Introduction.

There has been uncertainty about the existence of a strictly goat-pathogenic M. paratuberculosis strain in Norway. The aim of the present study was to obtain information about cross-infection of M. paratuberculosis between ruminant species in Norway.

Materials and methods.

From 1966 to 1999 samples from 5152 cattle and 33100 goats were examined for M. paratuberculosis by bacterial culture. All goat and 97 cattle-samples were collected from animals suspected for paratuberculosis. Samples from 5055 cattle were examined in a national control and surveillance program. In one cattle herd (A), positive seroreactions were found in eight cows. Paratuberculosis had been diagnosed in 31 goats before 1985, but there had been no goats in the herd since 1992. Paratuberculosis was confirmed by culture from one of these cows, and the animals were slaughtered. Pathogical and bacteriological examinations were performed on 45 animals. Altogether 58 goat isolates of M. paratuberculosis from 58 herds and 5 cattle isolates from 4 herds were typed by RFLP and AFLP analyses. One goat and two cattle isolates originated from herd A.

Results and discussion.

M. paratuberculosis infections has been more common in goats than cattle in Norway. In a few farms infection was diagnosed both in goats and cattle. Cross-infection between the different ruminant species cannot be excluded. Paratuberculosis was diagnosed in two cows in herd A, and the bacterial isolates had the same RFLP and AFLP patterns (BC1/g) as the isolate detected from a goat in this herd. There was no information about import of infected cattle to this herd. The majority of the other Norwegian goat isolates examined, and the isolates detected from cattle imported from Sweden and Denmark had the same pattern. These findings might indicate that the same M. paratuberculosis strains infect goats and cattle in Norway, and cattle in the neighbouring countries.