Exercise alters the immune response to equine influenza virus and increases susceptibility to infection.
Authors: Folsom R W, Littlefield-Chabaud M A, French D D, Pourciau S S, Mistric L, Horohov D W
Journal: Equine veterinary journal
Summary
# Editorial Summary Equine influenza continues to threaten vaccinated populations despite established immunisation protocols, and emerging evidence suggests that training schedules may inadvertently compromise vaccine efficacy. Folsom and colleagues investigated this possibility by vaccinating ponies and then subjecting half to five days of strenuous exercise whilst maintaining others at rest, before exposing all animals to live equine influenza virus challenge. The exercised group exhibited significantly depressed T cell responses—manifested as reduced lymphocyte proliferation and decreased interferon-gamma production in vitro—and subsequently developed clinical disease following viral exposure, whereas rested controls remained completely protected despite receiving identical vaccination and challenge protocols. These findings indicate that intensive exercise during the periimmune period triggers measurable immunosuppression specific to influenza-virus-directed cellular immunity, with real-world consequences for disease susceptibility. For practitioners managing performance horses, this work underscores the potential risks of high-intensity training schedules shortly after vaccination or during periods of immune system priming, and suggests that coordinating vaccination timing with reduced training loads may optimise protective immunity.
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Practical Takeaways
- •Avoid intense training programmes in the period immediately following influenza vaccination, as exercise suppresses the immune response needed to establish protective immunity
- •Rested recovery periods are essential after vaccination to allow adequate immune response development before returning to strenuous work
- •Even vaccinated horses may be vulnerable to infection if subjected to high-intensity exercise during the critical immune response window, suggesting exercise scheduling should be coordinated with vaccination timing
Key Findings
- •Strenuous 5-day exercise programme in vaccinated ponies resulted in significant suppression of T cell-mediated immune response to equine influenza virus
- •Exercise-suppressed ponies showed decreased lymphoproliferation and gamma interferon production compared to rested controls
- •Vaccinated and exercised ponies demonstrated increased susceptibility to influenza disease following virus challenge, while rested vaccinated ponies were completely protected
- •Exercise-induced immune suppression directly correlates with increased disease susceptibility despite prior vaccination