Overview: Japanese Encephalitis Virus (JEV) is a mosquito-borne virus affecting pigs, horses, and waterbirds. It has been established on the Australian mainland, though risks vary by season and local factors. Pigs play a key role as amplifying hosts, meaning they develop a level of the virus in their blood that allows mosquitoes to further spread the infection.
How JEV Spreads:
- Transmission:
JEV is transmitted via bites from infected mosquitoes. The virus circulates between waterbirds and mosquitoes and can spill over to pigs, humans, and other animals. Pigs develop enough of the virus in their bloodstream to infect more mosquitoes when bitten, perpetuating the cycle. - Risk to Humans:
While pigs are important in the spread of the virus, humans can also be infected via mosquito bites. Most human infections are asymptomatic, but severe cases can lead to neurological complications like fever, headache, convulsions, and, in some cases, coma.
Symptoms in Pigs:
- Sows:
- Abortion
- Stillbirths (at term or delayed)
- Mummified piglets
- Delayed farrowing
- Increased return rates after mating
- Piglets:
- Inability to stand or suck
- Birth abnormalities (e.g., deformed limbs, oedema, or reduced/absent brain tissue)
- Growing Pigs (up to 6 months):
- Neurological signs such as tremors or uncoordinated movements.
- Boars:
- Abnormal sperm production
- Infertility
- Testicular inflammation
Prevention and Control:
Mosquito Control:
Reducing the mosquito population on your farm is crucial in preventing the spread of JEV. Effective measures include:
- Inspect bodies of water and containers for mosquito larvae.
- Remove or cover any water-holding containers around the property.
- Fill in areas where water tends to collect.
- Clear gutters, downpipes, and drains to prevent water from pooling.
- Trim overhanging branches where mosquitoes may rest.
- Ensure proper drainage of effluent and that it doesn’t pool.
- Seal water containers with mesh screens.
Pig Management:
- Minimize pigs’ exposure to mosquitoes by improving housing and using mosquito nets/screens.
- Ensure your farm’s biosecurity practices include mosquito control, which is now a requirement under the Australian Pig Industry Quality Assurance (APIQ) program.
Vaccination and Treatment:
- Currently, no vaccine for JEV is available for pigs in Australia.
- There is no specific treatment for infected pigs; therefore, prevention through mosquito control remains the most effective strategy.
Reporting Suspected JEV Cases:
Japanese Encephalitis is a notifiable disease in South Australia. If you suspect JEV in pigs, contact your veterinarian or the Emergency Animal Disease Hotline at 1800 675 888. Your veterinarian can advise on subsidized testing options with PIRSA (Primary Industries and Regions SA).
Impact on Humans:
Although humans cannot contract JEV directly from pigs, infected mosquitoes can transmit the virus. While most human infections are mild, some cases can result in serious complications, including neurological damage. If you experience symptoms like fever or disorientation after potential mosquito exposure, seek immediate medical advice.
For more information, visit the PIRSA Japanese Encephalitis Virus resource page.
This fact sheet provides vital information for pig owners regarding the risks, symptoms, and prevention methods for Japanese Encephalitis Virus. Stay vigilant and prioritize mosquito control to protect your animals and farm.
