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Posted May 2009

The University of Sydney’s Richard Russell has contested claims that climate change will greatly increase mosquito-borne diseases in Australia.

The professor of medical entomology says the claims, based on the impacts of rising temperatures, fail to adequately consider other implications of climate change and factors about the diseases, how they are spread and the ability of health services to deal with new infections.

He argues that while warmer temperatures might be expected to increase mosquito numbers, reduced rainfall in many areas could reduce the insect’s breeding habitat. Lower humidity may also shorten mosquito lifespans, compromising the incubation and development of the malarial pathogen.

The greatest threat could in fact come from increased numbers of travellers and refugees from countries with high levels of malaria transmission. However, Russell considers the possibility of malaria re-establishing itself in Australia (it was declared eradicated in 1981) low because our health services are good enough to deal with new infections.

“The appropriate maintenance of these health services is the critical issue for questions of increased malaria risk – not whether climate warming will bring minor extensions of the receptive zone or the distribution of vectors,” he says.

Russell argues there is little value in broad area models for the Ross River and Barmah Forest viruses under climate change because both encompass too much environmental and biological variability that vary disease epidemiologies at local and regional scales.

It is also questionable whether dengue fever will spread because of climate change, he argues. A more serious issue is the recent establishment of the exotic mosquito Aedes albopictus on many of the Torres Strait islands. It is a known secondary vector of dengue (and a potential carrier of other viruses) and is far more tolerant of temperate climates. It could spread dengue to all the southern Australian states, and its spread could be exacerbated by climate change.

“Overall, it is likely there might be some increases in mosquito-borne disease in Australia with a warming climate, but with which mosquitoes and which pathogens, and where and when, cannot be easily discerned,” Russell concludes.

References
Russell R. 2009. Mosquito-borne disease and climate change in Australia: time for a reality check. Australian Journal of Entomology 48: 1-7.