Demodicosis - from biology to diagnosis

Demodex mites consitute a group of 140 known species and sub-species which reside in the hair follicles, sebacious or meibom-glands of mammals. Demodex mites are common inhabitants of the skin and due to unknown immune evasion mechanisms they usually do not have harmful effects on their hosts. In dogs, it is suspected that immune suppression or a defect in the cutaneous immune system causes a mass multiplication of mites. Thereby they change their status from commensals to ectoparasites with subsequent clinical signs. In dogs two Demodex species (D. canis und D. injai) can be differentiated and a third canine Demodex species, D. canis var cornei, is under debate. A great spectrum of clinical manifestations is described in dogs, ranging from localized to generalized demodicosis, the latter even with lethal outcome. Compared to dogs, demodicosis in cats is a rare condition and is caused by D. cati, D. gatoi and a third species with unclear phylo genetic status which is still unnamed. The classical diagnostic methods employing skin scrapings and trichograms have been extended by molecular biological tools. With these Demodex species can be detected and differentiated with increased sensitivity and specificity. These novel molecular biological techniques now allow the genetic differentiation and classification of the various Demodex species. New findings with biological and medical relevance have already been described which subsequently can be used for a targeted treatment and management of canine and feline demodicosis.