Serological investigation of major respiratory viruses in sheep in North Shewa, Ethiopia: Parainfluenza virus, bluetongue virus, maedi-visna virus and peste des petits ruminants virus

Background: Respiratory diseases significantly affect small ruminants, leading to considerable illness and mortality. These conditions are often multifactorial, resulting from interactions among pathogens, host immunity and environmental stressors.

Objective: This study aimed to detect antibodies against major respiratory viruses, bluetongue virus (BTV), maedi-visna virus (MVV), parainfluenza virus type 3 (PI-3) and Peste des petits ruminants virus (PPRV) in sheep from the North Shewa Zone, Ethiopia.

Methods: A cross-sectional serological survey was conducted between September and November 2018, involving 135 sheep from the Menz-Mama and Menz-Gera districts. Serum samples were analysed using enzyme-linked immunosorbent assays (ELISA): competitive ELISA for BTV and PPRV and indirect ELISA for MVV and PI-3. Data were analysed using STATA software, and descriptive statistics were used to estimate the frequency of antibodies against the target viruses.

Results: PI-3 showed the highest seropositivity (60.74%), followed by PPRV (27.41%), BTV (12.59%) and MVV (8.15%). Overall, 76.3% of sheep had antibodies to at least one virus, 26.67% to two viruses and 2.22% to three. In Menz-Mama, among 64 sheep tested, 3.13% were seropositive for MVV and PPRV, 37.5% for PI-3 and 18.75% for BTV. A total of 57.81% had antibodies to at least one virus and 3.13% to two. In Menz-Gera, higher seroprevalence was observed: 12.68% for MVV, 81.69% for PI-3, 49.3% for PPRV and 7.04% for BTV. A total of 92.96% of sheep had antibodies to at least one virus, 47.89% to two and 4.23% to three, indicating substantial viral exposure and potential co-infection.

Conclusions: These findings indicate widespread circulation of respiratory viruses, with PI-3 being the most seroprevalent. Integrated control measures, including enhanced surveillance, targeted vaccination and improved husbandry practices, are urgently needed to reduce the disease burden and support sustainable sheep farming in the region.