Japanese encephalitis in pigs

Japanese encephalitis virus was detected for the first time in Victorian piggeries in February 2022. For information regarding any current outbreaks visit: Japanese encephalitis current situation.

Japanese encephalitis is a mosquito-borne viral disease that can cause reproductive losses and encephalitis in susceptible animal species. It is caused by Japanese encephalitis virus which is a member of the Flavivirus genus.

The virus is primarily spread by mosquitoes feeding on infected animals and does not usually spread directly from animal to animal (i.e. it is not considered contagious). Certain types of mosquitoes, such as Culex sp. can become infected with Japanese encephalitis virus. and these tend to most active at dawn and dusk.

Pigs with the infection do not transmit the infection to other animals but may infect mosquitoes if bitten while they still have the virus in their blood.

Other livestock such as horses, cattle, sheep and goats are dead end carriers and cannot transmit the disease back to mosquitoes.

In general, spread is through the movement of infected mosquitoes, often over long distances due to wind dispersal and the movement of migratory water birds. Water birds can carry the virus but are not affected by it.

Clinical signs of Japanese encephalitis in pigs

Adult sows do not typically show overt signs of disease, but if infected before 60-70 days of pregnancy may either abort or give birth to mummified and stillborn or weak piglets, some with neurological signs. In a previously uninfected population, litters from sows and gilts would be expected to be equally affected. Boars, if present on farm, may experience infertility and swollen testicles.

I suspect my pigs have Japanese encephalitis

Japanese encephalitis is a notifiable exotic disease in Victoria. If you suspect Japanese encephalitis in your pigs, immediately contact your local Agriculture Victoria staff or phone the all-hours Emergency Animal Disease Watch Hotline on 1800 675 888.

Reducing the risk of spread

Japanese encephalitis virus is spread primarily through biting insects. There is a possibility of transfer of virus from an infected and viraemic pig to another animal via management practices that involve penetrating the skin, e.g., vaccination, blood collection, etc.

Reducing mosquito habitats and exposure to mosquitoes is an important part of breaking the transmission cycle.  Go to Farm Biosecurity to learn more about controlling mosquitoes around piggeries.

To minimise the risk of spreading the virus through management practices avoid reusing needles between animals when injecting and thoroughly wash and decontaminate other equipment between animals.

Information for pig producers and owners

Pig producers and owners can take steps to control mosquitoes and limit the spread of Japanese encephalitis. Watch the following video with Tim Kingmar, pig producer and Victorian Farmers Federation Pig president to find out more.

[On screen text: How to prevent identify and report Japanese Encephalitis]

[Vision:  Small piglets feeding. Tim talking on screen]

Tim Kingmar – Pig Famer:  In terms of Japanese encephalitis, I probably come from two angles; I come from my own business because we employ over 20 people, heaps of families rely on us, but I also come from an angle of my staff and human health in my community.

[Vision:  Farmer with pushing hay bales around for shed]

Tim:  For our staff it's really about the mosquitoes. In terms of the mosquitoes, we deal with them every year because we don't want them biting our pigs and irritating them for animal welfare reasons, for biosecurity reasons, so a normal procedure is keep grasses down, keep water down. This year we've taken to another level and we're consultation with our farm vet, we're using insecticides outside our sheds to also stop the breeding. And we're also, for our susceptible breeding sows, we're doing a back line of a product just to help kill them if they do come into the shed.

[Vision:  Group of young pigs feeding in the shed]

Tim:  In terms of testing for JEV, I've been tested. Do I know the results? No. But my understanding from talking with professionals around JEV is that 1% of people show symptoms of it. So there's probably a good chance I've already been bitten by an infected mosquito that I didn't keep control of.

[Vision:  Close up of young piglet ]

Tim:  Yeah, so I'm an intensive pig farmer, so we've spent a lot of money at our breed unit on automation; so there's lots of fans lots of airflow, and that's probably what I do at my own house. When we have friends out in the outdoor area, we get the fans going.

[Vision:  Tim spraying himself with insect repellent]

Tim: So I went to the supermarket and bought two big boxes of insect repellent so everyone can have one in their back pocket. Like I said, we're using insecticides outside the sheds, and really it's being aware. So in terms of Japanese encephalitis on my farm, we've only had minor signs.

[Vision:  Group of young pigs feeding in the shed]

Tim: But what the key signs have been is, an increase in mummified or an increase in stillbirth. Other signs some farms have seen is sow just don't farrow, and they might farrow two weeks late, and something like that, which is very uncommon.

[Vision:  Tim and Agriculture Victoria representative discussing and walking around the pig farm]

Tim: What I would encourage pig farmers, talk to your vet. We all have a great relationship with our vet. And keep talking to them about anything that's not normal. I think the next part of the challenging, especially over winter, is how do we, as communities, keep the mozzie levels down in the future; before next spring. And I think that's gonna be a harder conversation because it's easy for a small industry but harder for the wider community.

[Vision: Tim checking feeding equipment around the pig shed]

Tim: Japanese encephalitis has no impact on pork products. We're a significant player in the country, and I guess my encouragement to all of us is look after our staff, look after our communities, and our pigs, getting great mozzie controls. And yes, short term pain, but in the long term we're resilient, and pig farmers always have been and always will be.

[Vision: Tim smiling and holding a piglet]

[On screen text: Farmers should report any cases of unexplained pig deaths, especially piglets to the 24-hour Emergency Animal Disease Watch Hotline on 1800 675 888 to a vet or to Agriculture Victoria animal health staff. For more information visit agriculture.vic.gov.au/je]

[End transcript]

+ Expand all- Collapse all

Japanese encephalitis is a mosquito-borne viral disease that can cause reproductive losses and encephalitis in susceptible animal species. It is caused by Japanese encephalitis virus which is a member of the Flavivirus genus.

The virus is primarily spread by mosquitoes feeding on infected pigs or some species of water birds and does not usually spread directly from animal to animal (i.e. it is not contagious from animal to animal, animal to human or human to human). Certain types of mosquitoes can become infected with JE virus such as Culex spp. and these tend to most active at dawn and dusk.

Pigs with the infection do not transmit the infection to other animals but may infect mosquitoes if bitten while they still have the virus in their blood.

Other livestock such as horses, cattle, sheep and goats are dead end carriers and cannot transmit the disease back to mosquitoes.

In general, spread is through the movement of some waterbirds (herons and egrets) and through the movement of infected mosquitoes, often over long distances due to wind dispersal.

Farmers should report any cases of unexplained pig deaths, especially piglets, or any suspected JE symptoms in any animal to the 24-hour Emergency Animal Disease Watch Hotline on 1800 675 888 to a vet or to Agriculture Victoria animal health staff.

In pigs the virus affects reproductive performance. Adult sows do not appear to be ill but if infected before 60-70 days of pregnancy often either abort or give birth to mummified and stillborn or weak piglets, some with neurological signs. In a naïve population, litters from sows and gilts would be expected to be equally affected. Boars may experience infertility and swollen testicles.

If you suspect Japanese encephalitis in any animal, phone the all-hours Emergency Animal Disease Watch Hotline 1800 675 888.

Agriculture Victoria will arrange for staff to attend your property to collect samples for testing. Laboratory testing is undertaken at both the state and national diagnostic laboratories and may take from approximately three days to up to a couple of weeks to complete, depending on the type of samples submitted.

If samples from your pigs return a positive result for Japanese encephalitis virus, you will be contacted by Agriculture Victoria staff and will be provided with further advice and information.

The movement of pigs, pig semen, people, feed trucks or other vehicles are not impacted by a detection of JE.

Japanese encephalitis virus is spread primarily through biting insects. There is a possibility of transfer of virus from an infected and viraemic pig to another animal via management practices that involve penetrating the skin, e.g. vaccination, blood collection, etc.

Reducing mosquito habitats and exposure to mosquitoes is an important part of breaking the transmission cycle. Integrated vector control practices including the use of insecticides can reduce insect numbers and minimise further spread of the virus.

To minimise the risk of spreading the virus through management practices avoid reusing needles between animals when injecting and thoroughly wash and decontaminate other equipment between animals.

Vaccines for pigs are used in some countries where the disease is endemic. No vaccines for animals are registered for use in Australia.  A number of studies are underway.

What are the symptoms of Japanese encephalitis in humans?

More than 99 per cent of JE virus infections are asymptomatic (show no signs of disease). Less than one per cent of people infected with JE virus develop clinical disease.

A small number of people infected with JE virus may become seriously ill with encephalitis (inflammation of the brain).

Symptoms of encephalitis may include rapid onset of fever, headache, sensitivity to light, neck stiffness, vomiting, confusion or disorientation and sometimes seizures, progressing to coma. Anyone experiencing symptoms, particularly if they’ve visited regions near the border of Victoria and New South Wales or been in contact with pigs or with mosquitoes should seek urgent medical attention.

What should I do if I suspect I have Japanese encephalitis?

Anyone experiencing these symptoms, particularly if they’ve visited northern and north-west Victoria or southern New South Wales, along the Murray River and its surrounds, or been in contact with pigs, should seek urgent medical attention. Please visit the  Department of Health JE website for public health advice.

How do I protect myself from Japanese encephalitis?

There are two ways to protect yourself, your family and staff:

avoiding mosquito bites and vaccination.

Steps to protect yourself, your family and staff against mosquito-borne diseases include:

  • wearing long, loose fitting clothes outdoors.
  • using mosquito repellents containing picaridin or DEET on all exposed skin.
  • limiting outdoor activity if lots of mosquitoes are about.
  • using ‘knockdown’ fly sprays and plug-in repellent devices indoors.
  • using mosquito coils in small outdoor areas where you gather to sit or eat.
  • making sure your accommodation is mosquito-proof.
  • sleeping under mosquito nets treated with insecticides if you don’t have flywire screens on windows on your home or are sleeping in an untreated tent or out in the open.
  • making sure there is no stagnant water around your home.
  • remember, dusk and dawn are when most mosquitoes are more active but some will also bite during the day.

Find more information about how you can Protect yourself from mosquito-borne disease on the BetterHealth channel website.

People handling newborn litters on farms should wear PPE (gloves, masks and goggles), particularly when handling stillbirths, mummified piglets, and afterbirth.

In Victoria, stated-funded JE vaccine has been  made available free of charge for people who may be at risk of exposure to the JE virus. Speak to your health practitioner or Local Public Health Unit or visit the Victorian Department of Health to find out more details

Page last updated: 25 Oct 2022