16 February 2017

Biting insect and mosquito-borne disease risk increase across Western Australia

The Department of Health is warning residents and travellers to take precautions against biting insects following the widespread rainfall and recent flooding events across Western Australia.

Managing Scientist Environmental Health Hazards, Dr Michael Lindsay said the wet weather and flooding had created ideal conditions for breeding of mosquitoes and other biting insects across much of WA.

“While local government mosquito management programs are in place around WA, it is not realistic or logistically feasible to keep mosquitoes and biting flies below nuisance levels when such vast areas of the State are affected with the recent weather conditions,” Dr Lindsay said.

“Increased mosquito activity is likely to result in an increased risk of the mosquito-borne diseases Ross River virus (RRV), Barmah Forest virus (BFV), Murray Valley encephalitis virus (MVEV) and Kunjin virus (KUNV) in some parts of WA.”

Symptoms of infection with RRV and BFV include painful or swollen joints, sore muscles, skin rashes, fever, fatigue and headaches.

The warning comes as KUNV was recently detected in a sentinel chicken flock in the Pilbara. KUNV belongs to the same group of viruses as MVEV, both of which can only be transmitted by mosquitoes and are more common in northern regions of WA.

Dr Lindsay said for most people, disease caused by MVEV and KUNV had fairly mild symptoms such as headache, fever, aching, swollen joints and rash. However, in rare cases these viruses, especially MVEV, can lead to a serious inflammation of the brain and result in long term disability or even death.

“There are no specific cures or vaccines for mosquito-borne diseases in Western Australia, so it is very important that people take care to prevent being bitten,” he said.

An increase in the number of March flies has also been reported in the Pilbara region. At least one species of March fly, known to occur in parts of the Pilbara and northern Goldfields, has a bite that can cause serious allergic reactions in some people.

"Although March flies are not known to transmit diseases to humans in Australia, the bites of some species can cause allergic reactions, including skin redness and swelling. In rare cases, people may also experience serious symptoms such as hives, fever, wheezing and even anaphylaxis which requires urgent medical attention," Dr Lindsay said.

People living or travelling throughout Western Australia do not need to change their travel plans but should take extra precautions to avoid being bitten by mosquitoes and flies, including:

  • avoiding outdoor exposure particularly around dawn and dusk (and the first few hours after dark)
  • wearing protective (long, loose-fitting, light coloured) clothing when outdoors
  • applying a personal repellent containing 20 per cent diethyl toluamide (DEET) or picaridin to exposed skin or clothing. The most effective and long-lasting formulations are lotions or gels. Natural or organic repellents may not be as effective as DEET or picaridin, or may need to be reapplied more frequently
  • wearing head nets if outdoors
  • ensuring insect screens are installed and in good condition – the use of bed nets when sleeping will offer further protection
  • using mosquito nets or mosquito-proof tents when camping or sleeping outdoors
  • ensuring infants and children are adequately protected against biting insects, preferably with suitable clothing, bed nets or other forms of insect screening.

The recent rainfall is also a timely reminder for residents to minimise mosquito breeding around the home by taking some simple steps to remove or modify breeding sites such as:

  • disposing of all containers which hold water
  • stocking ornamental ponds with fish and keeping vegetation away from the water’s edge
  • keeping swimming pools well chlorinated, filtered and free of dead leaves
  • filling or draining depressions in the ground that hold water
  • fitting mosquito proof covers to vent pipes on septic tank systems and sealing all gaps around the lid and ensure leach drains are completely covered
  • screening rainwater tanks with insect proof mesh, including inlet, overflow and inspection ports
  • ensuring guttering does not hold water
  • emptying pot plant drip trays once a week or fill them with sand
  • emptying and cleaning animal and pet drinking water bowls once a week.

For more information on how to prevent mosquito bites visit: http://healthywa.wa.gov.au/fightthebite


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