Effect of infectious bursal disease (IBD) vaccine on Salmonella Enteritidis infected chickens

Background: Chickens infected with both infectious bursal disease virus (IBDV) and Salmonella had higher mortality. In this work, we investigated the effect of IBDV vaccine (modified live-virus bursal disease vaccine, Nobilis strain 228E (R)) on experimentally infected chickens with Salmonella Enteritidis (SE). Methods: Four experimental groups were included in this study, negative control group, 228E (R) group, 228E (R) + SE infected group, and SE infected group. Chickens were ocularly administrated 228E (R) at 12 days of age and orally infected with S. Enteritidis at 13 days of age. Sera, intestinal fluid, blood, cloacal swabs and tissue samples were collected at 1, 2 and 3 weeks post vaccination (PV). Results: The recorded mortalities were higher in the 228E (R) + SE infected group, compared to the SE infected group. The anti-S. Enteritidis serum antibody titer and the intestinal mucosal IgA level were higher in the SE infected group at 2 and 3 weeks PV, compared to 228E (R) + SE infected group. S. Enteritidis fecal shedding and organ colonization were significantly higher in the 228E (R) + SE infected group than the SE infected group at 2 and 3 weeks PV. The 228E (R) + SE group had significantly lower bursa to body weight ratios at 2 and 3 weeks PV, as well as had higher bursal lesion scores than the SE infected group. IBDV vaccine depressed the specific-SE systemic and mucosal antibody responses, but did not affect the specific-SE cellular immune responses. Conclusion: Chickens administrated IBDV vaccine, followed by S. Enteritidis infection, could cause a significant effect on the bursa of Fabricius, resulting in failure of systemic and mucosal antibody responses to the S. Enteritidis and reduce the elimination and the clearance of S. Enteritidis. (C) 2017 Elsevier Ltd. All rights reserved.