By Equestrian Life

Whether to vaccinate or not is the dilemma facing horse owners around the country, with fear of the deadly Hendra virus weighing against fear of adverse reactions to the vaccine. 

When it first appeared in the Hendra-based training stables of Vic Rail, trainer of champion galloper Vo Rogue, little was known about the deadly virus that killed a number of horses and Rail himself.

Later taking the name of the Brisbane suburb, the virus has gone on to kill nearly 100 horses and three more people since that first reported case. However, what was first celebrated as a lifesaving discovery quickly became a controversial topic amidst alleged cases of adverse reactions among the inoculated equine population.

Five years since becoming available, Equivac HeV vaccine remains as controversial as ever. In recent months, the Queensland Government concluded a lengthy parliamentary inquiry in response to recommendations released by the Agriculture and Environment Committee in October 2016. The government opted to support most recommendations from the report, with the main conclusion being that the Hendra vaccine should not be mandatory. The Government also supported the committee’s recommendations regarding equestrian event organisers having the right to make their own decisions around conditions of entry. Organisers can ban unvaccinated horses or impose entry conditions as they see fit.

As has been the case since the vaccine was introduced, vets can refuse to treat unvaccinated horses. The Queensland Agriculture and Environment Committee put forward a recommendation calling for new workplace safety laws to limit the liability of vets who treat unvaccinated horses. Currently, vets who treat unvaccinated horses infected with Hendra are open to prosecution if they risk the health of themselves, their staff or the horse owner. The committee recommended changing the laws so vets are only legally required to create a safe workplace for themselves and their staff, not the owner. The government opted not to amend workplace health and safety regulations as it felt the recommendations did not have sufficient regard for the accepted precedents of the statutory duty of care.

MOST EFFECTIVE

Despite its decision not to make vaccines mandatory, the Queensland Government continues to strongly recommend the use of the vaccine as the single most effective way to reduce the risk of Hendra virus infection in horses — and subsequently, in humans. 

The government’s decision isn’t surprising; there is no precedent for making vaccines mandatory in animal or human health in Queensland or Australia (recent laws for infant vaccinations have seen rights taken away from those who don’t vaccinate their children, however, vaccination itself isn’t considered mandatory). Given the vaccine was not mandatory in the first place, and vets were always allowed to refuse to treat unvaccinated horses, the government’s decision largely maintains the status quo.

Workplace Health and Safety Queensland will work with the industry to review its guidelines for veterinarians and other horse care professionals on how to fulfil their workplace health and safety responsibilities. In addition, Biosecurity Queensland has agreed to revise the guidelines for treatment of horses to include information on how to manage risks.

The committee’s recommendations also call for the development of rapid Hendra testing technology, and to investigate the feasibility of an additional diagnostics facility in north Queensland. Although the government supports new technologies, the expert advice was that technology for a rapid stall-side test was not advanced enough to assure safety and accuracy. The ability to have tests completed in north Queensland — which currently take place in Brisbane — was considered a good idea in theory but financially unfeasible.

FURTHER INCIDENTS

Following the government’s announcement, the Australian Veterinary Association (AVA) reignited calls for horses to be vaccinated in Hendra-prone areas — a call to action spurred on by the news that an infected pony in the Gold Coast hinterland was euthanised in late May. Biosecurity Queensland was forced to quarantine the property. Since then, there have been two cases recorded in NSW — one in Lismore and more recently, one in Murwillumbah. Both horses were unvaccinated. 

In addition, there were two recent incidents that further prompted the AVA to make a statement. A horse show at Brookfield in Brisbane was disrupted by a suspected Hendra virus case a few month ago, as was a show at Kilkivan, also in Queensland, after the owner of a sick horse falsified horse health declaration documentation.

Hendra is undoubtedly a scary disease; the majority of horses and humans who contract the disease die. Naturally occurring in flying fox populations, it is found in Queensland and parts of northern New South Wales and passed to horses via the bats' urine, faeces or foetal fluids.

The Equivac HeV vaccine — created by the CSIRO, Zoetis and international research partners — became available to horse owners late in 2012. A "subunit" vaccine, it contains only a small part of the Hendra virus in the form of a protein from the virus surface. The vaccine does not contain the complete virus. The vaccine was a world-first commercial vaccine for a Bio-Safety Level-4 disease agent.

NO EA POLICY

The Australian Pesticides and Veterinary Medicines Authority (APVMA) initially granted Equivac HeV a Minor Use Permit after the vaccine met all essential safety, quality and efficacy requirements. The initial scheduling protocol for healthy, microchipped horses over four months of age was two initial vaccinations administered three to six weeks apart, followed by a booster every six months.

In mid-2014, Equestrian Australia (EA) moved to introduce a Hendra by-law that would have made it compulsory for horses at certain events to be vaccinated — a necessary move in terms of “duty of care” to the membership, especially with litigation in mind. However, the by-law was revoked in early 2015 pending further investigation. At present, EA has no policy on Hendra vaccination; Equestrian Queensland has said the recent state government statement regarding non-mandatory vaccination is consistent with EQ's position. 

In 2015, CSIRO scientist Dr Deborah Middleton, who helped develop the vaccine, recommended fewer injections be given to horses to protect against the deadly illness; it was felt that perhaps horses were being over-vaccinated. This coincided with some horse owners raising concerns after horses who were fine with initial doses started to show adverse reactions to boosters. The push to reduce booster intervals was eventually backed by scientific evidence, and they were reduced to every 12 months early in 2016. This means that current protocol is two initial vaccinations administered three to six weeks apart, followed by a booster at six months and then boosters at 12-month intervals.

In August 2015 the APVMA announced it had fully registered Equivac HeV, following a detailed assessment process, with the vaccine meeting every assessment criteria for registration.

INCONCLUSIVE

During the initial permit period, vets and owners were required to report any reactions their horses faced after receiving the injection. The APVMA found 633 probable links between the vaccine and reactions and another 125 possible links out of more than 340,000 doses administered. Side-effects included oedemas (watery fluid build-up), lethargy, pain and anorexia, but almost half were reactions at the injecting site. Less than 0.8 per cent of horses suffered a possible or probable reaction. The APVMA found “possible” links between seven horse deaths and the vaccine; this meant the use of the vaccine could not be differentiated from other possible causes as the cause of death in the horses.

A parliamentary inquiry was later launched, with the Agriculture and Environment Committee releasing its findings in late 2016; the government has now drawn conclusions in response to these recommendations, which brings us to where we are today.

For horse owners, fear of this deadly disease is pitted against the fear of adverse reactions to the vaccine. With Equivac HeV to remain optional and event organisers retaining the right to stipulate entry requirements as they see fit, there is now an official response to the issue — but it remains to be seen whether or not this stops the debate. 

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