A virus that has killed more than half of the people who have contracted it has been detected in North Queensland.
A horse was found to be unwell at a Mackay property on Friday and its condition deteriorated quickly before it was euthanised.
Biosecurity Queensland has confirmed the horse wasn't vaccinated for the virus.
Officers said in a statement the infected horse hadn't moved from the property in several years and other animals had been vaccinated.
'Terrifying' virus
It's been five years since the last Hendra virus case in Queensland, which was in a horse on the Gold Coast.
Mackay vet Bruce Howlett Junior said the detection would make people in the equine industry nervous.
"Especially on the coast, any sick horse on the coast that's unvaccinated could well be a Hendra case," he said.
There have been multiple cases of Hendra throughout Queensland and parts of New South Wales since the virus was first detected in 1994 in Mackay and Brisbane.
About 80 per cent of horses that contract Hendra die from the virus or have to be euthanised.
But he said it was the risk to humans that had vets most worried.
He said the way the virus multiplied in infected horses was "terrifying".
Dr Howlett said testing at the Australian Animal Health Laboratory showed that almost every tissue within a subject horse had been infected within 48 hours.
Vaccination the key
A vaccine for horses has been available since 2012.
Doctor Bruce Howlett said it was developed largely because of the threat Hendra posed to humans.
"I love horses, but it's not about the horses, the aim of the vaccine is about protecting humans," he said.
Research shows the virus is passed from flying foxes to horses, which can then spread it to humans.
Biosecurity Queensland chief veterinary officer Allison Cook said vaccination was the single most effective way to reduce Hendra virus infection in horses.
"Hendra virus infection can occur throughout the year, so it's important that horse owners take steps to protect themselves and their animals at all times," Dr Cook said.
It's also recommended that feed and water troughs aren't kept under trees, or areas where flying foxes live.
