Post-vaccination sero-monitoring and Sero-surveillance of Peste des Petits Ruminants in small ruminants in Central Gondar zone, Northwest Ethiopia

Abstract

Peste des petits ruminants is a highly contagious, economically significant, and transboundary disease of small ruminants caused by the PPR virus (PPRV). Despite Ethiopia's goal of eradicating PPR by 2027 through risk-based vaccination strategies, outbreaks continue, with 554 PPR outbreaks recorded nationwide. The current cross-sectional study was conducted to assess flock immunity in vaccinated small ruminants and estimate the seroprevalence of PPRV in unvaccinated flocks in the East-Dembia and Gondar Zuria districts of the North Gondar zone, Ethiopia from June 2024 to February 2025. Multistage cluster sampling was used to select districts, peasant associations, and villages. Individual animals were selected haphazardly, mimicking simple random sampling. A total of 600 serum samples were collected: 300 from vaccinated and 300 from unvaccinated small ruminants. All samples were tested for anti-PPRV antibodies using the competitive enzyme-linked immunosorbent assay (c-ELISA). The overall flock immunity was found to be 75%, with 75.73% in sheep and 72.1% in goats. The seroprevalence of PPRV in unvaccinated small ruminants was 14.33% (95% CI: 10.6–18.82%). The final multivariable logistic regression model identified age and flock size as the most critical risk factors influencing differences in PPR seropositivity. Specifically, adult animals were 1.12 times more likely to be seropositive for PPRV infection compared to young animals (95% CI: 0.20–2.03). Additionally, sheep and goats in medium-sized flocks were more likely to test seropositive for PPR compared to those in small flocks (95% CI: 0.11–1.55). However, no significant variation in seropositivity was observed across districts, species, sex, production systems, newly introduced animals, or animal movement (p > 0.05). The study revealed that the overall flock immunity in vaccinated populations was slightly below the 80% threshold recommended by the global PPR control and eradication strategy. Also, serological results in unvaccinated flocks indicating the possible circulation of PPRV in the area. To effectively control and eventually eradicate PPR, further intensive vaccination programs, coupled with active surveillance, are required to make these districts PPR-free zones. Additionally, refining vaccination strategies in alignment with global and national PPR eradication plans is essential. Keywords: Antibody, Central Gondar, Peste des petits ruminants, Seroprevalance, Sero monitoring, Small ruminant, Ethiopia I