Ni Luh Putu Indi Dharmayanti *,† text Indonesian Research Center for Veterinary Science 2020

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17 Vaccination is one of the leading methods of controlling the spread of the Avian In?uenza (AI) viruses in Indonesia. The variety of circulating viruses and their ability to mutate must be followed by updating the vaccine master seed used in the ?eld. In this study, we identi?ed the reassortant H9N2 viruses in chicken farms that showed signi?cant problems in decreased egg production with high mortality. The reassortant H9N2 viruses derived the PB2 gene from the H5N1 virus. The pathogenicity test results of the reassortant virus showed various clinical signs of illness, a high mortality rate (10%), and decreased egg production down to 63.12% at two weeks post-infection. In a vaccine e?cacy test, the vaccinated groups showed minimally decreased egg production that started to increase to more than 80% at 4–7 weeks post-challenge. Our study showed that inactivated bivalent and monovalent reassortant H9N2 vaccines can induce antibody response, reducing the mortality and virus shedding caused by reassortant H9N2 virus infection. The reassortant H9N2 virus is a threat that requires vigilance in poultry farms and the industry. The vaccines used in this study can be one of the options for control or prevention measures on farms infected with the reassortant H9N2 viruses. Ni Luh Putu Indi Dharmayanti *,† Vaccine E?cacy ARTVET2414 ARTVET2414 250205 20250205020809 INLIS000000000019190 Converted from MARCXML to MODS version 3.5 using MARC21slim2MODS3-5.xsl (Revision 1.106 2014/12/19)