Constructed wetlands and mosquitoes: Health hazards and management options- An Australian perspective

Constructed wetlands are increasingly being installed to 'polish' urban dra inage and storm water by reducing contaminants before disposal into river s ystems. Unfortunately, they also provide habitat for mosquitoes that can be nuisance pests and transmit pathogens such as arboviruses and malaria. In Australia, Ross River virus is responsible for thousands of cases annually of a disease that is severely debilitating, has regional incidence rates of ten exceeding 1:1000, and costs millions of dollars in health and other imp acts. Disease transmission depends on mosquito species and abundance, and e xtent of contact with humans; the characteristics and siting of wetlands de termine hazards, and indicate risks for nuisance or disease. Mosquito contr ol should not rely solely on chemical and biological agents. Design of wetl ands is important: shallow water and dense vegetation promote mosquito prod uction. Deeper habitats with cleaner steeper margins, and more open water, produce fewer mosquitoes. Water and vegetation management can reduce mosqui toes: aeration and sprinkler systems, and flooding and drainage regimes, ca n reduce larval densities; vegetation thinning can assist mosquito predator s. Such measures may appear incompatible with objectives and operations of wetlands, but mosquito management must be an integral objective of modern w etland design and maintenance in order to minimise health hazards. (C) 1999 Elsevier Science B.V. All rights reserved.