Objectives: Now, Maedi-visna virus and Caprine arthritis -encephalitis are known as of Small Ruminant Lentiviruses(SRLV). Both of them cause chronic diseases in small ruminants. In sheep, Maedi-visna virus cause a disease as the same name. In farm animals, sheep and goat are the main reservoirs of infection for the disease. This research is the first study about Seroepidemiology of Maedi-visna disease in sheep populations of Khorasan Razavi province. Materials & Methods: 220 head of sheep from 30 herds in 12 counties were selected by multi-stage cluster random sampling. Sera were assayed for antibody against Maedi-visna virus/ Caprine arthritis - encephalitis. Results & Conclusion: Seroprevalence of infection in sheep was 34.5% (95% CI: 28.3 - 40.7%). In all studied counties, the infection were detected in the range of 6.7 - 72.2 %. In 26 (89.6%; 95%CI: 74.4 – 98.8%)sheep flocks at least one seropositive case was detected. The relationship between age, sex, flock size and breeds of sheep were statistically analyzed. In Logistic regression model, only age was correlated with SRLV seroprevalence (P<0.05). It seems, because of some points such as difficulty clinical diagnosis, chronic course of the disease, absence of effective vaccine and treatment and huge economic loss, more epidemiological studies and explanation of prevention and control strategies for the disease are necessary. This study showed relatively high seroprevalence against SRLV in sheep population in this province.

Keywords