The lesions may start as small nodules that exude serum, which hardens to form crusts. Later, the lesions may join to form heavy scabs. Affected areas may become thickened and wrinkled. The heaviest infestations occur in late winter and early spring. At that time, the lesions occur most commonly on the perineum and udder, extending to the back of the legs as well as over the rump and base of the tail in severe cases.
Light infestations occur during the summer months.
During this time, Chorioptes may persist on the hind legs. Although Chorioptes causes few problems during the summer months, animals are occasionally seen with thick, crusty scabs. Diagnosis is confirmed by finding the mite during microscopic examination of skin scrapings from affected areas. Mites can be isolated from animals that do not show clinical signs of disease. When scabs are present, the scraping should be taken at the edge of the lesion.