Pathological Investigation on different forms of E. coli infections (colibacillosis) in broiler chicken and molecular confirmation

Abstract

Avian colibacillosis is a significant global infectious disease in birds of all ages, leading to substantial economic losses in poultry production. This disease is caused by Escherichia coli infection which is a highly prevalent bacterial pathogen in man and animals. Colibacillosis is a multifaceted syndrome distinguished by various organ abnormalities, including air sacculitis (61.67%), pericarditis (58.33%), perihepatitis (33.33%), yolk sac infection (35%), enteritis (31.67%). Research involving pathological examinations was conducted on spontaneous occurrences of avian colibacillosis to investigate the prevalence and pathological manifestations of Escherichia coli infection. After necropsy, we collected samples from lung, liver and spleen for bacterial isolation and subsequently for histopathological examinations. Following the bacterial isolation process, when we cultured the bacteria on agar, the outcomes revealed colonies with a distinct pink coloration on MacConkey agar and a distinctive metallic sheen on EMB agar. These characteristics led to the identification and consideration of E. coli in 45 cases. To confirm the presence of E. coli, PCR was conducted using the housekeeping gene primer (adk), resulting in the confirmation of E. coli in 37 suspected cases initially identified from agar cultures. Microscopic examinations revealed severe congestion (83.33%), hemorrhage (90%), focal area of necrosis (76.67%), prominent nuclear and cytoplasmic changes in hepatocytes with like fatty change (33.33%) in liver. In lung, edema (20%) and congestion (75%) were commonly observed almost all cases with thickening of alveolar septa. Hemorrhage and congestion (66.67%) also observed commonly in spleen along with depletion of lymphoid elements and multiple focal areas of necrosis (33.33%) in the primary follicles resulted in the formation of secondary germinal centers. Depletion of lymphocytes at times also accompanied by reticular cell proliferation (50%) in spleen. This study underscores the significant cellular-level changes associated with colibacillosis in commercially raised broiler chickens and suggests the need for further investigation to identify the specific serotypes of E. coli present in these chicken populations.