Epidemiological Insights into Small Ruminant Lentiviruses in Portuguese Production Systems

Small ruminant lentiviruses are longstanding viral infections affecting sheep and goats worldwide, resulting in reduced efficiency and economic losses. In Portugal, updated epidemiological data are scarce. The aim of this study was to assess the seroprevalence and risk factors for SRLV in Portugal. The study was conducted in Portuguese flocks of ovine and caprine species. Flocks were randomly chosen, and producers were invited to answer a questionnaire. The indirect ELISA test, ID Screen^® MVV/CAEV Indirect, was made to detect infection. We collected samples from 59 flocks, of which 55.93% (CI 95%: 43.26-68.60%) had at least one positive animal. Of these flocks, 1302 individual samples presented a seroprevalence of 32.95% (CI 95%: 30.08-35.81%). Regarding the risk factor analysis, the multivariable mixed-effects logistic regression model at the individual level identified variables with increased odds of SRLV seropositivity. Caprine species (OR = 2.47; CI 95%: 1.01-6.03), non-autochthonous breed (OR = 2.95; CI 95%: 1.23-7.06), animals older than two years old (OR = 1.95; CI 95%: 1.29-2.94), dairy aptitude (OR = 8.15; CI 95%: 2.53-26.24), unknown serostatus of newly acquired animals (OR = 9.41; CI 95%: 2.93-30.23) and participation in livestock competitions (OR = 4.25; CI 95%: 1.42-12.73) were significantly associated with increased odds of seropositivity. SRLV has been confirmed in both regions of Portugal studied, with a significant regional disparity that is likely attributable to differences in management practices. The identification of risk factors specific to each production system is crucial for the development and implementation of voluntary control programs.