Hendra virus: What you need to know about the deadly disease

The re-emergence of the bat-borne Hendra virus in Queensland has raised alarm. Here is what you need to know and how to guard against infection.

The death of a horse from the Hendra virus in southeast Queensland, in what authorities say is the state’s first case of the disease since 2022, has raised alarm.

The unvaccinated horse tested positive for HeV on Friday and died after its “condition rapidly deteriorated”.

Horse owners are encouraged to vaccinate their animals against the disease to protect them. There is no vaccine for humans against Hendra virus and although instances of it spreading to people are rare, it can happen.

Here’s what you need to know about Hendra.

WHAT IS THE HENDRA VIRUS?

The Hendra virus (HeV) is a rare emerging disease that can be transmitted to humans from animals – often causing fatalities and severe symptoms in both humans and horses.

The name of the virus comes from the Brisbane suburb of Hendra, Australia, where the first outbreak of the disease was recorded in 1994.

Fruit bats of the Pteropodidae Family, Pteropus genus are the natural host of the virus, spreading the disease to other hosts when they come into contact with the bat’s urine, faces, or saliva.

A horse has died from a lethal bat-borne disease ‘Hendra’ for the first time in three years. Pic Jeff Camden

Humans usually do not contract the disease from bats – but rather domestic horses who have contracted the disease from an infected horse through close contact.

The disease is often spread from fruit bat to horse, infected horse to horse, horse to dog, and horse to human.

WHAT ARE THE SIGNS OF HENDRA?

Horses infected with HeV may display a range of symptoms, such as rapid onset of illness, fever, increased heart rate and rapid deterioration with respiratory and/or neurological signs – according to Health NSW.

Respiratory signs include difficulty breathing, rapid breathing and bloodstained froth, according to Department of Agriculture, Fisheries and Forestry.

Symptoms in people typically develop between five and 21 days after contact with an infectious horse.

Fever, cough, sore throat, headache and tiredness are all common symptoms, which can then develop into Meningitis or encephalitis – brain inflammation – which can result in headaches and drowsiness.

In extreme cases convulsions can occur, and people can even become comatose.

HOW DEADLY IS HENDRA?

Although not highly contagious – HeV has a high mortality rate, with 57 per cent of people infected with the virus dying.

Seven people have contracted the disease since 1994, with four dying, according to SA Health.

Most human transmission has resulted from very close contact with respiratory secretions from infected horses – such as mucus and blood.

There is no evidence of human to human transmission.

Since 1994, HeV has killed over 100 horses – some through horses coming in contact with infected fruit bats, some from direct transmission from other infected horses.

All recorded cases have occurred on the east coast, in Queensland and New South Wales.

HOW DO WE STOP HENDRA FROM SPREADING?

To prevent transmission, good hygiene and biosecurity measures need to be taken, throughout the country.

As most transmissions to humans come from infected horses, measures need to be taken to prevent fruit bats and horses from interacting.

The Department of Agriculture Fisheries and Forestry recommends removing feed bins and water troughs from under or near trees and removing or limiting horses’ access to paddocks with flowering or fruiting trees.

Humans who work with or around horses are urged to regularly wash their hands, cover any cuts or wounds with a water-resistant dressing, use appropriate personal protective equipment when handling sick horses, and to clean and disinfect equipment that has been in contact with a horse’s body fluids.

Experts have warned for people to maintain good health practices if they work with or around horses, and to minimise horses’ potential contact to fruit bats. Picture: CSIRO

CAN HENDRA BE TREATED OR CURED?

There is no specific treatment for HeV, with hospital or intensive care supportive treatment being the only course of action.

Antiviral medications have been ineffective against HeV – experimental treatments with different antibodies are offered to those who have had high exposure to the disease.

There is no vaccination available for humans against the virus.

Biosecurity Queensland Acting Chief Veterinary Officer Dr Fiona Thompson said the most effective management solution is prevention through vaccination of horses.

“Unfortunately, in this case, the deceased horse had not been vaccinated for Hendra virus,” Dr Thompson said.

“Hendra virus infection can occur throughout the year, so it’s important that horse owners and people in contact with horses take steps to protect themselves and their animals at all times.

“We’d urge them to continue to practice good biosecurity and personal hygiene measures – even if a horse is vaccinated against Hendra virus.

“If a horse becomes sick, owners should contact their veterinarian immediately.”

The disease is particularly concerning as there is no direct treatment, or vaccination for humans. AFP

Queensland chief health officer Dr Heidi Carroll said although human transmission does occur, it is unlikely.

“Our public health staff have contacted all known people who have been exposed to the infectious horse,” Dr Carroll said.

“While the Hendra virus can spread from horses to people, it is rare. We know from past cases of Hendra virus infection in horses that most people exposed remain well and don’t contract the infection.

“People who are assessed as having a high level of exposure to the infected horse will undergo prioritised testing for the virus.”

DO ALL BATS CARRY HENDRA?

Not all bats carry Hendra, or any other disease.

The risk of infection from bats to humans is low, but they do carry bacteria and viruses that can be harmful.

These include Australian bat lyssavirus – a fatal, rabies like disease, Hispotoplamosis – a very rare lung infection, and Leprospirosis – a bacterial disease.

People who are not trained or vaccinated should not handle bats themselves and should contact the RSPCA, Department of Environment and science or local groups for assistance instead

Not all bats carry diseases, but people have been warned to not handle the animals unless they are an expert.

ARE BATS MORE DANGEROUS THAN RATS FOR DISEASE?

Although bats and rats both host dangerous diseases and risk zoonotic (animal to human) disease outbreaks, humans are coming into increasing contact with bats as their natural habitats and food sources become decimated.

“Interactions between land-use change and climate now lead to persistent bat residency in agricultural areas, where periodic food shortages drive clusters of spillovers,” wildlife ecologist Peggy Eby and others wrote in a published paper on the increase of bat-related disease outbreaks.

The experts suggest that protecting native forests, especially those which could provide a source of food for bats during the winter time “could be a sustainable, long-term strategy to reduce spillover and protect the health of livestock and humans.”