Since late June eight horses have died from the Hendra virus and dozens of people who made contact with sick horses are now being tested. While rare in humans, the few known cases of Hendra infections have seen people unwell with influenza-like illness, occasionally progressing to high fever, convulsions and death.

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Experts say there are still major gaps in their knowledge of the spread and transmission of the virus, but are warning horse owners and the public to be vigilant and understand what they can do to limit the outbreak. Crikey spoke to Australian Veterinary Association president Barry Smith for clarification …

How does Hendra spread?

Fruit bats are the natural hosts of Hendra, so the virus is carried by the bats but has little effect on them. We know the bats pass the virus through their bodily secretions; so any feces, saliva or bodily fluids they excrete could potentially be carrying Hendra. Horses usually pick up Hendra by ingesting infected material or breathing it in by a droplet. From there, the virus can be present in the horse for several days before they show any signs of illness, and that is the real problem. Horses can be excreting the virus for days before it becomes obvious they are infected. People then contract the virus in much the same way horses do, by coming in contact with excretion or breathing it in in by a droplet.

Are we in control of Hendra?

That’s a good question. At this point it’s hard to give a definitive answer. Up until this year we would have had a different story to tell, but the recent outbreak of the virus has been unprecedented.

There seems to have been a change in the way the virus spreads; for some reason it has changed, and at this point we don’t know why. There are still a lot of gaps in our knowledge.

Is a bat cull the best way to contain the virus?

Flying foxes are a very mobile animal, and they fly all across Australia. We know that from north-west Queensland they can fly to Papua New Guinea, so it would be extraordinarily difficult to attempt a cull, and once a local population of bats is taken out there is nothing to stop new bats flying back in. Furthermore bats are important to pollination of plants and there would be a significant ecological cost to destroying bat populations.

How can we contain the spread of the virus?

Because we can’t control where and how far bats fly it is almost impossible to contain Hendra. Some time next year we may have a vaccine available for horses, but there is still a lot of work to do on that front.

How much risk does Hendra pose to those outside the horse industry in NSW and Queensland?

It is important people are made aware that the virus is out there and it is a risk. At the moment there have only been spillovers into Queensland and NSW, but due to the wide movements of fruit bats there is a possibility the virus could spread to other areas.

What can we do to minimise the risk of contracting Hendra?

At this point we need people to watch their personal hygiene and be careful around horses. Horse owners should look at getting a vet to check out any sick horses and do a risk assessment of their stock. The season for Hendra infections usually lasts from May to November, so there is still a long way to go in the season and people need to be vigilant.