Playing with fire – What is influencing horse owners’ decisions to not vaccinate their horses against deadly Hendra virus infection?

Abstract

Hendra virus is a zoonotic paramyxovirus, which causes severe respiratory and neurological disease in horses and humans. Since 2012, the Hendra virus sub-unit G vaccine has been available for horse vaccination in Australia. Uptake of the vaccine has been limited and spill-over events of Hendra virus infection in horses continue to occur. We conducted an online, questionnaire-based cross-sectional study of 376 horse owners belonging to a variety of different equestrian clubs in Queensland, Australia, to identify risk factors for non-vaccination against Hendra virus. A total of 43.1% (N = 162) of horse owners indicated that they currently did not vaccinate against Hendra virus infection, while 56.9% (N = 214) currently vaccinated against Hendra virus infection. A total of 52 risk factors were evaluated relating to equestrian activities, horse management, perceived risk and severity of horse and human infection with Hendra virus, side effects of Hendra vaccination, other vaccinations conducted by horse owners and horse owners’ attitudes towards veterinarians. The final multivariable logistics regression model identified the following risk factors associated with increased odds of non-vaccination against Hendra virus: 1) perceived low risk (compared to high) of Hendra virus infection to horses (considering the horse owners’ location and management practices) or horse owners were unsure about the risk of infection, 2) perceived moderate severity (compared to very severe or severe) of Hendra virus infection in humans, 3) horse owners non-vaccination of their pets, 4) horse owners non-vaccination against strangles disease in horses, 5) handling of more than three horses per week (compared to one horse only) and 6) perceived attitude that veterinarians had a high motivation of making money from Hendra virus vaccination (compared to veterinarians having a low motivation of making money from Hendra virus vaccination). Horse owners were more likely to vaccinate against Hendra virus if horses were used for dressage, show jumping or eventing. The study also identified horse owners’ concerns about side-effects and about the lack of evidence on vaccine efficacy.

Investigation of the effect of Equivac® HeV Hendra virus vaccination on Thoroughbred racing performance

“…18,19 The initial requirement for boosters to be administered at 6-monthly intervals, and the delay in APVMA approval for use in pregnant mares until 2016, were also likely reasons for some to conclude that there may have been early safety and efficacy concerns with the vaccine and that veterinarians' recommendations to vaccinate were largely motivated by financial gain. 18,19,31 All facets of the safety, efficacy and adverse reaction reporting process were reviewed by the Queensland Parliamentary Inquiry in 2016, with the vaccine being verified to be safe and effective. 20,32 Because of the very significant human health, horse health and welfare, biosecurity and workplace health and safety implications of HeV disease, the Australian Veterinary Association recommends that the vaccine should only be available to, and transported, stored and administered by registered veterinarians in order to fulfil the current label conditions.…”

“…19 The regulatory requirement for veterinary-only administration of the vaccine resulted in mistrust of private veterinarians, who were perceived by some in the horse industry to be motivated only by a vested financial interest. 19,31 Studies have also shown evidence of significant levels of distrust towards the vaccine manufacturer by some horse owners in regard to adverse vaccine reactions not being followed up or reported appropriately to the APVMA. Comments made by some horse owners suggest that veterinarians and the vaccine manufacturer were perceived to be in collusion.…”

Qualitative Research for One Health: From Methodological Principles to Impactful Applications

“…In relation to the use of an animal vaccine, for example, a quantitative study could determine the proportion and demographic characteristics of owners who give the vaccine to their animals over a set period of time. Similarly, questionnaires that try and capture people's intentions can test the relative importance of different factors thought to be important to their decisions through the statistical analysis of responses to a series of standardized closed questions [See (8,9) for example]. However, unless participants have the opportunity to respond to open questions in their own words then the research cannot capture novel and unanticipated information.…”

Serological responses of Australian horses using a commercial duplex indirect ELISA following vaccination against strangles

“…comm.). 1,12 Although a range of vaccine types are available internationally, there is only one commercially available in Australia (Equivac®S/Equivac 2 in 1®; Zoetis, NSW, Aust). This vaccine is derived from an acid-extracted preparation of S. equi, administered IM.…”