Uncovering Newcastle disease virus dynamics in Northern Nigeria: insights from an epidemiological survey in unvaccinated village poultry

Abstract Background Newcastle disease virus (NDV) remains a major constraint to village and backyard poultry production in Nigeria, where limited vaccination and low biosecurity may facilitate sustained virus circulation. This study investigated the serological and molecular epidemiology of NDV in unvaccinated village poultry across Plateau, Bauchi, and Kano States, northern Nigeria. Method A cross-sectional survey was conducted in 502 villages between 2020 and 2024. Serum samples ( n = 3,999) and pooled tracheal/cloacal swabs ( n = 2,113) were collected from extensively managed backyard poultry. After excluding flocks with a history of NDV vaccination, 3,831 sera from 481 villages were analyzed using indirect ELISA. Pooled swabs were screened by real-time RT-PCR and positive samples were sequenced for phylogenetic relatedness. Results Bird-level seropositivity was 16% in Plateau, 22% in Bauchi, and 22% in Kano, while 68–80% of villages in the three states had at least one seropositive bird, indicating widespread NDV exposure. Seroprevalence varied by species, flock size, and state, with turkeys generally showing higher exposure. Small and medium-sized flocks exhibited higher seropositivity than large flocks. Biosecurity measures, including fencing and shelter, were not significantly associated ( p > 0.05) with seropositivity. Of 2,113 pooled swab samples, 950 tested positive for NDV RNA. Phylogenetic analysis revealed widespread circulation of lentogenic genotype I.1.1, closely related to the NDV-I 2 vaccine strain, alongside velogenic genotype XIV.2, detected in chickens, ducks, and turkeys across all states. A velogenic pigeon-associated genotype XXI.1.1 was also identified in Bauchi State. Conclusions These findings revealed widespread NDV circulation in rural poultry systems across northern Nigeria, highlighting the need for improved surveillance, strengthened biosecurity, and adoption of genotype-matched vaccination strategies.