NSW Department of Primary Industries

Japanese Encephalitis

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What is Japanese encephalitis (JE)

Japanese encephalitis is an acute mosquito-borne viral disease that can result in reproductive losses and encephalitis in susceptible animal species, most commonly pigs and horses. It is caused by the Japanese encephalitis virus (JEV). The virus is transmitted between animals by certain mosquito species.

Other animals can be infected with the virus 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 other animals. Animals act as sentinels (or indicators), highlighting the presence of the virus in the environment.

People can also become infected with the virus from the bite of an infected mosquito. Most human cases of Japanese encephalitis will have no symptoms or very mild symptoms, however some people develop severe, life-threatening illness.

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

What are my responsibilities in reporting signs of possible JE

Japanese encephalitis is a notifiable disease in NSW.

This means that owners, managers or people working with animals, particularly pigs and horses, must immediately report all suspicion of disease to authorities.

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 all-hours Emergency Animal Disease Hotline on 1800 675 888 for assistance or advice.

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 all-hours Emergency Animal Disease Hotline on 1800 675 888 for assistance or advice.

Due to the clinical similarity to Hendra virus infection, a sporadic but serious zoonotic disease, your veterinarian will initially test affected horses for Hendra virus infection. It is important to take appropriate precautions when handling, assessing, sampling, and treating affected horses until Hendra virus has been excluded as the cause of illness in the horse.

What other responsibilities do I have

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. For further advice, plans and templates, visit Farm Biosecurity.

How is JE spread

The Japanese encephalitis virus is a member of the Flavivirus genus. The virus is primarily spread when mosquitoes feed on infected animals, and then transmit the virus to other animals. The virus does not usually spread directly from animal to animal (i.e. it is not considered contagious). Australia has a number of mosquito species that are capable of transmitting the virus to animals and humans, however Culex spp are believed to be the most common vector for the virus. These mosquitoes tend to be most active at dawn and dusk.

It is not known how the virus came onto mainland Australia, and the 2021 - 2022 season was 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.

Waterbirds, particularly wading birds, such as herons and egrets, are the main natural reservoirs of Japanese encephalitis virus. Pigs and waterbirds are an important part of the transmission cycle as they can amplify the virus and provide an ongoing source of virus to infect local mosquito populations.

Transmission is believed to be maintained in mosquito–waterbird or mosquito–waterbird–pig cycles (see Figure 1).

Detections of JE in Australia in 2022

In 2022, outbreaks of Japanese encephalitis 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 northern Australia surveillance strategy (NAQS).

In NSW, all confirmed cases of Japanese encephalitis 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. 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.

In 2022, South Australia had a confirmed case of Japanese encephalitis in an alpaca in the Adelaide Plains Local Government Area.

Results from surveillance projects undertaken in humans and animals late in the season indicate the JE virus is likely to be circulating more widely in NSW and other states than was previously suspected.

Management of JE in the 2022-2023 season.

The national policy is to closely monitor Japanese encephalitis  in domestic animal populations to support public health agencies and the affected industries. More information about national disease response activities is available at outbreak.gov.au

Strategies

  • Early recognition and laboratory confirmation of cases
    • Japanese encephalitis remains a notifiable disease in NSW. Owners, managers or people working with pigs and horses must continue to report all suspicion of disease to authorities.
  • Investigating confirmed cases of Japanese encephalitis to identify any high-risk movements of pigs to locations other than processing facilities and other piggeries.
  • NSW DPI and Local Land Services continue to work with NSW Health and the national Department of Health for mosquito (and Japanese encephalitis) surveillance and public health management.
  • Ongoing vector (mosquito) monitoring, management, and control to reduce the risk of Japanese encephalitis in animals and people.

Currently, there is no effective treatment for Japanese encephalitis 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).

Further information on controlling mosquitos around piggeries can be found at Farm Biosecurity.

Protecting you and your people

  • Undertake vector management where possible and manage human contact with mosquitos by limiting outdoor activities at prime mosquito feeding times (at dusk and dawn)
  • The best protection against JEV and other mosquito-borne diseases is to prevent bites:
    • Wear appropriate clothing (light coloured, long and loose fitted), particularly when working in areas with increased mosquito burdens and around livestock.
    • Regularly apply mosquito repellents containing Diethyltoluamide (DEET), Picaridin or oil of lemon eucalyptus on all areas of exposed skin
    • Install screens on windows, doors and vents where possible
    • Clean up stagnant water around the workplace where mosquitoes can breed to prevent mosquito bites.
  • If you work with animals or live in some areas of NSW, you may be eligible for a free JEV vaccine.
  • For more information, refer to NSW Health

Veterinary management of Japanese encephalitis: 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.

Additional information

NSW Chief Veterinary Officer (CVO) Bulletins on JE

Japanese encephalitis in Pigs

Clinical signs of Japanese encephalitis in pigs

Adult non-pregnant sows typically 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, some with neurological signs.

Piglets infected after birth:

  • Encephalitis which presents as paddling, tremors and convulsions or other neurological signs up to six months of age
  • Wasting, depression or hindlimb paralysis that may be seen in suckling piglets and weaners

Infertility in boars - this is most commonly temporary but may be permanent if the boar is severely affected.

  • If boars are present on farm, they may experience infertility and oedematous, and congested testicles.

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

Japanese encephalitis disease in pig herds

While JE 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:

  • initially, around 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.

Protecting 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

Sample and testing information

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:

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, mummified or stillborn foetuses are also suitable for submission where samples can't be collected on farm
    • 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

Live pigs

If breeder pigs are suspected of having JE, the vet may require blood samples for testing

  • 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

NOTE:

Japanese encephalitis is a notifiable livestock disease. Therefore, all laboratory testing for JE is covered by the NSW Government.

What to do while you're waiting for lab results

  • 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.
  • Ensure your Property Identify Codes (PICs) are current and update them when required
  • 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.

Japanese encephalitis in 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 until the veterinarian has sampled the horse for Hendra virus and the results have been reported as  negative for Hendra virus.

Clinical signs of Japanese encephalitis 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:

  • Neurological signs which can vary in severity
  • Neurological signs can include incoordination, difficulty swallowing, impaired vision, and rarely the horse becomes over excited
  • An elevated temperature
  • Lethargy (dull, lack of energy),
  • Anorexia (loss of appetite)

Japanese encephalitis has an incubation period of 4-14 days in horses. Horses do not develop a detectable viraemia and are a dead-end host i.e. a JEV infected horse is not able to infect mosquitoes at any stage.People do not get infected from horses.

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

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.

Protecting horses from mosquitoes

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.

  • 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.

Sample and testing information

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

Paired blood samples two to four weeks apart (acute and convalescent). A single sample will only alert to previous exposure at some time while paired sampling will provide a clearer indication of recent infection.

NOTE:

Japanese encephalitis is a notifiable livestock disease. Therefore, all laboratory testing for JE is covered by the NSW Government.

What to do while waiting for lab 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.
  • Ensure your Property Identify Codes (PICs) are current and update them when required

Additional information

Supporting 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.

Rural Financial Councelling Service (RFCS)

The 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

Rural Adversity Mental Health Program (RAMHP)

The 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

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.

During an emergency animal 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.

www.dpi.nsw.gov.au