The avian influenza virus subtype H9N2 is an LPAIV widely circulated in Asian poultry. In the future, the LPAI H9N2 virus-like H5N1 could pose a serious zoonotic threat because they have been isolated from the backyard and wild bird species. It was discovered in a variety of avian species throughout Eurasia, the poultry industry has suffered significant financial losses as a result of this. The H9N2 virus has gained much attention due to its rapid dispersion between native birds. This low pathogenic virus survives in chicks and transmits to unaffected birds via the fecal-oral routes despite causing extreme clinical signs. The avian influenza virus subtype H9N2 causes severe respiratory illness in immunocompromised chickens. It causes an increase in early chick mortality as well as a considerable decline in egg production in laying chickens, resulting in financial loss. When this virus is co-infected with other pathogens, the intensity of clinical symptoms, death rates, and viral replication can increase. H9N2 viruses with G1 lineages have been found in field epidemics of influenza in poultry in the Middle East and the Indian subcontinent since 1997. Since the early 1990s, H9N2 has evolved to create a more diversified genotype in grassland poultry birds by acquiring gene fragments from other viruses. The genomes of newly isolated avian influenza (H9N2) viruses showed significant genetic recombination in HPAI viruses.<\/p>\n\n
Oil-based inactivated H9N2 LPAI vaccines were used in the poultry sector in many countries to avoid H9N2 infection owing to the extensive essence of H9N2 viruses and their zoonotic potential. However, because the nature of HA antigenic epitopes is constantly changing, influenza vaccines must be updated each year to make sure strain-specific immunity, posing a significantly challenging task to vaccine manufacturers. As a result, a global flu vaccine with broad protection against conserved influenza protein regions is required.<\/p>\n\n
The poultry industry, as well as public health, are both affected by the avian influenza virus. This is a huge issue all around the world. This review addresses critical issues concerning the evolution of AI viruses and vaccination strategies. Vaccination against the LPAI H9N2 virus is also discussed, including recent advances and challenges. Oil-based inactivated bivalent and monovalent vaccinations produce detectable antibody titers for all structural proteins, especially nucleoprotein and matrix protein. Antigens for antibody testing can be one or both of these proteins. As a result, using this method, vaccinated birds cannot be discriminated from naturally sick birds. The inability to conduct surveillance has been a critical impediment to vaccination to combat avian influenza. There has been a lot of effort put into matching the vaccination to the field variations. This is partly because immunization with any H9 virus appears to protect against clinical illness from a low pathogenic avian influenza exposure of the same subtype, irrespective of genetic variations. Oil-based inactivated bivalent and monovalent vaccinations produce many serum antibodies. The heterogeneity between vaccine and field strain can be estimated by comparing genomic information in the HA gene. However, when the vaccine is utilized as a control tool, both clinical safety and virus replication are concerns. Genetic variation is a significant issue with avian influenza vaccines, as it reduces immunization effectiveness. Antigenic drift is considered to unfold when the field virus changes in response to the host\u2019s antibodies. This method could be owing to vaccination or natural infection. However, in any scenario, the virus is under evolutionary changes to elude the body\u2019s immunity, allowing multiplication at more significant titers in the host. There is a higher probability that a strain of the virus will spread to new hosts if the proliferative phase is better managed.<\/p>\n\n
The widespread use of AI vaccinations in populations of animals may raise immunological selection pressure and mutation rates, which can lead to fast antigenic drift at antigenic locations. Better vaccination procedures and regular updating of vaccine seed variants are needed to boost immunogenicity and protective efficacy on poultry and duck farms. These techniques might be involved in selecting highly immunogenic vaccine seed strains, using efficient adjuvants for chickens and ducks, and utilizing innovative technology. In Indonesia, the co-circulation of H9N2 and H5N1 viruses in the field and live bird markets will increase the chances of gene reassortment between the viruses. Continued intensive monitoring of chicken farms and live bird markets for new variant low pathogenic H9N2 viruses and investigation of relevant vaccine seed viruses should be explored for future prevention. In Indonesia, inactivated bivalent and monovalent vaccinations have been utilized, and numerous new technology vaccines have been proposed to create low-cost, high-immunogenic vaccines. Together with efficient adjuvants, these novel vaccinations will undoubtedly lead to improved immunity against low pathogenic avian influenza subtype H9N2. In Indonesia, vaccination must be included in a complete, integrated disease-control strategy. National monitoring must be maintained at all times, as well as agricultural biosecurity and the DIVA strategy. In Indonesia, the eradication of these viruses could only be accomplished if all components of the control are implemented.<\/p>\n\n
Corresponding author: Prof. Dr. Mustofa Helmi Effendi, drh., DTAPH<\/p>\n\n
Further information on the research can be viewed in: <\/p>\n\n
Saifur Rehman, Fedik Abdul Rantam, Khadija Batool, Aamir Shehzad, Mustofa Helmi Effendi, Adiana Mutamsari Witaningrum, Muhammad Bilal, Muhammad Thohawi Elziyad Purnama. Emerging threats and vaccination strategies of H9N2 viruses in poultry in Indonesia: A review. F1000Research 2022, 11:548 Last updated: 04 JUL 2022<\/p>\n\n