With growing concern over the safety of the Hendra vaccine, Fiona MacDonald talks to vets and horse owners to get the facts
In July 2009, Dr Alister Rodgers was called out to a stud farm near Rockhampton, Queensland to examine a couple of horses that had fallen ill. The 55-year-old did a full physical and took blood samples, but couldn’t determine what was wrong. A few days later, one of the fillies died, and the post-mortem confirmed that she was infected with the Hendra virus. Unfortunately, Rodgers had been exposed.
He was rushed to hospital for anti-viral medication but his health quickly deteriorated, and at the start of September, he passed away, becoming the fourth person in Queensland to die from the Hendra virus since it was discovered in 1994, in addition to almost 100 horses.
Rodger’s death, which came just months after the death of another young Queensland vet, was met with renewed demand for protection against the virus.
Hendra is transferred from bats to horses via bodily fluids, and then from horses to humans in the same way, and so vaccinating horses was determined the best way for us to stay safe.
In 2012, after more than a decade of research by the CSIRO, an Equivac HeV was released, and the equine industry breathed a sigh of relief.
Three years on, however, and the vaccine is still waiting to be registered by the Australian Pesticides and Veterinary Medicines Authority. Despite this fact, it’s already been widely pushed out by vets and event organisers across Australia. And there are now growing concerns over the safety of the vaccine, how necessary it is in areas that aren’t exposed to bats and also how often it’s being recommended.
Early in 2014, vets reported that the uptake of the vaccine had been “disappointingly slow”. Most likely because the immunisation costs around $110 per dose, and requires at least
three doses to ensure protection, plus ongoing boosters every six months are currently recommended.
Then, on July 1, the industry’s national governing body, Equestrian Australia (EA), put in place a by-law strongly recommending the Hendra vaccine to all members, and stating that all horses from Queensland and New South Wales would need to be vaccinated in order to enter competitions. The by-law was met with strong resistance from members, and in February this year was revoked.
“It’s a fear campaign,” says Dr Matthew Walker, a vet with Thirlmere Veterinary Clinic in NSW.
“The vaccine’s been released on a minor use permit, which means it’s supposed to be used to control outbreaks of the disease, but they’re now recommending vaccination of horses in Wagga Wagga, Perth and Canberra—places where there have never been outbreaks.”
To be clear, Dr Walker isn’t against the vaccine and believes it would play an important role in stopping an outbreak, “but the way it’s being used now is unnecessary”.
“They’re scaring pony club mums with the vaccine campaign and making them think their children’s lives are at risk. It’s irresponsible,” he adds, referring to the campaign by vaccine-manufacturer Zoetis. Some of the ads rolled out contain images of children, vets and equestrian competitors, and contain emotive slogans such as: ‘Don’t gamble with your horse’s life—or your own’.
There have now been around 120,000 horses vaccinated, and while many owners are happy with the results, there have been growing unverified reports of horses having adverse reactions to the injections, ranging from localised swelling, hair loss, rashes and fever, to colic, and horses dropping dead in the days following the vaccine.
Seven horse deaths are currently being invested by the Australian Pesticides and Veterinary Medicines Authority (APVMA) for a possible link to the vaccine.
While Zoetis claims that reactions are possible with any vaccine, they’ve seen a reaction rate of less than 0.3 per cent—that’s 960 reactions out of the 320,000 vaccines administered so far. And the majority of these reactions are localised swelling at the injection site.
Vicki Roycroft, a six-time Olympic equestrian rider, has seen many of these side effects first-hand, however, and believes that can be more severe than Zoetis describes.
“I knew a horse who, after the first injection, was so swollen that it couldn’t feed in the paddock for a week. I understand a bit of a sore neck and swelling, but if a horse can’t put their head down to feed, that’s not right,” she says.
She’s also seen more severe reactions develop after subsequent boosters. “A neighbour’s horse had a reaction the first time she gave him the vaccine, so she decided to inject it into his chest the next time. The next day he developed laminitis problems. I’ve also seen horses getting really sick and horses are dying after the vaccine. Of course, the two could be unrelated, but there are too many coincidences.”
Equestrian rider Sue Vickery has had both of her horses react to the vaccine. “The first two reactions were quite mild. The horses were off colour, not eating for 24 hours and very lethargic. The second reaction was far worse, with a temperature of 39 degrees for 24 hours, muscle soreness and swelling after a short walk. They didn’t eat normal feed for four days,” she says.
“My older horse is now 16 and has ongoing wind problems, green mucus continually comes out of one or other nostril at random, and he doesn’t have the energy to be trained for more than 10 to 15 minutes.”
All these reactions experienced by horses are reported by veterinarians to Zoetis, who then passes them onto the APVMA for investigation, which is standard practice for all animal pharmaceutical products in Australia.
The vaccine itself has been thoroughly researched—it’s made up of a protein called sG, which helps the Hendra virus infect cells. Because it doesn’t actually contain any of the live virus, there’s no risk of infection from the vaccine. And veterinarian Dr Stephanie Armstrong, a spokesperson for Zoetis, explains that its safety isn’t in question when used on a healthy horse over the age of four months.
“Equivac HeV went through the same safety and efficacy testing any vaccine goes through prior to being released,” says Dr Armstrong. “Efficacy was proved through challenge studies and serology studies, while safety studies were also completed. The vaccine performed very well in all studies.”
Dr Armstrong explains that all of the safety and trial information has been submitted to the APVMA, and that the vaccine has now been ‘gazetted’ by the APVMA, which is one of the final steps before registration is finalised. A spokesperson from the APVMA added that this is a normal processing time for the registration of a vaccine. However, there are also concerns from horse owners about how often they’re being told to vaccinate. In the current APVMA permit, PER14876, there is no clear evidence to show that, after the first six-month booster, it’s necessary to keep immunising every six months.
Zoetis explains that this is because the data on how long the antibodies last following subsequent boosters is still being analysed, but this frequency was shown to be safe in their trials.
But without the conclusive research showing how often booster shots are really needed, many are worried that they are over-vaccinating their horses unnecessarily.
“We love our horses and we want to protect them with vaccines, but not over-vaccinate at the expense of their immune systems,” says Madeline Horne, a horse owner and equestrian competitor for Queensland. “We have performance horses—they are athletes. We need them healthy not chronically unwell and unable to fight off infection,” she adds.
While Dr Armstrong can’t respond to individual reports of adverse reactions without further investigation, she says the way it’s currently being used has been supported by their studies, which have been submitted to the APVMA, and it will now be up to the APVMA to make the final decision on the frequency of boosters.
“The Hendra vaccine has been in the marketplace for over two years now with some horses having received five or six doses. We have not seen any trend that indicates the risk of adverse events increases over time,” she explains.
“Unfortunately, the internet can be a great source of misinformation. Some horse owners can be worried by what they read online, but the stories online do not reflect the real world data from hundreds of thousands of doses and they’re very different to what I hear from equine vets I talk to.”
Dr Armstrong also reminds horse owners that the Hendra virus mortality rate is more than 50 per cent in humans and 100 per cent in horses, as any sign of infection will result in an animal being put down. “As with other vaccines, the benefits of vaccination far outweigh the minimal risks,” she adds.
Dr David Searle, a vet from the Illawarra Equine Centre in NSW, agrees that we should be wary of listening too much to unverified claims. “The horse owners all wanted this vaccine when the outbreak was there. We are listening way too much to a minority.”
His practice has vaccinated around 1800 to 2000 horses, ranging from elderly to young foals, and haven’t seen reactions more severe than fever and swollen necks. “Just what’s to be expected,” he adds.
What’s more worrying, Dr Searle explains, are claims that vets are now refusing to treat horses that aren’t vaccinated.
Jo Moore, a member of the Say No To The Hendra Vaccine Facebook group, from Queensland, has heard reports some vets are refusing to touch a horse until it’s been cleared of Hendra infection.
“One horse had a broken neck propped up with a hay bale for three days waiting for a negative Hendra result before the vet would attend and put him to sleep,” she explains.
While Dr Searle understands vets’ concerns, he explains, he would never put a client in a position where they felt pressured to vaccinate. “It’s important to keep it scientific. All you can do is tell clients the risk of Hendra in your area, the risk factors, the side effects of the vaccine, what it costs, and let them decide what they want to do.”
Dr Walker agrees. “If I had a horse within a 10-kilometre radius of where there’s been an outbreak, then I’d definitely vaccinate. But if you’re not in a risk area, is it worth risking the horse’s health by vaccinating?” he asks.
He believes it’s important to also remind people of preventive measures, such as wearing personal protective equipment (PPE) when in contact with sick horses, and reminding owners to clear or fence off any trees that house bats.
“Until the vaccine is a registered product, it should be used as it states on its minor usage permit, which is purely around the disease itself to stop outbreaks,” he adds.
Registration is something that Zoetis expects to happen in 2015, and with that will come APVMA recommendations on the frequency of immunisations, as well as reassurances over its safety.
Until then, vets can expect to have question from concerned horse owners, and will need to have all the facts to answer them.
“We need to listen to our clients and talk to them about their risks, instead of just pressuring them to vaccinate,” says Dr Walker.