questions and answers

Questions and answers on hendra virus

5 August 2011

What is Hendra virus?

Hendra virus was first isolated in 1994 in a horse at a racing stable in the suburb of Hendra, Brisbane. Flying foxes are the natural hosts for Hendra virus. The virus can spread or “spill-over” from flying foxes to horses in a sporadic way in isolated incidents. Sometimes the virus can spread from horse-to-horse, but only through very close contact.

Unlike the situation with a highly contagious disease like equine influenza there is no need to restrict all horse movements, only those on properties directly involved with an incident. When Hendra virus is identified the property is quarantined until the risk of further infection from that incident has passed.
Very rarely, the virus can spread by very close contact from sick horses to people. One dog has also been infected, most likely from contact with an infected horse. There is no evidence of human-to-human, human-to-horse or flying fox-to-human spread of Hendra virus.

Hendra virus is a notifiable disease and all suspected cases must be reported. The virus can be deadly to both humans and horses.

Hendra virus is unrelated to Australian bat lyssavirus.

How do I reduce the chances of my horses becoming infected?

There are well-established guidelines issued by Queensland and NSW veterinary authorities to minimise the risk of horses contacting Hendra virus. These include limiting contact (direct or indirect) between flying foxes (and their droppings) and horses. This advice was updated and consolidated by Queensland authorities into an information pack release on 29 July 2011 and it is available from the Department of Primary Industries and Fisheries—QLD.

Recommendations to keep horses from becoming infected with Hendra virus are:

• Horse feed and water containers should be removed from under trees. If possible, place feed and water containers under a shelter.
• Owners should inspect and identify flowering/fruiting trees on their property. Horses should be removed from paddocks where flowering/fruiting trees are attracting flying foxes. Horses should be returned only after the trees have stopped flowering/fruiting and the flying foxes have gone. If horses cannot be removed from the paddock, consider fencing (temporary or permanent) to restrict access to flowering/fruiting trees. Clean up any fruit debris underneath the trees before returning horses.
• If it is not possible to remove horses from paddocks, try to temporarily remove your horses during times of peak flying fox activity (usually at dusk and during the night).
• Ensure that sick horses are isolated from other horses, people and animals until a veterinarian’s opinion is obtained.
• If there is more than one horse on your property, handle unaffected horses first and then only handle sick horses after taking appropriate precautions.
• Make sure gear exposed to any body fluids from horses is cleaned and disinfected before it is used on another horse. This includes things like halters, lead ropes and twitches. Talk to your veterinarian about which cleaning agents and disinfectants to use.
• When cleaning contaminated equipment from a sick horse, wear gloves, cover any cuts or grazes and wash your hands thoroughly afterwards.
• It is essential that horse owners practise good biosecurity and not travel with, work on or take sick horses to other properties or equestrian events.
• Do not allow visiting horse practitioners (e.g. farriers) to work on sick horses.
• Seek veterinary advice before bringing any sick horse onto your property.

What is the current situation in Queensland and NSW?

Please see the websites for each state for the latest situation with Hendra virus incidents:

Current situation in NSW
Current situation in Queensland.

There is no known link between these sporadic incidents other than exposure of horses to flying foxes or their excretions. Wherever flying foxes and horses are together, there is potential for the spill-over of this virus to horses and then to other horses or people through close contact.

A joint government taskforce has been established by the Queensland and NSW Premiers involving Queensland, New South Wales, Victoria, CSIRO’s Australian Animal Health Laboratory and the Commonwealth. The taskforce are working collaboratively to minimise the adverse impacts of Hendra virus on human and animal health. The Queensland Government and the NSW Government announced on 27 July 2011 that they would jointly commit an extra $6 million over three years to additional research on Hendra virus. On 29 July 2911, the Commonwealth Government announced that it would provide an extra $6 million to Hendra virus research.

What movement restrictions are imposed when a case of Hendra virus is detected?

Consistent restrictions are applied to incidents in Queensland and NSW. A property where an infected horse is found is quarantined and horse movements on and off the property are prohibited. Restrictions also apply to companion animals such as dogs and cats.

Hendra virus is not highly infectious and has only ever been transmitted from one horse to another when they are in very close contact (e.g. nose to nose). Sometimes a neighbouring property may need to be investigated if its horses could have had very close contact ‘over the fence’ with the infected horse. This is a different situation from equine influenza, which is highly contagious.

The horse industry is not subject to general movement restrictions for Hendra virus - except for the properties under quarantine.

Horse owners should practise good biosecurity, and not travel, work on or take unwell horses to other properties or equestrian events.

All owners or managers of properties with horses should develop a property biosecurity plan. Contact your veterinarian for advice and/or refer to the Horse Venue Biosecurity Workbook available from Animal Health Australia.

What should I do if I suspect Hendra virus in a horse?

Signs of Hendra virus infection in a horse include fever, nervous and respiratory signs, abnormal behaviour or unexpected deaths (also see below). If you notice such signs, keep everyone away from the horse and call your private veterinarian immediately. The veterinarian will notify the appropriate government agency if they consider the horse to be highly suspect for Hendra virus. If a veterinarian is not available, and the illness is progressing rapidly, call the national Emergency Animal Disease Watch Hotline on 1800 675 888.

Hendra virus infection is a notifiable disease in all Australian states and territories and all suspected cases in horses must be reported to authorities.

If a horse is suspected to have a Hendra virus infection it is important to keep it away from other horses, other animals and people on the property.

Horse owners should exercise extreme caution and limit contact with suspected cases.

Only experienced veterinary staff who are using appropriate personal protective equipment should have contact with the horses until the diagnosis is known.

All veterinary staff assessing or managing a sick horse should do so in accordance with the Biosecurity guidelines and other veterinary advice, which can be found in the 'For Veterinarians' section of the Biosecurity Queensland website (includes 'Guidelines' and 'Veterinary practice pack'). This information was written for Queensland veterinarians but the principles are applicable wherever there is a risk of Hendra virus infection.

Hendra virus signs in horses

Hendra virus should be suspected whenever a horse’s health deteriorates rapidly and the horse resides in an area within the range of flying foxes.
Hendra virus can cause a range of signs in horses. Usually there is a sudden fever and either respiratory or neurological illness and rapid death. In some cases the onset of illness is gradual.

The following signs have all been associated with Hendra virus cases, but not all of these signs will be found in any one infected horse:

• rapid onset of illness
• increased body temperature/fever
• increased heart rate
• discomfort/weight shifting between legs
• depression
• rapid deterioration with either respiratory and/or nervous signs.

Respiratory signs include:

• respiratory distress
• increased respiratory rate
• nasal discharge at death—can be initially clear, progressing to stable white froth and/or stable blood-stained froth.

Nervous signs include:

• wobbly gait
• apparent loss of vision in one or both eyes
• aimless walking in a dazed state
• head tilting and circling
• muscle twitching
• urinary incontinence
• inability to rise.

The virus is mostly fatal in horses, but occasionally a horse will survive the infection. The reported mortality rate in infected horses is greater than 70 per cent.

How is Hendra virus infection controlled?

Where Hendra virus has been confirmed as the cause of illness or death in horses, the state veterinary and human health authorities manage the situation.
Urgent biosecurity measures are taken to minimise the risk to people and other horses, and to track the likely cause and extent of the infection. A risk assessment is conducted on the possible exposure of people, other horses, dogs and cats. Further measures are implemented depending on the assessed level of risk.

How do people get the disease?

Seven people are known to have been infected with Hendra virus before 2011.

These infections resulted from very close contact with infected horses.

There is no evidence of spread of Hendra virus from flying fox-to-human, human-to-human or human-to-horse.

Keys to preventing the disease in people

Workplace health and safety measures should be implemented at workplaces where there is occupational contact with horses.

Hendra virus requires careful risk management. You should develop a plan for responding to a suspect or confirmed case of Hendra virus at your workplace. The plan should include how you will minimise the risk to yourself, any employees and others such as visiting horse practitioners (e.g. farriers). You should then train your workers in implementing the plan.

Sound hygiene and biosecurity measures should be adopted as a routine work practice for all horse contact.

For more information about managing the risk of Hendra virus in the workplace, contact your state or territory workplace health and safety authority.

Horses can shed Hendra virus for about three days before they show any sign of illness. All horse handlers should therefore protect themselves by routinely using good hygiene practices whenever handling horses.

Always cover any cuts or abrasions on exposed skin before handling your horse. Always wash your hands with soap and water, particularly after handling your horse’s mouth or nose. Do not smoke, eat or touch your eyes, nose or mouth until you have washed your hands.

Remember that every time you put a bitted bridle on your horse or take it off, you are likely to contact the horse’s saliva.

Great care should be taken with hygiene and personal protection when handling sick horses. In particular, avoid contact with blood and other body fluids (especially respiratory and nasal secretions, saliva and urine).

You should avoid all contact with suspect horses until a veterinarian has investigated and provided advice on the safe handling of sick horses.

Everyone handling or investigating a suspect case of Hendra virus should wear full protective clothing. The minimum standard is impervious overalls, boots, gloves, respirator mask and eye protection. Follow the procedures outlined in the 'For Veterinarians' section of the Biosecurity Queensland website.

State veterinary authorities will contact state human health authorities whenever Hendra virus is confirmed or strongly suspected. State human health authorities will then work with the horse owner, handlers and attending veterinarians to assess their risk from exposure to the infected horse.

Hendra virus symptoms in people

If you have been in contact with an infected horse, seek medical attention immediately.

Symptoms typically develop between five and 16 (possibly up to 21) days after contact with an infected horse.

Fever, cough, sore throat, headache and tiredness are common initial symptoms. Meningitis or encephalitis (inflammation of the brain) can then develop, causing headache, high fever, and drowsiness, convulsions and coma.

Hendra virus infection can be fatal and has to date infected seven people and killed four of them in Australia (since 1994).

For more information on Hendra virus infection in humans, refer to NSW Health or the Queensland Health.

Is a vaccine for horses available?

CSIRO scientists are testing a new vaccine that shows promise of preventing infection by Hendra virus. The vaccine has been shown to protect horses from experimental infection in the laboratory, but further testing is required to ensure its safety and effectiveness in the field.

The Commonwealth's vaccine regulators, the Australian Pesticides and Veterinary Medicines Authority and the Department of Agriculture, Fisheries and Forestry, are aware of the candidate Hendra virus vaccine for horses being trialled at CSIRO's Australian Animal Health Laboratory. This trial is being conducted using funding from the Commonwealth and Queensland Governments.

Commonwealth vaccine regulators have yet to receive an application to assess and authorise the supply and use of such a Hendra virus vaccine in horses in Australia. Should a vaccine be developed to the point where it can be supplied for use, application can be made for a permit or product registration and the assessments can be urgently progressed.

No veterinary vaccine is one hundred percent effective in all animals. Therefore, measures to reduce the risk of flying fox-to-horse exposure and horse-to-person exposure will still be required into the future, even after a veterinary vaccine is available.

For more information on progress with vaccine development see information from the CSIRO. There are no immediate plans for development of a vaccine for humans.

What control measures for flying foxes are in place to prevent the spread of the Hendra virus?

It is not practicable to cull flying foxes just because of Hendra virus risks to horses. Increasing stress levels in flying foxes by attempting to scare them off or eradicate them may increase shedding of the virus and therefore increase the risk of transmission of Hendra virus (if present) to horses.

Flying foxes are protected native fauna in Australia. To enable better management of the risk of infection, research is underway to understand how the infection is maintained in flying fox populations and what factors are associated with the spread of the virus to horses. More information is available from state environmental agencies, including in Queensland.

Why are there so many more cases of Hendra virus now than in the past?

The reasons for this are not clear, but research is underway to try and answer this question.
One possibility is that Cyclone Yasi has destroyed flying fox habitat and food sources, driving flying foxes south. These hungry stressed flying foxes may have been carrying Hendra virus, and under stress would be more likely to excrete virus.   If some of the southern flying fox populations had not been previously exposed to Hendra virus, then they may be more susceptible to infection with the virus, resulting in spread into the southern flying fox population.
Another possibility is that the unusual widespread heavy rain and flooding last year and early this year in eastern Australia has disrupted the flowering patterns of trees creating more growth in leaves rather than flowers.  This means that flying foxes become undernourished and must break into small groups and travel further afield to search for food.  This can impact on the immune systems of flying foxes leading to potentially higher than normal levels of Hendra virus in their populations.

Can companion animals get the disease?

Queensland authorities confirmed on 26 July 2011 that a dog had tested positive for Hendra virus infection. This is the first time outside a laboratory that an animal other than a flying fox, horse, or person, has been confirmed with Hendra virus infection. The dog was euthanased on 31 July 2011.

The dog was on a property in Queensland that was quarantined for Hendra virus infection in horses and it was subject to routine testing. The dog had no history of recent illness. It is most likely that the dog contracted the infection from one of the horses on this property that died from Hendra virus between mid-June and early July 2011.

Cats have been infected with Hendra virus only under laboratory conditions.

If your horse becomes ill, particularly if it has been exposed to Hendra virus, it is recommended that other animals be isolated from horses on the property to reduce their potential exposure to the virus. People should have limited access to all animals that are undergoing testing for Hendra virus.

If you are not located on a property quarantined for Hendra virus, the risk of companion animals contracting Hendra virus is very low. If your companion animal becomes ill in this situation, contact a veterinarian.

Are companion animals checked?

State veterinary authorities risk-assess properties to determine if companion animals have had close contact with an infected horse. If there has been close contact, dogs and cats are tested for Hendra virus. In all previous cases, all companion animals were negative for Hendra virus, except for the single dog in Queensland that tested positive in July 2011. There is no need to test dogs or cats that have not had contact with an infected horse. Any properties on which Hendra virus is identified are quarantined and movement restrictions are imposed on domestic animals.

What is the advice for dog and cat owners?

State veterinary authorities in Queensland and NSW recommend that people keep dogs and cats away from sick horses (suspect Hendra virus cases) to reduce the possible risk of exposure to the virus.

All dogs and cats that could have had contact with infected horses are tested at the same intervals as the remaining horses on these properties. Their health is also monitored.

Under national policy, domesticated animals that have evidence of infection with Hendra virus, even if they are not ill, are euthanised because of the potential risk they pose to people.

Can other animals be infected with Hendra Virus?

When Hendra virus was first found researchers tested other animals in the area where the first equine cases were seen. More than 150 individual animals from 16 species of rodents, marsupials, birds, amphibians and insects were tested in 1995.  All tested negative. 

The marsupials tested included bandicoots, brush-tailed possums, different species of wallabies and bettongs. The birds tested included magpies, whistling, plumed and black ducks, turkeys, guinea fowl and peacocks.  Rats, mice, cane toads, lizards and snakes were also tested.  As well, other domestic animals such cattle, dogs, cats and poultry were investigated. 

In 2001 a survey of piggeries in Queensland was undertaken to see if pigs had been exposed to Hendra virus.  No evidence of any exposure was found.
Under experimental conditions Hendra virus has infected pigs, cats, guinea pigs and hamsters. The only clear evidence of Hendra virus infection in dogs is the recent field case in Queensland (26 July 2011). 
  
Research is continuing to better understand what other animals are susceptible to the virus and how they may become infected. Flying foxes are the natural host for Hendra virus and they are largely unaffected clinically by infection with the virus. The involvement of other species in the maintenance of the virus has not been definitively ruled out.