The deadly Hendra virus might have finally met its match. A vaccine is now available for use in horses in Australia, which should stop the virus killing them as well as preventing transmission to humans.
Hendra occurs naturally in flying foxes ? a kind of fruit bat ? without harming them. The virus was originally identified when it killed 13 racehorses and their trainer in a town called Hendra in Queensland, Australia, in 1994. It is thought to have spread between the animals when the horses ate grass that has been defecated on.
Then the virus almost disappeared for a decade, with only one outbreak in 1999, before re-emerging every year since 2004. Since it was discovered, the virus has killed about 80 horses and spread to seven people who came into contact with the bodily fluids of infected animals. Four of the seven died.
In recent years, the virus has been infecting horses more frequently. In 2011 there were as many Hendra outbreaks in horses in Australia as there were in the previous 15 years, says Deborah Middleton, a veterinary pathologist at the Commonwealth Scientific and Industrial Research Organisation (CSIRO) in Geelong, Australia, who led the development of the new vaccine. "We don't know if these waves of spillover are just part of the life cycle of the virus, but the worry was there was a trend."
In 2011, a team at the Uniformed Services University of the Health Sciences in Bethesda, Maryland, developed a vaccine that protected monkeys against Hendra. Researchers from there collaborated with the drug company Pfizer and CSIRO to produce the vaccine for horses. Middleton says the vaccine could potentially be modified for use in humans.
Human vaccine?
But Dominic Dwyer, a medical virologist at Westmead Hospital in Sydney, Australia, who runs one of the country's few high-security pathology labs, says that because there have only been a few human cases, it will be hard to develop and test a vaccine, as well as justify the effort. If the vaccine could be used as a treatment post-exposure, as the rabies vaccine can, then this would bolster the case for a human Hendra vaccine, he points out.
Ben Gardiner, the president of the Australian Veterinary Association, has urged that all horses, even those not in Queensland and north New South Wales ? the high-risk areas ? be vaccinated.
Dwyer says it is essential to understand and deal with animal viruses, since the majority of new human viral pathogens arise from contact with animals. According to Dwyer, three-quarters of new viruses that have infected humans in the past 20 years have come from animals. "And probably the other 25 per cent have too ? we just couldn't figure it out," he says.
He adds that Hendra should be monitored in bat populations around the country, as the virus will never be totally eradicated and could pose a threat to people who handle them.
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