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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

SYNERGISTIC IMPACTS OF MALATHION AND PREDATORY STRESS ON SIX SPECIES OF NORTH AMERICAN TADPOLESRelyea, Rick A.2004

SYNERGISTIC IMPACTS OF MALATHION AND PREDATORY STRESS ON SIX SPECIES OF NORTH AMERICAN TADPOLES

Keywords

Predation;Stress;Synergy;Frog;Toad, WNV

Abstract

The decline of many amphibian populations is associated with pesticides, but for most pesticides we know little about their toxicity to amphibians. Malathion is a classic example; it is sprayed over aquatic habitats to control mosquitoes that carry malaria and the West Nile virus, yet we know little about its effect on amphibians. I examined the survival of six species of tadpoles (wood frogs, Rana sylvatica; leopard frogs, R. pipiens; green frogs, R. clamitans; bullfrogs, R. catesbeiana; American toads, Bufo americanus; and gray tree frogs, Hyla versicolor) for 16 d in the presence or absence of predatory stress and six concentrations of malathion. Malathion was moderately toxic to all species of tadpoles (median lethal concentration [LC50] values, the concentration estimated to kill 50% of a test population, ranged from 1.25–5.9 mg/L). These values are within the range of values reported for the few amphibians that have been tested (0.2–42 mg/L). In one of the six species, malathion became twice as lethal when combined with predatory stress. Similar synergistic interactions have been found with the insecticide carbaryl, suggesting that the synergy may occur in many carbamate and organophosphate insecticides. While malathion has the potential to kill amphibians and its presence is correlated with habitats containing declining populations, its actual role in amphibian declines is uncertain given the relatively low concentration in aquatic habitats.

Authors

Relyea, Rick A.

Year Published

2004

Publication

Environmental Toxicology and Chemistry

Locations
DOI

10.1897/03-259

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15095908

Susceptibility of greater sage-grouse to experimental infection with West Nile virusClark, L2006

Susceptibility of greater sage-grouse to experimental infection with West Nile virus

Keywords

Centrocercus urophasianus experimental infection greater sage-grouse vaccine West Nile virus

Abstract

Populations of greater sage-grouse (Centrocercus urophasianus) have declined 45-80% in North America since 1950. Although much of this decline has been attributed to habitat loss, recent field studies have indicated that West Nile virus (WNV) has had a significant negative impact on local populations of grouse. We confirm the susceptibility of greater sage-grouse to WNV infection in laboratory experimental studies. Grouse were challenged by subcutaneous injection of WNV (10(3.2) plaque-forming units [PFUs]). All grouse died within 6 days of infection. The Kaplan-Meier estimate for 50% survival was 4.5 days. Mean peak viremia for nonvaccinated birds was 10(6.4) PFUs/ml (+/- 10(0.2) PFUs/ml, standard error of the mean [SEM]). Virus was shed cloacally and orally. Four of the five vaccinated grouse died, but survival tune was increased (50% survival = 9.5 days), with 1 grouse surviving to the end-point of the experiment (14 days) kith no signs of illness. Mean peak viremia for the vaccinated birds was 10(2.3) PFUs/ml (+/- 10(0.6) PFUs/ml, SEM). Two birds cleared the virus from their blood before death or euthanasia. These data emphasize the high susceptibility of greater sage-grouse to infection with WNV.

Authors

Clark, L; Hall, J; McLean, R; Dunbar, M; Klenk, K; Bowen, R; Smeraski, CA

Year Published

2006

Publication

Journal of Wildlife Diseases

Locations
SUSCEPTIBILITY OF GREATER SAGE-GROUSE TO EXPERIMENTAL INFECTION WITH WEST NILE VIRUSClark, Larry2006

SUSCEPTIBILITY OF GREATER SAGE-GROUSE TO EXPERIMENTAL INFECTION WITH WEST NILE VIRUS

Keywords

Centrocercus urophasianus, experimental infection, greater sage-grouse, vaccine, West Nile virus, WNV

Abstract

Populations of greater sage-grouse (Centrocercus urophasianus) have declined 45– 80% in North America since 1950. Although much of this decline has been attributed to habitat loss, recent field studies have indicated that West Nile virus (WNV) has had a significant negative impact on local populations of grouse. We confirm the susceptibility of greater sage-grouse to WNV infection in laboratory experimental studies. Grouse were challenged by subcutaneous injection of WNV (103.2 plaque-forming units [PFUs]). All grouse died within 6 days of infection. The Kaplan-Meier estimate for 50% survival was 4.5 days. Mean peak viremia for nonvaccinated birds was 106.4 PFUs/ml (±100.2 PFUs/ml, standard error of the mean [SEM]). Virus was shed cloacally and orally. Four of the five vaccinated grouse died, but survival time was increased (50% survival=9.5 days), with 1 grouse surviving to the end-point of the experiment (14 days) with no signs of illness. Mean peak viremia for the vaccinated birds was 102.3 PFUs/ml (±100.6 PFUs/ml, SEM). Two birds cleared the virus from their blood before death or euthanasia. These data emphasize the high susceptibility of greater sage-grouse to infection with WNV.

Authors

Klenk, Kaci, Bowen, Richard, Clark, Larry, Hall, Jeffrey, McLean, Robert, Dunbar, Michael and Smeraski, Cynthia A.

Year Published

2006

Publication

Journal of Wildlife Diseases

Locations
DOI

10.7589/0090-3558-42.1.14

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16699144

Survey of Aedes triseriatus (Diptera: Culicidae) for Lacrosse Encephalitis Virus and West Nile Virus in Lorain County, OhioScheidler, Lydia C.2006

Survey of Aedes triseriatus (Diptera: Culicidae) for Lacrosse Encephalitis Virus and West Nile Virus in Lorain County, Ohio

Keywords

West Nile virus, La Crosse encephalitis virus, surveillance, arbovirus, Aedes triseriatus, WNV

Abstract

From June through September 2003, we conducted a survey of female Aedes triseriatus (Say) for infection with La Crosse encephalitis virus (family Bunyaviridae, genus Orthobunyavirus, LACV) and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) at three locations in Lorain County, Ohio. To determine infection rate and seasonal variation of both viruses in the Ae. triseriatus population, Ae. triseriatus were collected weekly by using gravid traps and CO2-baited CDC light traps and tested for virus by using reverse transcriptase polymerase chain reaction. In total, 170 pools comprised of 2,143 females were tested for LACV, of which seven were positive; the maximum likelihood estimate of infection rate combined throughout the season was 3.22/1,000. None of 170 pools comprised of 2,158 females tested for WNV were positive. LACV-positive pools were detected between late July and early September.

Authors

Scheidler, Lydia C., Dunphy-daly, Meagan M., White, Bradley J., Andrew, David R., Mans, Nicole Z. and Garvin, Mary C.

Year Published

2006

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2006)43[589:SOATDC]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16739420

Surveillance of Above- and Below-Ground Mosquito Breeding Habitats in a Rural Midwestern Community: Baseline Data for Larvicidal Control Measures Against West Nile Virus VectorsKronenwetter-Koepel, T. A.2005

Surveillance of Above- and Below-Ground Mosquito Breeding Habitats in a Rural Midwestern Community: Baseline Data for Larvicidal Control Measures Against West Nile Virus Vectors

Keywords

Mosquito control, Breeding, Environment, West Nile virus, Culex, WNV

Abstract

Background Mosquitoes in the genus Culex are thought to play a major role as vectors in the transmission cycle of West Nile virus (WNV) and other arboviruses in the United States. Effective control of mosquitoes through larviciding and adulticiding is expensive for communities and should be guided by reliable surveillance data on the distribution of mosquito breeding habitats. However, few small to medium sized cities in rural areas of the midwestern United States have this type of baseline information available. Objective During the summer of 2004, we investigated the characteristics of Culex and other mosquito-breeding habitats in a rural central Wisconsin community with a population of approximately 19,000. Such baseline information will aid in the development of rational strategies to control mosquito populations and prevent human exposure to WNV and other mosquito-transmitted viruses. Methods Mosquito larvae were collected and identified weekly from 14 below-ground storm water catch basins and 10 above-ground standing water sites distributed throughout the community. Collection began June 4, 2004 and continued through September 24, 2004. For each collection site the primary and adjacent land use patterns were determined. Results Over the study period, 1,244 larvae were collected from catch basins; 94% were Culex species. Breeding activity was first detected in early July. Peak breeding was observed during a period of several weeks when average daily temperatures were at the maximum observed and rainfall had declined. Organically enriched catch basins in low intensity urban sites adjacent to forests and wetlands were found to be more productive breeding habitats compared to catch basins having little organic debris located in isolated high intensity urban sites. Above-ground standing water sites produced 1,504 larvae; 66% of which were Culex species. Flood control ditches and permanent wetlands with stagnant water were most productive, while ditches with moving water were least productive habitats. Larvae were produced earlier in the season by above-ground sites than were produced by catch basins. However, larvae production was more variable in above-ground sites since half the sites became dry at some point during the study period. Conclusion The observed differences in Culex larvae production based on the variables of habitat-type, temperature, and precipitation support the need for ongoing surveillance in communities to guide public health officials in planning for and prioritizing mosquito control efforts.

Authors

Kronenwetter-Koepel, T. A., Meece, J. K., Miller, C. A. and Reed, K. D.

Year Published

2005

Publication

Clinical Medicine & Research

Locations
DOI

10.3121/cmr.3.1.3

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15962015

Studies on Hibernating Populations of Culex pipiens from a West Nile Virus Endemic Focus in New York City: Parity Rates and Isolation of West Nile VirusAndreadis, Theodore G.2010

Studies on Hibernating Populations of Culex pipiens from a West Nile Virus Endemic Focus in New York City: Parity Rates and Isolation of West Nile Virus

Keywords

WNV

Abstract

A 3-year study was undertaken to examine the parity status, survival, and prevalence of West Nile virus (WNV) in overwintering populations of Culex pipiens pipiens collected from a hibernaculum located in a WNV endemic region in New York City. Nearly 6,000 females were collected from December through April. Parity rates were highest among females collected in December and January, ranging from 12.3% to 21.9%, depending on the year. In each year of the study, the proportion of parous females declined significantly during the course of the winter; the percentage of parous females found in April ranged from 0.9% to 10%. Results provide unequivocal evidence that parous Cx. p. pipiens females from this region of the northeastern US enter hibernacula in the fall in comparatively high proportions not previously recognized for this species, and while these females experience significant mortality during the winter, some survived to April to emerge in the spring. The absence of any detectible blood remnants in overwintering females reaffirms that blood feeding does not occur among diapausing females during the winter. The possibility that a portion of the diapausing population may be autogenous as a result of hybridization with sympatric belowground populations of Cx. p. pipiens "form molestus" is discussed. A single isolation of WNV was obtained in Vero cell culture from a pool of 50 females collected on January 11, 2007, representing an infection prevalence of 0.07% in the overwintering population in 2007 (n = 1,370 mosquitoes, 33 pools). No isolations of WNV were made from mosquitoes collected in 2008 (n = 1,870 mosquitoes, 190 pools) or 2009 (n = 1,767 mosquitoes, 184 pools). Findings provide further evidence for local overwintering of WNV in diapausing Cx. p. pipiens, albeit at very low rates, consistent with the paucity of WNV-positive mosquitoes detected in June and early July despite the emergence of females from hibernacula in early May in this region.

Authors

Andreadis, Theodore G., ARMSTRONG, PHILIP M. and Bajwa, Waheed I.

Year Published

2010

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/10-6004.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21033052

STORMWATER PONDS, CONSTRUCTED WETLANDS, AND OTHER BEST MANAGEMENT PRACTICES AS POTENTIAL BREEDING SITES FOR WEST NILE VIRUS VECTORS IN DELAWARE DURING 2004GINGRICH, JACK B.2006

STORMWATER PONDS, CONSTRUCTED WETLANDS, AND OTHER BEST MANAGEMENT PRACTICES AS POTENTIAL BREEDING SITES FOR WEST NILE VIRUS VECTORS IN DELAWARE DURING 2004

Keywords

Stormwater ponds, breeding sites, mosquito, West Nile virus, WNV

Abstract

We performed longitudinal surveys of mosquito larval abundance (mean mosquito larvae per dip) in 87 stormwater ponds and constructed wetlands in Delaware from June to September 2004. We analyzed selected water quality factors, water depth, types of vegetation, degree of shade, and level of insect predation in relation to mosquito abundance. The 2004 season was atypical, with most ponds remaining wet for the entire summer. In terms of West Nile virus (WNV) vectors, wetlands predominantly produced Aedes vexans, Culex pipiens pipiens, and Culex restuans. Retention ponds generally produced the same species as wetlands, except that Cx. p. pipiens was more abundant than Cx. restuans in retention ponds. Aedes vexans and Culex salinarius were the most abundant species in Conservation Restoration Enhancement Program ponds. Sand filters uniquely produced high numbers of Cx. restuans, Cx. p. pipiens, and Aedes japonicus japonicus, a newly invasive vector species. Sites that alternately dried and flooded, mostly detention ponds, forebays of retention ponds, and some wetlands often produced Ae. vexans, an occasional WNV bridge vector species. Overall, seasonal distribution of vectors was bimodal, with peaks occurring during early and late summer. Ponds with shallow sides and heavy shade generally produced an abundance of mosquitoes, unless insect predators were abundant. Bright, sunny ponds with steep sides and little vegetation generally produced the fewest mosquitoes. The associations among mosquito species and selected vegetation types are discussed.

Authors

GINGRICH, JACK B., ANDERSON, ROBERT D., WILLIAMS, GREGORY M., O'CONNOR, LINDA and HARKINS, KEVIN

Year Published

2006

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/8756-971X(2006)22[282:SPCWAO]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17019774

Spatially Explicit West Nile Virus Risk Modeling in Santa Clara County, CaliforniaKonrad, Sarah K.2009

Spatially Explicit West Nile Virus Risk Modeling in Santa Clara County, California

Keywords

WNV

Abstract

A geographic information system model designed to identify regions at risk for West Nile virus (WNV) transmission was calibrated and tested with data collected in Santa Clara County, California. American Crows that died from WNV infection in 2005 provided spatial and temporal ground truth. When the model was run with parameters based on Culex tarsalis infected with the NY99 genotype of the virus, it underestimated WNV occurrence in Santa Clara Co. The parameters were calibrated to fit the field data by reducing the number of degree-days necessary to reach the mosquito's extrinsic incubation period from 109 to 76. The calibration raised model efficiency from 61% to 92% accuracy, and the model performed well the following year in Santa Clara Co.

Authors

Konrad, Sarah K., Miller, Scott N., Reeves, Will K. and Tietze, Noor S.

Year Published

2009

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2008.0084

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19514810

Spatial Analysis of West Nile Virus: Rapid Risk Assessment of an Introduced Vector-Borne ZoonosisBrownstein, John S.2002

Spatial Analysis of West Nile Virus: Rapid Risk Assessment of an Introduced Vector-Borne Zoonosis

Keywords

WNV

Abstract

The distribution of human risk for West Nile virus was determined by spatial analysis of the initial case distribution for the New York City area in 1999 using remote sensing and geographic information system technologies. Cluster analysis revealed the presence of a statistically significant grouping of cases, which also indicates the area of probable virus introduction. Within the cluster, habitat suitability for potentially infective adult mosquitoes was measured by the amount of vegetation cover using satellite imagery. Logistic regression analysis revealed satellite-derived vegetation abundance to be significantly and positively associated with the presence of human cases. The logistic model was used to estimate the spatial distribution of human risk for West Nile virus throughout New York City. Accuracy of the resulting risk map was cross-validated using virus-positive mosquito sample sites. These new epidemiological methods aid in rapid entry point identification and spatial prediction of human risk of infection for introduced vector-borne pathogens.

Authors

Miller, James R., Brownstein, John S., Rosen, Hilary, Purdy, Dianne, Merlino, Mario, Mostashari, Farzad and Fish, Durland

Year Published

2002

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/15303660260613729

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/12737545

Recent Articles

Effects of Temperature on Emergence and Seasonality of West Nile Virus in California

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