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United States Articles found through PubMed 2000-2012

Description

West Nile Virus (WNV) is a mosquito-borne virus that can infect humans. Originally known in East Africa, WNV has now spread throughout the world. The first case of WNV in the western hemisphere was identified in New York in 1999, and within 5 years the disease had spread throughout the United States and into Canada, Latin America, and the Caribbean. While most of WNV infections cause no symptoms, the remaining cases show flu-like symptoms, and can lead to neurological disease or death.

latest article added on November 2013

ArticleFirst AuthorPublished
Temporal and Spatial Patterns of West Nile Virus Transmission in Saginaw County, Michigan, 2003-2006Chuang, Ting-Wu2011

Temporal and Spatial Patterns of West Nile Virus Transmission in Saginaw County, Michigan, 2003-2006

Keywords

West Nile virus, Aedes vexans, Culex pipiens, Culex restuans, sentinel pheasants, WNV

Abstract

The dynamics of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection in mosquitoes, sentinel pheasants, and wild dead birds were evaluated during 2003–2006 in Saginaw Co., MI. Mosquitoes were collected by New Jersey Light Traps at 22 sites during May–September, pooled by species and sample location, and tested for presence of WNV RNA by using a real-time reverse transcription-polymerase chain reaction assay. Oral swabs from wild dead birds submitted by the public were tested by Vec-Test assay. Sentinel pheasants were bled weekly, and serum was tested for antibodies with an inhibition enzyme immunoassay. In total, 37,225 mosquitoes [Aedes vexans (Meigen), Culex pipiens L., and Culex restuans Theobald] were tested in 5,429 pools, of which 59 (1.1%) were positive. Ae. vexans was most abundant but had a comparatively low infection rate (0.06–2.11) compared with Cx. pipiens (1.75–4.59) and Cx. restuans (1.22–15.67). Mosquito abundances were temporally related to variations in 2-wk average weather variables. Infected dead crows appeared earlier each transmission season than blue jays, but infection prevalence for both peaked approximately mid-August. Space-time clusters were found in different locations each year. Sentinel pheasant seroprevalence was 19.3% (16/83), 12.7% (10/79), and 7.7% (5/65) during 2003–2005, respectively. We demonstrated temporal patterns of WNV activity in corvid birds and Culex spp. mosquitoes during the study period, suggesting virus transmission within an enzootic cycle. Despite the absence of human case reports nearby, this surveillance system demonstrated WNV transmission and possible human risk. Maintained surveillance using more appropriate gravid traps and CDC CO2 light traps could improve sensitivity of vector collection and virus detection.

Authors

Chuang, Ting-Wu, Knepper, Randall G., Stanuszek, William W., Walker, Edward D. and Wilson, Mark L.

Year Published

2011

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10138

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21936324

Surveillance for West Nile Virus and Vaccination of Free-Ranging Island Scrub-Jays ( Aphelocoma insularis ) on Santa Cruz Island, California BOYCE, WALTER M.2011

Surveillance for West Nile Virus and Vaccination of Free-Ranging Island Scrub-Jays ( Aphelocoma insularis ) on Santa Cruz Island, California

Keywords

WNV

Abstract

Abstract Transmission of West Nile virus (WNV) on mainland California poses an ongoing threat to the island scrub-jay (ISSJ, Aphelocoma insularis), a species that occurs only on Santa Cruz Island, California, and whose total population numbers 750 migrating and resident birds on the island from 2006 to 2009 indicated that WNV had not become established by the end of 2009. Several species of competent mosquito vectors were collected at very low abundance on the island, including the important mainland vectors Culex tarsalis and Culex quinquefasciatus. However, the island was generally cooler than areas of mainland California that experienced intense WNV transmission, and these lower temperatures may have reduced the likelihood of WNV becoming established because they do not support efficient virus replication in mosquitoes. A vaccination program was initiated in 2008 to create a rescue population of ISSJ that would be more likely to survive a catastrophic outbreak. To further that goal, we recommend managers vaccinate >100 ISSJ each year as part of ongoing research and monitoring efforts.

Authors

BOYCE, WALTER M., Vickers, Winston, Morrison, Scott A., Sillett, T. Scott, Caldwell, Luke, Wheeler, Sarah S., Barker, Christopher M., Cummings, Robert and Reisen, William K.

Year Published

2011

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2010.0171

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21438695

Weather and Land Cover Influences on Mosquito Populations in Sioux Falls, South DakotaChuang, Ting-Wu2011

Weather and Land Cover Influences on Mosquito Populations in Sioux Falls, South Dakota

Keywords

West Nile virus, Culex tarsalis, Aedes vexans, weather, land cover, WNV

Abstract

This study compared the spatial and temporal patterns of Culex tarsalis Coquillett and Aedes vexans Meigen populations and examined their relationships with land cover types and climatic variability in Sioux Falls, SD. Between 24 and 30 CDC CO2-baited light traps were set annually in Sioux Falls from May to September 2005–2008. Land cover data were acquired from the 2001 National Land Cover Dataset and the percentages of selected land cover types were calculated within a 600-m buffer zone around each trap. Meteorological information was summarized from local weather stations. Cx. tarsalis exhibited stronger spatial autocorrelation than Ae. vexans. Land cover analysis indicated that Cx. tarsalis was positively correlated with grass/hay, and Ae. vexans was positively correlated with wetlands. No associations were identified between irrigation and the host-seeking population of each species. Higher temperature in the current week and 2 wk prior and higher precipitation 3–4 wk before collection of host-seeking adult mosquitoes had positive influences on Cx. tarsalis abundance. Temperature in the current week and rainfall 2–3 wk before sampling had positive influences on Ae. vexans abundance. This study revealed the different influences of weather and land cover on important mosquito species in the Northern Great Plains region, which can be used to improve local vector control strategies and West Nile virus prevention efforts.

Authors

Chuang, Ting-Wu, Hildreth, Michael B., Vanroekel, Denise L. and Wimberly, Michael C.

Year Published

2011

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10246

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21661329

Meteorological and Hydrological Influences on the Spatial and Temporal Prevalence of West Nile Virus in Culex Mosquitoes, Suffolk County, New YorkShaman, Jeffrey2011

Meteorological and Hydrological Influences on the Spatial and Temporal Prevalence of West Nile Virus in Culex Mosquitoes, Suffolk County, New York

Keywords

West Nile virus, hydrology, meteorology, transmission, amplification, WNV

Abstract

The factors determining the spatial and temporal distribution of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) activity are not well understood. Here, we explore the effects of hydrological and meteorological conditions on WNV infection among Culex genus mosquitoes collected during 2001–2009 in Suffolk County, Long Island, NY. We show that WNV infection rates in assayed pools of Culex mosquitoes are associated in both space and time with hydrological and meteorological variability. Specifically, wet winter, warm and wet spring conditions, and dry summer conditions are associated with the increased local prevalence of WNV among Culex mosquitoes during summer and fall. These findings indicate that within Suffolk County, and for a given year, areas at risk for heightened WNV activity may be identified in advance by using hydrology model estimates of land surface wetness and observed meteorological conditions.

Authors

Shaman, Jeffrey, Harding, Kerri and Campbell, Scott R.

Year Published

2011

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10269

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21845947

Predictive Mapping of Human Risk for West Nile Virus (WNV) Based on Environmental and Socioeconomic FactorsRochlin, Ilia2011

Predictive Mapping of Human Risk for West Nile Virus (WNV) Based on Environmental and Socioeconomic Factors

Keywords

WNV

Abstract

A West Nile virus (WNV) human risk map was developed for Suffolk County, New York utilizing a case-control approach to explore the association between the risk of vector-borne WNV and habitat, landscape, virus activity, and socioeconomic variables derived from publically available datasets. Results of logistic regression modeling for the time period between 2000 and 2004 revealed that higher proportion of population with college education, increased habitat fragmentation, and proximity to WNV positive mosquito pools were strongly associated with WNV human risk. Similar to previous investigations from north-central US, this study identified middle class suburban neighborhoods as the areas with the highest WNV human risk. These results contrast with similar studies from the southern and western US, where the highest WNV risk was associated with low income areas. This discrepancy may be due to regional differences in vector ecology, urban environment, or human behavior. Geographic Information Systems (GIS) analytical tools were used to integrate the risk factors in the 2000-2004 logistic regression model generating WNV human risk map. In 2005-2010, 41 out of 46 (89%) of WNV human cases occurred either inside of (30 cases) or in close proximity (11 cases) to the WNV high risk areas predicted by the 2000-2004 model. The novel approach employed by this study may be implemented by other municipal, local, or state public health agencies to improve geographic risk estimates for vector-borne diseases based on a small number of acute human cases.

Authors

Rochlin, Ilia, Turbow, David, Gomez, Frank, Ninivaggi, Dominick V. and Campbell, Scott R.

Year Published

2011

Publication

PLOS One

Locations
DOI

10.1371/journal.pone.0023280

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21853103

Fine-Scale Variation in Vector Host Use and Force of Infection Drive Localized Patterns of West Nile Virus TransmissionHamer, Gabriel L.2011

Fine-Scale Variation in Vector Host Use and Force of Infection Drive Localized Patterns of West Nile Virus Transmission

Keywords

WNV

Abstract

The influence of host diversity on multi-host pathogen transmission and persistence can be confounded by the large number of species and biological interactions that can characterize many transmission systems. For vector-borne pathogens, the composition of host communities has been hypothesized to affect transmission; however, the specific characteristics of host communities that affect transmission remain largely unknown. We tested the hypothesis that vector host use and force of infection (i.e., the summed number of infectious mosquitoes resulting from feeding upon each vertebrate host within a community of hosts), and not simply host diversity or richness, determine local infection rates of West Nile virus (WNV) in mosquito vectors. In suburban Chicago, Illinois, USA, we estimated community force of infection for West Nile virus using data on Culex pipiens mosquito host selection and WNV vertebrate reservoir competence for each host species in multiple residential and semi-natural study sites. We found host community force of infection interacted with avian diversity to influence WNV infection in Culex mosquitoes across the study area. Two avian species, the American robin (Turdus migratorius) and the house sparrow (Passer domesticus), produced 95.8% of the infectious Cx. pipiens mosquitoes and showed a significant positive association with WNV infection in Culex spp. mosquitoes. Therefore, indices of community structure, such as species diversity or richness, may not be reliable indicators of transmission risk at fine spatial scales in vector-borne disease systems. Rather, robust assessment of local transmission risk should incorporate heterogeneity in vector host feeding and variation in vertebrate reservoir competence at the spatial scale of vector-host interaction.

Authors

Hamer, Gabriel L., Chaves, Luis F., Anderson, Tavis K., Kitron, Uriel D., Brawn, Jeffrey D., Ruiz, Marilyn O., Loss, Scott R., Walker, Edward D. and Goldberg, Tony L.

Year Published

2011

Publication

PLOS One

Locations
DOI

10.1371/journal.pone.0023767

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21886821

Mosquito Host Selection Varies Seasonally with Host Availability and Mosquito DensityThiemann, Tara C.2011

Mosquito Host Selection Varies Seasonally with Host Availability and Mosquito Density

Keywords

WNV

Abstract

Host selection by vector mosquitoes is a critical component of virus proliferation, particularly for viruses such as West Nile (WNV) that are transmitted enzootically to a variety of avian hosts, and tangentially to dead-end hosts such as humans. Culex tarsalis is a principal vector of WNV in rural areas of western North America. Based on previous work, Cx. tarsalis utilizes a variety of avian and mammalian hosts and tends to feed more frequently on mammals in the late summer than during the rest of the year. To further explore this and other temporal changes in host selection, bloodfed females were collected at a rural farmstead and heron nesting site in Northern California from May 2008 through May 2009, and bloodmeal hosts identified using either a microsphere-based array or by sequencing of the mitochondrial cytochrome c oxidase I (COI) gene. Host composition during summer was dominated by four species of nesting Ardeidae. In addition, the site was populated with various passerine species as well as domestic farm animals and humans. When present, Cx. tarsalis fed predominantly (>80%) upon the ardeids, with Black-crowned Night-Herons, a highly competent WNV host, the most prevalent summer host. As the ardeids fledged and left the area and mosquito abundance increased in late summer, Cx. tarsalis feeding shifted to include more mammals, primarily cattle, and a high diversity of avian species. In the winter, Yellow-billed Magpies and House Sparrows were the predominant hosts, and Yellow-billed Magpies and American Robins were fed upon more frequently than expected given their relative abundance. These data demonstrated that host selection was likely based both on host availability and differences in utilization, that the shift of bloodfeeding to include more mammalian hosts was likely the result of both host availability and increased mosquito abundance, and that WNV-competent hosts were fed upon by Cx. tarsalis throughout the year.

Authors

Thiemann, Tara C., Wheeler, Sarah S., Barker, Christopher M. and Reisen, William K.

Year Published

2011

Publication

PLoS Neglected Tropical Diseases

Locations
DOI

10.1371/journal.pntd.0001452

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/22206038

Factors Associated With the Risk of West Nile Virus Among Crows in New York StateDeCarlo, C. H.2011

Factors Associated With the Risk of West Nile Virus Among Crows in New York State

Keywords

WNV

Abstract

West Nile virus (WNV) is transmitted between avian hosts in enzootic cycles by a mosquito vector. The virus has significant disease effects on humans and equines when it bridges into an epizootic cycle. As the initial epidemic of WNV in 1999, perennial outbreaks in New York State suggest the local establishment of natural foci with perpetuation of the virus among susceptible hosts rather than reintroduction of the virus. The factors that play a role in the perpetuation of the virus are not fully understood. American crows (Corvus brachyrhynchos) are known to be highly susceptible to infection with the virus. We investigate the factors that put crows at risk of infection in Tompkins County, New York during the period of 2000-2008 in a case-control study. Cases were crow carcasses that were found dead and tested positive for WNV using real time reverse transcription or VecTest. Data on putative risk factors were collected and assessed for significance of association with the presence of WNV using logistic regression analysis to evaluate the significance of each factor while simultaneously controlling for the effect of others. The risk of a crow carcass testing WNV positive varied with age, season of the year and ecological area where the carcass was found. Crows that were more than 1-year-old were four times more likely to be WNV positive in comparison to birds that were less than 1 year of age. It was three times more likely to find WNV positive carcasses in residential areas in comparison to rural areas. The risk of testing WNV positive did not vary by sex of the crow carcasses.

Authors

DeCarlo, C. H., Clark, A. B., McGowan, K. J., Ziegler, P. E., Glaser, A. L., Szonyi, B. and Mohammed, H. O.

Year Published

2011

Publication

Zoonoses and Public Health

Locations
DOI

10.1111/j.1863-2378.2010.01346.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20707862

Decelerating Spread of West Nile Virus by Percolation in a Heterogeneous Urban LandscapeMagori, Krisztian2011

Decelerating Spread of West Nile Virus by Percolation in a Heterogeneous Urban Landscape

Keywords

WNV

Abstract

Vector-borne diseases are emerging and re-emerging in urban environments throughout the world, presenting an increasing challenge to human health and a major obstacle to development. Currently, more than half of the global population is concentrated in urban environments, which are highly heterogeneous in the extent, degree, and distribution of environmental modifications. Because the prevalence of vector-borne pathogens is so closely coupled to the ecologies of vector and host species, this heterogeneity has the potential to significantly alter the dynamical systems through which pathogens propagate, and also thereby affect the epidemiological patterns of disease at multiple spatial scales. One such pattern is the speed of spread. Whereas standard models hold that pathogens spread as waves with constant or increasing speed, we hypothesized that heterogeneity in urban environments would cause decelerating travelling waves in incipient epidemics. To test this hypothesis, we analysed data on the spread of West Nile virus (WNV) in New York City (NYC), the 1999 epicentre of the North American pandemic, during annual epizootics from 2000-2008. These data show evidence of deceleration in all years studied, consistent with our hypothesis. To further explain these patterns, we developed a spatial model for vector-borne disease transmission in a heterogeneous environment. An emergent property of this model is that deceleration occurs only in the vicinity of a critical point. Geostatistical analysis suggests that NYC may be on the edge of this criticality. Together, these analyses provide the first evidence for the endogenous generation of decelerating travelling waves in an emerging infectious disease. Since the reported deceleration results from the heterogeneity of the environment through which the pathogen percolates, our findings suggest that targeting control at key sites could efficiently prevent pathogen spread to remote susceptible areas or even halt epidemics.

Authors

Magori, Krisztian, Bajwa, Waheed I., Bowden, Sarah and Drake, John M.

Year Published

2011

Publication

PLoS Computational Biology

Locations
DOI

10.1371/journal.pcbi.1002104

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21829332

Host Reproductive Phenology Drives Seasonal Patterns of Host Use in MosquitoesBurkett-Cadena, Nathan D.2011

Host Reproductive Phenology Drives Seasonal Patterns of Host Use in Mosquitoes

Keywords

WNV

Abstract

Seasonal shifts in host use by mosquitoes from birds to mammals drive the timing and intensity of annual epidemics of mosquito-borne viruses, such as West Nile virus, in North America. The biological mechanism underlying these shifts has been a matter of debate, with hypotheses falling into two camps: (1) the shift is driven by changes in host abundance, or (2) the shift is driven by seasonal changes in the foraging behavior of mosquitoes. Here we explored the idea that seasonal changes in host use by mosquitoes are driven by temporal patterns of host reproduction. We investigated the relationship between seasonal patterns of host use by mosquitoes and host reproductive phenology by examining a seven-year dataset of blood meal identifications from a site in Tuskegee National Forest, Alabama USA and data on reproduction from the most commonly utilized endothermic (white-tailed deer, great blue heron, yellow-crowned night heron) and ectothermic (frogs) hosts. Our analysis revealed that feeding on each host peaked during periods of reproductive activity. Specifically, mosquitoes utilized herons in the spring and early summer, during periods of peak nest occupancy, whereas deer were fed upon most during the late summer and fall, the period corresponding to the peak in births for deer. For frogs, however, feeding on early- and late-season breeders paralleled peaks in male vocalization. We demonstrate for the first time that seasonal patterns of host use by mosquitoes track the reproductive phenology of the hosts. Peaks in relative mosquito feeding on each host during reproductive phases are likely the result of increased tolerance and decreased vigilance to attacking mosquitoes by nestlings and brooding adults (avian hosts), quiescent young (avian and mammalian hosts), and mate-seeking males (frogs).

Authors

Burkett-Cadena, Nathan D., McClure, Christopher J. W., Ligon, Russell A., Graham, Sean P., Guyer, Craig, Hill, Geoffrey E., Ditchkoff, Stephen S., Eubanks, Micky D., HASSAN, HASSAN K. and UNNASCH, THOMAS R.

Year Published

2011

Publication

PLOS One

Locations
DOI

10.1371/journal.pone.0017681

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21408172

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by Hartley, D. M., Barker, C. M., Le Menach, A., Niu, T., Gaff, H. D. and Reisen, W. K.

Temperature has played a critical role in the spatiotemporal dynamics of West Nile virus transmission throughout California from its introduction in 2003 through establishment by 2009. We compared two novel mechanistic measures of transmission risk, the temperature-dependent ratio of virus extrinsic incubation period to the mosquito gonotrophic period (BT), and the fundamental reproductive rati...

published 2012 in American Journal of Tropical Medicine and Hygiene

Weather Variability Affects Abundance of Larval culex (diptera: Culicidae) in Storm Water Catch Basins in Suburban Chicago

by Gardner, Allison M., Hamer, Gabriel L., Hines, Alicia M., Newman, Christina M., Walker, Edward D. and Ruiz, Marilyn O.

Culex pipiens L. (Diptera: Culicidae) and Culex restuans Theobald are the primary enzootic and bridge vectors of West Nile virus in the eastern United States north of 36° latitude. Recent studies of the natural history of these species have implicated catch basins and underground storm drain systems as important larval development sites in urban and suburban locales. Although the presence of la...

published 2012 in Journal of Medical Entomology


Wild Birds as Sentinels for Multiple Zoonotic Pathogens Along an Urban to Rural Gradient in Greater Chicago, Illinois

by Hamer, S. A., Lehrer, E. and Magle, S. B.

Wild birds are important in the maintenance and transmission of many zoonotic pathogens. With increasing urbanization and the resulting emergence of zoonotic diseases, it is critical to understand the relationships among birds, vectors, zoonotic pathogens, and the urban landscape. Here, we use wild birds as sentinels across a gradient of urbanization to understand the relative risk of diseases ...

published 2012 in Zoonoses and Public Health

Completeness of West Nile Virus Testing in Patients with Meningitis and Encephalitis During an Outbreak in Arizona, Usa

by WEBER, I. B., LINDSEY, N. P., BUNKO-PATTERSON, A. M., BRIGGS, G., WADLEIGH, T. J., SYLVESTER, T. L., LEVY, C., KOMATSU, K. K., LEHMAN, J. A., FISCHER, M. and STAPLES, J. E.

Accurate data on West Nile virus (WNV) cases help guide public health education and control activities, and impact regional WNV blood product screening procedures. During an outbreak of WNV disease in Arizona, records from patients with meningitis or encephalitis were reviewed to determine the proportion tested for WNV. Of 60 patients identified with meningitis or encephalitis, 24 (40%) were te...

published 2012 in Epidemiology and Infection