Facing the threat of equine influenza.
Authors: Elton D, Bryant N
Journal: Equine veterinary journal
Summary
# Editorial Summary: Facing the threat of equine influenza Despite widespread vaccine availability, equine influenza virus (EIV) remains a significant threat to the equine industry, with large-scale outbreaks in South Africa (2003) and Australia (2007) demonstrating the capacity for billion-pound economic losses. Elton and Bryant review the landscape of EIV surveillance and control, examining how antigenic drift enables the virus to evade vaccine-induced immunity and highlighting the UK's participation in international collaboration to select appropriate vaccine strains based primarily on haemagglutinin (HA) characterisation. Recent advances in vaccine technology and increasingly sensitive diagnostic methods have improved our ability to control disease spread, yet gaps remain: viral pathogenicity is poorly understood despite potentially playing a crucial role in outbreak dynamics and inter-species transmission (notably the documented transfer to dogs in the USA), whilst severity of infection appears polygenic with the NS1 protein influencing the host cytokine response. Mathematical modelling approaches offer valuable predictive information about outbreak risk factors and vaccination impact, though application of these tools to real-world decision-making remains inconsistent. For practitioners, this work underscores the importance of maintaining vaccination protocols aligned with current strain selection, supporting surveillance efforts, and recognising that vaccine effectiveness depends not only on technological improvements but on sustained international cooperation and ongoing research into poorly understood viral factors affecting transmission and severity.
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Practical Takeaways
- •Maintain current vaccination protocols for horses in racing and competitive environments, as antigenic drift means immunity from previous years may not provide complete protection
- •Monitor for clinical signs of EIV infection (rapid spread in unvaccinated populations) and report suspected cases to support surveillance programmes that inform vaccine strain selection
- •Understand that vaccination remains essential despite antigenic variation, combined with biosecurity measures during outbreaks to minimize spread and economic losses
Key Findings
- •Equine influenza continues to threaten the racing industry despite vaccine availability, with large outbreaks costing billions of pounds (e.g., South Africa 2003, Australia 2007)
- •EIV undergoes antigenic variation enabling evasion of antibodies from previous infection or vaccination, requiring ongoing surveillance and vaccine strain selection based on viral haemagglutinin characterization
- •Mathematical modelling demonstrates the impact of vaccination on outbreak risk factors, and NS1 protein differences may influence cytokine response and pathogenicity
- •Improved vaccine technology and increasingly sensitive diagnostic methods are crucial for international horse movement and disease control