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Horse Health: Vaccination Woes

Kentucky Equine Research Staff  | Published on 9/20/2017
Every year, hundreds of horses die from illnesses that could have been prevented through vaccination. Saddened and frustrated by the needless loss of horse lives, one group of researchers* created a survey to find out what’s stopping owners from vaccinating against preventable diseases.

Based on the results of that survey, the key reasons owners declined recommended vaccines included:

Concerns regarding the safety of vaccines and the potential for vaccine reactions, including death;
Cost of the vaccines; and
Lack of perceived risk of infection, making vaccination unnecessary.
In addition, some respondents suggested a financial arrangement between the pharmaceutical companies that manufacture the vaccine and veterinarians who administer it (and thereby benefit financially).

In the United States, rabies, tetanus, the Eastern and Western equine encephalitis viruses (EEE and WEE, respectively), and the West Nile virus (WNV) all fall under the umbrella term “core vaccines,” according to the American Association of Equine Practitioners (AAEP). This means that almost every horse the United States should be vaccinated against these diseases, and yet they are not.

In 2016, 377 horses were diagnosed with WNV according to the United States Department of Agriculture Animal and Plant Health Inspection Service. More horses were likely affected, but because laboratory samples were not collected and submitted, those cases were not included in the overall count.

In Australia, a similar situation occurs with the Hendra virus which can cause serious disease and fatalities in both horses and humans. The Queensland Department for Agriculture and Fisheries and the New South Wales Department of Primary Industries clearly states that vaccination is “the single most effective way of reducing the risk of Hendra virus infection in horses. Many equestrian events and facilities require full vaccination as a condition of entry. ” Adoption of the vaccine by horse owners, however, has been slow. Researchers suggest that the majority of horses remain unvaccinated, estimating only 11-17% of horses are fully vaccinated in endemic Hendra areas.

When survey respondents were asked what would make them reconsider vaccination, 37-49% would vaccinate if the vaccine was either free or less expensive, if they could administer the vaccine themselves, or if one of their own horses or a neighbor’s/friend’s horses became infected.

Other means of minimizing disease involves altering management practices. For example, not turning out horses at dusk and dawn can help minimize the chances of mosquitoes transmitting EEE, WEE, or WNV to a horse. In the case of the Hendra virus, owners are advised to reduce contact between horses and flying foxes by covering food and water sources in the paddock, removing horses from pasture when bats are most active, and eliminating access by horses to fruiting and flowering trees.

Unfortunately, even these strategies prove difficult to implement, with many horse owners reporting recommended strategies as ineffective and impractical.

In sum, the survey results suggested that some owners believe vaccines can be unsafe and are unnecessary. In reality, reactions to vaccines occur only rarely, and the benefits of vaccination far outweigh the risks. Diagnosing and treating horses for diseases that could have been prevented, loss of use, and loss of life cost more than a lifetime of vaccines.

“To maximize a horse’s response to vaccination, consider supplementing horses with omega-3 fatty acids such as EO•3 or maintaining horses on a higher quality feed that supports immune health, like KER Brand Alliance Partner products,” advised Kathleen Crandell, Ph.D., a nutritionist for Kentucky Equine Research (KER).

*Manyweathers, J., H. Field, N. Longnecker, et al. 2017. "Why won't they just vaccinate?" Horse owner risk perception and uptake of the Hendra virus vaccine. BMC Veterinary Research. 13(1):103.