VIGILANCE is being urged among horse owners after the latest Hendra virus case near Casino exhibited unusual signs and aspects of the deadly disease.
A 22-year-old stock horse gelding died last month after an "unusually protracted" illness and despite appearing to recover after being given medication.
"What's different about this case is that the horse initially tested negative for Hendra virus after losing weight for two weeks and presenting with a sore mouth," said Dr Ben Poole, the vice-president of Equine Veterinarians Australia.
"The facts of the case would suggest the horse may have initially received a low infectious dose of the virus that eventually led to the horse succumbing to the disease, after an unusually protracted illness.
"A week later the horse deteriorated rapidly and died a few days later.
"A nasal swab taken from the carcass a week after the horse died returned a positive test for Hendra virus.
"The summer timing of this case in the Northern Rivers is unusual and is probably due to food shortages and environmental stress on the bats in the area, so it's really important to be vigilant all year round."
Reduce the risks
The horse was initially treated by a veterinarian on November 27, when the owner reported the animal had shown vague signs of illness for a few weeks.
Dr Poole said further testing of tissue samples indicated the horse had mounted an immune response to the virus.
He said this demonstrated the difficulty of making an initial diagnosis of Hendra virus infection, and highlighted the risk it posed to anyone including horse owners, vets and those who come in contact with horses displaying vague signs of illness.
"That's why vaccination of horses against Hendra virus is important for managing the risks involved with the disease," he said.
He said all unvaccinated horses in the region, no matter their background, were equally at risk of contracting this virus and suffering a painful death, not to mention infecting humans.
"Even though the probability is relatively low, any vaccinated horse in this geographic band is equally at risk," he said.
'Misinformation and scuttlebutt'
Dr Poole urged horse owners to contact their local vet for more information about the Hendra virus vaccination.
People looking to buy a horse, he said, needed to check the animal's medical history before purchase.
"The beauty of the Hendra vaccination is that it is safe and there is a national database as every horse vaccinated has a microchip," he said.
"So by scanning the horse for a microchip you can check how recently the horse was vaccinated.
"The only way to protect (against) Hendra virus in a controlled way is to vaccinate, but unfortunately there's a lot of misinformation and scuttlebutt on social media campaigning against the ethics and safety of the vaccine which is completely unfounded.
"This is extremely disappointing as it's a good and highly effective vaccine."
Dr Poole said according to data, about 0.2-0.3% per 1000 doses could result in a negative reaction.
"The government regulator investigated these and put seven as possible but not probable deaths out of around 550,000 horses vaccinated," he said.
"From the work that has been done in the Australian Animal Health Laboratory in Geelong, the Hendra virus is as close to 100% effective as a vaccine can be."
Dr Poole said the cost of vaccination was roughly $100 per dose.
"The protocol is to administer two priming doses three to six weeks apart and then a six month booster," he said.
"After this it's an annual vaccination."
Update your news preferences and get the latest news delivered to your inbox.