New strain of deadly Hendra virus discovered

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new strain Hendra virus
Photo: Olga Yastremska 123RF

The Australian veterinarian-led research project, ‘Horses as Sentinels’, has identified a new strain of the deadly Hendra virus as the cause of a previously unexplained horse death in September 2015.

Hendra virus (HeV) is highly lethal in both horses and humans, with mortality rates approximately 79 per cent and 60 per cent respectively. The originally recognised strain of Hendra virus has resulted in the deaths of four humans and over 100 horses in Australia since 1994. 

The newly recognised variant has not been detected previously by routine biosecurity testing in horses. But the new strain was detected in grey-headed flying fox samples from Adelaide in 2013 and it shares ~99 per cent sequence identity with the 2015 horse case strain. Partial sequences of the variant have also been detected in flying foxes in other states.  

Grey-headed flying foxes migrate, and their range includes parts of southern Australia, which previous advice classed as low risk—with some interpreting this to mean negligible risk of Hendra virus spillover. 

Up until now, the original strain of HeV has only been known to occur within the range of black flying foxes and spectacled flying foxes. 

The ‘Horses as Sentinels’ research team has developed updated diagnostic laboratory techniques capable of identifying the new strain, and will be sharing them with relevant laboratories. They have also established that the current HeV horse vaccine is expected to be equally effective against the new strain.

The research team have alerted chief veterinary officers and the chief health officers are being informed. All members of the Australian Veterinary Association have also been alerted to the implications of this discovery for both human and animal health. 

The finding indicates that HeV should be considered as a differential diagnosis in unvaccinated horses anywhere in Australia that flying foxes are present, and that unwell, suspect horses which return an initial negative Hendra virus test should continue to be treated with the same caution as a Hendra virus positive case, until testing for the new variant is performed. 

This article was sourced from a news release on the AVA website.

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