1 the University of Reading, UK; 2 the University of Reading, UK
DiscussionFollicular mites are members of the Acari, family Demodicidae. They infest the hair follicles of most mammals, including wild and domestic animals. Demodex species are some of the most specialised arthropod parasites of mammals. Humans are no exception; two species of follicular mites have been detected in human skin, namely Demodex folliculorum (Simon, 1842) and D. brevis (Akbulatova, 1963). D. folliculorum and D. brevis are common intracutaneous parasites of the hair follicles and sebaceous and meibomian glands. They can be found on the face, forehead, chest, neck, eyelids, eyebrows and scalp, as well as in the ear canal. The pathogenesis of human Demodex mites is far from being understood. It has been suggested that the development of skin diseases like dermatitis, rosacea and pityriasis folliculorumare caused by Demodex mites, in addition to scabies-like eruptions, pigmentation on the face, gland dysfunction, hair loss on the scalp and even follicular basal cell carcinoma. Furthermore, it has been proposed that D. folliculorum and D. brevis are the cause of blepharitis. In contrast, Demodex species are also inhabiting the skin of healthy individuals; where they are harmless and their presence has an unknown pathogenesis. A species from dogs, D. canis has been confirmed as causative of severe mange in young puppies or those with compromised immune system, and have also been detected, although rarely, on humans. Demodex mite cross infection between dogs and humans is suspected.
We are currently studying the biology of human follicular mites and developing new tools to assist dermatologists in their diagnosis. Methods for microscopic identification of the human Demodexspecies have been revised. A single multiplex PCR reaction for the differentiation between the three most common Demodexspecies, D. folliculorum, D. brevis and D. canis has also been developed. Their prevalence of on human subjects has been analysed by screening a localised population, and a variety of artificial rearing media are being currently tested.