Exploring the epidemiology of Newcastle disease in Northern Nigeria: A mixed approach.

Newcastle disease (ND) remains one of the most significant constraints to backyard poultry production in Nigeria. This study investigated the epidemiology of ND in three northern states (Plateau, Bauchi and Kano) between 2020 and 2024, using a mixed-methods approach combining conventional and participatory epidemiology. A total of 52 villages where both components were surveyed were included in this analysis. In each of them, eight birds were sampled for serological and virological testing, and focus group discussions were held with farmers to explore their knowledge and practices regarding ND. Laboratory results revealed that ND virus was actively circulating in the study area, with vaccine-like lentogenic strains predominating over virulent velogenic strains. Twelve local disease terms were identified as possibly referring to ND. They were characterized mainly by respiratory and digestive signs, weakness, and high morbidity. The farmers use different terms depending on the predominance of the observed clinical signs and on their location. Furthermore, the disease terms were likely to be often used to refer to diseases caused by infectious agents other than ND virus. Farmers frequently attributed disease outbreaks to climatic factors and commonly used herbal remedies or over-the-counter drugs, while request for veterinary services and vaccination uptake remained low. Comparison of participatory and laboratory findings revealed both convergences and discrepancies between the two sets of findings, highlighting the importance of considering both scientific and local knowledge for effective disease surveillance and control strategies. Our findings are consistent with widespread circulation of NDV in backyard poultry in northern Nigeria, and emphasize the need for context-adapted communication about disease management and improved vaccination delivery.