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Infectious bursal disease virus led to severe necrotic enteritis in broiler chickens raised without antibiotics

2022 CPRF,Health & Immunity
Necrotic enteritis (NE) caused by Clostridium perfringens (CP) is an economically important, re-emerging disease in the poultry industry across the world. Incidence and severity of NE is influenced by several predisposing factors such as nutrition, management practices and immunosuppressive diseases. Immunosuppressive agents such as variant infectious bursal disease virus (vIBDV) predisposes birds to secondary bacterial infections. Similarly, withdrawal of prophylactic antimicrobials in the poultry industry has led to a substantial increase in bacterial infections including NE. This current study was designed to explore effects of immunosuppression and sudden changes in the protein content of feed as predisposing factors for NE in broiler chickens raised without antibiotics (RWA). Day-old Ross broiler chickens (n=120) were randomly allocated into six experimental groups each containing 20birds/group [1= control; 2= CP in feed (20% protein); 3= CP in feed (28% protein); 4= vIBDV + CP in feed (20% protein); 5= vIBDV + CP in feed (28% protein); and 6= vIBDV + CP via oral gavage (28% protein)]. Birds in groups 4, 5, and 6 were immunosuppressed with vIBDV at 17 days of age (3 days prior to exposure of CP). Broiler chickens were fed antibiotic free chicken starter with 20% protein for 18 days followed by an abrupt increase of protein to 28%. Feed was withdrawn for 12 h prior to exposure of birds to CP. Birds were challenged with CP by providing feed containing CP twice daily either in feed or oral gavage for 3 consecutive days. Birds were observed for clinical signs and mortality and the experiment was terminated at 4 days post-challenge. No mortality was observed in the control group while in group 4 administered with vIBDV + CP in feed (20% protein) and group 6 administered with vIBDV + CP by oral gavage (28% protein in feed) had 15% and 10% mortality respectively. Birds challenged with CP had classical histopathological lesions of severe diffuse necrosis of intestinal mucosa associated with bacterial colonization and filtration of minimal number of inflammatory cells. Incidence of histopathological lesions of NE in-group 4 administered with vIBDV + CP in feed (20% protein) had higher (45-50%) NE lesions compared to the control group 2 given CP in feed (20% protein). Similarly, incidence of histopathological lesions of NE in-group 5 administered with vIBDV+ CP in feed (28% protein) had higher (20-30%) incidence of NE compared to the control group 3 administered with CP in feed (28% protein). It was demonstrated that the pattern of mortality, gross and histopathological lesions in this NE animal model were comparable to field cases of NE. Moreover, severity of NE lesions was higher in the vIBDV administered birds without sudden change in protein content in the feed. It appears that control of vIBDV is an important consideration in the broiler chicken industry in order to control NE following withdrawal of prophylactic antibiotic use.
Tags :
antibiotic,broilers,necrotic enteritis
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Presenter

PhD Candidate

University of Saskatchewan

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