First detection of Japanese encephalitis in Victorian pigs

Biosecurity Alert issued 27 February 2022 by Chief Veterinary Officer, Victoria

Japanese encephalitis (JE) has been confirmed for the first time in Victoria in a piggery in northern Victoria. There have also been concurrent detections in pigs in New South Wales and Queensland.

Japanese encephalitis is an acute mosquito-borne viral disease that can cause reproductive losses and encephalitis in susceptible species. Disease occurs most commonly in pigs and horses but can also, rarely, cause disease in other animals. It is caused by a flavivirus, Japanese Encephalitis virus.

Animals and people become infected through the bite of infected mosquitoes. The disease is maintained and spread through transmission cycles between mosquitoes (Culex, Aedes and Anopheles genera) and some wild and domestic bird species and pigs.

Clinical signs of JE in animals

In pigs the most common clinical signs are 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. Piglets infected after birth can develop encephalitis (paddling, other neurological signs) in the first six months of life. In other cases, wasting, depression or hindlimb paralysis may be seen in suckling piglets and weaner piglets. Adult sows do not typically show overt signs of disease, and boars, if present on farm, may experience infertility and oedematous, congested testicles.

In horses many cases are asymptomatic and most clinical disease is mild; however, more severe encephalitis can occur which may be fatal. Signs include fever, jaundice, lethargy, anorexia and neurological signs which vary with severity of the clinical disease. Neurological signs can include incoordination, difficulty swallowing and impaired vision; and, rarely, a hyperexcitable form occurs. Disease has also been reported in donkeys.

Reports of disease in other species are rare.

Japanese Encephalitis virus in people

Japanese Encephalitis virus (JEV) is transmitted to humans through infected mosquitoes. Most JEV infections in people are asymptomatic. However, encephalitis is the most serious clinical consequence of JEV infection. The best protection is to avoid mosquito bites by using mosquito repellent containing picaridin or DEET on all exposed skin; wearing long, loose fitting clothing when outside; and ensuring that accommodation, including tents, is properly fitted with mosquito nettings or screens.

People experiencing symptoms should seek medical advice and contact the Communicable Disease Prevention unit at the Department of Health on 1300 651 160 (24 hours).

Actions to take if you suspect Japanese Encephalitis in your animals

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

For information related to public health, please visit the Victorian Department of Health website ( or Better Health Channel on Viral encephalitis.

Further reading and more information