Paratuberculosis in sheep flocks in Morocco: a serological, microscopical and cultural survey

In an attempt to estimate the importance of Johne's disease in sheep in Morocco, a diagnostic survey was made in three flocks suspected of being infected with Mycobacterium paratuberculosis. Blood and faeces samples collected randomly from 188 adult sheep were investigated using direct microscopy of fecal smears, fecal culture and the serum complement fixation test (CFT). Microscopical examination of faeces revealed acid-fast bacteria in 67 (35.6%) samples. However, Ziehl-Neelsen staining lacks specificity and furthermore, acid-fast bacteria could only be demonstrated in 34 (60%) animals found to be culturally positive. Fecal culture succeeded in the isolation of mycobactin dependent strains of M. paratuberculosis in 56 (29.8%) of the sheep examined, with three strains growing in yellow-pigmented colonies. The CFT was regarded as positive (titres of 1:10 and higher) in 55 (29.2%) sera of animals, demonstrating a sensitivity of 48.2% and a specificity of 74.5% in relation to fecal culture From the results, it can be concluded that the combination of CFT and fecal culture might be a practical and useful procedure for detecting infected sheep within flocks and for controlling Johne's disease. This study supports the suspicion that paratuberculosis may constitute a serious problem in Morocco, particularly in sheep flocks involved in cross-breeding programmes.