Outbreaks of Japanese encephalitis virus (JEV) have been reported in piggeries in Queensland, New South Wales, Victoria and South Australia. This is the first time the virus has been detected in southern Australia.
Japanese encephalitis is a viral zoonotic disease that is spread by mosquitoes. Waterbirds act as natural reservoirs for the virus, and mosquitos can spread the virus to people, horses, pigs and other animals.
People and horses are considered ‘dead end’ hosts - once infected, they do not play a role in transmitting the virus. Pigs and some species of wild birds are amplifying hosts.
In animals, signs of disease are most common in horses and pigs. Other animals can be infected
but typically do not show signs of illness, these include cattle, sheep, goats, dogs, cats, bats, rodents, reptiles, amphibians, and birds.
Reporting requirements
Horse owners need to be alert to signs of this disease. Japanese encephalitis is a nationally notifiable disease, which means it must be reported to a veterinarian or biosecurity authority.
To report, call the national Emergency Animal Disease Watch Hotline on 1800 675 888. This number will put you in contact with the biosecurity authority in your state or territory.
Horses
In horses, many cases are subclinical, meaning they are infected but show no signs of disease. Most clinical disease is mild, however, more severe encephalitis can occur, which may be fatal.
Signs of disease include an elevated temperature, jaundice, lethargy, anorexia and neurological signs, which can vary in severity. Neurological signs can include incoordination, difficulty swallowing, impaired vision, and rarely the horse becomes over excited.
While reports of the disease in other species are rare, overseas the disease has been reported in donkeys.
Preventative measures
Rugging and hooding horses with a lightweight summer rug and fly mask can help protect against mosquito bites.
Where available, stabling horses between dusk and dawn may also be beneficial. For horses not stabled overnight, rugging and hooding with lightweight permethrin fabric may help protect them.
If the horse allows, apply a safe insect repellent. To apply the repellent to the horse’s face and ears, spray it onto a cloth and rub it on, avoiding around and above the eyes.
Human health advice
Most Japanese encephalitis virus infections in people are asymptomatic, however, those with severe infection (which occurs in less than one per cent of cases) may experience neck stiffness, coma, and more rarely, permanent neurological complications or death.
Encephalitis is the most serious clinical consequence of infection.
Illness usually begins with symptoms such as sudden onset of fever, headache and vomiting.
People should also try to prevent mosquito bites by using a mosquito repellent containing picaridin, DEET or oil of lemon eucalyptus on all exposed skin and reapply every few hours; wear long, light coloured and loose-fitting clothes; and covered footwear.
Government response
The Australian, state and territory governments are working with the pig and horse industries through the Consultative Committee on Emergency Animal Diseases in response to this outbreak. We are also working closely with human health authorities.
There are no movement restrictions currently in place for horses moving within an Australian state or territory, or interstate. Horses being exported from Australia must meet the conditions set by the importing country.
The response strategy for this disease is outlined in the Japanese encephalitis AUSVETPLAN.
Further information is available at outbreak.gov.au including links to AUSVETPLAN, and your state or territory department of agriculture or primary industries.