Hendra virus is a zoonotic virus, which means it can be transmitted from animals to humans. The natural host of Hendra virus is the flying fox (fruit bat). Occasionally the virus can spread from flying foxes to horses and, rarely, from horses to people. Infection has also occurred in a dog and it is possible other animals can get infected.
Since the discovery of Hendra virus in 1994 until March 2012, more than 50 horses have been confirmed to be infected with Hendra virus.
In that time there have also been 7 confirmed Hendra virus infections in humans, all in Queensland. Unfortunately 4 of these people died, the most recent in 2009.
Currently the outbreaks have been restricted to Queensland and northern NSW. No known cases of Hendra virus infection in horses nor humans have occurred in the Northern Territory despite large flying fox populations in the Top End.
There is nevertheless evidence that Hendra virus exists in flying foxes in the NT so there is potential for spread to horses.
In humans, symptoms typically develop between 5 and 21 days after contact with an infected horse.
People infected by the Hendra virus have become unwell with:
- an influenza-like illness (which led to pneumonia in one case) with symptoms such as fever, cough, sore throat, headache and tiredness
- encephalitis (inflammation of the brain) with symptoms such as headache, high fever and drowsiness, which progressed to convulsions and/or coma and death.
Hendra virus can cause a wide range of symptoms in horses, usually with rapid onset. Early signs usually include fever, increased heart rate and restlessness.
Other common features include difficulty breathing and/or weakness and neurological signs such as uncoordinated gait, muscle twitching, head tilting and circling, quickly leading to death in most cases.
None of the symptoms in horses are specific to Hendra virus infection.
Hendra virus does not cause illness in flying foxes.
How it is spread
While the exact route of infection is unknown, it is thought that horses may contract Hendra virus infection from eating food recently contaminated by flying fox urine, saliva or birth products. Spread of the infection to other horses can then follow, especially within stables where horses are in close contact with one another.
The 7 confirmed human cases all became infected following close contact with respiratory secretions and/or blood from a horse infected with Hendra virus. There is no evidence of transmission from one human to another.
There is no evidence that the virus can be passed directly from flying foxes to humans or from the environment to humans. Horses can be infectious for some days before they get sick.
Who is at risk
People are at risk if they have had close contact with a horse that has Hendra virus infection, especially contact with blood and other body fluids including respiratory and nasal secretions and saliva.
People who have cared for an infected horse or veterinary staff who have treated or performed a post mortem on an infected horse without wearing appropriate personal protective equipment are most at risk.
Preventing horse infection
It is important to protect horse food from contamination by fluids from flying foxes, isolate sick horses early while awaiting test results, and pay attention to personal hygiene, cleaning and biosecurity practices commensurate with the level of suspicion and/or risk.
A Hendra virus vaccine for horses has been developed and was released in November 2012.
Preventing human infection
Standard hygiene practices should be performed in all contact with horses because they may be infectious with Hendra virus before becoming noticeably unwell. The use of personal protective equipment, gloves, eye protection, respirator (mask) and overalls, is recommended when it is likely that a person will come into contact with body fluids from any horse.
If the exposure involves a cut or puncture wound, gently encourage bleeding and then wash the area with soap and water.
Where water is not available, wipe the area clean, then use a waterless cleanser or antiseptic. Cover any cuts or abrasions on exposed skin with a waterproof dressing before handling horses and wash your hands well with soap and water regularly, but especially after handling your horse's mouth or nose (eg fitting or removing a bridle) and before eating, smoking or touching your eyes, nose or mouth.
Hendra virus is killed by heat, drying and cleaning with detergents and disinfectant products.
If a person thinks they have come into close contact with a horse which is displaying symptoms of Hendra virus infection they should contact both their local veterinarian and the Centre for Disease Control.
Much of the information here is derived from the Queensland Health Hendra virus infection resource kit. For more information go to the Queensland Government Department of Health website.
For more information call your nearest Centre for Disease Control.
Last updated: 20 March 2020
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