Background: Avian pathogenic Escherichia coli (APEC) induces colibacillosis, an acute and systemic disease, resulting in substantial economic losses in the poultry sector. Aim: This study determined the gross and microscopic changes associated with Escherichia coli (E. coli) (APEC serotype O1KI) infection in layer chickens. Methods: A total of 10 layer chickens (20 weeks old) were acquired and assigned, at random, into two groups (infected and control) of 5 layers each. Each bird in the infected group was challenged with 0.5 ml of bacterial aliquot containing 109 colony-forming units (CFU) of the bacteria, administered intra-tracheally. The birds from both groups were humanely sacrificed on tenth day post-infection and subjected to post-mortem examination for gross and microscopic changes. Results: Gross lesions observed in the infected chickens included congested lungs, enlarged liver and kidney, hyperaemic intestine, congested ovarian follicles and yellowish fibrinous material in the infected group. While microscopic lesions observed were congested ovarian blood vessels, mononuclear cellular infiltration and generalised necrosis of the liver, kidney, and heart. Conclusion: This study revealed various lesions of congested lungs, enlarged liver, hyperaemic intestine, enlarged kidney, and congested ovarian follicles, yellowish fibrinous material, congested blood vessels of the oviduct that were typical of the natural infection and may be attributable to colisepticaemia.
Key words: E coli, Experimental, Gross, Layer Chickens, Microscopic Lesions
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