Spread and detection of psoroptic scabies of cattle in the United States.

Psoroptic scabies of cattle causes substantial economic losses. An eradication program begun in 1905 virtually eradicated the disease by 1950. Complacency was followed by a resurgence of the disease, particularly in the 1970s, when more than 1,000 outbreaks were reported. Program effectiveness was reduced when the disease was often not detected or reported for several months after herds became infested. Further spread was enhanced by infested cattle moving undetected through market channels.