Japanese encephalitis information for vets – pigs
Japanese encephalitis (JE) is a mosquito-borne viral disease that can cause reproductive losses in pigs, and encephalitis in horses and very rarely in other species. Other animals do not usually show any signs, and pigs and horses may often show no signs at all. It is caused by Japanese encephalitis virus (JEV), which is a member of the Flavivirus genus. In infected human around 1% will develop clinical disease.
Japanese encephalitis was first detected in Victoria in February 2022, with pig cases, human cases and evidence of some horses being exposed to the virus.
In the 2021–22 summer, the disease was reported on 23 pig farms in northern Victoria. While there have been no confirmed cases in Victorian pigs since the initial outbreak, the disease is now considered as sporadically and seasonally endemic in mainland eastern Australia.
If you suspect Japanese encephalitis in any animal, phone the all-hours Emergency Animal Disease Hotline on 1800 675 888
If you suspect Japanese encephalitis in any animal phone the all-hours - Emergency Animal Disease Hotline on 1800 675 888.
Information for Veterinarians for pigs
The virus is primarily spread by mosquitoes feeding on infected animals and does not usually spread between animals (i.e. it is not considered contagious). Certain types of mosquitoes, such as Culex sp., can become infected with and transmit JEV. These mosquitoes are generally most active at dawn and dusk.
Infected pigs 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’ hosts and cannot transmit the disease back to mosquitoes.
Generally, JEV is spread through the movement of infected mosquitoes, often over long distances due to wind dispersal, and the movement of some water birds such as herons and egrets. While water birds can carry the virus, they are not affected by it.
Adult non-pregnant sows typically show no obvious signs of infection. However, if sows are infected before 60–70 days of pregnancy, reproductive failure may be evident, which can present as:
- an increase in stillborn, mummified or weak piglets
- piglets born with obvious deformities or abnormalities
- neurologically affected piglets trembling, shaking, or making paddling motions
- increased abortions
- over-term sows with delayed farrowing, extending beyond 118 days
If present on farm, infected boars may experience infertility and swollen or inflamed testicles.
What should be collected in the field?
Post-mortem samples from deceased (<12 hours) and euthanised piglets from affected litters
Necropsy 3 aborted/stillborn/neonatal piglets:
- Fresh samples (or frozen) of cerebral cortex or CSF if no tissue, placenta in individual containers, plus another container of pooled tissues from the spleen, heart, lung, liver and kidney.
- Fixed samples from one (1) piglet (i.e. not from mummified foetuses): brain, cervical spinal cord, lung, heart, liver, kidney and placenta.
Undertake the investigation, complete the RODE forms (PDF - 384.1 KB) as described and follow the sample submission guidelines in the Significant Disease Investigation Guide – Pigs
Download:
- Significant Disease Investigation Guide - Pigs (PDF - 897.7 KB)
- Significant Disease Investigation Guide - Pigs- accessible (WORD - 900.0 KB)
Be aware of this and other potential zoonoses – collect samples carefully and wear appropriate PPE including gloves, eye protection and a mask. The danger during sample collection is from splash or stick injuries.
Submitting samples and reports
Veterinary Diagnostic Services
AgriBio Specimen reception
Main loading dock
5 Ring Rd
La Trobe University
Bundoora 3083
Phone: (03) 9032 7515
Email: vet.diagnostics@agriculture.vic.gov.au.
If the samples return a negative result at this initial stage, you will be contacted by Agriculture Victoria staff.
Positive samples may go to the CSIRO Australian Centre for Disease Preparedness for further testing which may take several weeks.
There are 2 ways to protect yourself: avoiding mosquito bites and vaccination.
The Department of Health recommends people protect themselves and their families against mosquito-borne diseases:
- Wear long, loose fitting clothes outdoors.
- Use effective mosquito repellents containing picaridin or DEET on all exposed skin.
- Try to limit outdoor activity if lots of mosquitoes are about.
- Use ‘knockdown’ fly sprays and plug-in repellent devices indoors.
- Mosquito coils can be effective in small outdoor are\as where you gather to sit or eat.
- Make sure your accommodation is mosquito-proof.
- Sleep 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.
- Remove mosquito breeding sites like stagnant water around your property.
- Remember dusk and dawn are when 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, state-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.
More than 99% of JE virus infections are asymptomatic (show no signs of disease). Less than 1% of people infected with JE virus develop clinical disease.
A small number of people infected with JE virus may become seriously ill with encephalitis.
Symptoms of human 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.
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.
Vaccines for horses and 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.
No, the movement of horses, pigs, pig semen, people, feed trucks or other vehicles will not be impacted by a detection of JE.
Download the Information for Veterinarians for pigs (PDF - 266.4 KB)