Japanese encephalitis

Japanese encephalitis (JE) 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 cannot transmit the Japanese encephalitis virus (JEV).

The Department of Industry, Tourism and Trade is currently supporting the NT Health response to JEV by undertaking surveillance in animals and testing at the Berrimah Veterinary Laboratory. There is preliminary evidence to suggest that the virus is present in the Territory, and people should remain vigilant to protect themselves from mosquitoes and manage the risk to their animals.

Horse health

Horses can be infected but show no signs of the disease. Most of the time the disease is mild, however more severe JE can occur which may be fatal.

Signs of the disease can include:

• high temperature
• jaundice
• lethargy
• anorexia
• neurological signs including incoordination, difficulty swallowing, impaired vision, and rarely the horse becomes over excited.

Prevention measures for horses

Rugging horses with a lightweight summer rug and fly mask can help protect against mosquito bites. If possible, stabling horses between dusk and dawn may also reduce the risk of the horses being affected. Horse owners can also apply a safe insect repellent to reduce the risk. The Australian horse industry is currently working to secure access to a JE virus vaccine for horses. More information and further updates are available at outbreak.gov.au

Pig health

Most infections with JE are subclinical. This means they do not show signs. Clinical disease in animals is most commonly associated with pigs and horses.

Symptoms in pigs include:

• mummified and still born piglets
• weak piglet and some with neurological signs.

Piglets infected after birth can develop encephalitis (paddling, other neurological signs) in the first 6 months of life. In other cases, wasting, depression or hind limb paralysis may be seen in suckling piglets and weaner pigs.

Adult sows do not typically show sign of the disease. However boars may experience infertility, oedematous and congested testicles.

Prevention measure for pig owners

The best prevention is to have a mosquito management plan in place.

This could involve a range of methods as seen below:

• reduce mosquito breeding sites
• treat larvae and adults
• remove water lying around to reduce breeding areas for mosquitos
• inspect water filled containers for mosquito larvae and empty to reduce mosquito numbers
• chemical residues in pork is trade and food quality risk
• do not use chemicals that are not registered for use on pigs, pig feed, surfaces or the potential for chemical to drift onto pigs
• spray or fog sheds with approved insecticide.

Japanese encephalitis is a nationally notifiable disease. This means it must be reported to a veterinarian or biosecurity authority. To report, call the Emergency Animal Disease Watch Hotline on 1800 675 888.

More information about JE in animals can be found on DITT’s website: nt.gov.au/japanese-encephalitis

Northern Territory animal biosecurity measures for JE

The Department of Industry, Tourism and Trade has been running a free, voluntary testing program for pig keepers who have registered their animals through the property identification code (PIC) system.

Horse owners and livestock producers with animals registered through the PIC system have also been contacted by the department about JE detections in the Territory.

If you are interested in taking part in this program, contact your local biosecurity office. DITT’s website has the details for your nearest livestock biosecurity staff and local registered vet.

Additional information about the testing process  is also available online.

Human health

Most Japanese encephalitis virus infections in people are asymptomatic, however, on rare occasions severe infection can happen (which occurs in less than one per cent of cases). It usually takes 5 to 15 days between getting bitten and becoming unwell.

Symptoms include:

• headache
• vomiting
• fever
• neck stiffness
• coma
• more rarely, permanent neurological complications or death.

If you believe you may be infected with the Japanese encephalitis virus, seek urgent medical assistance.

Prevention

There are two safe and effective vaccines for Japanese encephalitis available in Australia which are recommended to be used for:

• travellers spending time in Asia
• all residents (aged  one year and over) living on the outer islands of Torres Strait
• anyone working in the outer areas of the Torres Strait for 30 days or more especially during the wet season
• travellers spending a month or more in rural areas of:
  • Papua New Guinea
  • East Timor
  • Asia

Other preventive measures include avoiding mosquito bites by:

• staying away from areas with an abundance of mosquitos that are close to wet lands where birds and feral pigs may be present
• wearing protective light-coloured, loose fitting, clothing outdoors
• sleeping in a mosquito proof tent if camping
• using insect repellent containing DEET, picaridin or oil of lemon eucalypt.

Treatment

There are no treatments for Japanese encephalitis. You can relieve the symptoms by:

• getting plenty of rest
• drinking plenty of fluids
• taking paracetamol for pain or fever.

In more severe cases, hospitalisation for supportive care and close observation may be required.

More information on human health can be found on the NT Health website: https://nt.gov.au/wellbeing/health-conditions-treatments/viral/japanese-encephalitis

More information

For national updates on JE in animals, head to the Australian Government’s biosecurity website: https://www.outbreak.gov.au/

To get more information about how to ensure you have good biosecurity measures in place on your property, go to: https://www.farmbiosecurity.com.au/