Racing performance unaffected by Hendra vaccine

A study in Australia has found no evidence that the vaccination against the deadly Hendra virus affects the racing performance of thoroughbreds.

The work of University of Sydney researcher Kathrin Schemann and her colleagues involved analysis of data from horses competing at six south-eastern Queensland racetracks.

They began by looking at 4208 race starts by 755 horses. For each horse, they focused on a six-month racing window, covering three months before and three months after they received their initial shot of the Equivac HeV Hendra virus vaccine.

The researchers, writing in the Australian Veterinary Journal, said they found no significant difference in performance before and after the initial Hendra vaccination based on a range of parameters – Timeform rating performance data, the margin to winner, prize money, wins, or placings.

Since 1948, Timeform ratings have been an internationally recognised standard for the global measurement of thoroughbred racetrack performance.

Further analysis of Timeform ratings for a further 7844 race starts by 928 horses failed to identify any significant change in rating trends relating to second and subsequent Hendra vaccinations, or any evidence of a cumulative effect for the number of vaccines received.

The authors, discussing their findings, said their aim was to assess any potential adverse effects of the vaccination on horse performance. They found none for the variables examined in the study.

“Immune-related adverse reactions to vaccinations are more likely to occur with doses subsequent to the primary dose. By comparing the performance before and after two or more vaccinations in the same horse, this study also found no evidence of a cumulative effect on racing performance of multiple vaccinations.”

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