Spatio-temporal cluster analysis of county-based human West Nile virus incidence in the continental United States

<p>Abstract</p> <p>Background</p> <p>West Nile virus (WNV) is a vector-borne illness that can severely affect human health. After introduction on the East Coast in 1999, the virus quickly spread and became established across the continental United States. However, there have been significant variations in levels of human WNV incidence spatially and temporally. In order to quantify these variations, we used Kulldorff's spatial scan statistic and Anselin's Local Moran's I statistic to uncover spatial clustering of human WNV incidence at the county level in the continental United States from 2002–2008. These two methods were applied with varying analysis thresholds in order to evaluate sensitivity of clusters identified.</p> <p>Results</p> <p>The spatial scan and Local Moran's I statistics revealed several consistent, important clusters or hot-spots with significant year-to-year variation. In 2002, before the pathogen had spread throughout the country, there were significant regional clusters in the upper Midwest and in Louisiana and Mississippi. The largest and most consistent area of clustering throughout the study period was in the Northern Great Plains region including large portions of Nebraska, South Dakota, and North Dakota, and significant sections of Colorado, Wyoming, and Montana. In 2006, a very strong cluster centered in southwest Idaho was prominent. Both the spatial scan statistic and the Local Moran's I statistic were sensitive to the choice of input parameters.</p> <p>Conclusion</p> <p>Significant spatial clustering of human WNV incidence has been demonstrated in the continental United States from 2002–2008. The two techniques were not always consistent in the location and size of clusters identified. Although there was significant inter-annual variation, consistent areas of clustering, with the most persistent and evident being in the Northern Great Plains, were demonstrated. Given the wide variety of mosquito species responsible and the environmental conditions they require, further spatio-temporal clustering analyses on a regional level is warranted.</p

Ecological Niche Modeling of Potential West Nile Virus Vector Mosquito Species in Iowa

Ecological niche modeling (ENM) algorithms, Maximum Entropy Species Distribution Modeling (Maxent) and Genetic Algorithm for Rule-set Prediction (GARP), were used to develop models in Iowa for three species of mosquito — two significant, extant West Nile virus (WNV) vectors (Culex pipiens L and Culex tarsalis Coquillett (Diptera: Culicidae)), and the nuisance mosquito, Aedes vexans Meigen (Diptera: Culicidae), a potential WNV bridge vector. Occurrence data for the three mosquito species from a state-wide arbovirus surveillance program were used in combination with climatic and landscape layers. Maxent successfully created more appropriate niche models with greater accuracy than GARP. The three Maxent species' models were combined and the average values were statistically compared to human WNV incidence at the census block group level. The results showed that the Maxent-modeled species' niches averaged together were a useful indicator of WNV human incidence in the state of Iowa. This simple method for creating probability distribution maps proved useful for understanding WNV dynamics and could be applied to the study of other vector-borne diseases

Landscape, demographic and climatic associations with human West Nile virus occurrence regionally in 2012 in the United States of America

After several years of low West Nile virus (WNV) occurrence in the United States of America (USA), 2012 witnessed large outbreaks in several parts of the country. In order to understand the outbreak dynamics, spatial clustering and landscape, demographic and climatic associations with WNV occurrence were investigated at a regional level in the USA. Previous research has demonstrated that there are a handful of prominent WNV mosquito vectors with varying ecological requirements responsible for WNV transmission in the USA. Published range maps of these important vectors were georeferenced and used to define eight functional ecological regions in the coterminous USA. The number of human WNV cases and human populations by county were attained in order to calculate a WNV rate for each county in 2012. Additionally, a binary value (high/low) was calculated for each county based on whether the county WNV rate was above or below the rate for the region it fell in. Global Moran’s I and Anselin Local Moran’s I statistics of spatial association were used per region to examine and visualize clustering of the WNV rate and the high/low rating. Spatial data on landscape, demographic and climatic variables were compiled and derived from a variety of sources and then investigated in relation to human WNV using both Spearman rho correlation coefficients and Poisson regression models. Findings demonstrated significant spatial clustering of WNV and substantial inter-regional differences in relationships between WNV occurrence and landscape, demographic and climatically related variables. The regional associations were consistent with the ecologies of the dominant vectors for those regions. The large outbreak in the Southeast region was preceded by higher than normal winter and spring precipitation followed by dry and hot conditions in the summer

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

<p>Abstract</p> <p>Background</p> <p>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 variables for census block groups with and without WNV disease incidence were carried out. Entomological data from Iowa were considered at the state level to add context to the potential ecological events taking place.</p> <p>Results</p> <p>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 disease incidence. Census block groups with WNV disease incidence had significantly lower population densities than those without. Landscape variables showing differences included stream density, road density, land cover compositions, presence of irrigation, and presence of animal feeding operations. Statistically significant differences in the annual means of precipitations, dew point, and minimum temperature for both the year of WNV disease incidence and the prior year, were detected in at least one year of the analysis for each parameter. However, the differences were not consistent between years.</p> <p>Conclusion</p> <p>The analysis of human WNV disease 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 disease incidence. In a significant novel finding, rural agricultural settings were shown to be strongly associated with human WNV disease incidence in Iowa.</p

A Biodiverse Rich Environment Does Not Contribute to a Better Diet: A Case Study from DR Congo

The potential of biodiversity to increase and sustain nutrition security is increasingly recognized by the international research community. To date however, dietary assessment studies that have assessed how biodiversity actually contributes to human diets are virtually absent. This study measured the contribution of wild edible plants (WEP) to the dietary quality in the high biodiverse context of DR Congo. The habitual dietary intake was estimated from 2 multiple-pass 24 h dietary recalls for 363 urban and 129 rural women. All WEP were collected during previous ethnobotanical investigations and identified and deposited in the National Botanical Garden of Belgium (BR). Results showed that in a high biodiverse region with precarious food security, WEP are insufficiently consumed to increase nutrition security or dietary adequacy. The highest contribution came from Dacryodes edulis in the village sample contributing 4.8% of total energy intake. Considering the nutrient composition of the many WEP available in the region and known by the indigenous populations, the potential to increase nutrition security is vast. Additional research regarding the dietary contribution of agricultural biodiversity and the nutrient composition of WEP would allow to integrate them into appropriate dietary guidelines for the region and pave the way to domesticate the most interesting WEP

The Development, Evaluation, and Utilization of a Coupled ArcPRZM3 Pesticide Modeling System

A closely-coupled system comprised of PRZM-3 and Arc View has been developed. A windows version of PRZM3 (Visual PRZM3) was developed using the Visual Basic programming language and development software. Visual PRZM3 can be a stand-alone program or used in conjunction with two Arc View extensions that were created. The advantages of this system include: Visual PRZM3 allows for easy data entry and running of the standard PRZM3 model; Visual PRZM3 connections to a Microsoft Access database that contains chemical, crop, soil and other data tables which helps provide user-assistance for input parameterization; Database also stores all simulation scenarios, which allows for easily running the model numerous times after a small number of input changes; Arc View extensions allow pre-processing, in vector or raster environment, of soils, DEM, and land cover data into a format that can be used for batch processing in Visual PRZM3; Visual PRZM3 can be run in batch processing mode using input table developed with created Arc View extensions; Outputs from Visual PRZM3 batch processing can be post-processed with Arc View extensions for representation in tables, graphs, and maps. This is one of the first fully automated coupled GIS-solute transport modeling systems and greatly simplifies the process of simulating pesticide fate on a watershed or county scale. This closely-coupled system has the potential to be used for the spatial modeling of pesticide fate in the environment for various applications such as land use planning, regulatory agency management of pesticides, watershed water quality protection, and registration of pesticides.United States Department of Agriculture and the University of Wisconsin System Agriculture/Natural Resources Consortium. Funding was provided by USDA-NRI grant #96-35102-3774

Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USA-2

Alysis distance. The values above 2.0 represent statistically significant hot-spots while below -2.0 are statistically significant cold-spots. The majority of census block groups fall in the statistically insignificant middle categories.<p><b>Copyright information:</b></p><p>Taken from "Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USA"</p><p>http://www.ij-healthgeographics.com/content/7/1/19</p><p>International Journal of Health Geographics 2008;7():19-19.</p><p>Published online 1 May 2008</p><p>PMCID:PMC2396613.</p><p></p

Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USA-0

Alysis distance. The values above 2.0 represent statistically significant hot-spots while below -2.0 are statistically significant cold-spots. The majority of census block groups fall in the statistically insignificant middle categories.<p><b>Copyright information:</b></p><p>Taken from "Landscape, demographic, entomological, and climatic associations with human disease incidence of West Nile virus in the state of Iowa, USA"</p><p>http://www.ij-healthgeographics.com/content/7/1/19</p><p>International Journal of Health Geographics 2008;7():19-19.</p><p>Published online 1 May 2008</p><p>PMCID:PMC2396613.</p><p></p