Evaluation of the immunoprotection efficacy of Riemerella anatipestifer fur-deficient mutant as an attenuated vaccine

Riemerella anatipestifer (R. anatipestifer, RA) is an infectious pathogen that causes septicemia and polyserositis in ducks. Our previous studies showed that RA CH-1 Afur was significantly attenuated in ducklings, which highlights the potential of this strain as a live atten-uated vaccine. In this study, it was shown that infection with 109 CFU of the fur mutant did not cause any clinical symptoms or significant histological lesions in 3-day-old ducklings and that the bacteria were readily cleared by the host within 3 d. Compared with the nonvaccinated group, the group inoculated with the mutant strain RA CH-1 Afur exhibited protection of ducklings against a high-dose (2.28 pound 1010 CFU) challenge with the wild-type strain RA CH-1. Moreover, the average body weights and body weight gains of the Dfur-inoculated group were not signifi-cantly affected by the challenge. Further analysis revealed that RA CH-1 Afur elicited higher IgY titers and that the serum antibody levels persisted for at least 49 d after immunization. Overall, our study showed that RA CH-1 Afur is a safe and effective vaccine candidate that is expected to play an important role in RA CH-1 infection prevention in the duck industry.

Automated summary

This study demonstrates that the RA CH-1 Afur strain is significantly attenuated and provides effective protection against high-dose RA CH-1 infection in ducklings. Inoculation with the mutant strain did not cause clinical symptoms or significant histological lesions, and the bacteria were cleared by the host within 3 days. Furthermore, RA CH-1 Afur induced high levels of IgY antibodies, which persisted for at least 49 days.