Land Cover Variation and West Nile Virus Prevalence: Patterns, Processes, and Implications for Disease Control

Abstract

Identifying links between environmental variables and infectious disease risk is essential to understanding how human-induced environmental changes will effect the dynamics of human and wildlife diseases. Although land cover change has often been tied to spatial variation in disease occurrence, the underlying factors driving the correlations are often unknown, limiting the applicability of these results for disease prevention and control. In this study, we described associations between land cover composition and West Nile virus (WNV) infection prevalence, and investigated three potential processes accounting for observed patterns: (1) variation in vector density; (2) variation in amplification host abundance; and (3) variation in host community composition. Interestingly, we found that WNV infection rates among Culex mosquitoes declined with increasing wetland cover, but wetland area was not significantly associated with either vector density or amplification host abundance. By contrast, wetland area was strongly correlated with host community composition, and model comparisons suggested that this factor accounted, at least partially, for the observed effect of wetland area on WNV infection risk. Our results suggest that preserving large wetland areas, and by extension, intact wetland bird communities, may represent a valuable ecosystem-based approach for controlling WNV outbreaks.

Meteorological Conditions Associated with Increased Incidence of West Nile Virus Disease in the United States, 2004–2012

“…Among these are seasonal shifts in mosquito feeding preferences from amplifying bird hosts to humans after birds have migrated 42 or differences in land use that impact bird reservoir community composition or viral prevalence. [52][53][54][55] Enzootic transmission of the virus can be decreased if mosquitoes feed on low reservoir-competent avian hosts 56 or by herd immunity in the bird population. 57 Others have documented the impact of human behavior and interventions on WNV incidence patterns such as mosquito control, neglected swimming pools that provide mosquito breeding habitat, or having water-holding containers in the backyard.…”

Regional Differences in the Association Between Land Cover and West Nile Virus Disease Incidence in Humans in the United States

“…Numerous studies have reported associations between different land cover types and WNV disease incidence in humans, [3][4][5][6] seroprevalence or infection rates in birds 7 and wild and domesticated mammals, [8][9][10] and infection rates in mosquitoes. 11,12 However, the strength and direction of these correlations have varied considerably. For instance, both positive 6 and negative 9 associations with crop land cover were reported in the South Central state of Texas.…”

Deforestation and avian infectious diseases

“…Indeed, a recent study reported a lower incidence of human WNV in counties of the United States that have greater avian (viral host) diversity (Swaddle and Calos, 2008). Similarly, infection rates of mosquitoes with WNV have been shown to be inversely correlated with the species richness of non-passerine birds and wetland cover (Ezenwa et al, 2006;Ezenwa et al, 2007). However, another study in the Chicago area suggests that other factors such as variation in mosquito host preference, reservoir host competence, temperature and precipitation, may be more important than species richness in predicting the spread of WNV (Loss et al, 2009).…”