Seroprevalence of Psoroptes sp. mites in free-ranging elk (Cervus elaphus) as determined by kinetic ELISA

Western blots and a kinetic ELISA were used to characterize and quantify the prevalence of antibodies to Psoroptes sp. mites in elk (C. elaphus) from 9 herds in North America. Sera from infested (n = 18) and non-infested (n = 22) elk were used to optimize test methodology and to define cut-off values for negative, suspect and positive samples. Among 357 samples, 35 (9.8%) of the animals were seropositive, 259 (73%) were negative and 63 (18%) were suspect. Six of 9 herds (67%) contained positive animals and 2 additional herds (22%) had suspect animals. Sex was not associated with prevalence of antibodies, but adults >2 years old were ~5 times more likely (95% confidence interval = 2.6-15.4) to be seropositive than calves. Based on these results, it is proposed that exposure to Psoroptes sp. mites may by widespread in free-ranging elk of North America.