High salt marsh mosquito numbers increase Ross River virus risk

The Top End Health Service is urging people to protect themselves from salt marsh mosquitoes, as they can transmit the Ross River virus (RRV). High mosquito numbers in NT coastal areas are expected to persist from 6 December 2019 for around 10 days.

Director of Medical Entomology, Nina Kurucz, said that despite more than 140 hectares of salt marsh mosquito breeding area aerially sprayed in the swamps close to the northern Darwin suburbs extensive ground control in Darwin and Palmerston urban areas, high numbers of these mosquitoes will make their way into the suburbs and rural areas from outside the control areas. Once on the wing, these mosquitoes can fly up to 50km. Further significant rain is also expected to cause subsequent hatches of these mosquitoes over the festive season.

The poor 2018-19 wet season has led to extensive favourable breeding sites available for these mosquitoes, enabling them to lay eggs in areas of moist mud usually not available during normal wet seasons. High tides in late October 2019 have already led to record salt marsh mosquito numbers and there will be countless eggs again all hatching simultaneously following inundation by the high November 2019 tide.

Due to the humidity, the salt marsh mosquitoes now survive long enough to be able to transmit the RRV, a debilitating disease characterised by painful swollen joints.

“This means people need to take precautions to avoid being bitten and avoid getting the virus,” Ms Kurucz said.

NT residents are also encouraged to empty out all water holding containers including pot plant drip trays, tyres, buckets in their backyards, as mosquitoes breeding in those places can also transmit the RRV.

To avoid being bitten Top Enders are advised to:

  • avoid locations near coastal swamps and mangrove areas
  • use mosquito-proof accommodation and camping facilities at night
  • wear light-coloured clothing with long sleeves, long trousers and socks, especially between dusk and dawn in areas where mosquito bites are likely
  • use a protective repellent containing 20 per cent DEET or Picaridin as a supplement to protective clothing, with creams providing best protection
  • use mosquito coils, mosquito lanterns, and barrier sprays in patio and outdoor areas near houses
  • ensure children and animals are adequately protected against mosquito bites.

A salt marsh mosquito pest calendar is available on the Medical Entomology website.

Source: NT Government