Paratuberculosis in sheep: an emerging disease in South Africa

During a serological survey for ovine paratuberculosis a total of 145 934 ovine serum samples from 2019 farms throughout South Africa were tested by means of the AGID assay. Fifty-two infected farms were identified in the Western Cape and Eastern Cape provinces. Links between infected farms in the two provinces were established. Examination of the distribution of infected farms in the Western Cape indicated a positive correlation between acid soils and occurrence of infection. In an attempt to increase the sensitivity and facilitate screening of large numbers of sera two commercial ELISA systems were evaluated for their potential use in a future monitoring program. Sera from histologically positive sheep and known negative sheep flocks were used. The highest sensitivity (50.9%) was found if both ELISA systems were run concurrently and the results of both systems combined.