Developing Farm-Level Post-vaccination Sero-Monitoring Systems for H5N1 Highly Pathogenic Avian Influenza in an...

Area of Science:

• Veterinary Virology
• Immunology
• Poultry Health

Background:

• Field studies on avian influenza H5N1 vaccination responses in poultry are scarce, especially in endemic regions with diverse circulating clades and vaccine strains.
• Interpreting field serological data is challenging due to multiple factors in routine vaccination programs.

Purpose of the Study:

• To evaluate the serological responses of layer hens in Indonesia following vaccination against highly pathogenic avian influenza H5N1.
• To compare the effectiveness of locally produced homologous H5N1 vaccines versus imported heterologous H5N2 vaccines in field conditions.
• To establish a robust methodology for field vaccination effectiveness studies in commercial layer flocks.

Main Methods:

• A sampling regime was implemented before and after vaccination in point-of-lay pullets.
• Serological responses were assessed using a panel of test antigens.
• Hemagglutination inhibition (HI) assays were employed to measure antibody titers.

Main Results:

• High antibody titers were observed in birds vaccinated with two or more doses of locally produced homologous H5N1 vaccines.
• Flocks vaccinated with imported heterologous H5N2 vaccines showed significantly lower median titers, potentially insufficient for full production cycle protection.
• The use of a test antigen panel allowed for the detection of exposure to different vaccine antigens and identification of mislabeled vaccine seed strains.
• Test antigens did not require exact matching to assess sero-protection in adequately vaccinated birds.

Conclusions:

• The study highlights the importance of vaccine type, origin, and homologous/heterologous matching for effective avian influenza H5N1 control in layer hens.
• Point-of-lay vaccination can serve as a valuable reference point for monitoring flock immunity throughout the production cycle.
• The developed methodology supports robust field effectiveness studies for avian influenza vaccines in commercial poultry settings.