harm. However, some people develop allergies to dust mites, which can trigger asthma attacks. Other types of mites are parasites of birds and other animals, and can rarely bite people for a short period of time. However, the only mites that are human parasites are Sarcoptes scabiei (the cause of human scabies) and Demodex (which lives in our skin, but usually doesn't cause problems). Therefore, to answer your question, you might find mites in contaminated compost, although they are also all around us and usually cause no problems. The world is full of microorganisms!