Clinicopathological investigations into concurrent fowl adenovirus-induced inclusion body hepatitis and mycotoxicosis on commercial broiler farms in Kerala, South India

Broiler farming is a significant segment of the global economy, valued at 1.5 trillion in 2020, with India among the leading producers. Disease outbreaks continue to threaten the profitability and sustenance of the industry, impacting growth and feed conversion efficiency. The present study investigated the impact of Inclusion Body Hepatitis (IBH) and mycotoxicosis in commercial broiler farms in Kerala, South India, by examining 21 outbreaks between May 2023 and November 2024, that resulted in the mortality of 2946 birds out of an affected population of 52,022. Detailed necropsy examinations were performed on 130 birds, with gross and histopathological lesions recorded, and aflatoxin B1 levels in 6 feed samples were estimated using fluorimetry. Samples subjected to hexon gene (590 bp) amplification using polymerase chain reaction (PCR) were found positive for fowl adenovirus (FAdV). Poultry feed analyses presented Aflatoxin B1 levels far above the recommended maximum levels (20 ppb). Acute mortality ranged from 0.44 to 61.9% in broiler flocks aged 6 to 37 days. The liver was the primary organ affected, followed by the kidneys, spleen and lungs. Pathognomonic histopathological lesions, such as basophilic intranuclear inclusion bodies in hepatocytes with necrosis, were observed in all the outbreaks. The present study emphasizes the association of the immunosuppressive role of aflatoxin B1 and the consequent IBH infection, and provided insights into the development of suitable biosecurity and preventive strategies. Further studies are warranted to identify major FAdV serotypes, and to study differences in the pathogenesis of IBH.