Survey for antibodies against maedi-visna in sheep in Poland.

Eighteen flocks of sheep were serologically tested for antibody to maedi-visna virus. A total of 4284 serum samples were tested by agar gel diffusion test and 1015 (24%) were found positive. Prevalence of infection increased with the age of sheep. Within age groups, the lowest prevalence was in the group at 1 year or less (7%) and gradually increased to the highest prevalence at 5 years of older (52%). A difference in prevalence of infection among breeds and sexes was seen but not proven because of inadequate numbers. All flocks tested were infected with a range of serological prevalence from 1.2% to 45.9%.