Some biological characteristics of Riemerella anatipestifer HAN-RA2020 strain causing hemolytic anemia in waterfowl isolated in Hung Yen province

Abstract

Riemerella anatipestifer (RA) infection in waterfowl causes serious economic losses in the duck industry due to high mortality and weight gain reduction. This study aimed to evaluate some biological characteristics of the RA strain isolated in Hung Yen province from ducks in 2020 (HAN-RA2020 strain). The HAN-RA2020 strain grew well on chocolate agar medium, having all biochemical characteristics of RA. The HAN-RA2020 strain belonged to serotype 6 and had 100% of similarity level in comparison with the RA strains reported in China in 2015, 2017, and 2019. The HANRA2020 strain was susceptible with tetracycline, doxycycline, enrofloxacin; resistant to ampicillin, oxytetracycline, norfloxacin, gentamicin, colistin sulfate. The result of testing virulence of this strain showed that the minimum lethal dose of the HAN- RA2020 strain was 109 CFU/ml, causing hemolytic
activity in ducks with typical lesions. Also, the HAN-RA2020 strain had immunogenicity with a protection rate of 100%, which is an important characteristic in selection for vaccine production.