Paratuberculosis in sheep - an emerging disease in South Africa

The first case of ovine paratuberculosis in South Africa was diagnosed in an imported Merino ram in 1967. During the late 1980s outbreaks occurred on two agricultural research farms in Gauteng and Mpumalanga Provinces, respectively. It was not until 1993 that paratuberculosis was confirmed in the Western Cape Province. Following a considerable increase in the number of infected farms it was decided in 1996 to conduct a nationwide pilot survey using the AGID test. A total of 145,934 samples from 2,019 farms were tested. Fifty-two infected farms were identified in the Western and Eastern Cape provinces. Links between infected farms in the two provinces could be 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 test sensitivity and facilitate screening of large numbers of sera two commercial ELISA systems were evaluated for their potential use in a future monitoring programme. Sera from histologically positive sheep and known noninfected sheep flocks were used. The highest sensitivity (50.9%) was found if both ELISA systems were used in combination.