Answer to the Parasite Case of the Week 702: Demodex species; most likely D. brevis due to the short length of the posterior body (opisthosoma). As noted by Florida Fan, D. brevis inhabits the human sebaceous glands. This is in contrast to its lengthier neighbor, D. follicularis, which typically inhabits hair follicles. They are both primarily found in the face, including the eyelashes, eyebrows, and around the nose. Demodex spp. have 8 legs like other arachnids. The stubby legs end in blunt claws without pulvilli or suckers. Demodex mites also have short, blunt mouthparts and the body is elongated to a posterior point. Note that the mites do not have antennae; the structures seen below are artifacts from a neighboring air bubble.
Demodex species are considered commensals in humans and do not usually cause disease. However, they have been associated with certain inflammatory conditions when present in large numbers, including folliculitis and rosacea. Therefore, they are worth reporting, but there is no need to urgently call the ordering provider with this finding. Thanks again to the Mycology lab for this beautiful photograph!
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