Vaccine Efficacy on the Novel Reassortant H9N2 Virus in Indonesia

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.

The potency of newly development H5N8 and H9N2 avian influenza vaccines against the isolated strains in laying hens from Egypt during 2019

“…Also, the mean HI titers in groups 7 and 8 showed a high increase against the homologous antigen and was significantly higher than the commercial H9N2 vaccine. Our results agreed with Dharmayanti et al (2020) who recorded the antibody titre in the vaccinated chickens with the inactivated monovalent H9N2 vaccine against the AI H9N2/2017, homolog BLi25Ut/18 and H5N1/2013 antigens and the titers were 8 log2, 8.3 log2 and 0 after three WPV. This is also coordinated with Lee et al (2011) , who stated that one dose of inactivated H9N2vaccine is very protective and immunogenic in SPF chickens.…”

Dose immunogenicity study of a plant-produced influenza virus-like particle vaccine in layer hens

“…In LPAI challenge models in SPF chickens, the correlation of a specific antibody titre with prevention of morbidity has been harder to define. In the field LPAI viruses like H9N2 and H6N2 can cause respiratory disease and weight loss with increases in weekly mortalities, egg quality drop, and production drops of between 5 and 60 %, that are exacerbated by concomitant infections with other pathogens [ 3 , 35 ], which is difficult to duplicate under experimental conditions. Studies on efficacy of vaccines in preventing egg production losses due to LPAI infection are few, and all thus far have used inactivated whole virus vaccines [ 35 , 36 , 37 ].…”

“…In the field LPAI viruses like H9N2 and H6N2 can cause respiratory disease and weight loss with increases in weekly mortalities, egg quality drop, and production drops of between 5 and 60 %, that are exacerbated by concomitant infections with other pathogens [ 3 , 35 ], which is difficult to duplicate under experimental conditions. Studies on efficacy of vaccines in preventing egg production losses due to LPAI infection are few, and all thus far have used inactivated whole virus vaccines [ 35 , 36 , 37 ]. Dharmayanti and co-workers [ 35 ] performed an efficacy study in laying hens with inactivated whole virus vaccines, comparing a vaccine that was homologous with the H9N2 challenge strain they used to a commercial bivalent vaccine that contained H9N2, but was not matched to the challenge virus.…”

Avian influenza overview May – August 2020

“…Information extracted from the scientific literature Dharmayanti et al (2020b) described two A(H9N2) viruses isolated in Indonesia in 2018: one of these from a chicken flock with respiratory disease, decrease in egg production and an observed mortality rate of more than 10%; the other strain was obtained from a live bird market surveillance programme of chickens. Both viruses were reassortants deriving their PB2 gene segment from clade 2.3.2.1c HPAI A(H5N1) viruses and the rest of their segments from A(H9N2) strains circulating in Indonesia and Vietnam (H9 gene belonging to the Y280/G9 lineage).…”