Screening for antibodies against the sheep scab mite (Psoroptes ovis) Pso o 2 antigen in experimentally infested Swifter sheep may fail to identify affected animals

Sheep scab, caused by Psoroptes ovis mites, represents a significant threat to sheep health and welfare. Infestations are diagnosed by parasite identification in skin scrapings, and more recently with a commercial ELISA against serum antibodies to the Pso o 2 mite allergen. However, little is known about the performance of the ELISA in non-UK sheep populations. In this study, six Swifter sheep were experimentally infested with P. ovis. Lesion sizes were monitored and serum IgG against Pso o 2 and the novel Pso-EIP-1 antigens were measured by ELISA. Although all sheep showed signs of infestation, serum from two animals failed to react with Pso o 2. However, they did react to Pso-EIP-1. This indicates that cases of sheep scab in (Swifter) sheep may remain undetected using the Pso o 2 ELISA, which may have implications for routine screening of non- UK sheep breeds.