Seropositive bucks and within-herd prevalence of small ruminant lentivirus infection

Caprine arthritis-encephalitis is an economically important disease of goats. It is evident that horizontal transmission through respiratory secretions and milk plays an important part in the disease spread whereas the role of sexual transmission remains questionable. The cross-sectional study was carried out to investigate the relationship between presence of small ruminant lentivirus (SRLV)-sero-positive bucks and seroprevalence of SRLV infection in does in herds. The analysis included 76 goat herds seropositive for SRLV infection. A sample of adult female goats from each herd was selected in a simple random fashion. All males present in a herd were also enrolled in the study. The animals were screened with commercial serological immunoenzymatic tests. Standardized questionnaires were used to gather knowledge of 3 hypothesized herd-level confounding factors: number of years for which a herd had existed until testing, goat replacement from other herds in Poland and use of machine milking. Three-level hierarchical linear regression model was developed to evaluate the relationship (alpha = 0.05). Median (interquartile range) within-herd seroprevalence of SRLV was 60.1% (35.7% to 87.9%) and 35.8% (10.1% to 49.6%) in herds where seropositive males were present and absent, respectively. Controlling for possible confounders presence of SRLV-seropositive bucks proved to be an independent factor linked to the higher within-herd seroprevalence of SRLV (p = 0.001). The study indicates that seropositive bucks may facilitate the spread of SRLV infection in goat herds and therefore their presence should be considered as a risk factor.