A Case of Avian Influenza Co-Infection and Multifactorial Diseases in a Broiler Chicken Farm in Majalengka, West Java, Indonesia

Poultry disease outbreaks are frequently multifactorial, involving complex interactions between infectious agents and environmental stressors. This report describes a case of avian influenza (AI) co-infection in a commercial broiler farm located in Majalengka, West Java, Indonesia, where a total of 11,000 birds exhibited increased mortality during the grow-out period. Diagnostic investigations included pathological examination, serological testing—such as hemagglutination inhibition (HI) assays for AI H5 and H9, enzyme-linked immunosorbent assay (ELISA) for infectious bronchitis, and rapid testing for Mycoplasma gallisepticum—Polymerase Chain Reaction (PCR) analysis, fecal flotation for coccidiosis, and an environmental assessment measuring ammonia levels, humidity, and heat stress index. Pathological findings revealed tracheitis, airsacculitis, thymitis, bursitis, perihepatitis, ascites, petechial hemorrhages, nephromegaly, and enteritis, indicating a complex disease process. Serological results demonstrated exposure to AI H9 and H5, with differing infection dynamics, while the uneven distribution of infectious bronchitis antibodies suggested field challenges. Additionally, partial exposure to Mycoplasma gallisepticum was observed. PCR results were negative at the time of sampling, consistent with post-infection phases. Environmental evaluation revealed elevated ammonia levels, excessive humidity, and a high heat stress index. In conclusion, the increased mortality was associated with avian influenza co-infection, complicated by secondary infections and adverse environmental conditions.