Seroprevalence of Maedi-Visna and Border Disease in Switzerland

3866 sheep from 226 flocks of breeding associations and 1218 sheep from 15 independent sheep owners were tested for the presence of serum antibodies a gainst Maedi-Visna and Border Disease viruses. The flocks were randomly sel ected based on the relative proportion and the geographical distribution of the 4 predominant Swiss sheep breeds (Braunkopfiges Fleischschaf, Schwarzb raunes Berg- und Juraschaf, Walliser Schwarznasenschaf, Weiss Alpenschaf). Additionally two smaller breeds were included in the study (Charollais Suis se, Milchschafe). Sera of all sheep older than 1 year were collected togeth er with data characterizing host and management factors. The sera were tested using established ELISAs for detection of antibodies t o Maedi-Visna and Bovine Virus Diarrhea/Border Disease viruses. ELISA resul ts of Maedi-Visna serology were confirmed by iommunoblotting. 9% of the sheep of breeding associations were antibody-positive for Maedi-V isna virus. The results of the different breeds varied between 0.4% and 36% . A multiple logistic regression procedure identified breed, age, airing in barns, herd size, pasturing on alps and way of keeping the animals during winter as associated factors with individual serostatus. The prevalence of antibodies to Border Disease was 20% in sheep of breeding associations and 65% in those of independent sheep owners.