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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
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

Meteorologically Conditioned Time-Series Predictions of West Nile Virus Vector MosquitoesTrawinski, P.R.2008

Meteorologically Conditioned Time-Series Predictions of West Nile Virus Vector Mosquitoes

Keywords

WNV

Abstract

An empirical model to forecast West Nile virus mosquito vector populations is developed using time series analysis techniques. Specifically, multivariate seasonal autoregressive integrated moving average (SARIMA) models were developed for Aedes vexans and the combined group of Culex pipiens and Culex restuans in Erie County, New York. Weekly mosquito collections data were obtained for the four mosquito seasons from 2002 to 2005 from the Erie County Department of Health, Vector and Pest Control Program. Climate variables were tested for significance with cross-correlation analysis. Minimum temperature (Tmin), maximum temperature (Tmax), average temperature (Tave), precipitation (P), relative humidity (RH), and evapotranspiration (ET) were acquired from the Northeast Regional Climate Center (NRCC) at Cornell University. Weekly averages or sums of climate variables were calculated from the daily data. Other climate indexes were calculated and were tested for significance with the mosquito population data, including cooling degree days base 60 degrees (CDD_60), cooling degree days base 63 (CDD_63), cooling degree days base 65 (CDD_65), a ponding index (IP), and an interactive CDD_65-precipitation variable (CDD_65 × Pweek_4). Ae. vexans were adequately modeled with a (2,1,1)(1,1,0)52 SARIMA model. The combined group of Culex pipiens-restuans were modeled with a (0,1,1)(1,1,0)52 SARIMA model. The most significant meteorological variables for forecasting Aedes vexans abundance was the interactive CDD_65 × Pweek_4 variable at a lag of two weeks, ET × ET at a lag of five weeks, and CDD_65 × CDD_65 at a lag of seven weeks. The most significant predictive variables for the grouped Culex pipiens-restuans were CDD_63 × CDD_63 at a lag of zero weeks, CDD_63 at a lag of eight weeks, and the cumulative maximum ponding index (IPcum) at a lag of zero weeks.

Authors

Trawinski, P.R. and MacKay, D.S.

Year Published

2008

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2007.0202

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18279008

Identification of Environmental Covariates of West Nile Virus Vector Mosquito Population AbundanceTrawinski, Patricia R.2010

Identification of Environmental Covariates of West Nile Virus Vector Mosquito Population Abundance

Keywords

WNV

Abstract

The rapid spread of West Nile virus (WNv) in North America is a major public health concern. Culex pipiens-restuans is the principle mosquito vector of WNv in the northeastern United States while Aedes vexans is an important bridge vector of the virus in this region. Vector mosquito abundance is directly dependent on physical environmental factors that provide mosquito habitats. The objective of this research is to determine landscape elements that explain the population abundance and distribution of WNv vector mosquitoes using stepwise linear regression. We developed a novel approach for examining a large set of landscape variables based on a land use and land cover classification by selecting variables in stages to minimize multicollinearity. We also investigated the distance at which landscape elements influence abundance of vector populations using buffer distances of 200, 400, and 1000 m. Results show landscape effects have a significant impact on Cx. pipiens-estuans population distribution while the effects of landscape features are less important for prediction of Ae. vexans population distributions. Cx. pipiens-restuans population abundance is positively correlated with human population density, housing unit density, and urban land use and land cover classes and negatively correlated with age of dwellings and amount of forested land.

Authors

Trawinski, Patricia R. and Mackay, D. Scott

Year Published

2010

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2008.0063

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20482343

Effect of Holding Conditions on the Detection of West Nile Viral RNA by Reverse Transcriptase-Polymerase Chain Reaction from Mosquito (Diptera: Culicidae) PoolsTurell, Michael J.2002

Effect of Holding Conditions on the Detection of West Nile Viral RNA by Reverse Transcriptase-Polymerase Chain Reaction from Mosquito (Diptera: Culicidae) Pools

Keywords

WNV

Abstract

We evaluated the effect of holding temperature and time between mosquito death and processing mosquito pools for virus detection on our ability to detect West Nile (WN) viral RNA from pools of mosquitoes by reverse transcriptase-polymerase chain reaction (RT-PCR). Pools of 24 uninfected Culex pipiens L. mosquitoes were "spiked" with either a single Cx. pipiens that had been inoculated previously with WN virus or with an uninfected mosquito. These pools were held dry at 20, 4, -20, or -70 degrees C for selected time intervals before all mosquito pools were triturated in TRIzol LS reagent and processed for detection of WN viral RNA. While infectious virus virtually disappeared from pools maintained at 20 degrees C by 48 h after mosquito death, neither holding temperature (20 to -70 degrees C) nor holding period (up to 2 wk) affected detection of WN viral RNA by real-time RT-PCR. These findings suggest that we need not keep mosquitoes chilled to be able to detect WN viral RNA effectively by RT-PCR. This should enhance the feasibility of field-based WN virus surveillance programs where only detection of WN viral RNA is the objective and maintenance of a cold chain may not be possible.

Authors

Turell, Michael J., Spring, Alexandra R., Miller, Melissa K. and Cannon, Charles E.

Year Published

2002

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585-39.1.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/11931239

Evidence of vertical transmission of West Nile virus in field-collected mosquitoesUnlu, Isik2010

Evidence of vertical transmission of West Nile virus in field-collected mosquitoes

Keywords

West Nile virus;mosquitoes;vertical transmission, WNV

Abstract

Male and nulliparous female mosquitoes were surveyed for evidence of vertical WNV infection in East Baton Rouge Parish, Louisiana. Adult male mosquitoes collected by trapping and aspiration, and adult male and nulliparous female mosquitoes reared from field-collected larvae were tested. Adult male Culex spp., female Aedes albopictus (Skuse), and female Culex quinquifasciatus Say mosquitoes that were collected as larvae were test-positive for WNV RNA. Infectious WNV was detected using virus isolation in field-collected male Aedes triseriatus Say and Culex salinarius Coquillett; these data represent the first field evidence of vertical transmission of WNV in Ae. triseriatus and Cx. salinarius.

Authors

Unlu, Isik, Mackay, Andrew J., Roy, Alma, Yates, Matt M. and Foil, Lane D.

Year Published

2010

Publication

Journal of Vector Ecology

Locations
DOI

10.1111/j.1948-7134.2010.00064.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20618654

Detection of West Nile Virus RNA in Mosquitoes and Identification of Mosquito Blood Meals Collected at Alligator Farms in LouisianaUnlu, Isik2010

Detection of West Nile Virus RNA in Mosquitoes and Identification of Mosquito Blood Meals Collected at Alligator Farms in Louisiana

Keywords

mosquitoes, Alligator mississippiensis, Culex quinquefasciatus, Culex nigripalpus, cytochrome B, WNV

Abstract

Since 2001, alligator farms in the United States have sustained substantial economic losses because of West Nile virus (WNV) outbreaks in American alligators (Alligator mississippiensis). Once an initial infection is introduced into captive alligators, WNV can spread among animals by contaminative transmission. Some outbreaks have been linked to feeding on infected meat or the introduction of infected hatchlings, but the initial source of WNV infection has been uncertain in other outbreaks. We conducted a study to identify species composition and presence of WNV in mosquito populations associated with alligator farms in Louisiana. A second objective of this study was to identify the origin of mosquito blood meals collected at commercial alligator farms. Mosquitoes were collected from 2004 to 2006, using Centers for Disease Control light traps, gravid traps, backpack aspirators, and resting boxes. We collected a total of 58,975 mosquitoes representing 24 species. WNV was detected in 41 pools of females from 11 mosquito species: Anopheles crucians, Anopheles quadrimaculatus, Coquillettidia perturbons, Culex coronator, Culex erraticus, Culex nigripalpus, Culex quinquefasciatus, Mansonia titillans, Aedes sollicitans, Psorophora columbiae, and Uranotaenia lowii. The blood meal origins of 213 field-collected mosquitoes were identified based on cytochrome B sequence identity. Alligator blood was detected in 21 mosquitoes representing six species of mosquitoes, including Cx. quinquefasciatus and Cx. nigripalpus. Our results showed that mosquitoes of species that are known to be competent vectors of WNV fed regularly on captive alligators. Therefore, mosquitoes probably are important in the role of transmission of WNV at alligator farms.

Authors

Unlu, Isik, Kramer, Wayne L., Roy, Alma F. and Foil, Lane D.

Year Published

2010

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME09087

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20695278

Seasonal variation in susceptibility to West Nile virus infection in Culex pipiens pipiens (L.) (Diptera: Culicidae) from San Joaquin County, CaliforniaVaidyanathan, Rajeev2006
Assessment of methods for prediction of human West Nile virus (WNV) disease from WNV-infected dead birdsVeksler, Anna2009

Assessment of methods for prediction of human West Nile virus (WNV) disease from WNV-infected dead birds

Keywords

WNV

Abstract

BACKGROUND: West Nile virus (WNV) is currently the leading cause of arboviral-associated encephalitis in the U.S., and can lead to long-term neurologic sequelae. Improvements in dead bird specimen processing time, including the availability of rapid field laboratory tests, allows reassessment of the effectiveness of using WNV-positive birds in forecasting human WNV disease. METHODS: Using New York State integrated WNV surveillance data from transmissions seasons in 2001-2003, this study determined which factors associated with WNV-positive dead birds are most closely associated with human disease. The study also addressed the 'delay' period between the distribution of the dead bird variable and the distribution of the human cases. In the last step, the study assessed the relative risk of contracting WNV disease for people who lived in counties with a 'signal' value of the predictor variable versus people who lived in counties with no 'signal' value of the predictor variable. RESULTS: The variable based on WNV-positive dead birds [(Positive/Tested)*(Population/Area)] was identified as the optimum variable for predicting WNV human disease at a county level. The delay period between distribution of the variable and human cases was determined to be approximately two weeks. For all 3 years combined, the risk of becoming a WNV case for people who lived in 'exposed' counties (those with levels of the positive dead bird variable above the signal value) was about 2 times higher than the risk for people who lived in 'unexposed' counties, but risk varied by year. CONCLUSION: This analysis develops a new variable based on WNV-positive dead birds, [(Positive/Tested)*(Population/Area)] to be assessed in future real-time studies for forecasting the number of human cases in a county. A delay period of approximately two weeks between increases in this variable and the human case onset was identified. Several threshold 'signal' values were assessed and found effective at indicating human case risk, although specific thresholds are likely to vary by region and surveillance system differences.

Authors

Veksler, Anna, Eidson, Millicent and Zurbenko, Igor

Year Published

2009

Publication

Emerging Themes in Epidemiology

Locations
DOI

10.1186/1742-7622-6-4

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19500367

A MULTIPLE CAGE–HOLDING, WIND-SENSITIVE VANE DESIGN FOR USE IN GROUND ADULTICIDING EFFICACY TESTING IN HARRIS COUNTY, TEXASVESSEY, NATHAN Y.2007

A MULTIPLE CAGE–HOLDING, WIND-SENSITIVE VANE DESIGN FOR USE IN GROUND ADULTICIDING EFFICACY TESTING IN HARRIS COUNTY, TEXAS

Keywords

Wind-sensitive vane apparatus, treatment cages, ground ultra-low volume testing, WNV

Abstract

A wind-sensitive vane apparatus was designed and implemented specifically to accommodate the attachment of otherwise unidirectional insecticide treatment cages used in ground ultra-low volume mosquito adulticide field tests. This cage support system is useful in keeping the potential West Nile virus and St. Louis encephalitis vector Culex quinquefasciatus caged mosquitoes oriented into the wind during field efficacy tests. Testing capacity for resistance surveillance was tripled during the 2005 season, and more reliable results were achieved as a consequence.

Authors

Bueno, Rudy, VESSEY, NATHAN Y., STARK, PAMELA M. and FLATT, KYLE L.

Year Published

2007

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/8756-971X(2007)23[237:AMCWVD]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17847862

From the field: Outbreak of West Nile virus in greater sage-grouse and guidelines for monitoring, handling, and submitting dead birdsWalker, BL2004

From the field: Outbreak of West Nile virus in greater sage-grouse and guidelines for monitoring, handling, and submitting dead birds

Keywords

Centrocercus urophasianus, emerging infectious disease, greater sage-grouse, lek count, Montana, population decline, Powder River Basin, survival, West Nile virus, Wyoming

Abstract

West Nile virus (WNV) resulted in a 25% decline in survival in four populations of radiomarked greater sage-grouse (Centrocercus urophasianus) across Alberta, Wyoming, and Montana in 2003. Unexpected impacts of WNV are disturbing because range-wide habitat loss and degradation already threaten sage-grouse populations. In the Powder River Basin of Wyoming and Montana, late-summer survival of sage-grouse was lower at a site with confirmed WNV mortalities (20%) than at two sites without (76%). Dramatic declines in both male and female lek attendance at the WNV site the following spring suggest that outbreaks may threaten some local populations with extirpation. The key to understanding broader impacts of WNV on sage-grouse is to monitor additional populations and to determine whether populations infected in 2003 are again impacted this year. To facilitate this process, we describe a strategy for monitoring WNV mortality in the field and provide information on how to handle, store, and submit dead birds for testing.

Authors

Walker, BL; Naugle, DE; Doherty, KE; Cornish, TE

Year Published

2004

Publication

Wildlife Society Bulletin

Locations
DOI

10.2193/0091-7648(2004)032[1000:FTFOOW]2.0.CO;2

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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...

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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...

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