Demographic and Spatial Analysis of West Nile Virus and St. Louis Encephalitis in Houston, Texas

Abstract

This descriptive prevalence study describes the relationships between mosquito density and the presence of arboviruses (in mosquitoes and humans) with various socioeconomic and environmental factors present near the time of teh arbovirus outbreak in Harris County, Texas, in 2002. This study suggests that mosquito density increased if the trap was located in an area with a large number of containers that may inadvertently retain rainwater (P = 0.056). When considering only virus-positive mosquitoes, significant relationships were observed if the trap was located near waste materials (P < 0.001) or near containers that may inadvertently retain rainwater (P = 0.037). Furthermore, the presence of arbovirus activity (in mosquitoes or humans) in a geographic area tended to be associated with the socioeconomic status of the local community. Although the results of socioeconomic comparisons were not significant, they were suggestive, demonstrating an interesting trend. Compared with communities where virus activity was not observed, the socioeconomic status of the arbovirus-positive community was consistently lower. Specifically, results showed that the populations residing in virus-positive census tracts attained less education, earned less income per household, and were more likely to be below the poverty level. In addition, this study found that virus-positive mosquitoes were randomly distributed throughout the study area, whereas severe human infection cases were clustered. Based on the results of this study, we conclude that the health outcome of a local community as it relates to West Nile virus and St. Louis encephalitis is dependent on many factors, including eh socioeconomic and environmental characteristics of the community.

Socioeconomic Status Affects Mosquito (Diptera: Culicidae) Larval Habitat Type Availability and Infestation Level

“…Urban aquatic habitats generally have higher ambient temperatures than forested or pastural areas, which can favor mosquito production in cities (Leisnham et al 2006). Within urban areas, socioeconomic factors can be associated with mosquito infestation and mosquito-borne disease (e.g., Reisen et al 1990, Braks et al 2003, Rios et al 2006, Honó rio et al 2009, Reisen et al 2009, Harrigan et al 2010. Additionally, much research has been devoted to the identiÞcation of "key container" types that produce high pupae densities, and therefore serve as a focus of elimination efforts (e.g., TunÐLin et al 1995, Kay et al 2008, Richards et al 2008, BartlettÐ Healy et al 2012.…”

“…In the United States, higher abundance of adult mosquitoes (e.g., Reisen et al 1990 and prevalence of West Nile virus (WNV) and Saint Louis encephalitis viruses (e.g., Rios et al 2006, Reisen et al 2009, Harrigan et al 2010) have been associated with socioeconomic status (SES), but the underlying ecological factors for variation in mosquito infestation are not well understood. Differences in larval microhabitat abundance, type, and quality can all contribute to differences in the production of adult mosquitoes, and in residential areas, these could vary with SES.…”

Entomologic Investigations during an Outbreak of West Nile Virus Disease in Maricopa County, Arizona, 2010

“…8,9 In Suffolk County, NY, disease risk was also associated with middle class suburban neighborhoods, but not with population age, 10 and in Harris County, TX (metropolitan Houston), and Orange County CA, south of Los Angeles, WNV disease risk was highest in low-income areas. 11,12 Our control area most closely resembles an older, inner suburban residential area, and the outbreak area comprises newer, more affluent outer suburban neighborhoods. The precise behavioral and ecologic correlates that led to increased disease risk in the above studies are not well understood.…”

Temporal and spatial alterations in mutant swarm size of St. Louis encephalitis virus in mosquito hosts

“…West Nile virus invaded Texas and California in 2002 and 2003, respectively (Reisen et al, 2004; Lillibridge et al, 2004). Interestingly, WNV has appeared to displace SLEV in California yet the two continue to coexist in Texas (Rios et al, 2006; Reisen et al, 2008). The combination of the close antigenic relationship and the sharing of transmission cycles by WNV and SLEV make their interaction inevitable.…”

“…In addition, over 75 mosquito species have been demonstrated to become infected with WNV (Higgs et al, 2004), although Culex mosquitoes are implicated as the predominant vectors of both viruses (Bernard and Kramer, 2001; Reisen, 2003). In recent years, WNV has appeared to displace SLEV in California (Reisen et al, 2008), yet both viruses currently coexist in Texas (Lillibridge et al, 2004; Bradford et al, 2005; Rios et al, 2006). Previous studies demonstrate that WNV strains exist as highly diverse mutant swarms in nature and that the source of this genetic diversity is likely the mosquito (Jerzak et al, 2005).…”