Psorergate ovis: Itch mite.

General Description: Very minute mites, one third the size of psoroptic mites. Body is nearly spherical with legs arranged radially from body margin. Prestarsi are present.

Life Cycle: Unknown.

Location: Skin, preferred areas not known.

Geographical Distribution: Australia, New Zealand, Tasmania, United States (Ohio, California, New Mexico). Information on further distribution is sparse.

Significance: Itch mite has been known to be a serious problem in merino sheep of Australia. Fine-wooled sheep are apparently more susceptible to disease, which causes decreased wool production.

Effect on Host: Mild but chronic irritation of skin. Fleece is weakened; wool breaks easily, and light dry scabs may develop. Sheep resemble those which are infested with lice. Mites may burrow in skin, causing irritation and itching. The infection spreads slowly, taking 3 to 4 years to involve most of the skin. Wool growth is disturbed, and the fleece is weakened so that breaks occur readily.

Diagnostic Information: Small mites may be found microscopically with skin scrapings. Sodium hydroxide liquefies debris in scrapings and may aid in the visualisation of mites.

Control: Dipping in insecticide preparations may kill these mites. Ivermectin given orally during routine control programs promotes excellent control of itch mite.