In 2022, Japanese encephalitis virus was detected in eastern and southern parts of Australia.
Mosquitoes carry the virus from infected waterbirds.
The disease is spread by mosquitoes and can infect pigs.
A mosquito infected with the virus can transmit it to a pig through its bite.
Japanese encephalitis can cause stillborn or weak piglets and deformities in piglets up to six months old.
It can also cause infertility in boars.
Once a pig has Japanese encephalitis, it can transmit the virus to other mosquitoes and those mosquitoes can pass it on to more pigs.
Pigs cannot pass the virus to humans or other animals.
Only an infected mosquito can transmit the virus to a person.
But humans are known as “dead end” hosts and cannot transmit the virus back to mosquitoes, other people, or animals.
Horses are also “dead end” hosts and cannot pass the virus on to mosquitoes, people, or other animals.
Find out more about the symptoms of Japanese encephalitis and how to keep mosquitoes under control on your property.
If you are a veterinarian, please go to our Japanese encephalitis information for veterinarians page for more information and resources.
Disease situation in animals
In February 2022, Japanese encephalitis (JE) was detected and confirmed in piggeries in Victoria, Queensland and New South Wales. On 4 March, cases were detected in South Australia. There are currently 85 infected piggeries and 55 detections in feral pigs across the four states.
On 30 March a rare case of JE in one alpaca was confirmed in the Adelaide Plains local government area. Alpaca’s, like horses, are a dead-end host.
Also in March, the Northern Territory Government confirmed that a small number of feral pigs from the West Daly region tested positive for JE. The testing was conducted in mid-March as part of a routine animal health survey conducted by the Northern Australia Quarantine Strategy. Further surveys and testing of feral pigs, horses and other animals for JE will continue as part of the northern Australia surveillance strategy for exotic diseases.
In May 2022 the NSW Chief Veterinary Officer issued a bulletin stating that testing of horse samples had identified 26 horses with probable JE and a further 4 horses as possible cases. These horses were probably exposed to the virus during summer to mid-autumn 2022. No cases have been definitively confirmed. However, the combination of clinical signs and test results suggests that JE infection is a probable or possible cause for the disease.
The locations of infected piggeries are not published due to government privacy and biosecurity requirements. The disease is widespread so regardless of where you are, protect yourself and your animals against mosquito bites.
Japanese encephalitis virus is a disease that’s spread by mosquitoes and can infect waterbirds, pigs, horses and on rare occasions, humans.
The virus has been detected in Australia in piggeries across several states, including Queensland, Victoria, New South Wales and South Australia.
It is important to know, that Japanese encephalitis is not a food safety concern and commercially produced pork products are safe to eat.
In pigs, the virus can cause reproductive losses, paralysis and wasting disease in piglets.
In horses and people, it can cause encephalitis or swelling of the brain.
Animals and people can only become infected through the bite of a mosquito that is carrying the virus, and the virus doesn’t spread directly between animals and people.
We’re responding to the situation by working with health and agricultural agencies, and industries across the Commonwealth, states and territories, to ensure a swift and coordinated response.
To stop the spread of Japanese encephalitis virus, the most important action to protect people and animals against the mosquito bites is to apply insecticides.
Blankets and covers on horses are also a good deterrent.
People who live or work near river systems should be vigilant, particularly piggery workers.
And we’re also monitoring whether the feral pig population is contributing to the outbreak.
Human vaccines are available and are prioritised for people working in the pig industry.
And while vaccines haven’t yet been approved for pigs in Australia, they’re available for horses to meet export requirements.
We expect the virus to abate during the winter months, but our surveillance activities will continue.
If you suspect your animal is showing signs of Japanese encephalitis virus, you must report it.
You can do this by contacting your local veterinarian or simply call the national Emergency Animal Disease Watch Hotline on 1800 675 888.
For the latest information or to report an outbreak, please visit the Australian Government website: outbreak.gov.au
About Japanese encephalitis
Japanese encephalitis is a viral zoonotic disease that is spread by mosquitoes. The virus can cause reproductive losses and encephalitis in pigs and horses. In rare cases, Japanese encephalitis can cause disease in people. People and horses are considered 'dead end' hosts. Once infected, they do not play a role in transmitting the virus. Pigs and some species of wild birds are amplifying hosts.
It is not known how the virus came onto mainland Australia, and it's the first time the virus has been detected in southern Australia. It is likely that the movement of infected mosquitoes or migratory waterbirds may have played a part in the virus’ spread.
In animals, signs of disease are most common in horses and pigs. Other animals can be infected but typically do not show signs of illness, such as cattle, sheep, goats, dogs, cats, bats, rodents, reptiles, amphibians and birds. Cattle, dogs, sheep, alpacas, and goats are dead end hosts that do not infect mosquitoes or people. Waterbirds such as herons and egrets (in the Ardeidae family) are the main reservoir for spreading the virus to mosquitoes. Pigs act as amplifying hosts, spreading the virus to mosquitoes.
Japanese encephalitis disease spread pathway
Japanese encephalitis virus is a nationally notifiable disease which means if you suspect an animal is showing signs of the disease, you must report it.
You can do this by contacting your local veterinarian or call the national Emergency Animal Disease Watch Hotline on 1800 675 888. This will put you in touch with your state or territory’s agriculture department.
The Australian, state and territory governments are working with the pig and horse industries through the Consultative Committee on Emergency Animal Disease (CCEAD) in response to this outbreak. We are also working closely with human health authorities on a range of activities including surveillance and trapping, mapping and public awareness.
Mosquito trapping and control is being conducted at all infected piggeries.
Mapping of infected piggeries and suspected infected piggeries is being shared across jurisdictions and with state human health authorities. The maps will help identify potential higher risk transmission areas for communities. Locations of feral pigs, waterbirds and major watercourses will be added, along with locations of vector surveillance.
Retrospective testing of stored samples from domestic and feral pigs, horses and wildlife are being tested for JE virus. Any positive results may assist in determining when JE virus started to appear in southern locations.
A longer-term animal surveillance plan for JE virus is being developed that will include surveillance of susceptible species, including pigs (feral pigs included), horses and other animals.
In addition to movement restrictions applying to infected piggeries, there are some additional interstate movement conditions for live pigs and pig semen moving from infected areas to uninfected jurisdictions. Check with your state or territory agriculture authority.
Japanese encephalitis is not a food safety concern and commercially produced pork meat or products are safe to consume.
Signs of the disease in pigs
Japanese encephalitis is primarily spread by mosquitoes. It is not spread from pigs to people or normally from pig to pig.
In pigs, the most common clinical signs are mummified and stillborn or weak piglets, some with neurological signs. Piglets infected after birth can develop encephalitis, which presents as paddling, or other neurological signs in the first six months of life. In other cases, wasting, depression or hindlimb paralysis may be seen in suckling piglets and weaners.
Adult sows do not typically show overt signs of disease. If boars are present on farm, they may experience infertility, and swollen and congested testicles.
Pig to pig transmission is rare, and on occasion can occur through infected genetic material such as pig semen.
Signs of the disease in horses
Symptoms in horses are usually mild and signs of the disease include high temperature, jaundice, lethargy, anorexia and neurological signs which can vary in severity.
Neurological signs can include incoordination, difficulty swallowing, impaired vision, and rarely, the horse becomes over excited. Reports of the disease in other species are rare, but there are cases reported in donkeys overseas.
The clinical presentation of JE is similar to other mosquito-borne diseases such as infection with West Nile/Kunjin virus, Murray Valley encephalitis virus, and Hendra virus. As Hendra virus can be transmitted directly from horses to people, it is important to take precautions and use personal protective equipment (PPE) as directed by your veterinarian, if caring for a sick horse and/or while waiting for test results.
Horses are known to be a ‘dead end host’. They do not carry enough virus in their blood to infect people or reinfect mosquitoes.
Human health advice
Most Japanese encephalitis virus infections in people are asymptomatic, however, those with severe infection (which occurs in less than one per cent of cases) may experience neck stiffness, coma, and more rarely, permanent neurological complications or death.
Encephalitis is the most serious clinical consequence of infection. Illness usually begins with symptoms such as sudden onset of fever, headache and vomiting. Anyone experiencing these symptoms should seek urgent medical attention.
People should try to prevent mosquito bites by using mosquito repellent containing picaridin, DEET or oil of lemon eucalyptus on all exposed skin and reapply every few hours.
Wear long, light coloured and loose-fitting clothing as well as covered footwear when outside. Ensure accommodation, including tents, are properly fitted with mosquito nettings or screens.
For updates and advice regarding human health, including vaccination programs, visit Australian Government Department of Health
Caring for your pigs
People working or otherwise in contact with pigs, including those who may have a small herd or pet, should take steps to control mosquitoes (see below) and protect themselves from mosquito bites. The Department of Health has detailed information for piggery workers about Japanese encephalitis.
Pig producers should be highly vigilant for signs of Japanese encephalitis in their herds and report unexpected abortions or stillbirths. JE is a nationally notifiable disease which means suspect animals must be reported to a vet or the Emergency Animal Disease Watch Hotline on 1800 675 888.
Mosquito control in piggeries
Key activities that will help reduce the mosquito load around piggeries include:
- Monitoring for mosquitoes at the various stages of their lifecycle. This can help determine the most effective control methods and help break the breeding cycle.
- To monitor, inspect bodies of water and containers for wrigglers, as well as areas where adult mosquitoes will rest like ceilings and walls.
- There are non-chemical measures that can be used including removing anything in the open that is filled with water or has the potential to hold water.
- Fill in potholes or other areas around the piggery that collect water.
- Clear debris from gutters, downpipes, and drains around buildings so that water doesn’t pool, and trim overhanging tree branches.
- Ensure effluent drainage is free flowing, flushed regularly and does not pool.
- Tanks, wells or other large water containers should be sealed, or screened with 1mm mesh.
- Reduce vegetation around the piggery to minimise areas where adult mosquitoes can rest.
- Ensure all windows and doors are covered by well-maintained mosquito proof screens.
- If you are opting for chemical control, be aware that:
- chemical residues in pork are a trade and food quality risk.
- chemicals must only be used in accordance with the directions on the label.
- chemicals must be registered for use around pigs and approved for use against mosquitoes. It can only be used in areas that require treatment.
- treatment should be applied by people authorised to use chemicals in accordance with state or territory training and licensing requirements.
- chemical control can be applied to water sources, the outside of sheds and buildings, effluent ponds, and staff facilities.
You can find out more at farmbiosecurity.com.au particularly the guide to controlling mosquitoes around piggeries, and the National Pork Biosecurity Manual which provides in-depth detail on biosecurity practices and management in piggeries.
Caring for your horse
Putting a hooded rug and fly mask on your horse when mosquitoes are active can help protect against their bites. Where available, stabling horses between dusk and dawn may also be beneficial.
If the horse allows, apply a safe insect repellent. To apply the repellent to the horse’s face and ears, spray it onto a cloth and rub it on, avoiding around and above the eyes.
Zoos should also practice good vector management, including avoiding pooled water sources etc.
People visiting zoos or places where there are mixed species of animals gathered, should apply mosquito repellent and wear long, loose fitting clothing.
Exports and trade
The Department of Agriculture, Water and the Environment provides the certification for live animals, meat and meat products for export to overseas markets.
The department is working with horse exporters to ensure horses meet importing country requirements for Japanese encephalitis virus (JEV). There are 12 markets that Australia exports horses to that have import requirements in place for this disease.
The department has worked with New Zealand to negotiate changes to the entry requirements for Australian horses travelling to New Zealand. Specific certification in relation to JEV is no longer required.
Work is also underway with the Australian Pesticides and Veterinary Medicines Authority (APVMA) to obtain an emergency use permit for a JEV vaccine for use in horses as part of Australia’s JEV response.
Ongoing use of a JEV vaccine in the general horse population will require a full APVMA assessment of a vaccine and will require a commercial import and distribution network.
The department will work with trading partners should any other issues arise around the export of pig meat, offal and pet food, due to this outbreak.
- Japanese encephalitis AUSVETPLAN - Animal Health Australia
- Emergency Animal Diseases Guide - field guide for veterinarians
- Emergency Animal Disease Bulletins
- Australian Government Department of Agriculture, Water and the Environment media centre
- Advice for beekeepers on mosquito control activities
- Advice from Safe Work Australia on duty of care
- Integrated mosquito management principles for piggeries (PDF 1.5 MB)
- Controlling mosquitoes around piggeries (PDF 254 KB)
- Pigs – Emergency animal disease alert (PDF 215 KB)
- Pigs – Emergency animal disease alert (DOCX 162 KB)
- Horses - Emergency animal disease alert (PDF 212 KB)
- Horses - Emergency animal disease alert (DOCX 214 KB)
- Vets – Emergency animal disease alert (PDF 283 KB)
- Vets – Emergency animal disease alert (DOCX 243 KB)