15 October 2010
An uncharacteristically wet October means salt marsh mosquito numbers will continue to climb until the end of the month, according to DHF Director of Medical Entomology, Peter Whelan.
"Populations have remained relatively high since a big hatch in late September, but
we're in for an even greater surge in coming days, following the flooding monthly Spring tide which occurred on 9 October," Mr Whelan said.
"Further rain and more Spring tides could cause a further rise in mosquito numbers for extended pest periods from now until January."
Salt marsh mosquitoes can carry the Barmah Forest and Ross River viruses, and Mr Whelan says recent rains and unusually high monthly tides from August to October have increased the risks of mosquitoes carrying these diseases.
"The substantial numbers of salt marsh mosquitoes this season means enormous numbers of eggs in the breeding sites. Flooding tides and rain cause massive egg hatches, followed by the emergence of huge numbers of adult mosquitoes 9 days later. Large mosquito numbers, combined with humid conditions, means many mosquitoes will have an extended life of up to two or more weeks. This will substantially increase the probability of mosquito borne disease, and areas on the north coast are expected to be worst affected," Mr Whelan said.
DHF is therefore reminding people to guard against bites by covering up, using DEET-based repellents and avoiding breeding areas such as tidal creeks and brackish swamps.
Extensive aerial spraying of a bacteria-based insecticide has been undertaken over large areas of Leanyer, Holmes Jungle and Mickett's Creek swamps from August to October.
Other Darwin areas were treated with slow release mosquito hormone pellets or briquettes.
"Such large hatches over extensive areas all around the north coast will cause severe pest problems, including around Darwin. We expect that the very large breeding areas around Shoal Bay between 5 km and 20 km from the northern suburbs, including Howard Swamp, will result in influxes of salt marsh mosquitoes into many urban areas, despite all of our control operations near to urban areas," Mr Whelan said.
Areas where mosquitoes are expected to be most prevalent are:
Darwin:
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Palmerston:
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Rural Area:
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Tidal Floodplains:
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Inland Areas:
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The rest of the Northern Territory can expect elevated numbers of mosquitoes within 10 km to 20 km of large brackish swamps and the larger tidal creeks and rivers.
Mr Whelan says people infected with Ross River or Barmah Forest virus may develop a wide range of symptoms, the most common of which are:
- painful or swollen joints (particularly in the hands, ankles and knees)
- sore muscles
- aching tendons
- skin rash
- fatigue
- fever
- headache
- swollen lymph nodes
"Symptoms generally last for a few weeks to months, although in some cases they can linger for up to 12 months," Mr Whelan said.
Protectionagainst bites is the best course of action as there is no vaccine to prevent Ross River or Barmah Forest virus disease.
People in the Top End experiencing mosquito pest problems are advised to:
- avoid locations near coastal swamps and mangrove areas;
- avoid outdoor exposure around dusk and at night near areas of dense vegetation and other areas of high mosquito activity;
- reduce outdoor activity in the evening and at night if mosquitoes are present;
- use mosquito-proof accommodation and camping facilities at night;
- wear light coloured clothing with long sleeves, long trousers and socks between dusk and dawn in areas where mosquito bites are likely;
- use a protective repellent containing 20% DEET or Picaridin as a supplement to
protective clothing when outdoors at night in areas of mosquito activity;
- use mosquito coils, mosquito lanterns, and barrier sprays containing bifenthrin in patio and outdoor areas near houses;
- ensure children and animals are adequately protected against mosquito bites
Media Contact: Bridget Wild 89 992 751, 0401 116 144
