MOSQUITO-BORNE DISEASE AND MOSQUITO MANAGEMENT IN AUSTRALIA FOR THE OLYMPIC GAMES IN THE YEAR 2000

Abstract:
Mosquito-borne disease is an increasing concern in Australia. Endemic malaria has been eradicated but up to 1,000 infections are imported annually and local cases occur occasionally in the northeast, where local Dengue infections are reported annually and Japanese encephalitis virus has been introduced and caused deaths. Murray Valley encephalitis virus and/or Kunjin virus are active almost annually in the northwest and there are occasional human cases. Barmah Forest virus is increasing in distribution and activity with hundreds of cases recorded each year. Overall, Ross River virus is the most important pathogen, being active annually throughout the country and almost 40,000 cases reported for 1991-1998 with an increasing number of urban infections in all states. Provision of irrigation for agriculture, conservation of natural wetlands and construction of treatment wetlands, and development of residential areas near wetlands, have provided for increased contact between mosquitoes and humans in urban areas, and increased risk of disease. Management of mosquitoes is not well established or organised overall for urban communities, although there are examples of authorities being effective with individual or cooperative efforts using environmental and pesticide methodologies. There has been a concern for mosquitoes and mosquito-borne disease posing a threat for the Olympic and Paralympic Games to be held in Sydney in 2000. There is a perceived threat of exotic pathogens being imported with international visitors arriving for the Games and being transmitted by local mosquitoes. The site for the Games is being developed at Homebush Bay, Sydney, and the new sporting venues and residential areas are relatively close to extensive saline wetlands that are known to produce significant populations of pest mosquitoes and are being conserved for various environmental reasons. Local freshwater wetlands are also being enhanced, and constructed wetlands for water storage and treatment are being established at the site. The local mosquitoes have been intensively studied in recent years. There are important pest and vector species, such as Aedes vigilax and Culex sitiens in saline habitats, and Culex annulirostris and Coquillettidia linealis in freshwater habitats, and the period of greatest pest mosquito activity is from December through April. Restoration of tidal flushing in the mangroves, and runnelling the saltmarshes, will reduce numbers of saline mosquitoes. Appropriate design, water and vegetation management, and predatory fish, will mean the freshwater wetlands will produce fewer mosquitoes. Pesticide use will be minimised, with biorational agents such as Bacillus thuringiensis israelensis and methoprene preferred. The Olympic/Paralympic Games will be held in September/October 2000, prior to the pest mosquito ‘season’ in Sydney, and thus few mosquitoes should be evident. Additionally, although there is little evidence that humans acquire mosquito-borne disease in metropolitan Sydney, the arbovirus season in coastal regions of the state is January through May. There should be little or no concern for mosquitoes or mosquito-borne disease during the Games. Continuing recreational and residential use of the area beyond 2000 will require a commitment to continuing mosquito management at the site.