Seroprevalence and Pathological Study of Salmonella Infections in Layer Chickens and Isolation and Identification of Causal Agents

The present research work was conducted to study about the seroprevalence and pathology of Salmonella infections in layer chickens of Dhaka and Gazipur regions of Bangladesh and to isolate and characterize Salmonellae from layer chickens during the period from January to May 2006. The used materials were blood sample, cloacal and liver swabs from live and dead birds respectively, and visceral organs (liver, lungs, spleen and intestine). The used methods were serum plate agglutination (SPA) test; necropsy and histopathology; cultural, morphological and biochemical test. The overall seroprevalence was 43.4%. During necropsy, congested and enlarged liver with focal necrosis, haemorrhagic and discoloured ovary with stalk formation and mild haemorrhagic to catarrhal enteritis in intestine were detected. Microscopically, the liver showed congestion, focal necrosis with multifocal infiltration of histiocytes in liver parenchyma. In ovum, infiltration of leukocytes, bacterial colony, RE cell proliferation and fibrinoid necrosis were recorded. The intestinal mucosa exhibited infiltration of mononuclear cells in mucosa, submucosa as well as muscularis mucosa. A total of 33 (21.02%) Salmonellae from live and dead birds were isolated. The isolation rate of Salmonellae was higher in seronegative (31.6%) group than seropositive (3.2%) group. Out of 33 Salmonella isolates, 25 were S. pullorum, 3 were S. gallinarum and the rest 5 were motile Salmonellae. The isolates obtained in the study may be investigated for serotyping, pathogenesis study, antibiogram and vaccine production in future.