Japanese encephalitis (JE) is a rare but serious disease caused by the Japanese encephalitis virus (JEV). The virus is transmitted to humans by infected mosquitoes and is more common in areas of increased mosquito activity.

JEV has been detected in commercial piggeries in Southern, Western and New England areas of NSW, and in Queensland, Victoria and South Australia.

How it is spread

JEV is spread by the bite of infected Culex mosquitoes which are commonly found in NSW. Mosquitoes can become infected with the virus from biting infected animals such as pigs and some species of waterbirds.

The virus cannot be transmitted from human to human, by touching an infected animal or by eating animal products including pork or poultry products.

Who is at risk

The risk of exposure is highest among people who work or live near piggeries which have tested positive for JEV. Workers who work in close contact with pigs and/or are exposed to mosquitoes may be more at risk of infection unless they have been vaccinated for Japanese encephalitis or have prior immunity. This may include:

  • Piggery workers and farmers
  • Pork abattoir and rendering plant workers
  • Pig transport workers
  • Veterinary personnel including veterinarians, vet nurses and students
  • Mosquito and animal surveillance, control and management workers such as environmental health officers and entomologists
  • Laboratory workers who work with specimens and virus cultures

People who engage in outdoor activities near significant mosquito populations, particularly near waterways (such as wetlands and national parks) in areas where JEV has been detected, are also at high risk.

Symptoms and treatment

Most JEV infections are asymptomatic - less than 1% of people infected will experience symptoms which typically include fever and headache. Occasionally JEV can cause severe illness with symptoms such as neck stiffness, disorientation, tremors, coma and seizures. Among those who develop severe infection, some will experience permanent neurological complications and death. Where symptoms do occur, they will usually develop 5 to 15 days after being bitten by infected mosquitoes.

There is no specific treatment available for Japanese encephalitis. If you believe you may be infected with the virus, seek urgent medical assistance.

Managing the risk of exposure

If your workers carry out work in an area where JEV is known to be present, it is unlikely that eliminating the risk of exposure to the virus will be reasonably practicable. This means that a PCBU must minimise the risk so far as is reasonably practicable.

Japanese encephalitis can be prevented by receiving a vaccination for the virus and by avoiding being bitten by mosquitos. A PCBU must apply a risk management approach to determine the control measures implemented at the workplace to minimise the risk of JEV infection for workers.

Vaccination

SafeWork NSW considers vaccination a high order risk control measure against vaccine-preventable disease. Where available, vaccination should be considered as part of a broader range of control measures to minimise exposure to disease so far as is reasonably practicable.

A safe and effective vaccine for Japanese encephalitis is available in Australia. Vaccination is currently recommended for those at the highest risk of infection. The Communicable Disease Network of Australia (CDNA) has identified groups for priority vaccination including people with direct exposure or close proximity to pigs and mosquitos and high-level occupational exposures.

Avoid mosquito bites

Vaccinated people should still use precautions to avoid mosquito bites. Mosquitoes that transmit JEV are most active during dawn and dusk and into the evening. Control measures to prevent mosquito bites may include a combination of environmental and personal protective controls such as:

Environmental controls

  • eliminate mosquito breeding sites around the workplace where possible, including removing any debris which may collect standing water
  • prevent mosquito entry at the workplace by closing windows, doors, vents and other entrances or covering them with insect screens
  • use insecticide sprays, vapour dispensing units (indoors) and mosquito coils (outdoors) to clear rooms or repel mosquitoes from an area.

Personal protective controls

  • protect workers and others at the workplace from being bitten by mosquitoes by:
    • ensuring they wear long, light-coloured, loose-fitting clothing and covered footwear when outside to minimise skin exposure,
    • providing an effective insect repellent (such as those containing diethyltoluamide (DEET), picaridin, or oil of lemon eucalyptus) and ensure that it is applied correctly on exposed skin. Always check the label for reapplication times. Repellent may need to be reapplied more frequently during hot weather and after strenuous activity and perspiration as the duration of protection is reduced at these times.
    • ensuring any accommodation provided, including tents, is properly fitted with mosquito netting or screens.

Administrative controls

  • provide information to workers on the risks and symptoms of Japanese encephalitis, and train workers in the use of controls including any personal protective equipment and repellents.

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