The natural host for Hendra virus is the flying fox (fruit bat). Occasionally, Hendra virus can pass from flying foxes to horses. It causes severe illness, usually resulting in death.
On rare occasions, close contact with infected horses have caused illness in humans, with fatal consequences.
New Hendra virus genotype
A second genotype of Hendra virus was reported in Australia in 2021. The genotype, designated HeV-g2, was classified by researchers from CSIRO’s Australian Centre for Disease Preparedness (ACDP) following detection of the virus in grey-headed flying-foxes from Victoria and South Australia.
HeV-g2 has also been detected in sick horses. It was initially detected in an historical sample from a horse euthanased in Queensland in 2015. The second detection was in a sick horse near Newcastle, New South Wales (NSW), in October 2021. The case from Newcastle is the most southern detection of Hendra virus in a horse to date.
These findings confirm that Hendra virus exists in all areas of Australia where flying-foxes occur. Hendra virus remains a potentially fatal zoonotic threat anywhere where flying foxes and horses co-exist.
Hendra exclusion testing performed in Victoria is performed at ACDP using extended screening that can detect both known Hendra genotypes.
Laboratory studies by ACDP show the Hendra vaccine is effective against the new virus type.
Hendra virus is a notifiable disease in Australia. This means it's a legal requirement to report cases of Hendra, even if there is only a suspicion of disease.
Hendra is a rare disease, however the death rate related to infection is very high – more than 70 per cent in horses. A small number of people have been infected with the virus, via close contact infected horses. Tragically 4 of the 7 people who were infected have died. Five of these people were veterinary health professionals.
While cases in horses have only been identified in Queensland and NSW to date, all areas in Australia where flying-foxes and horses co-exist are considered to be at risk of Hendra virus spillover.
Typically, Hendra virus infection causes an acute illness that is rapidly fatal, however some cases have shown variable and sometimes vague clinical signs. Signs have included:
- increased heart rate
- difficulty or rapid breathing
Neurological signs such as:
- uncoordinated gait
- head tilt
- muscle twitching
- apparent vision loss
- aimless walking.
The incubation period in natural infections has ranged from 5 to 16 days. There are no specific or unique clinical signs for Hendra virus infection in a sick animal.
If you notice a sudden onset of illness in your horse or your horse dies suddenly and your horse could have come into contact with flying foxes, contact your vet or the Emergency Animal Disease Hotline on 1800 675 888.
Protecting your horses from Hendra virus
Hendra disease has not yet been detected in Victoria, but precautions should always be taken in areas where there are flying fox populations in close proximity with horses.
An effective way to reduce the risk of Hendra virus infection in horses is to vaccinate. Annual boosters, (following the initial priming course of injections) has been proven to protect horses from infections and reduce viral shedding in clinical cases.
You can also minimise the risks by:
- removing horse feed and water containers from under trees where flying foxes may be roosting or feeding
- early isolation of a sick horse whilst awaiting veterinary attention
- good hygiene and cleaning practices
- isolate new horses to your property. Carefully monitor their health and report any signs of illness early.
The destruction or relocation of flying foxes is not an effective risk management practice and is illegal. Flying foxes are protected species that are critical to our environment because they pollinate native trees and spread seeds. There are more effective ways of reducing the risk of Hendra disease.
Vaccinating horses against Hendra virus
There is an effective vaccine to protect horses against Hendra virus that is available through vets. This vaccine has been shown to be effective against known variants of the Hendra virus, including the recently detected HeV-g2.
Vaccination has been proven to protect horses from Hendra infection and reduce the amount of virus shed by clinical cases. This reduces the risk to other nearby animals and handlers.
Your horse is confirmed positive to Hendra virus
If your horse tests positive to Hendra virus Agriculture Victoria will work with you and your local vet to manage the situation.
The property where the horse is located will be placed under quarantine until all other horses on the property can be cleared of infection. In most circumstances horses with a current Hendra vaccination status will still be permitted to move.
Once there is enough evidence to suggest that no other horses have been infected, and the risk of further disease spread has been managed, the quarantine will be lifted.
Any decision to euthanise infected horses, (or other animals) will be made on a case-by-case basis. This decision will be based on the welfare of the infected animal, human health risks, biosecurity risks and in consultation with the owner. Euthanasia of all infected horses is no longer mandatory.
For further information on Hendra virus please contact your local animal health staff on 136 186.
Human exposure to Hendra virus
Hendra virus is a public health concern and requires careful management.
Agriculture Victoria works closely with the Department of Health whenever Hendra virus is confirmed or strongly suspected and there is reason to believe humans are at risk of exposure to the virus.
Infection of Hendra virus in people is rare and all previous human cases have been associated with close contact with infected horses.
If infection does occur, the incubation period usually ranges from about 5 to 15 days. Evidence suggests that the virus cannot be passed from one person to another.
The symptoms of infection in a person can include:
- dry cough
- sore throat
- breathing difficulties
- unusual sleepiness and confusion.
People at increased risk of infection include:
- equine dentists
- feed delivery merchants
- horse owners
- stud workers.
If you are concerned you have been exposed to Hendra virus you should immediately seek medical advice, (GP or local hospital).
Currently there is no cure or specific treatment for infection with Hendra virus. Treatment aims to ease symptoms and reduce the risk of complications while the person or animal recovers.
What to do while waiting for Hendra test results
There are several steps you should take while you are waiting for veterinary confirmation:
- Avoid close contact with infected horses and other horses that have been in contact with them.
- Isolate the suspected horse and relocate your other animals.
- Observe the infected horse from a distance and notify your vet if you notice changes in their condition.
If you must have close contact with the infected horse take the following precautions:
- If you have any cuts or abrasions, ensure they are covered with a water-resistant dressing.
- Use personal protective equipment (PPE), covering hands with gloves, feet with boots, and clothing with overalls.
- Wear a P2 mask (particulate respirator) and safety glasses to protect your face from potential contact with the suspect horse's bodily fluids (saliva, nasal secretions, blood and urine).
- Remove and dispose of PPE carefully.
- Wash your hands carefully with soap or disinfectant after all activities.
Ask your vet for advice about putting on, taking off and safe disposal of PPE.
Ensure P2 masks are fitted correctly to reduce your risk of infection.
For further information on human health and Hendra virus please contact Department of Health Communicable Diseases Section on 1300 651 160.
Flying foxes and Hendra virus
Flying-foxes (also called fruit bats) are a natural host of Hendra virus, although they do not show any apparent signs of illness when infected. There are four species of flying-fox on mainland Australia:
- black flying-fox
- spectacled flying-fox
- little red flying-fox
- grey-headed flying-fox.
Hendra virus has been found in all four species.
Horses can be infected with the virus when they come into contact with flying-fox urine and faeces. This is why it is important to keep feed and water bins away from under or near trees. Infection can also occur through contact with flying-fox saliva – such as the horse eating or coming into contact with partially chewed fruit or flowers.
Horses are the only known species reported to have been infected naturally from Pteropid bats.
The predominant bat species in Victoria are grey-headed flying foxes which can be found in both urban and rural environments. Information about flying fox camp distribution and populations is available of the Department of Fisheries and Forestry national flying-fox monitoring viewer.
Flying-foxes are a protected species. They are critical to our environment because they pollinate our native trees and spread seeds. Without flying-foxes we would not have our eucalypt forests and rainforests.
Wildlife Health Australia has further advice about handling bats.
All cases of Hendra (including suspected cases of illness) must be reported to the Emergency Animal Disease Watch Hotline on 1800 675 888.