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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
Field-Based Estimates of Avian Mortality from West Nile Virus InfectionWard, Michael P.2010

Field-Based Estimates of Avian Mortality from West Nile Virus Infection

Keywords

WNV

Abstract

One of the unique characteristics of West Nile virus (WNV) in North America is the large number of bird species for which the virus can be fatal. WNV mortality has been documented through experimental infections of captive birds and necropsies of free-ranging birds. Investigations of WNV-related mortality in wild birds often focus on species with dramatic population declines (e.g., American Crow, Corvus brachyrhynchos); however, few studies have addressed WNV-related mortality in species not exhibiting marked population declines since the arrival of WNV. We conducted a mark-recapture study of 204 Northern Cardinals (Cardinalis cardinalis) in an area with endemic WNV activity to estimate WNV-related mortality. Previous research has shown that once a bird is infected and recovers from WNV it develops antibodies making it resistant to future infection. Assuming that mortality risks from non-WNV causes were the same for individuals with (had been exposed to WNV) and without antibodies (had not been exposed to WNV), we compared the survival rates of birds with and without WNV antibodies to estimate the impact of WNV on wild birds. An information theoretic approach was used, and the apparent survival was found to be 34.6% lower for individuals without antibodies during the period when WNV was most active (July-September). However, the apparent survival rate was 9.0% higher for individuals without antibodies over the rest of the year. These differences in apparent survival suggest that WNV increases mortality during the WNV season and that chronic effects of WNV infection may also be contributing to mortality. Although WNV appears to have increased mortality rates within the population, population trend data do not indicate declines, suggesting that some cardinal populations can compensate for WNV-related mortality.

Authors

Ward, Michael P., Beveroth, Tara A., Lampman, Richard, Raim, Arlo, Enstrom, David and Novak, Robert

Year Published

2010

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2008.0198

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20370425

WILD BIRD MORTALITY AND WEST NILE VIRUS SURVEILLANCE: BIASES ASSOCIATED WITH DETECTION, REPORTING, AND CARCASS PERSISTENCEWard, Marsha R.2006

WILD BIRD MORTALITY AND WEST NILE VIRUS SURVEILLANCE: BIASES ASSOCIATED WITH DETECTION, REPORTING, AND CARCASS PERSISTENCE

Keywords

American crow, carcass, house sparrow, persistence, scavenging, surveillance, West Nile virus, WNV

Abstract

Surveillance targeting dead wild birds, in particular American crows (Corvus brachyrhynchos), plays a critical role in West Nile virus (WNV) surveillance in the United States. Using crow decoy surrogates, detection and reporting of crow carcasses within urban and rural environments of DeKalb County, Georgia were assessed for potential biases that might occur in the county's WNV surveillance program. In each of two replicated trials, during July and September 2003, 400 decoys were labeled with reporting instructions and distributed along randomly chosen routes throughout designated urban and rural areas within DeKalb County. Information-theoretic methods were used to compare alternative models incorporating the effects of area and trial on probabilities of detection and reporting. The model with the best empirical support included the effects of area on both detection and reporting of decoys. The proportion of decoys detected in the urban area (0.605, SE=0.024) was approximately twice that of the rural area (0.293, SE=0.023), and the proportion of decoys reported in the urban area (0.273, SE=0.023) was approximately three times that of the rural area (0.103, SE=0.028). These results suggest that human density and associated factors can substantially influence dead crow detection and reporting and, thus, the perceived distribution of WNV. In a second and separate study, the persistence and fate of American crow and house sparrow (Passer domesticus) carcasses were assessed in urban and rural environments in Athens-Clarke, Madison, and Oconee counties, Georgia. Two replicated trials using 96 carcasses of each species were conducted during July and September 2004. For a portion of the carcasses, motion sensitive cameras were used to monitor scavenging species visits. Most carcasses (82%) disappeared or were decayed by the end of the 6-day study. Carcass persistence averaged 1.6 days in rural areas and 2.1 days in urban areas. We analyzed carcass persistence rates using a known-fate model framework in program MARK. Model selection based on Akaike's Information Criteria (AIC) indicated that the best model explaining carcass persistence rates included species and number of days of exposure; however, the model including area and number of days of exposure received approximately equal support. Model-averaged carcass persistence rates were higher for urban areas and for crow carcasses. Six mammalian and one avian species were documented scavenging upon carcasses. Dead wild birds could represent potential sources of oral WNV exposure to these scavenging species. Species composition of the scavenger assemblage was similar in urban and rural areas but “scavenging pressure” was greater in rural areas.

Authors

Ward, Marsha R., Stallknecht, David E., Willis, Juanette, Conroy, Michael J. and Davidson, William R.

Year Published

2006

Publication

Journal of Wildlife Diseases

Locations
DOI

10.7589/0090-3558-42.1.92

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16699152

Dry weather induces outbreaks of human West Nile virus infectionsWang, Guiming2010

Dry weather induces outbreaks of human West Nile virus infections

Keywords

WNV

Abstract

BACKGROUND: Since its first occurrence in the New York City area during 1999, West Nile virus (WNV) has spread rapidly across North America and has become a major public health concern in North America. By 2002, WNV was reported in 40 states and the District of Columbia with 4,156 human and 14,539 equine cases of infection. Mississippi had the highest human incidence rate of WNV during the 2002 epidemic in the United States. Epidemics of WNV can impose enormous impacts on local economies. Therefore, it is advantageous to predict human WNV risks for cost-effective controls of the disease and optimal allocations of limited resources. Understanding relationships between precipitation and WNV transmission is crucial for predicting the risk of the human WNV disease outbreaks under predicted global climate change scenarios. METHODS: We analyzed data on the human WNV incidences in the 82 counties of Mississippi in 2002, using standard morbidity ratio (SMR) and Bayesian hierarchical models, to determine relationships between precipitation and human WNV risks. We also entertained spatial autocorrelations of human WNV risks with conditional autocorrelative (CAR) models, implemented in WinBUGS 1.4.3. RESULTS: We observed an inverse relationship between county-level human WNV incidence risk and total annual rainfall during the previous year. Parameters representing spatial heterogeneity in the risk of human exposure to WNV improved model fit. Annual precipitation of the previous year was a predictor of spatial variation of WNV risk. CONCLUSIONS: Our results have broad implications for risk assessment of WNV and forecasting WNV outbreaks. Assessing risk of vector-born infectious diseases will require understanding of complex ecological relationships. Based on the climatologically characteristic drought occurrence in the past and on climate model predictions for climate change and potentially greater drought occurrence in the future, we suggest that the frequency and relative risk of WNV outbreaks could increase.

Authors

Wang, Guiming, Minnis, Richard B, Belant, Jerrold L and Wax, Charles L

Year Published

2010

Publication

BMC Infectious Diseases

Locations
DOI

10.1186/1471-2334-10-38

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20181272

The Role of Hydrogeography and Climate in the Landscape Epidemiology of West Nile Virus in New York State from 2000 to 2010Walsh, Michael G.2012

The Role of Hydrogeography and Climate in the Landscape Epidemiology of West Nile Virus in New York State from 2000 to 2010

Keywords

WNV

Abstract

The epidemiology and ecology of West Nile virus (WNV) have not yet been completely described. In particular, the specific roles of climate and water in the landscape in the occurrence of human WNV cases remain unknown. This study used Poisson regression to describe the relationships between WNV cases and temperature, precipitation, and the hydrogeography of the landscape in New York State from 2000 to 2010. Fully adjusted models showed that hydrogeographic area was significantly inversely associated with WNV cases (incidence rate ratio (IRR) = 0.99; 95% C.I. = 0.98-0.997< p = 0.04), such that each one square kilometer increase in hydrogeographic area was associated with a 1% decrease in WNV incidence. This association was independent of both temperature, which was also associated with WNV incidence (IRR = 2.06; 95% C.I. = 1.84-2.31, ps express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Authors

Walsh, Michael G.

Year Published

2012

Publication

PLOS One

Locations
DOI

10.1371/journal.pone.0030620

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/22328919

West Nile Virus and Greater Sage-Grouse: Estimating Infection Rate in a Wild Bird PopulationWalker, Brett L.2007

West Nile Virus and Greater Sage-Grouse: Estimating Infection Rate in a Wild Bird Population

Keywords

Centrocercus urophasianus, coal-bed natural gas, energy development, flavivirus, greater sage-grouse, infection rate, sagebrush-steppe, West Nile virus

Abstract

Understanding impacts of disease on wild bird populations requires knowing not only mortality rate following infection, but also the proportion of the population that is infected. Greater sage-grouse (Centrocercus urophasianus) in western North America are known to have a high mortality rate following infection with West Nile virus (WNv), but actual infection rates in wild populations remain unknown. We used rates of WNv-related mortality and seroprevalence from radiomarked females to estimate infection rates in a wild greater sage-grouse population in the Powder River basin (PRB) of Montana and Wyoming from 2003 to 2005. Minimum WNv-related mortality rates ranged from 2.4% to 13.3% among years and maximum possible rates ranged from 8.2% to 28.9%. All live-captured birds in 2003 and 2004 tested seronegative. In spring 2005 and spring 2006, 10.3% and 1.8% respectively, of newly captured females tested seropositive for neutralizing antibodies to WNv. These are the first documented cases of sage-grouse surviving infection with WNv. Low to moderate WNv-related mortality in summer followed by low seroprevalence the following spring in all years indicates that annual infection rates were between 4% and 29%. This suggests that most sage-grouse in the PRB have not yet been exposed and remain susceptible. Impacts of WNv in the PRB in the near future will likely depend more on annual variation in temperature and changes in vector distribution than on the spread of resistance. Until the epizootiology of WNv in sagebrush-steppe ecosystems is better understood, we suggest that management to reduce impacts of WNv focus on eliminating man-made water sources that support breeding mosquitoes known to vector the virus. Our findings also underscore problems with using seroprevalence as a surrogate for infection rate and for identifying competent hosts in highly susceptible species.

Authors

Walker, Brett L.; Naugle, David E.; Doherty, Kevin E.; Cornish, Todd E.

Year Published

2007

Publication

Avian Diseases

Locations
DOI

10.1637/0005-2086(2007)51[691:WNVAGS]2.0.CO;2

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

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

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

Seasonal variation in susceptibility to West Nile virus infection in Culex pipiens pipiens (L.) (Diptera: Culicidae) from San Joaquin County, CaliforniaVaidyanathan, Rajeev2006
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

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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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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 ...

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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...

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