Seroprevalence of infectious bursal disease, co‑infection with Newcastle disease and salmonellosis and the associated risk factors in backyard chickens, Wag‑Lasta, Amhara, Ethiopia

Infectious bursal disease (IBD) is a highly contagious, immunosuppressive disease that primarily affects young chickens. It causes substantial economic losses to the poultry industry due to mortality and reducing productivity, and it weakens chickens' immune systems, making them more susceptible to other infections. A cross-sectional study was conducted in the Wag-Lasta districts of the Amhara region, Ethiopia, to determine the seroprevalence of IBD and coinfection with Newcastle disease (ND) and salmonellosis. Serological investigations were carried out using enzyme-linked immunosorbent assay (ELISA) for IBD, hemagglutination inhibition (HAI) for ND, and slide agglutination test (SAT) for salmonellosis. A total of 329 blood samples were collected from apparently healthy unvaccinated chickens. Serological testing found that 53.8% (95% CI 48.3–57.3) of the samples were positive for IBD. IBD prevalence was 40.4% (95% CI 35.5–44.7%) in lowland areas, 48.1% (95% CI 43.3–51.3%) in highland areas, and highest in midland areas at 74.7% (95% CI 70.8–78.1%) (P < 0.001). Among IBD-seropositive chickens, 108 (32.8%) were seropositive for both IBD and Newcastle disease (ND), 120 (36.8%) were seropositive for IBD and salmonellosis, and 75 (22.8%) were seropositive for all three infections. The study found a strong association between the prevalence of IBD and the agroecological zones and chicken breeds (P < 0.001). Exotic chickens demonstrated higher odds of IBD seropositivity (OR = 34.6; 95% CI 16.4–72.7; P < 0.001) compared to local chickens, and highland areas (OR = 4.9; 95% CI 2.2–10.9; P < 0.001) exhibited higher odds of IBD seropositivity than lowlands did. In conclusion, IBD prevalence was found to be alarming and can even co-occur with other infections, increasing chickens’ susceptibility to secondary diseases and exacerbating the economic impact in the region. Therefore, the assessment of epidemiology and risk factors associated with IBD is crucial for developing effective control strategies to reduce the burden of this economically significant poultry disease in the region.