Flu vaccination practices could leave some British horses with suboptimal protection – study

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A British survey has shown that veterinarians were more likely to comply with competition guidelines than with datasheet advice on equine influenza vaccinations.
A British survey has shown that veterinarians were more likely to comply with competition guidelines than with datasheet advice on equine influenza vaccinations. Image by Dsr40

Current equine influenza vaccination practices in the United Kingdom may leave some horses with suboptimal immunity, according to researchers.

A survey of vets revealed greater adherence to competition guidelines than with the datasheet advice issued by the vaccine manufacturers.

Researchers in a University of Liverpool study set out to learn more about the current vaccination practices advised by vets treating horses in Britain and compare them with the manufacturers’ datasheets and current guidelines.

Amie Wilson and her fellow researchers distributed an online questionnaire through professional registration listings and social media targeting vets who treat horses in Britain.

In all, 304 vets responded, variously working with horses engaged in leisure, competition and racing spheres, as well as breeding stallions and broodmares.

The study team, reporting in the Equine Veterinary Journal, found variations in vaccine protocols for competition and non-competition horses.

Fifty‐seven percent of respondents reported variation in the advised booster-shot frequency. Most commonly (in the case of 118 vets), they advised a six‐monthly booster vaccination in competition horses and annual vaccinations in non-competition horses.

The most common vaccination guidelines mentioned were those of the British Horseracing Authority (68.8%) and the International Equestrian Federation (FEI), at 66.4%.

“Most vaccination practices were not consistent with datasheet guidance,” the researchers reported. “Only 7.7% of respondents complied with datasheet timeframes between the second and third vaccination.”

Two-thirds of the vets had seen adverse events in the previous year, mostly of a transient nature, such as stiffness, localised swelling or fever. This represented 2760 adverse events, but only 526 cases (19.1%) were reported to the Veterinary Medicines Directorate.

Factors influencing vaccination protocols chosen by UK veterinary surgeon respondents.
Factors influencing vaccination protocols chosen by UK veterinary surgeon respondents. https://doi.org/10.1111/evj.13377

“This is an area which requires improvement as a profession in order to provide necessary feedback to pharmaceutical companies and the veterinary medicines directorate for drug safety,” the authors wrote.

The study team said that 86.4% of the vets reported vaccine hesitancy from horse owners, most commonly due to perceptions of over‐vaccination, cost and concern regarding adverse events.

“The concern about the risk of adverse drug reactions appears to be a significant contributing factor when encountering vaccine hesitancy in horse owners,” they said.

The study team reported that current equine vaccination practices, although complying with competition rules, are mostly noncompliant with datasheet guidelines, potentially risking suboptimal immunity. The lack of compliance with manufacturers’ datasheets identified in the study may promote immunity gaps, leading to a reduction in the effectiveness of vaccination programmes among Britain’s horses.

“Such gaps may increase the risk of EI outbreaks, even among competition animals complying with the competition’s ruling.

“One reason for poor compliance with manufacturers’ datasheets and OIE (World Organisation for Animal Health) recommendations may be the number and variability of vaccination guidelines, recommendations and regulations available to horse owners and vets.

“This study identified 25 different types of resource in use by 304 veterinary surgeons and demonstrated a greater consistency with competition guidelines than the datasheet advice.

“It is not surprising that there is variation in vaccine practices among veterinary surgeons when there is such disparity among different vaccine regulations.

“Updating competition requirements to one strategy across all equestrian disciplines could reduce the number of differing guidelines and, in turn, improve equine welfare.”

They noted that all manufacturers of authorised equine flu vaccines available in Britain advise a third vaccination five months after the second one because of the duration of immunity (5 months) following the second vaccination.

However, this is not in accordance with competition guidelines which largely state the third vaccination can be given from 5 to 7 months.

The FEI offers differing advice from that of the British Horseracing Authority (BHA) and British Equestrian Federation (BEF), as the third vaccination must only be administered within seven months of the second one.

Although unlikely, the third vaccination can, in theory, be given one day after the second one in accordance with the FEI rules, and up to seven months after second one in the cases of the FEI, BHA and BEF.

“This is not compliant with the datasheets’ advice.”

Equine influenza vaccination in the UK: Current practices may leave horses with suboptimal immunity
Amie Wilson, Gina Pinchbeck, Rachel Dean and Catherine McGowan
Equine Veterinary Journal, 30 October 2020, https://doi.org/10.1111/evj.13377

The study, published under a Creative Commons License, can be read here.

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