Hendra Vaccine Offers Hope for Australian Horse Owners

Hendra virus researcher, Deborah Middleton, BVSc (Hons), MVSc, PhD, Dipl. VCS, who is leading the Hendra vaccine project at the Australia's Commonwealth Scientific and Industrial Research Organization (CSIRO) Animal Health Laboratory, provided an update on its progress and the challenges so far, at the Australian Veterinary Association's national conference in Canberra May 22.

Middleton said the high number of hendra cases reported in 2011 emphasized the need for a vaccine in a bid to eradicate the killer disease.

"The initial flurry of research activity that followed the emergence of the hendra virus in Queensland in 1994 waned somewhat towards the late 1990s after there had been a limited number of cases reported," she explained. "Interest was renewed after the outbreak of the nipah virus in Malaysia in 1999 which was identified as being closely related to the hendra virus, and caused the deaths of hundreds of people.

"Like hendra, nipah virus can be transmitted to humans from animals, and some strains can also be transmitted directly from human-to-human; in Bangladesh, half of reported cases between 2001 and 2008 were due to human-to-human transmission."

Middleton and her team at CSIRO participated in the development of an experimental vaccine that was shown to successfully protect horses against hendra last year. They have continued to carry out further experiments to determine the lowest dose of antigen needed for the vaccination to be effective while keeping the cost of the product down.

"The vaccine works by stimulating the production of neutralizing antibodies which means that if a horse is exposed to hendra virus after effective vaccination it can't spread the disease to other animals or the environment," Middleton explained. "Stopping the disease in horses will also help protect people. A horse vaccine is crucial to breaking the cycle of hendra virus transmission from flying foxes to horses and then to people, as it prevents both the horse developing the disease and passing it on.

"The high incidences of Hendra virus outbreaks during 2011 however highlight the ongoing relevance of this important project in breaking the transmission cycle of this disease and reducing its impact on the horse-owning community," she continued. "We will continue to work closely with authorities to ensure the vaccine is available as soon as possible after essential safety and efficacy requirements are met."

The conference also featured a presentation from hendra virus researcher Hume Field, BVSc, MSc, PhD, MACVS. He shared current details on the virus and its natural host, flying foxes (a type of Australian fruit bat).

Common signs to look out for with hendra infections in horses include respiratory distress, neurologic deficiencies, elevated body temperature (above 40°C, or 104°F), elevated heart rate, and depression. Veterinarians stress that although these signs are commonly associated with hendra cases, there are no specific signs of infection.

Since 1994, hendra virus has been confirmed in 68 horses and seven humans. In these cases all horses either died or were euthanized and four of the people died.

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