Pathogenic species include:
- Eutrombicula alfreddugesi
The larval stage of this free-living mites are the usual cause of skin disease in dogs. Adult (harvest mites) and nymphs look like small spiders and live on rotting detritus. In temperate areas from summer to fall, dogs and cats can acquire the larvae as parasites when lying on the ground or walking in suitable habitat. In warmer regions, infestation occurs throughout the year. The larvae (0.25 mm long) attach to the host, feed for a few days, and leave when engorged. At that time, they are easily identified as ovoid, 0.7 mm long, orange to red, immobile dots, usually found clustering on the head, ears, feet, or ventrum. Pathogenicity is through traumatic and proteolytic activities.
Clinically affected dogs display erythema, papules, excoriations, hair loss, and crusts. Modular lesions are common with this parasite. When present, intense pruritus can persist even after the larvae have left the animal.
Diagnosis is based on clinical signs and identification of the parasite in the dermis obtained from skin scrapings.
Symptomatic treatment may be required in cases of severe pruritus.