Japanese encephalitis

What is Japanese encephalitis (JE)?

Japanese encephalitis (JE) virus is a mosquito borne virus, a flavivirus, that may infect a range of species including waterbirds, pigs, horses and donkeys, cattle, sheep, goats, water buffalo, chickens and others. These animals act as sentinels (or indicators), highlighting the presence of the disease in the environment.

Japanese encephalitis virus is a serious, emergency animal disease of animals. It is notifiable in Australia, meaning any suspected cases need to be reported immediately.

How is JE characterised?

Japanese encephalitis virus (JEV) is a mosquito-borne viral disease, which is maintained in nature by transmission cycles involving Culex sp. mosquitoes, certain species of wild and domestic birds. Pigs are a known amplifying host of the JE virus.

Horses may become infected, but they do not spread the virus to other horses, animals or people. They are a dead-end host.

People may also become infected resulting in encephalitis (inflammation of the brain) and death in severe cases.

How do I report JE?

Pigs: If you see any unusual signs of disease or death in your pigs or suspect JE in pigs, you must report it to your Local Land Services District Veterinarian immediately on 1300 795 299 or call the 24-hour Emergency Animal Disease Hotline on 1800 675 888.

Horses: Due to the clinical similarity to Hendra virus infection, a sporadic but serious zoonotic disease, it is important to take appropriate precautions when assessing, sampling, and treating affected horses.

If you see any unusual signs of disease or death in your horse(s) or you suspect JE in horses, you must report it to your veterinarian or call the 24-hour Emergency Animal Disease Hotline on 1800 675 888.

How is JE spread?

Australia has a number of mosquito species that are capable of transmitting the virus. This is the main route of infection. Few additional species play a significant role in transmission, mainly waterbirds and pigs, and few species show clinical signs of disease.

The primary mechanism of spread of JEV between hosts is by bites from infected mosquito vectors. Transmission is believed to be maintained in mosquito–waterbird or mosquito–waterbird–pig cycles (see Figure 1).

Waterbirds, particularly wading birds, such as herons and egrets, are the main natural reservoirs of JEV and are important amplifying hosts.

Horses are a dead-end host, while they can become infected with JE, they cannot pass on infection to other horses or people. People do not get infected from horses.

The Japanese encephalitis transmission cycle

Detections of JE

In 2022, outbreaks of JE were reported in domestic pigs and people in Queensland, New South Wales, Victoria and South Australia. In addition, cases of JE were reported in the Northern Territory in a number of feral pigs as part of their NAQS program.

In NSW, all confirmed cases of JE in pigs were detected in inland regional areas that were predominantly concentrated along water courses and west of the Great Dividing Range.

In addition, evidence of JE virus infection was detected in horses from the North Coast, Hunter, Greater Sydney, Central West and Riverina Local Land Services regions of NSW.

What are my responsibilities?

Japanese encephalitis remains a notifiable disease in NSW.

This means that owners, managers or people working with pigs and horses must continue to report all suspicion of disease by immediately reporting to the Emergency Animal Disease Hotline on 1800 675 888.

All owners or managers of susceptible animals, whether for production or companionship, have a responsibility, a biosecurity duty, to manage the risk of Japanese encephalitis introduction and spread on their property. This can be done by developing and actioning a mosquito management plan, based on environmental and operational factors to control mosquitoes and manage the risk of JE for pig, horse and public health management.

How do I manage JE?

The national policy is to control JE in domestic animal populations to support public health agencies and the affected industries. More information about national disease response activities is available at Outbreak. Strategies include:

  • Early recognition and laboratory confirmation of cases
  • Coordination and cooperation with public health response activities
  • Ongoing vector (mosquito) monitoring, management, and control in high-risk areas
  • Risk assessment of JE cases and development of management plans to minimise the risk of spread
  • NSW DPI and Local Land Services continue to work with NSW Health and the national Department of Health for mosquito (and JE) surveillance and proactive planning, preparedness

Currently, there is no effective treatment for JE in animals in Australia.

The best way to protect your pigs, horses and your local community is by developing and implementing an integrated mosquito management plan. This involves targeting all stages of the mosquito life cycle to break the breeding cycle (see Figure 2).

The mosquito lifecycle. Taking an integrated approach in controlling mosquitoes at the adult, egg and larval stages is recommended for an effective mosquito management program.

Protecting you and your people

Veterinary management of JE

What to do if a producer calls with suspect JE

  • Does the producer have a private or company vet that can conduct the on-farm investigation and sampling?
  • Where a private vet does not support a suspect property, a DV should complete the investigation where possible.
  • Producers and staff may be able to assist with sample collection.
  • Call the Emergency Animal Disease Hotline on 1800 675 888 to advise samples for JE exclusion are being submitted or for assistance / advice.

Who do I call?

If you observe unusual signs of disease, behaviour or death consistent with JEV, and require assistance, contact your Local Land Services District Veterinarian (DV) on 1300 795 299 or the Emergency Animal Disease Watch Hotline on 1800 675 888 for assistance or advice.

Sample collection and submission

The Elizabeth Macarthur Agricultural Institute has provided the following advice for taking and submitting sample for JE exclusion.

Post-mortem samples from deceased (<12 hours) and ​euthanised animals

  • Fresh brain, spleen, thoracic fluid/serum, liver, CSF
  • Brain, spleen, liver, kidney, heart, lung in neutral buffered formalin

Whole fresh aborted or stillborn foetuses are also suitable for submission where samples can't be collected on farm.

Live Pigs

  • 10 mL of serum or clotted blood from dams of affected and unaffected litters (10 of each depending on numbers of affected litters).
  • 10 mL of serum or clotted blood from several animals in the convalescent stage or from cohorts (if disease was being seen in pigs up to 6 months old vs the repro losses we are currently seeing)
  • Fresh semen from boars with sperm abnormalities or azoospermia

Test turnaround time

Expect 12-48 hours after sample arrival at the laboratory for PCR results.

Transporting samples

  • Chill blood samples and unpreserved tissue samples at either 4°C or with ice bricks.
  • Do not freeze samples at -20°C as it reduces the sensitivity of virus isolation testing.
  • Send samples in appropriate packaging via courier to the NSW APHL:

    NSW Animal and Plant Health Laboratories
    Elizabeth Macarthur Agricultural Institute (EMAI)
    Woodbridge Road
    Menangle NSW 2568
    Phone: 1800 675 623

Additional Information

NSW Chief Veterinary Officer (CVO) Bulletins on JE

Japanese encephalitis in pigs

Signs of JE in pigs

Adult non-pregnant sows show no obvious signs of infection. JE is associated with reproductive failure in pigs, with 50–70% losses reported in affected populations:

  • Pregnant sows and gilts may abort, produce mummified or malformed foetuses, or give birth to stillborn or weak piglets at term,
  • Infertility in boars - this is most commonly temporary but may be permanent if the boar is severely affected.
  • Nervous signs such as tremors and convulsions are occasionally seen in pigs up to 6 months of age.

Adult sows do not typically show overt signs of disease. If boars are present on farm, they may experience infertility and oedematous, and congested testicles.

In pigs, clinical signs include:

  • Abortion, mummified foetuses, 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
    • Wasting, depression or hindlimb paralysis that may be seen in suckling piglets and weaners.

JE spread in pigs

While Japanese encephalitis has an incubation period of up to 21 days in pigs it is typically 1-3 days.  The incubation period is the period of time from when the pig is bitten by an infected mosquito to showing the first clinical signs of JE.

Pigs (feral and domestic) develop high levels of infection and are also major amplifiers of the virus.

Outbreaks in previously unexposed pig populations typically consist of 2 cycles:

  • 20% of pigs become infected
  • Most remaining non-immune pigs become infected approximately 1–2 weeks later. Vectors – Australia has a number of mosquito species that are capable of transmitting the virus. This is the main route by which people and other animals become infected.
  • Pig-to-pig contact – pigs rarely transmit JE directly, through oral or nasal routes. There are no reported cases of humans being infected from direct contact with live pigs.
  • Semen and embryos – there are reports of transmission of infection via artificial insemination or embryo transfer, but this is not an important route of transmission.
  • JE virus does not survive for long in the environment and windborne spread of the virus is not reported.

How are suspect JEV cases investigated

If you observe signs of disease or death consistent with JE virus, contact the Emergency Animal Disease (EAD) Hotline on 1800 675 888 for advice.

Either your private veterinarian or a Local Land Services District Veterinarian will coordinate collecting samples for testing. Samples required for testing include:

  • Mummified, stillborn or affected and deceased piglets
    • Place samples in a sealed plastic bag and keep refrigerated until the vet arrives – do not freeze the samples
    • DO NOT DISPOSE OF AFFECTED PIGLETS or SAMPLES
  • If breeder pigs are suspected of having JE, the vet may require blood samples for testing.
  • Japanese encephalitis is a notifiable livestock disease. Therefore, all laboratory testing for JE is covered by the NSW Government.

More information on clinical presentation and investigation can be found at:

What to do while you’re waiting for laboratory results

  • Monitor the health of your pigs and report any unusual signs of disease, behaviour, or death to the EAD Hotline (1800 675 888), immediately.
  • Undertake vector control where possible
  • Manage human contact with mosquitos by limiting outdoor activities at prime feeding times (at dusk and dawn)
  • Wear appropriate clothing and repellents, particularly when working in areas with increased mosquito burdens and around livestock. If you have any concerns about your health, seek immediate medical attention.
  • If moving pigs, remember, in NSW, all pigs (pets and commercial) need to be tagged or branded to assist with identification as part of the National Livestock Identification System (NLIS). The NLIS enhances Australia's ability to quickly contain a major zoonotic disease incident to help protect our livestock industries and communities.

Protecting your pigs from mosquitoes

The best way to protect your pigs is by developing and implementing an integrated mosquito management plan. This involves a targeting all stages of the mosquito life cycle to break the breeding cycle.

Effective mosquito management on-farm includes:

  • Monitoring larval and adult mosquito numbers to know when to take action
  • Environmental management to reduce the number of breeding and resting sites
  • For example, fill potholes, remove standing water from containers, and ensure drains are free flowing
  • Applying larvicide control in large bodies of water OUTSIDE OF SHEDS
  • Applying adulticide control, such as residual spraying and fogging OUTSIDE OF SHEDS
  • Maintaining chemical and mosquito control records
  • For more information, refer to the Integrated mosquito management principles for piggeries and Controlling mosquitoes around piggeries guide

NOTE:

  • Always use chemicals strictly as per the product label
  • Seek professional advice if you are unsure about how to use a chemical
  • Chemical residues in pork are a trade and food quality risk
  • Misuse of chemicals can create environmental risks to bees, wildlife, aquatic life and people

Additional Information

Japanese encephalitis in horses

JE in horses in NSW

In May 2022, evidence of JE virus infection was detected in horses from the North Coast, Hunter, Greater Sydney, Central West and Riverina Local Land Services regions of NSW.

Australia has a number of mosquito species that are capable of transmitting the virus. This is the main route by which people and other animals, including horses, become infected.

Who do I call?

Due to the clinical similarity to Hendra virus infection, a sporadic but serious zoonotic disease, it is important to take appropriate precautions when assessing, sampling, and treating affected horses.

If you observe unusual signs of disease, behaviour, or death in your horse(s), contact your veterinarian or the Emergency Animal Disease Watch Hotline on 1800 675 888 for assistance or advice.

Signs of JE in horses

Horse owners are encouraged be aware of the clinical signs of JE:

  • The disease may be subclinical, meaning that they can be infected but show no signs of the disease
  • Most clinical disease is mild, however more severe encephalitis can occur which may be fatal
  • Clinical signs may include:
  • An elevated temperature,
  • Jaundice (yellowing around the eyes, nose and mouth),
  • Lethargy (dull, lack of energy),
  • Anorexia (loss of appetite) and
  • Neurological signs which can vary in severity
    • Neurological signs can include incoordination, difficulty swallowing, impaired vision, and rarely the horse becomes over excited

Japanese encephalitis has an incubation period of 4-14 days in horses.

While reports of the disease in other species are rare, overseas, the disease has been reported in donkeys.

People do not get infected from horses.  Horses are a dead-end host, that is, they do not transmit the virus to other horses, animals, or people.

What to do while you’re waiting for laboratory results

  • Monitor the health of your pigs or horses and report any unusual signs of disease, behaviour or death to the EAD Hotline, immediately.
  • Undertake vector control where possible
  • Manage human contact with mosquitos by limiting outdoor activities at prime feeding times (from dusk to dawn)
  • Wear appropriate clothing and repellents, particularly when working in areas with increased mosquito burdens and around livestock. If you have any concerns about your health, seek immediate medical attention.

Protecting your horses

Horse owners are encouraged to reduce the risk of horses being exposed to mosquitoes, after the confirmation of Japanese encephalitis in pigs New South Wales in 2022.

Stabling horses between dusk and dawn could help, as the mosquito most likely to carry diseases of concern is a night-time feeder that stays outdoors.

While there have been no confirmed cases of JE in horses in NSW, horse owners are encouraged to take mosquito risk prevention measures where possible, including:

  • Physical barriers - rugging and hooding horses in lightweight permethrin treated material (if climatically appropriate)
  • Eliminating mosquito breeding sites on the premises such as dripping or leaking taps and water troughs, as well as discarding old tyres which are a common breeding ground
  • Stabling horses overnight
  • Turning off lights inside stables during the night
  • Using fluorescent lights in stables that do not attract mosquitoes
  • Ensuring all screens and mesh at building openings are intact and any holes or tears are fully repaired
  • Using fans to eliminate mosquitoes within stables
  • Topical treatment of horses using registered vector repellents such as DEET
  • Thoroughly clean your horse vehicles using a high-pressure wash to remove all organic material that may provide a breeding ground for mosquitoes.

Additional Information

Support for affected livestock owners and producers

There has been considerable impact on both human health, animal industries as well as socio- economic impacts.

For those livestock owners who have had stock affected by JE, the impacts may be far reaching and beyond production losses alone. There are a number of Farm Business and Wellbeing resources that are available to support pig owners and producers affected by JE.

Financial support

RFCS logoThe Rural Financial Counselling Service (RFCS) NSW are available to help affected producers manage the financials at play and lessen the stress. RFCS NSWs completely free services specialise in helping primary producers with the risk management and regulatory requirements that are in place to manage JE.

RFCS NSW has local counsellors who are experienced in guiding farmers though the toughest of conditions, come flood, drought, mouse plagues or emergency disease events.

For more details or to contact support staff, call 1800 319 458 or visit www.rfcsnsw.com.au

FarmHub connects Australian farmers to a range of helpful services and support. Services include farm business assistance to help farmers navigate financial challenges, as well as mental health tools and services designed to strengthen wellbeing.

The Farm Business Assistance directory brings together assistance and support options for you and your farm business from a wide range of Government and private sources.

For more details, visit https://farmhub.org.au/explore-assistance/

Wellbeing support

ramhp logoThe Rural Adversity Mental Health Program (RAMHP) has 20 Coordinators based across regional, rural and remote NSW. RAMHP Coordinators educate and connect individuals, communities and workplaces to mental health services and support.

RAMHP can help link people to local mental health support, as well as offer training to workplaces and community groups about mental health and wellbeing in times of adversity.

For more details, or to find a RAMHP coordinator near you, visit www.ramhp.com.au

FarmHub logoFarmHub connects Australian farmers to a range of helpful services and support. Managing a serious disease event, like Japanese encephalitis, and other challenges, it is more common for people to experience distress, including anxiety and depression.

With a little help, you can employ tools and strategies that support stronger mental health and wellbeing – making you, your family and your business more resilient.

The Farm Hub provides a Mental Health Resource hub, summarising a range of services that are available to help strengthen mental wellbeing for the farming community.

For more details, visit https://farmhub.org.au/mental-health/