Hendra ready to kill again as horses not immunised

A LITTLE boy shrieks in delight as he makes his way from one puddle to the next along the sodden sidewalk.

His bright green gumboots, dazzling though the misty blanket, are his only protection against the falling rain but he cares nought, evading his mother's outstretched hand as she tries to guide him and an oversized black pram into the temporary haven of the Racing Cafe.

A few metres along, the newsagent is doing a brisk business in lotto tickets, the promise of $20 million warming the long line as it snakes out the door and past the hairdresser who is putting out her "specials" board in hopeful expectation.

Across the road a largish trampoline behind a white picket fence creaks under the weight of the growing pool in its belly while the lillipilly hedge screening the Queenslander next door shivers in sympathy.

Except for the distant clopping of hooves which can be heard every so often, there is little to distinguish this small slice of suburbia with its leafy backyards and quaint cafes from any other on Brisbane's fringe.

But this is Hendra. A stone's throw from the Eagle Farm and Doomben racecourses and 5km from the bustle of the city, its beautiful streets seem a lifetime away from the deadly virus that shares its name.

It was here in 1994 that the bat-borne disease first came to light claiming the life of racing trainer Vic Rail and 13 of his horses. Samples from the property were sent to CSIRO's Australian Animal Health Laboratory in Geelong where the Hendra virus was isolated and identified but it wasn't until it showed itself again some 13 months later, with the death of a 35-year-old Mackay farmer Mark Preston, that officials and scientists really sat up and took notice.

Initial research showed that Hendra is a zoonotic disease, one that can be passed from animal to human. In this case it is transmitted from flying fox to horse, from horse to horse and from horse to human. The bats themselves seem immune to the disease but death is ugly and comes quickly for horses primarily from respiratory and neurological symptoms while in people it presents as pneumonia or encephalitis.

Hendra disappeared as suddenly as it appeared, going to ground for almost a decade. The non-activity saw a wane in research as money dried up and other new diseases dwarfed its explosion onto the world stage.

It was not until 1999 when the Nipah virus resulted in the deaths of 105 people and the culling of one million pigs in Malaysia that attention focused once more on the work being done by veterinary pathologist Deborah Middleton and her team in Geelong. Hendra and Nipah are cousins, both spread by flying foxes and both deadly.

In a twist of fate, the terrorist attacks on the twin towers of the World Trade Centre helped accelerate the research. The US Congress increased funding for the development of vaccines and anti-viral drugs for viruses that could be used as bioterror threats with Nipah and Hendra, by association, the big winners.

"The frequency of Hendra virus incidents after 2005, particularly the Redlands outbreak of 2008 and infections at Cawarral in 2009 in which two people died following contact with infected animals, brought the desirability of a vaccine for horses more urgently into the frame," Dr Middleton recalls.

"As part of the ongoing research into countermeasures against biological threats, we'd developed the Hendra virus sG subunit vaccine with our US collaborators and tested it under laboratory conditions. The vaccine was formulated for use with an adjuvant (a substance that enhances the body's immune response to an antigen) to enhance its efficacy."

Additional funding by the Queensland and Federal Governments, as well as the decision by Pfizer Animal Health to join the team as a commercial partner, hurried the matter along. But the vaccine was still in testing when in 2011 Queensland and NSW suffered their largest outbreak to date, with 21 horses dying during 17 incidences over two months.

Experts are unsure of the reason for such a dramatic rise but point to the floods of 2010-11 and the stress they caused to flying foxes, particularly in terms of food supply and habitat, as the strongest factor. Whatever the reason, the outbreaks were a stark reminder of the ferocity of the disease, its disdain for life and the impact of its spread on the equine industry.

Efforts were intensified and the prototype vaccine which had shown such positive results on smaller animals during lab work was put to the test on horses deliberately infected with Hendra. It passed, says the CSIRO team, with flying colours, preventing horses from getting sick or shedding the virus and, thanks to Zoetis Australia (the animal health division of Pfizer), the Equivac HeV vaccine was rushed into production and released in November last year.

But despite eight outbreaks of Hendra in 2012 and three incidences this year - the latest on a property in Macksville on the NSW mid north coast just last week - the response to the availability of the vaccine has been a little underwhelming. This has been the vaccine the horse industry has been calling for, yet as we approach peak Hendra season fewer than 25,000 of the 190,000 animals potentially at risk of the disease have been inoculated.

The reasons are varied - a few based on fact; many more on fear. Horse owners, it seems, are wary of any effect the vaccine may have on fertility and gestational foals, as well as the length of immunity and restrictions on export.

The vaccine has to be administered by a vet in two doses three to six weeks apart and costs between $100 and $200 per horse.

Trainer Robbie Heathcote, who numbers-wise at least, probably runs the biggest stables in Brisbane, has not vaccinated his horses. That doesn't mean he won't, he says, just that he doesn't as yet have all the information he needs.

"Look, we all know that Hendra virus is extremely serious and it kills," he says. "A couple years ago we saw the impact that it could have and we certainly don't want it to get out of hand.

"Even just here at Eagle Farm you have 500-600 horses constantly moving all the time from races to agistments to the stables so we are all very aware of it. We have put all the biosecurity measures for Hendra into practice but as for the vaccine I just don't know.

"I may still do it but we really need to delve into it a bit more. Maybe now the vaccine is here it should be mandatory so that it's the same for all trainers across the board. I know many people in this industry who feel if one has to do it then everyone should."

There has been a concerted drive by the NSW and Queensland Governments, aided by their federal counterparts, to support the vaccine and together with the CSIRO, manufacturer Zoetis and the Australian Veterinary Association, they are hopeful that educating horse owners about the disease and vaccine will improve the numbers.

"I think that initially there was hesitation and concern, especially about breeding and export but we are slowly gaining momentum," says Australian Veterinary Association spokesman Christopher Reardon who is a practising vet in Warwick.

"There has been a rolling roadshow of sorts to educate people and I think there has been increased market penetration. We have to realise that this vaccine is about saving people and to that end the benefits far outweigh the risks. This vaccine is an answer to the call for help from the horse industry so they need to act now. "

Lack of action may impact on the price of the vaccine and eventually its availability. There is also talk from veterinary industry bodies that their members will not put their lives at risk by attending to horses that have not been inoculated.

It is understandable that some horse owners and trainers are apprehensive about the use of a new product but Hendra has already claimed four human lives and more than 80 horses. Given a chance it will not hesitate to kill again.

Spreading the cost

Zoetis, manufacturer of Equivac HeV, is providing horse owners with a free second dose of the Hendra vaccine through participating veterinarians until July 31.

"With 60% of Hendra outbreaks occurring between May and July, the offer has been timed to give horse owners the best chance possible to help protect themselves, their families and the wider community," said Dr Stephanie Armstrong from Zoetis.

Equivac HeV can be administered to horses from four months of age.

Two shots are given three to six weeks apart, with the vaccine offering at least six months protection following the second dose.

Horse owners should visit http://www.health4horses.com.au for further information.

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