Human Demodex Mite: The Versatile Mite of Dermatological Importance

Abstract

Demodex mite is an obligate human ecto-parasite found in or near the pilo-sebaceous units. Demodex folliculorum and Demodex brevis are two species typically found on humans. Demodex infestation usually remains asymptomatic and may have a pathogenic role only when present in high densities and also because of immune imbalance. All cutaneous diseases caused by Demodex mites are clubbed under the term demodicosis or demodicidosis, which can be an etiological factor of or resemble a variety of dermatoses. Therefore, a high index of clinical suspicion about the etiological role of Demodex in various dermatoses can help in early diagnosis and appropriate, timely, and cost effective management.

Clinical aspects of demodecosis in veterinary and human medicine

“…The protonymph is converted into the nymph after about 3 days, and its size depends on the species of Demodex. Adult males or females develop from the nymphs after 2-3 days (44). Adult mites have 4 pairs of well-developed legs.…”

Demodex hominis

“…It is so common that it has been said to occur in most mid-to-older-aged humans. It is asymptomatic and harmless in most cases, 19,20 but it can sometimes produce pathological disturbances, with various degrees of aggressiveness and a large spectrum of clinical manifestations. The extent and severity may be affected by the clinical characteristics of the host.…”

“…Dermatological infestation outside the eye may produce facial itching, 36 facial acne, 4 nasal rosacea sometimes in paranasal areas and eyebrows, 37,38 cutaneous desquamative pityriasis, 39 (scalp/crown of the head or bald spots on the chin, perioral area and cheek, 19,40,41 tympanic myringitis, 42 etc.). Demodex parasitation has also been associated with gestational diabetes, 43 (immunodepression as in leukemia or HIV infection, 19 cancer chemotherapy, 44 etc.…”

Blepharitis and Demodex spp. infection

“…At the time of writing, two species have been found in humans: Demodex brevis (Akbulatova, 1963) and D. folliculorum (Simon, 1842). Recently these two species have been classified as parasites after previously being described as commensals [2]. However, the pathogenicity of these two species of mites is controversial because they can also be found in healthy individuals [3].…”