Maedi-Visna is a complex production-limiting ovine lentiviral disease caused by small ruminant lentivirus (SRLV) infection widespread throughout the world. It is characterized by long immunological and clinical latencies and chronic progressive inflammatory pathology. Several genomic regions associated with susceptibility or resistance to the infection were reported, indicating great genetic complexity. In Switzerland, the Valais blacknose sheep breed was found to have the highest prevalence of Maedi-Visna among Swiss sheep breeds. Breeding for less susceptible sheep could therefore make a sustainable contribution to animal health. However, possible correlations between the genotypes of the sheep and other breeding traits should be known or monitored in order to identify possible negative effects on other traits.
