First cases of Australian bat lyssavirus in horses show need for awareness, say vets

Roosting Grey-headed flying-foxes
Roosting Grey-headed flying-foxes. © Justin Welbergen

Confirmation of the first two cases of Australian bat lyssavirus (ABLV) in horses last year highlights the need for greater awareness of the disease in all domestic animals, the Australian Veterinary Association says.

The rabies-like virus had previously been detected only in bats and humans and until 2013 Australia had been considered free from these types of viruses in feral and domestic animals, including horses. All three confirmed human cases proved fatal, the most recent in February last year.

Two veterinarians, who have studied the two cases in-depth, have published a paper in this month’s issue of the Australian Veterinary Journal on their findings.

The authors want horses and other domestic animals that show progressive neurological disease or symptoms reflecting diffuse neurological dysfunction to be tested for the virus so that appropriate post-exposure and treatment assessment can take place.

Testing will also provide a greater understanding of the disease’s prevalence in Australia.

The paper’s co-authors, Dr Ed Annand and Dr Peter Reid, said the two cases demonstrated that the virus can infect domestic animals.

“This possibility had previously been acknowledged but never before confirmed,” they said.

“ABLV presents a significant zoonotic risk and, as with other lyssaviruses worldwide, under-diagnosis is likely.

“In the past, people have become infected with the deadly lyssavirus by being scratched or bitten by a flying fox or micro-bat, but the spillover to horses reported in our paper indicates that animals other than bats can pose potential human health threats.

“Further neurological disease surveillance would be beneficial to increase our understanding and identification of the disease’s zoonotic risk,” the pair said.

“There are two recognised variants of Australian bat lyssavirus which are genetically very similar to the rabies virus and cause a disease clinically indistinguishable from rabies in humans and horses,” they said.

The Australian Veterinary Association recommends that vets and wildlife carers in contact with bats should be vaccinated against rabies.

Vets should also practice good personal biosecurity when attending sick horses.

Annand and Reid reported in their paper that the two cases occurred in the same week in May last year in paddock mates in south-east Queensland.

Both cases resulted in euthanasia, they said.

In the first case, an 18-month-old sport horse filly presented with subtle signs of hindlimb ataxia (lack of co-ordination). Over the preceding three weeks, she had been observed to have intermittent periods of reduced interaction with paddock mates and other subtle behavioural changes.

The poor co-ordination worsened to the point that 54 hours after the initial presentation of the disease the recumbant mare was euthanised.

The other case was in an 18-month-old sport horse gelding. The disease progressed in a similar fashion.

“These two equine cases highlight that ABLV should be considered as a differential diagnosis in animals with similar clinical presentations in Australia.

“There is a need for greater awareness regarding the zoonotic risk, use of personal protective equipment, pre- and post-exposure prophylactic measures and laboratory diagnostic options,” they said.

The paper can be read online here

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