Japanese encephalitis in animals

Japanese encephalitis (JE) is a mosquito-borne viral disease that mostly occurs in pigs and horses.

It can cause:

  • reproductive losses and neurological disease in pigs
  • encephalitis (a rare but serious infection of the brain) in horses.

In rare cases, it can cause disease in other animals and people.

JE is not spread directly from pigs to people. Read more about JE in people.

Watch the latest update and find out more below.

In February 2022, JE was detected in Australian piggeries in Victoria, New South Wales and Queensland.

In March 2022, cases were detected in South Australia. Read more about JE interstate on the Australian Government’s Outbreak website.

Northern Territory

JE has been detected in a small number of feral pigs in the West Daly region.

Evidence of previous exposure in animals was found during the 2020 to 2021 wet season. This means the animals were bitten by a mosquito infected with the virus but did not develop the disease.

In March 2022, JE was declared a communicable disease incident of national significance.

Notifiable diseases are those that:

  • pose a threat to livestock production industries or public health and
  • could have a major impact on international trade.

Suspected cases of notifiable diseases must be reported.

Food safety

JE is not a food safety concern and pork products are safe to eat.

The NT does not have any commercial piggeries. However, pig owners, hunters and landowners should report signs of the disease.

It is not known how the virus has come into Australia. The movement of infected mosquitoes or migratory waterbirds may have played a part in the virus’ spread.

Movement restrictions have been applied to infected pig properties in Australia.

Life cycle

Animals and people become infected with the virus through the bite of infected mosquitoes.

The normal lifecycle of JE is between waterbirds and mosquitoes, which may then accidentally spill over to pigs and horses.

The spread from pig to pig through genetic material such as semen is rare.

Horses are known to be a ‘dead end host’. They do not carry a blood infection that will reinfect mosquitoes.

You should monitor your pigs and horses for signs of JE.


  • Mummified and stillborn or weak piglets, some with neurological signs.
  • Boars may experience infertility, fluid retention (oedematous) and congested testicles.


In many cases, horses can be infected but not show signs of the disease. Most clinical disease is mild. However, more severe encephalitis can occur which may be fatal.

Signs include:

  • elevated temperature
  • jaundice
  • lethargy
  • anorexia
  • neurological signs such as:
    • incoordination
    • difficulty swallowing
    • impaired vision
    • over-excitement.

To find out more about signs, go to the Australian Government's Outbreak website.

If you're a pig owner with a property identification code (PIC), you can get your registered pigs tested for free.

To arrange testing, contact your local vet or livestock biosecurity officer.

Read more about the testing process PDF (388.5 KB).

There are steps you can take to reduce the impact of the disease.

This includes making sure that any stagnant water does not become a breeding ground for mosquitoes.

How to protect pigs

If you work with or have contact with pigs, you should:

  • take steps to control mosquitoes
  • continue to use effective biosecurity measures.

How to protect horses

If you own horses, there are steps you can take to protect them from mosquito bites.

  • During hotter months, cover your horse with:
    • a light cotton rug
    • a fly mask and
    • a safe insect repellent if the horse allows. Don't spray it around or above the eyes.
  • Stable horses between dusk and dawn.
  • Horses left outside overnight can wear a lightweight permethrin (insect repellent) fabric.

To find out more, read the JE AUSVETPLAN response strategy on the Animal Health Australia website.

How to protect yourself

Find out how to protect yourself against mosquitoes and how JE affects people.


Surveillance and testing are underway in the NT, and you must follow instructions given by biosecurity authorities.

If you notice anything unusual or suspicious, you must report it.

It is important to maintain good biosecurity practices on your property. This includes having a property identification code (PIC) for your animals.

Get more advice on the Farm Biosecurity website.

How to report

If you notice anything unusual or suspicious:

More information

The Berrimah Veterinary Laboratory is testing blood samples for JE and can be contacted on 08 8999 2049.

You can also read the Australian Government’s field guide on emergency animal diseases on the Outbreak website.

Last updated: 11 May 2022

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