Japanese Encephalitis Detected in Pilbara Region

The Department of Health is sending an additional mosquito surveillance team to the Pilbara after evidence of Japanese encephalitis virus (JEV) was detected in the region.

Residents and travellers in the north of Western Australia are being urged to avoid being outside at peak times of mosquito activity, apply an effective mosquito repellent and wear long, loose-fitting clothing to avoid being bitten.

Recent JEV activity has now been identified in both the Pilbara and Kimberley through the Department’s sentinel chicken surveillance program, which acts as an early warning system for mosquito-borne virus disease.

The most recent positive sample was collected in February 2023 from a chicken flock in Newman in the east Pilbara, indicating infection occurred in the past two months.

JEV is transmitted through the bite of an infected mosquito and can cause Japanese encephalitis (JE) in humans.

Department of Health’s Senior Medical Advisor, Communicable Disease Control, Dr Jelena Maticevic said JEV activity in the Pilbara was new and represented a significant risk to human health.

“This is the first time evidence of JEV has been found in the Pilbara but follows on from recent evidence of JEV in the Kimberley. Combined, these results indicate ongoing risk of JEV infection in the northern part of the state,” Dr Maticevic said.

“Most people infected will have no or very mild symptoms and will fully recover, however, a small percentage develop severe illness including an encephalitis (brain inflammation), which can lead to serious complications and death.”

“Anyone who develops a sudden onset of fever, headache, vomiting, seizures or disorientation should seek urgent medical attention.”

There have been 45 human cases of the mosquito-borne disease JE reported in Australia since January 2021, from New South Wales, Queensland, South Australia, Victoria and the Northern Territory. Sadly, seven people have died.

There have been no cases of JE reported in people in WA to date.

Children under five years of age and older people who are infected with JEV are at a higher risk of developing more severe illness.

“JE is a vaccine-preventable disease in people, and the Department of Health is currently working to expand eligibility of the JE vaccination program to residents of highest risk areas,” Dr Maticevic.

“Avoiding mosquito bites will also protect against other mosquito-borne diseases for which there is no vaccine, including Murray Valley encephalitis.”

The Department of Health has recently detected widespread evidence of Murray Valley encephalitis and Kunjin virus activity in the Kimberley and Pilbara regions.

The Department of Health continues to undertake enhanced surveillance for mosquito-borne viruses across the State.

Mosquitoes may carry viruses that can make people seriously ill. Fight the Bite – take the following simple steps to avoid being bitten:

  • Cover up while outside – Wear loose, long-sleeved, light-coloured clothing, particularly at dawn and dusk when mosquitoes are most active.
  • Ensure infants and children are adequately protected against mosquito bites, preferably with suitable clothing, shoes/socks, bed nets or other forms of insect screening.
  • Apply mosquito repellent, containing picaridin, DEET or oil of lemon eucalyptus (OLE – also known as PMD), evenly to all areas of exposed skin. Read the instructions to find out how often to reapply repellent.
  • Mosquito wristbands and patches are not recommended as there is no evidence that these provide good protection against mosquito bites.
  • Avoid outdoor exposure, particularly at dawn and early evening.

Limit the number of mosquitoes in and around homes by:

  • Cutting grass often and keeping it short to minimise mosquitoes seeking shelter around homes.
  • Removing water holding containers from around the home and garden to ensure mosquitoes do not breed in backyards.
  • Ensuring insect screens are installed and in good condition on houses and caravans.
  • Using mosquito nets and mosquito-proof tents if sleeping outside.
  • Using mosquito coils and mosquito lanterns.
  • Applying a residual surface spray (containing bifenthrin) to outdoor walls, patios etc where mosquitoes might land – this will kill them. These products can be purchased from hardware stores.

JEV is a nationally notifiable disease in both humans and animals.

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