Paratuberculosis in sheep: its possible role in the epidemiology of paratuberculosis in cattle

A total of 50 sheep originating from 15 Dutch farms with a known paratuberc ulosis infection in their cattle herd, but with no history of paratuberculo sis infection in their sheep Rock, were examined for infection with Mycobac terium avium subsp. paratuberculosis (Map). The sheep had been grazing on t he same pastures as the cattle or on pastures fertilised with manure from t hese cows. The sheep were screened for paratuberculosis by serum biochemist ry, serology and intradermal skin tests. At necropsy they were examined mac roscopically, microscopically and bacteriologically for paratuberculosis. From 10 sheep, originating from eight hocks, Map could be isolated from var ious tissues but not from the intestinal contents, after an incubation peri od of 2.5-4 months. Six of these culture-positive sheep had no macroscopic signs of paratuberculosis at necropsy. Seven sheep were Map, culture negati ve but showed macroscopic and microscopic lesions consistent with a paratub erculosis infection. Results of serology and skin tests did not correlate w ith the results of bacteriological culture. Serum concentrations of calcium , albumin and total protein of the infected, suspected and negative sheep w ere not different. These results indicate that a substantial number of the sheep examined were infected with Map. Even though this bacterium was not i solated from their farces, the possibility that these sheep could have been shedding Map with their faeces below detection level or at a later stage o f the disease cannot be eliminated. Map infected sheep should, therefore, b e considered as a possible factor in the epidemiology of with Map infected cattle herds in The Netherlands. At necropsy bacteriological culture of Map should be performed on a routine basis to improve the diagnosis of paratub erculosis in sheep. (C) 2001 Elsevier Science B.V. All rights reserved.