Exposure to Psoroptes sp. mites is common among bighorn sheep (Ovis canadensis) populations in California

Sera (n = 806) from 50 populations of bighorn sheep (O. canadensis) in California, USA, were evaluated for antibodies to Psoroptes sp. mites using a kinetic ELISA. Test values for each sample were determined to be either positive or negative at each of 2 ELISA cutoff values that provided either 100% sensitivity (low cutoff) or 100% specificity (high cutoff), respectively. 168 (20.8%) sera were seropositive at the low cutoff value, and 87 (10.8%) of these sera also were seropositive at the high cutoff values. 11 populations were designated as scabies-suspect and 25 populations were designated as scabies-positive because they had at least 1 seropositive animal at the low and the high cutoff values, respectively. Based on these results, exposure to Psoroptes sp. mites appeared to be widely distributed among bighorn sheep populations from 1980 to 1990 and infested animals may have been present prior to 1980.