Hendra virus

Hendra virus is a virus carried by flying-foxes (fruit bats) in Australia. While the virus does not visibly harm flying-foxes, it can spread from flying-foxes to horses, and occasionally from infected horses to people. The virus can cause highly fatal disease in horses and humans that become infected.

Hendra virus was first diagnosed in Australia in 1994. Cases of Hendra virus have only been reported in Australia. The virus can be carried by all four species of flying-foxes found on mainland Australia:

• black flying-fox
• spectacled flying-fox
• little red flying-fox
• grey-headed flying-fox.  

The little red flying-fox and black flying-fox can be found in northern Western Australia and the Gascoyne with the little red flying- occasionally being sighted in the Mid-West and the northern Wheatbelt regions of Western Australia.

Hendra virus has been detected in flying-foxes in NSW, Queensland, Victoria, South Australia and Western Australia, and horse and human cases of Hendra virus have occurred in Queensland and NSW.  Hendra virus infection has been confirmed in two dogs on properties in NSW where horses had been infected with Hendra virus. The dogs did not display any signs of illness.  

The likelihood of a Hendra virus infection in Western Australia in horses and humans is considered low because of the relatively low concentrations of flying foxes and the low numbers of horses that live in the same area as flying-foxes.

There is no specific treatment or cure for infection with Hendra virus. 

A vaccine (Equivac HeV®) is available for use in horses. DPIRD does not require horses to be vaccinated against Hendra virus and there are no import restrictions on unvaccinated horses into Western Australia.  Some veterinarians who work with horses in high risk areas may only work with horses that are vaccinated. 

No signs have been reported in infected flying-foxes.

In horses, the onset of disease is rapid and characterised by:

• fever (above 38.5°C)
• increase in heart rate
• rapid deterioration with either respiratory and/or nervous signs
  • respiratory signs include laboured breathing, clear, frothy and/or blood-stained nasal discharge
  • neurological signs include, wobbly gait, lack of coordination, apparent loss of vision, aimless walking in a dazed state, head tilting and circling, muscle twitching, urinary incontinence, inability to rise.

It may take between 5 to 16 days to see signs of disease in a horse from the time the horse is infected with Hendra virus.  Horses may be able to shed the virus for 2 days prior to any signs of disease. 

Snake bite or other poisonings can present similarly to Hendra virus. 

Other reportable diseases such as anthrax and Murray Valley encephalitis can also present like Hendra virus as well as exotic diseases such as African horse sickness, equine influenza and West Nile Virus. 

Flying-fox urine is likely to be the most important route of transmission of Hendra virus, although other flying fox body fluid, such as placental fluid can also play a role. 

Hendra-virus spill-over from flying-foxes to horses is thought to occur when horses eat feed or pasture or drink water contaminated with infected flying-foxes body fluids.

Close contact between horses or horses and people is required for spread of infection between horses or to people.  All confirmed cases in people to date have been following high levels of exposure to infected horses body fluids (i.e. performing post-mortems without wearing appropriate personal protective equipment or being exposed to respiratory excretions). 

There is no evidence of human to human, flying-fox to human, flying-fox to dog or dog to human transmission.