Sensitivity of pooled faecal culture for detecting Mycobacterium avium subsp. paratuberculosis infection in dairy herds and its relationship with the ELISA test

Abstract

The aim of the present study was to evaluate the sensitivity and specificity of pooled faecal culture as a better alternative for the diagnosis of paratuberculosis in dairy herds compared to the conventional faecal culture and the ELISA test. Individual faecal and blood samples were collected from 50 cows in each one of 12 dairy herds (n = 598) with a history of paratuberculosis. Faecal samples were cultured on Herrold's medium individually and in pools of 5 and 10 animals strategically grouped according to age. Sensitivity and specificity of both tests were evaluated by means of two by two tables using the conventional faecal culture as the reference test. 10 (83.3%) herds and 42 (7%) animals resulted positive for Map, and 15.8% and 22% of pooled faecal samples (5 and 10 animals, respectively) were also positive. The sensitivity of the pooled faecal samples was 43.2% for the 5 animal pools and 46.4% for the 10 animal pools whilst the sensitivity of the ELISA test was 42.9%. The cost of using pooled faecal culture in 5 animals was similar to that of the ELISA test but four times less than the conventional faecal culture; however, the sensitivity and specificity of this pool was similar to the conventional faecal culture. These results suggest that faecal culture with pooled samples could be successfully used in combination with ELISA test for detection of Map infection in dairy herds.