HIGHER MOSQUITO-BORNE DISEASE RISK IN ANTHROPOGENICALLY MODIFIED ENVIRONMENTS IN THE KAPITI COAST REGION, NEW ZEALAND.

Abstract

The recent worldwide spread of disease-vector mosquitoes is a serious threat to public health. The ‘emergence’ and ‘re-emergence’ of some major arboviral diseases (eg. Dengue Fever virus and Ross River virus) in recent decades have been linked to the flow-on effects of anthropogenic environmental change on the physical structure and biodiversity of mosquito larval habitats. Although New Zealand has so far remained free from arboviral human diseases an eventual outbreak is very probable in the long term. Four exotic disease vector species have already become well established in New Zealand. Escalating international travel and commerce may introduce more exotic disease vectors as well as disease-infected people, which both exotic and native species may ingest from. To predict how anthropogenic environmental change alters the risk of exposure to disease-vector mosquitoes we need an intimate knowledge of the ecology and biology of species currently in New Zealand. The overarching aim of this paper is to compare the effects of different land uses on the productivity of container breeding species in the Kapiti Coast region, New Zealand. In 2002–03, disease-vector mosquito productivity was examined in artificial containers and other resident water bodies in three land use types, farmland, suburban area and native bush, at three sites in the Kapiti Coast region. Additionally, nutrient and shade levels were experimentally manipulated in mosquito container habitats placed in native bush to approximate the effects of deforestation and agriculture on larval populations. In the field survey, suburban and farmland sites had lower resident biodiversity and substantially higher numbers of disease-vector mosquitoes than native bush sites. Disease-vector mosquitoes also colonised experimental containers in an open, non-forested environment with medium to high nutrient additions more quickly and in greater numbers than in containers under a forest canopy with low or ultra high nutrient levels. These results suggest that modified environments have increased mosquito-borne disease risk from invading species, and that ecosystem integrity in the form of aquatic macro-invertebrate biodiversity may play a fundamental role in protecting against arboviral introduction and spread.