Research

Landscape, demographic, entomological, and climatic associations with human incidence of West Nile virus in the state of Iowa, USA

John P DeGroote , Ramanathan Sugumaran , Sarah M Brend , Brad J Tucker and Lyric C Bartholomay

International Journal of Health Geographics 2008, 7:19doi:10.1186/1476-072X-7-19

Published:	1 May 2008

Abstract (provisional)

Background

West Nile virus (WNV) emerged as a threat to public and veterinary health in the Midwest United States in 2001 and continues to cause significant morbidity and mortality annually. To investigate biotic and abiotic factors associated with disease incidence, cases of reported human disease caused by West Nile virus (WNV) in the state of Iowa were aggregated by census block groups in Iowa for the years 2002-2006. Spatially explicit data on landscape, demographic, and climatic conditions were collated and analyzed by census block groups. Statistical tests of differences between means and distributions of landscape, demographic, and climatic conditions for census block groups with and without WNV incidence were carried out. Entomological data from Iowa is considered at the state level to add context to the potential ecological phenomenon taking place.

Results

Numerous statistically significant differences were shown in the means and distributions of various landscape and demographic variables for census block groups with and without WNV incidence. Variables showing differences included stream density, road density, land cover compositions, population density, presence of irrigation, and presence of animal feeding operations. Climatic means and distributions varied in census block groups with or without incidence. Precipitation, dew point, and minimum temperature in year of and for the previous year exhibited statistically significantly different means in at least one year of analysis. However, the differences were not consistent between years.

Conclusions

The analysis of human WNV incidence by census block groups in Iowa demonstrated unique landscape, demographic, and climatic associations. Our results indicate that multiple ecological WNV transmission dynamics are most likely taking place in Iowa. In 2003 and 2006, drier conditions were associated with WNV incidence. Most significantly, rural agricultural settings were shown to be strongly associated with human WNV incidence in Iowa.