[Development and evaluation of an inactivated bivalent vaccine against duck viral hepatitis].

The rapid mutation and widely spread of duck hepatitis A virus (DHAV) lead to the vast economic loss of the duck industry. To prepare and evaluate bivalent inactivated vaccine laboratory products of DHAV, 6 strains were screened from 201 DHAV-1 strains and 38 DHAV-3 strains by using serotype epidemiological analysis in most of the duck factory. Vaccine candidate strains were selected by ELD50 and LD50 tests in the 6 strains. Continuously passaged, the 5th passaged duck embryos bodies grinding fluid was selected as vaccine virus seeds. The virus seeds were treated with formaldehyde and water in oil in water (W/O/W) emulsions, making into three batches of two bivalent inactivated vaccine laboratory products. The safety test, antibody neutralization test, challenged protection and cross immune protection experiment suggested that the vaccines possessed good safety, and neutralizing antibodies were detected at 7th day and the challenged protection rate reached 90% to 100% at the 14th and 21st day. Moreover, immune duration of ducklings lasted more than five weeks. However, cross-immunity protection experiments with DHAV-SH and DHAV-FS only had 20%-30%. The two bivalent inactivated vaccine laboratory products of duck viral hepatitis were effective and reliable, providing a new method as well as a new product for DHAV prevention and control.