Pathological Investigation of Avian Colibacillosis in Commercial Poultry Flocks in Anambra State, South East Nigeria

Avian colibacillosis caused by pathogenic strains of Escherichia coli (APEC) remains among the most economically significant bacterial diseases affecting commercial poultry production in Nigeria's South East geopolitical zone. This study investigated the gross and histopathological features of colibacillosis in commercial layer and broiler flocks in Onitsha, Awka, and Nnewi areas of Anambra State, between January and July 2023. A total of 80 chickens from affected flocks with clinical signs of respiratory distress, pericarditis, and sudden death were submitted for post-mortem examination. Tissue samples from the pericardium, air sacs, liver, spleen, and lungs were processed for histopathological evaluation with haematoxylin and eosin stain. Microbiological isolation and identification of Escherichia coli from representative organs were also conducted. Gross lesions included fibrinous pericarditis, perihepatitis, airsacculitis, and splenomegaly. Microscopically, fibrinosuppurative inflammation of the pericardium and air sac epithelium with heterophilic infiltration and bacterial colonies were prominent. Hepatic lesions included periportal mononuclear hepatitis with focal necrosis. Escherichia coli was isolated from 87.5 percent of culture-positive specimens. These findings emphasise the role of poor biosecurity, overcrowding, and sub-optimal ventilation in predisposing poultry flocks to APEC infection. Keywords: colibacillosis, APEC, poultry, histopathology, Anambra