What Is Hendra Virus?

Hendra virus infection is a disease caused by the Hendra virus (HeV). The virus was first identified and named equine morbillivirus when it was isolated in 1994 from specimens obtained during an outbreak of acute, fatal respiratory disease in horses and humans in Hendra, a suburb in Brisbane. 14 horses and their trainer (Vic Rail) died during this outbreak.

HeV is one of the world's deadliest emerging viruses, and while human cases are rare, the mortality rate is 50%. All of these cases involved people in close contact with infected or dead horses.

Clinical Signs

Horses develop an acute respiratory or neurological syndrome quickly leading to death in most cases. The reported mortality rate in affected horses is over 70%. Those that have recovered have been euthanased.

Dogs are known to have been infected naturally, but have not shown any signs of illness.

Clinical signs in humans have included:

• an influenza-like illness, which can progress to pneumonia; or

• encephalitis (inflammation of the brain) type symptoms i.e. headache, high fever, and drowsiness, which can progress to convulsions or coma.

Transmission

While Hendra virus does not appear to be very contagious, humans and horses are susceptible to the disease. Dogs can also be infected with the virus, but have not shown any clinical signs of illness. All human infections have occurred following direct exposure to tissues and secretions (especially respiratory and nasal secretions, saliva, and urine) from infected or dead horses. There is no evidence of human to human or dog to human transmission.

The incubation period in humans has been estimated at 5-16 days.

The disease appears to spread from flying foxes (fruit bats) to horses and dogs, especially during the fruit bat breeding season (spring to early summer). The flying fox is the natural host, that is it remains unaffected by the virus. It is suspected that horses may become infected by eating food contaminated with bat urine or birthing products.

Transmission from horse to horse does sometimes occur, probably through direct contact with the respiratory secretions of an infected animal.

Treatment

There is no known cure or treatment for affected horses or humans. Death occurs rapidly. Suspected cases may be euthansed to prevent spread of infection.

A person suspected with Hendra virus infection should be promptly admitted to hospital for monitoring and supportive care, such as intravenous therapy and mechanical ventilation.

Prevention

In November 2012, a Hendra virus vaccine was made available for horses through accredited veterinarians. Vaccination is the single most effective way of reducing the risk of infection in horses and has important public health and safety benefits.

Hendra is a notifiable emergency animal disease, so if you suspect a horse on your property might be infected, you must report it. Contact with suspect horses should be avoided until a veterinarian has investigated and provided advice on handling affected horses safely. Horse feed and water troughs should not be placed under trees where bats may feed or roost.

Contact your vet regarding vaccinating your horses, to report suspected cases of the virus or for further advice.

- Last updated 7 April 2014