Effect of a booster vaccination against influenza and equine herpes virus on cardio-respiratory adjustments to strenuous exercise and training in thoroughbred horses.

The study investigated the impact of a booster vaccination against influenza and equine herpesvirus-1 on cardiorespiratory responses to intense exercise and training in horses, finding no detrimental effects and a successful rise in relevant antibodies post-vaccination.

Objective and Methodology

• The research aimed to assess how cardiorespiratory adjustments related to exercise and training are affected in the 10-day period after a booster vaccination against equine influenza and equine herpesvirus-1.
• It involved nine thoroughbred horses who had been previously vaccinated. Six were given a revaccination (booster shot), while three were kept as a control group.
• All horses were taken through a standardised exercise test (SET) four times: 10 days and 2 days before revaccination, and 2 days and 10 days after revaccination.
• Throughout the study period, the horses were put through an intense interval training schedule six days a week.
• Various parameters, including respiratory airflow, tidal volume, respiratory rate, and expired minute volume (VE), were measured using special equipment. Oxygen uptake (VO2) and carbon dioxide production (VCO2) were obtained on a breath-by-breath basis.
• The heart rate was continuously monitored, and venous blood was drawn before and after each test for biochemical examination. Blood was also taken before and 21 days after revaccination to measure antibody levels.

Findings

• An established measure of cardiorespiratory fitness (peak VO2, VCO2, VE/VO2 and VO2/HR) was notably improved following the three-week training period. However, neither training nor revaccination affected the other cardiorespiratory and blood parameters measured.
• No adverse impacts on these physiological parameters were observed in the revaccinated horses during the SETs, showing that the vaccination did not hinder their cardiorespiratory adjustments to intense workouts or training.
• The antibody titers against influenza virus types A1 and A2, and equine herpesvirus-1 increased in revaccinated horses compared with controls. This suggests that the revaccination yielded a successful immune response.

Conclusion

• The booster vaccination using an oily adjuvanted inactivated vaccine against equine influenza and herpesvirus-1 did not hinder the cardiovascular and metabolic responses to strenuous exercise and training in horses.
• The revaccination effort resulted in a successful increase in relevant antibodies, and this immune response was unaffected by the intense daily exercise the horses underwent post-vaccination.