Evaluation of protection induced by Riemerella anatipestifer-E. coli O78 bacterin in white pekin ducks

Riemerella anatipestifer infection accounts for the most significant economic losses due to infectious disease in commercial White Pekin ducks in the United States. An inactivated bacterin and a live attenuated vaccine are approved for use against R. anatipestifer in the United States. This study aimed to evaluate the duration of protection induced by the commercial bacterin containing formalin-inactivated strains of R. anatipestifer serotype 1, 2, 5 (RA1, RA2, RA5) combined with E. coli 078 (RA-EC). Pekin ducks were vaccinated twice at 2 and 3 wk of age with 0.5 mL of RA-EC bacterin containing approximately 10⁸ colony forming units (CFU) of E. coli and 10⁹ CFU of RA1, RA2 and RA5 per dose (0.5 mL). Four-, 6-, and 8-week-old vaccinated and non-vaccinated control ducks were subsequently challenged with virulent strains of either: E. coli 078, RA1, RA2 and RA5. Evaluation of the vaccine protective index, histopathology, and bacteriology indicate RA-EC bacterin provides protection against virulent stains of RA1, RA2, RA5, and E. coli O78 throughout the 8-wk commercial Pekin grow-out period.