Worrying aspects to latest Hendra horse case in Australia, say vets

A coloured transmission electron micrograph of the Hendra, virus. Photo: The Electron Microscopy Unit of the Australian Animal Health Laboratory, part of the CSIRO science agency CC BY 3.0 via Wikimedia Commons
A coloured transmission electron micrograph of the Hendra virus. Photo: The Electron Microscopy Unit of the Australian Animal Health Laboratory, part of the CSIRO science agency CC BY 3.0 via Wikimedia Commons

An unusual case of the dangerous Hendra virus in a horse in northern New South Wales has made dealing with cases of the disease even more complicated, according to vets.

Equine Veterinarians Australia (EVA), a division of the Australian Veterinary Association, said the case near Casino, confirmed by the state’s Department of Primary Industries on December 23, highlighted the risk to horse owners and vets.

Hendra is a bat-borne virus capable of infecting horses, probably through contact with bodily fluids. The disease is able to cross over to humans from horses, again through close contact with bodily fluids containing the virus. Of the seven known cases in humans, four have proved fatal.

The EVA said there were unusual signs and aspects with the latest Hendra case, which spokesman Dr Ben Poole said made dealing with Hendra “even more complicated and concerning”.

“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,” he said.

“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. It was given medication and the horse started recuperating while in quarantine on the farm.

“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. Further testing of tissue samples indicated that the horse had mounted an immune response to the virus.”

Poole said the case in the 22-year-old horse showed the difficulty of making an initial diagnosis of Hendra virus infection, and highlighted the risk the virus 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.

“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.”

The property where the horse lived was quarantined by authorities

Chief Veterinary Officer Dr Christine Middlemiss, with the state’s primary industries department, confirmed that the horse had been in a paddock in an area which had regular flying fox activity.

The case was the first Hendra infection reported in the state in 2016.

Middlemass said vaccination remained the most effective way of reducing the risk of Hendra virus infection in horses. Good biosecurity and personal hygiene measures should be practiced, too, she added.

“Horses should also be kept away from flowering and fruiting trees that are attractive to bats. Do not place feed and water under trees and cover feed and water containers with a shelter so they cannot be contaminated from above.

“If a horse becomes sick, owners should contact their veterinarian immediately. People in contact with horses need to practice good biosecurity and personal hygiene measures even if a horse is vaccinated against Hendra virus.”

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