Friday, 15 February 2013

GIS describes links between Ross River virus and mosquito wetlands

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mosquito RRVCompared with an urban region to the south, there was a different relationship between RRV disease incidence and proximity to saltmarsh mosquito habitat observed east of the Leschenault Estuary. Image: USP HospitalesLIVING close to the eastern margins of the Leschenault inlet increases your risk of contracting Ross River virus (RRV) says new research.

RRV is a mosquito-borne disease that occurs throughout many areas of Australia. Activity of RRV is largely dependent on environmental conditions favouring mosquito breeding.

Unusually wet conditions in late spring and early summer can lead to large numbers of mosquito vectors of RRV on the South West coast.

Despite this, residential developments continue to be built close to wetlands.

New research has investigated the relationship between risk of RRV infection and proximity to mosquito-breeding habitat, using the Leschenault Estuary as a case study.

It is the first study in Australia to use GIS to examine the links between risk of mosquito-borne disease and proximity of residence to known mosquito-breeding habitat.

Department of Health Lead researcher Dr Michael Lindsay says “opportunities for such studies are limited by availability of reliable data about time and place of exposure of a statistically significant number of patients with confirmed infection”.

Geographic information systems (GIS) were used to map historical RRV case data from the Leschenault region during one of the largest outbreaks in WA, between July 1995 and June 1996.

Half kilometre buffer zones were constructed around the Leschenault Estuary and associated waterways. RRV disease case counts were then calculated for each zone.

Compared with an urban region to the south, there was a different relationship between RRV disease incidence and proximity to saltmarsh mosquito habitat observed east of the Leschenault Estuary.

Disease incidence showed a decreasing trend away from the eastern margins of the Estuary, particularly for the first two kilometres.

In the urban region, RRV disease risk was low close to the Estuary, but increased further out and remained steady across the remainder of that region.

Lack of disease in Bunbury area may reflect mosquito breeding habitat that has disappeared due to construction of the harbour says Dr Lindsay.

Dr Lindsay says he wasn't entirely surprised at the results but that it was important to formally test what has until recently only been perceived 'clustering' of RRV disease cases in residential areas close to known mosquito breeding habitat.

“The results of the study provide robust evidence that mosquito management considerations should be part of land-use planning considerations in areas with high mosquito-borne disease risk.”

The study further highlights how historical data combined with GIS, can improve understanding of the epidemiology of RRV disease says Dr Lindsay.

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