Development study of the inflammatory process during colibacillosis enteritis in broiler chickens: anatomo-pathology and clinical repercussions in poultry farming

Abstract

Colibacillosis constitutes a serious danger to poultry production in eastern Algeria. Escherichia coli, particularly the avian pathogenic strain (APEC), is the primary pathogen affecting broiler chickens, causing substantial economic losses through high mortality rates, decreased meat yield and quality, elevated veterinary expenses, antibiotic resistance concerns, and public health risks. APEC, an extraintestinal pathotype, induces various infections including septicemia, airsacculitis, and enteritis. In this study our objective was to highlight histopathological lesions caused by avian pathogenic Escherichia coli (APEC) infection, in addition to the evolution of the lesion score of the intestine during colibacillosis enteritis. This study aimed to characterize the histopathological lesions caused by APEC infection and track the progression of intestinal lesion scores during colibacillosis enteritis. We collected 150 samples from 15 poultry farms in Constantine, eastern Algeria, where broilers exhibited clinical signs such as: dehydration, watery diarrhea, and elevated mortality. Necropsy revealed intestinal distension filled with fluid and mucus flecks. Additionally, to assess APEC's immunosuppressive effects, 51 bursa of Fabricius samples were obtained from chickens with coli septicemia for histological examination. APEC infection was confirmed via a Congo red dye assay, and the number of Escherichia coli was estimated via the Miles and Misra method. APEC infection was confirmed using the Congo red assay, with bacterial quantification performed via the Miles and Misra method. Samples were fixed in 10% formalin and processed for histology following the Luna protocol. Results showed that 137 of 150 samples (91.3%) were Congo red positive, with E. coli counts ranging from 5*10⁷ to 2*10⁹ CFU/ml. Microscopic analysis of 236 slides revealed characteristic intestinal degenerative lesions from APEC infection, including congestion, edema, expanded lamina propria with inflammatory cell infiltration, crypt atrophy, epithelial desquamation and necrosis of villi and crypts, most prominent in the duodenum. The bursa of Fabricius displayed significant pathological changes, such as gland-like follicular structures with corrugated epithelium, interfollicular edema, enlargement, hemorrhage and inflammatory cells infiltration, medullary vacuolization and necrosis, excessive fibrous connective tissue, epithelial plicae vacuolization, necrotic debris accumulation, lymphocytic depletion, and follicular atrophy. To conclude, avian pathogenic Escherichia coli infection triggers substantial histological alterations in the intestine, predominantly in the duodenum. The bursa of Fabricius exhibits marked changes that closely mimic those seen in infectious bursal disease virus infections. These striking morphological similarities indicate a profound effect on humoral immunity.