Hendra – Some Risk Perspective

Craig Elliott, a biosecurity specialist who was incident controller with the National Biosecurity Rapid Response Team, said words from Ben Cunneen, a vet who died from the disease still send a chill through him.

“He gave us a lot of information before he passed at the PA hospital and he said, ‘if anything good comes out of this use my words so that nobody else goes through this’ and even remembering him saying that still sends a chill down my spine, because it was a turning point for Queensland and vets in general,” said Mr Elliott.

“We need people working in animal health to take proper precautions every day, especially with sick animals and I often say, ‘you don’t see doctors drawing blood without gloves, so why is that ok in animal health?’” he said.

“The numbers of humans that became infected were extremely low, it’s a horrible disease, but the rates are extremely low, especially if you take the basic precautions,” he said.

“We did have some (Hendra) in Queensland that was in the pony club belt where every property had three or four horses and I don’t remember any jumping boarders, we always managed to contain it to a single property,” Craig Elliot said.

Dr David Westcott, a bat ecologist with the CSIRO agrees the risk of contracting Hendra is extremely low, with simple precautions lowering risk further and was keen to provide context and statistics for people to better understand the risk.

“It’s (Hendra) been in Australia longer than us white fellas have been, this is not a new disease in Australia,” said Dr Westcott.

“With Hendra and lyssavirus virus, when you think that we have lived in Australia relying on horses for 200 years before we even realised those diseases occurred here and we used to live in very close proximity to horses and they were economically and everything else important to us; that sort of information suggests that risk is really, really low,” he said.

To put the risk in perspective Dr Westcott usually draws attention to the following:

• In the past 10 years there have been four human deaths in Queensland;
• Since 1994 when Hendra was identified several hundred people have been exposed to Hendra, seven have been infected and four have died;
• No one with a low level of exposure has developed the infection;
• Everyone who became infected did so after very high levels of exposures to respiratory secretions and or blood of a horse;
• If you own a bath you are seven times more likely to drown in a bath than contract Hendra;
• You are four times more likely to be struck by lightening, and
• If you ride horses you are eight times more likely to die falling off your horse.

“So if people are worried about going to a horse riding event because of Hendra, riding the horse is more of a risk,” said Dr Westcott.

However, Dr Westcott stresses that he presents this relative risk, not to minimise the impact of the disease, but to explain the low level of risk and encourage people to lower the risk even further through simple precautions.

“Yes, you can get a very nasty disease, but there are a set of simple rules that can be put in place to reduce that already small risk to even lower risk,” said Dr Westcott.

“We deal with reducing risk every day, the chances of being hit by a car when you step across the street are x, but the consequence can be significant, so you put in place a set of rules to reduce the risk and that is exactly the sort of approach that should be taken with flying foxes,” he said.

“We are much more likely to get hit by a car if we don’t obey the rules than we are to get Hendra if we don’t obey the rules, basically you have to bath in the bodily fluid of a horse with Hendra, but simple personal protection lowers the already small risk even further and that’s what we need to focus on, simple steps to reduce risk,” he said.

“With Hendra we don’t feed or water our horses under flying fox feeding trees, such as fig trees and flowering eucalyptus, we keep our horses away from those and we wear PPE and take proper precautions around infected horses,” Dr Westcott said.

Update: Animal Health Australia cautions that due to Hendra being transmitted by droplet, there is no safe exposure level to the virus and the most stringent infection control practices must be adhered to when interacting with an animal which is suspected to have the virus.

The number of bats infected with lyssavirus virus is less than one percent and a study in 2011 over three years showed only 2.5 percent of bat urine contained Hendra.

Lyssavirus virus can be transferred directly to humans, rather than indirectly through horses and even though people may be scratched by a bat, if they follow treatment the risk of death is extremely low.

“If you are a bat carer or a bat researcher then you should get the vaccination and nobody else should be handling bats, but if for some reason you are bitten or scratched by a bat, it may be that a bat swoops down and scratches you, it’s rare, but it does happen, then you should wash the wound out, see a doctor and get the vaccination,” he said.

“If you treat promptly it is pretty much 100 percent and the reason we know so much about that is people get bitten by rabid animals in England and North America all the time and the deaths there in every case it is where someone hasn’t gone and got their vaccinations,” he said.

The three lyssavirus virus deaths in Australia were exactly that, the first two were bat carers who refused to get their post exposure vaccination and died and the third was a young boy where nobody responsible knew he’d been bitten, until a young friend later mentioned he’d been bitten by a bat,” said Dr Westcott.

With Hendra while there is no conclusive proof the virus is passing from bats via urine to horses, all the current evidence points to bats droppings being the vehicle for the virus.

Most cases of Hendra occur in coastal areas and no cases have been reported in central areas of Australia.

There is an interplay between the virus and the outside environment, but Dr Westcott cautions not to be complacent based on that connection.

“Hendra has to survive in the outside environment and Hendra doesn’t do very well in hot, dry conditions or cold and dry conditions, it means a particular range of conditions you get on the coast compared to inland, now that doesn’t mean you can’t get those conditions inland but they are not as prevalent,” Dr Westcott said.

“The right conditions can occur in all kinds of places at all different times, so it is highly variable and subject to change,” he said.

“But there are vaccines available for both lyssavirus and Hendra, which can lowers risk further still,” Dr Westcott said.

It is estimated there are approximately 2 million horses in New South Wales and less than 20 percent are currently vaccinated, a figure that includes the north coast.

Related stories:

• Hendra Case See Spike in Class Action Applicants – June 19, 2019.
• Hendra: Authorities Say Business as Usual in Scone – June 14, 2019.
• Hendra: Ongoing Investigations – June 14, 2019.
• First Hendra Case in Scone – June 13, 2019.