Abstract
Vaccination is one of the leading methods of controlling the spread of the Avian Influenza (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 field. In this study, we identified the reassortant H9N2 viruses in chicken farms that showed significant 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 efficacy 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.
Highlights
Avian Influenza (AI) is a type A influenza virus that belongs to the Orthomyxoviridae family.The AI virus genome is a negative-sense single-stranded RNA with eight segments that encode 10 proteins including Polymerase Acidic (PA), Polymerase Base (PB1 and PB2), Nucleoprotein (NP), Hemagglutinin (HA), Neuraminidase (NA), Matrix (M1 and M2) and Non-Structural (NS1 and NS2).Influenza A subtypes can be categorized based on these HA and NA genes
We identified a reassortant virus between the H9N2 and H5N1 viruses, which cause a high mortality on the chicken farm
Virus Analysis analysis showed that BLi25Ut/18 and SLO.105/18 isolates, which are the viruses,The areresults suspected of havinganalysis reassortment with the Highly Pathogenic Avian Influenza (HPAI)
Summary
Influenza A subtypes can be categorized based on these HA and NA genes. Reassortment is a mechanism for genetic changes in influenza viruses that can occur through the exchange of gene segments by two or more different types of influenza viruses. Genetic reassortment can produce new variants/strains or subtypes that may have different biological characteristics from virus ancestral [2,3]. The reassortment process can occur if two different virus strains infect the same cell simultaneously (co-infection) [4]. The segmented genome structure of influenza A viruses allows the exchange of gene segments when viral co-infection occurs in a cell that can create stable reassortant viruses [3,5]
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