Ecological correlates of risk and incidence of West Nile virus in the United States

Department of Biology, Washington University, One Brookings Drive, Campus Box 1137, Saint Louis, MO, 63130, USA.
Oecologia (Impact Factor: 3.25). 11/2009; 158(4):699-708. DOI: 10.1007/s00442-008-1169-9
Source: PubMed

ABSTRACT West Nile virus, which was recently introduced to North America, is a mosquito-borne pathogen that infects a wide range of vertebrate hosts, including humans. Several species of birds appear to be the primary reservoir hosts, whereas other bird species, as well as other vertebrate species, can be infected but are less competent reservoirs. One hypothesis regarding the transmission dynamics of West Nile virus suggests that high bird diversity reduces West Nile virus transmission because mosquito blood-meals are distributed across a wide range of bird species, many of which have low reservoir competence. One mechanism by which this hypothesis can operate is that high-diversity bird communities might have lower community-competence, defined as the sum of the product of each species' abundance and its reservoir competence index value. Additional hypotheses posit that West Nile virus transmission will be reduced when either: (1) abundance of mosquito vectors is low; or (2) human population density is low. We assessed these hypotheses at two spatial scales: a regional scale near Saint Louis, MO, and a national scale (continental USA). We found that prevalence of West Nile virus infection in mosquito vectors and in humans increased with decreasing bird diversity and with increasing reservoir competence of the bird community. Our results suggest that conservation of avian diversity might help ameliorate the current West Nile virus epidemic in the USA.

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Available from: Larry Clark, Jul 30, 2015
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    • "The dilution effect hypothesis predicts that greater host diversity should result in lesser disease incidence (Ostfeld and Keesing 2000). This has been shown for WNV and nonpasserine diversity (Ezenwa et al. 2006, Allan et al. 2009) because nonpasserines tend to be poor WNV hosts (Komar et al. 2003, Blitvich 2008). Our dataset contains a large number of meals from Cooper's Hawks and Mourning Doves, which as Accipitriformes and Columbiformes, respectively , are poor hosts of WNV (Komar et al. 2003). "
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    ABSTRACT: Abstract Arboviral activity tracks vector availability, which in temperate regions means that transmission ceases during the winter and must be restarted each spring. In the northeastern United States, Culex restuans Theobald resumes its activity earlier than Culex pipiens L. and is thought to be important in restarting West Nile virus (WNV) transmission. Its role in WNV amplification, however, is unclear, because viral levels commonly remain low until the rise of Cx. pipiens later in the season. Because a vector's feeding habits can reveal key information about disease transmission, we identified early-season (April-June) blood meals from Cx. restuans collected throughout New Jersey, and compared them to published datasets from later in the season and also from other parts of the country. We found significantly higher avian diversity, including poor WNV hosts, and fewer blood meals derived from American Robins (17% versus over 40% found in later season). Critically, we identified blood meals from significantly more female than male birds in species where females are the incubating sex, suggesting that Cx. restuans is able to feed on such a wide variety of hosts in early spring because incubating birds are easy targets. Because WNV amplification depends on virus consistently reaching competent hosts, our results indicate that Cx. restuans is unlikely to be an amplifying vector of WNV in the early season. As the season progresses, however, changes in the availability of nesting birds may make it just as capable as Cx. pipiens, although at somewhat lower abundance as the summer progresses.
    Vector Borne and Zoonotic Diseases 04/2014; 14(6):447-453. DOI:10.1089/vbz.2013.1536
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    • "In Utah's Great Basin Desert, pinyon mice (Peromyscus truei) appear to reduce hantavirus antibody prevalence , whereas kangaroo rats (Dipodomys ordii) seem to increase hantavirus antibody prevalence (Clay et al. 2009), and in Montana, estimated Sin Nombre antibody prevalence in deer mice was reduced in the presence of voles (Microtus spp.), although vole abundance was not important (Carver et al. 2011). At a larger spatial scale, some studies have demonstrated negative correlations between measures of diversity and disease, for example, human WNV incidence at the county level negatively correlated with data from breeding bird atlases or surveys (Ezenwa et al. 2006; Swaddle & Calos 2008; Allan et al. 2009). In contrast, mammal diversity at a global scale has been linked to increased likelihood of emerging zoonotic pathogens (Jones et al. 2008). "
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    ABSTRACT: Zoonotic pathogens are significant burdens on global public health. Because they are transmitted to humans from non-human animals, the transmission dynamics of zoonoses are necessarily influenced by the ecology of their animal hosts and vectors. The 'dilution effect' proposes that increased species diversity reduces disease risk, suggesting that conservation and public health initiatives can work synergistically to improve human health and wildlife biodiversity. However, the meta-analysis that we present here indicates a weak and highly heterogeneous relationship between host biodiversity and disease. Our results suggest that disease risk is more likely a local phenomenon that relies on the specific composition of reservoir hosts and vectors, and their ecology, rather than patterns of species biodiversity.
    Ecology Letters 03/2013; 16. DOI:10.1111/ele.12101
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    • "This association has been shown also for a number of animal and human viruses (e.g. Langlois et al. 2001; Allan et al. 2009; Olson et al. 2010; Rabaa et al. 2010). Consequently, the relationships between landscape heterogeneity and virus epidemiology described here illustrates a phenomenon relevant for pathology at large. "
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    ABSTRACT: Knowledge on how landscape heterogeneity shapes host-parasite interactions is central to understand the emergence, dynamics and evolution of infectious diseases. However, this is an underexplored subject, particularly for plant-virus systems. Here, we analyse how landscape heterogeneity influences the prevalence, spatial genetic structure, and temporal dynamics of Pepper golden mosaic and Pepper huasteco yellow vein begomoviruses infecting populations of the wild pepper Capsicum annuum glabriusculum (chiltepin) in Mexico. Environmental heterogeneity occurred at different nested spatial scales (host populations within biogeographical provinces), with levels of human management varying among host population within a province. Results indicate that landscape heterogeneity affects the epidemiology and genetic structure of chiltepin-infecting begomoviruses in a scale-specific manner, probably related to conditions favouring the viruses' whitefly vector and its dispersion. Increased levels of human management of the host populations were associated with higher virus prevalence and erased the spatial genetic structure of the virus populations. Also, environmental heterogeneity similarly shaped the spatial genetic structures of host and viruses. This resulted in the congruence between host and virus phylogenies, which does not seem to be due to host-virus co-evolution. Thus, results provide evidence of the key role of landscape heterogeneity in determining plant-virus interactions.
    Molecular Ecology 02/2013; 22(8). DOI:10.1111/mec.12232
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