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Published on: August 29, 2017
Avian influenza: genetic evolution under vaccination pressure
Magdalena Escorcia1, Lourdes Vázquez, Sara T Méndez
1Departamento de Producción Animal Aves, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, DF 04510, México. magdaescorcia@exalumno.unam.mx
Virology Journal
|January 26, 2008
Summary
Avian influenza viruses (AIVs) in Mexico show constant genetic drift, particularly H5N2 strains, despite extensive vaccination. This evolution, evidenced by hemagglutinin gene changes, may explain increased farm outbreaks and highlights challenges in controlling AIV epidemics.
Area of Science:
- Veterinary Virology
- Molecular Evolution
- Epidemiology
Background:
- Antigenic drift in avian influenza viruses (AIVs) is a significant concern in poultry, mirroring patterns seen in human influenza.
- High vaccination pressure, with approximately 2 billion doses of AIV vaccines administered in Mexico over 12 years, necessitates understanding viral evolution.
Purpose of the Study:
- To evaluate the evolutionary properties of endemic low pathogenicity (LP) H5N2-AIV in Mexico under sustained vaccination.
- To analyze genetic changes in the hemagglutinin (HA) gene of AIV isolates to understand antigenic drift.
Main Methods:
- Pilot phylogenetic analysis of the hemagglutinin (HA) gene.
- Comparison of AIV isolates from 1994 to 2006, including vaccine strains and field isolates.
Main Results:
- Mexican LP H5N2-AIVs exhibit continuous genetic drift.
- Recent isolates (2002-2006) show significant molecular drift compared to earlier isolates and the vaccine strain.
- HA gene drift demonstrates a yearly trend, indicating cumulative sequence mutations.
Conclusions:
- The observed molecular drifts in the HA gene may explain the rising incidence of LP H5N2-AIV in commercial avian farms.
- These findings underscore the challenge of AIV antigenic drift in controlling influenza epidemics in poultry populations.
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