Prevalence and risk factors for Maedi-Visna in sheep farms in Mecklenburg-Western-Pomerania.

Despite indications of a considerable spread of Maedi-Visna among sheep flocks in Germany, prevalence studies of this important infection are hardly available. Prior to any health schemes and guidelines, knowledge about regional disease distribution is essential. Depending upon herd size, 70 farms were randomly selected, of which 41 cooperated. A total of 2229 blood samples were taken at random and serologically examined. For assessment of selected farm characteristics a questionnaire exercise was conducted at all farms involved. The average herd prevalence is 51,2%, the within-herd prevalence is 28,8%. In the unvariate analysis of risk factors, small (10-100 sheep) and large (> 250 sheep) farms are more MW-affected than medium sized farms. The average stable and pasture space per sheep is larger at non-infected- compared to infected farms. Owners judgement on general herd health turns out to be better at non-infected compared to infected farms. Taking infected farms only, the risk of within-herd prevalence above 20% is significant higher in crossbred than in purebred flocks.