Creating a disease risk map for West Nile virus for surveillance in Central Texas using a Geographic Information System and Remote Sensing technologies

Authors: Zindler, Catherine; OLSON, JIMMY - TEXAS A&M UNIVERSITY

Submitted to: Journal of Vector Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 11/19/2008
Publication Date: N/A
Citation: N/A

Interpretive Summary: West Nile is a disease transmitted by mosquitoes that mainly effects birds, but can cross over into human populations. After the West Nile virus was detected in Brazos County Texas, mosquito researchers at Texas A&M University established a program to collect mosquitoes and test them for the West Nile virus to determine where the virus was located in the county. In 2004, a map of Brazos County was created showing the land divided into different areas or risk zones depending on how likely it is that a human will get bit by a mosquito and get West Nile. This was done by using a computer program called a Geographic Information System to describe and organize the habitats where sick and dead birds were found that were most likely infected with West Nile virus. The habitat elements common to all the locations where the sick and dead birds were found were used to make the risk zones on the map. Those habitat elements were amount of sewer drains, amount of vegetation, creeks and areas that flood. When and where the sick and dead birds were reported was also mapped so the movement of the West Nile virus could be determined. To confirm that this West Nile disease risk map did a good job of showing high risk areas, the locations where West Nile virus infected mosquitoes had been found for four years and where humans who got West Nile virus in 2003 lived, where plotted on the map. This study shows that it is possible to create a useful and accurate disease risk map by showing landscape elements associated with suspected cases of the disease.

Technical Abstract: Following the discovery of the West Nile virus (WNv) in Brazos County, TX in 2002, mosquito research personnel at Texas A&M University established a routine WNv mosquito vector surveillance program in the county. In 2004, a map of Brazos County was created depicting areas that had a heightened level of risk of humans contracting WNv. Locations of sick and dead birds reported to the county health department in 2003 known for their high susceptibility to the WNv were analyzed to determine with which habitat elements they were associated. Using a Geographic Information System and Remote Sensing technologies, habitat elements that had a high association with reported sick and dead bird sites were determined to be density of manhole covers, vegetative index, creeks and flood zones. The time period and locations when and where sick and dead birds were reported in 2003 were also analyzed to depict the movement or spread of the virus over the year. Four years later, validation of the WNv risk map was confirmed by plotting the locations of positive mosquitoes collected from 2003 to 2007 and the 2003 human cases. This study shows that it is possible to create a useful and accurate disease risk map by depicting landscape elements associated with unconfirmed epizootic data.