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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
Local impact of temperature and precipitation on West Nile virus infection in Culex species mosquitoes in northeast Illinois, USARuiz, Marilyn O2010

Local impact of temperature and precipitation on West Nile virus infection in Culex species mosquitoes in northeast Illinois, USA

Keywords

WNV

Abstract

Background Models of the effects of environmental factors on West Nile virus disease risk have yielded conflicting outcomes. The role of precipitation has been especially difficult to discern from existing studies, due in part to habitat and behavior characteristics of specific vector species and because of differences in the temporal and spatial scales of the published studies. We used spatial and statistical modeling techniques to analyze and forecast fine scale spatial (2000 m grid) and temporal (weekly) patterns of West Nile virus mosquito infection relative to changing weather conditions in the urban landscape of the greater Chicago, Illinois, region for the years from 2004 to 2008. Results Increased air temperature was the strongest temporal predictor of increased infection in Culex pipiens and Culex restuans mosquitoes, with cumulative high temperature differences being a key factor distinguishing years with higher mosquito infection and higher human illness rates from those with lower rates. Drier conditions in the spring followed by wetter conditions just prior to an increase in infection were factors in some but not all years. Overall, 80% of the weekly variation in mosquito infection was explained by prior weather conditions. Spatially, lower precipitation was the most important variable predicting stronger mosquito infection; precipitation and temperature alone could explain the pattern of spatial variability better than could other environmental variables (79% explained in the best model). Variables related to impervious surfaces and elevation differences were of modest importance in the spatial model. Conclusion Finely grained temporal and spatial patterns of precipitation and air temperature have a consistent and significant impact on the timing and location of increased mosquito infection in the northeastern Illinois study area. The use of local weather data at multiple monitoring locations and the integration of mosquito infection data from numerous sources across several years are important to the strength of the models presented. The other spatial environmental factors that tended to be important, including impervious surfaces and elevation measures, would mediate the effect of rainfall on soils and in urban catch basins. Changes in weather patterns with global climate change make it especially important to improve our ability to predict how inter-related local weather and environmental factors affect vectors and vector-borne disease risk. Local impact of temperature and precipitation on West Nile virus infection in Culex species mosquitoes in northeast Illinois, USA.

Authors

Ruiz, Marilyn O, Chaves, Luis F, Hamer, Gabriel L, Sun, Ting, Brown, William M, Walker, Edward D, Haramis, Linn, Goldberg, Tony L and Kitron, Uriel D

Year Published

2010

Publication

Parasites & Vectors

Locations
DOI

10.1186/1756-3305-3-19

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20302617

West Nile Virus Infection Rates in Culex nigripalpus (Diptera: Culicidae) Do Not Reflect Transmission Rates in FloridaRutledge, C. Roxanne2003

West Nile Virus Infection Rates in Culex nigripalpus (Diptera: Culicidae) Do Not Reflect Transmission Rates in Florida

Keywords

West Nile virus, infection rate, field transmission, arbovirus, WNV

Abstract

We describe the first documented field transmission of West Nile (WN) virus by a North American mosquito. WN was first detected in northern Florida in 2001. An intensive mosquito trapping and surveillance program was conducted in this region for four nights to assess mosquito transmission of WN. Four mosquito traps, each with a single sentinel chicken, were placed at five different locations on each of four nights. A total of 11,948 mosquitoes was collected, and 14 mosquito pools were found to contain WN, giving a minimum infection rate between 1.08 and 7.54 per 1,000. Only one of the 80 sentinel chickens seroconverted to WN, demonstrating a single mosquito transmission event during the study and a mosquito transmission rate of between 0.8 and 1 per 1,000. Culex nigripalpus Theobald was responsible for WN transmission to the sentinel chicken, although both Cx. nigripalpus and Culex quinquefasciatus Say were found infected with WN. Mosquito transmission rates are reported in this study for the first time for a WN outbreak. This information is essential to determine risk of human and animal infection.

Authors

Lord, Cynthia C., Day, Jonathan F., Rutledge, C. Roxanne, Stark, Lillian M. and Tabachnick, Walter J.

Year Published

2003

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585-40.3.253

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/12943101

Wicking Assays for the Rapid Detection of West Nile and St. Louis Encephalitis Viral Antigens in Mosquitoes (Diptera: Culicidae)Ryan, J.2003

Wicking Assays for the Rapid Detection of West Nile and St. Louis Encephalitis Viral Antigens in Mosquitoes (Diptera: Culicidae)

Keywords

arbovirus, West Nile virus, St. Louis encephalitis, rapid detection, wicking assay, surveillance, WNV

Abstract

The recent outbreaks of West Nile (WN) encephalitis and St. Louis encephalitis (SLE) in the United States have highlighted the need for rapid and specific methods of detecting arboviral antigens in mosquitoes. We evaluated rapid, field-usable assays for detecting and differentiating WN and SLE viruses in mosquito pools, based on a patent-pending, immunochromatographic technology (VecTest) formatted on a dipstick. The device provides results in less than 20 min and can be used in laboratories with adequate containment facilities. In laboratory assessments, both the SLE and WN virus tests demonstrated sensitivity comparable with that of an antigen capture ELISA, but less than can be achieved with Vero cell plaque or reverse-transcriptase polymerase chain reaction assays. There was no evidence of cross-reaction when tested with high concentrations of heterologous flavivirus antigens or with Eastern equine encephalitis or Western equine encephalitis viruses. Both the WN and SLE dipstick tests delivered a clear positive result with a single positive specimen in a pool of 50 mosquitoes. This virus assay technology reduces the time required to obtain test results and will allow rapid medical threat assessment and effective targeting of vector control measures.

Authors

Ryan, J., Davé, K., Emmerich, É., Fernández, B., Turell, M., Johnson, J., Gottfried, K., Burkhalter, K., Kerst, A., Hunt, A., Wirtz, R. and Nasci, R.

Year Published

2003

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585-40.1.95

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/12597660

Oviposition Activity Patterns and West Nile Virus Infection Rates for Members of the Culex pipiens Complex at Different Habitat Types within the Hybrid Zone, Shelby County, TN, 2002 (Diptera: Culicidae)Savage, Harry M.2006

Oviposition Activity Patterns and West Nile Virus Infection Rates for Members of the Culex pipiens Complex at Different Habitat Types within the Hybrid Zone, Shelby County, TN, 2002 (Diptera: Culicidae)

Keywords

Culex pipiens complex, oviposition activity period, West Nile virus, pipiens, hybrid zone, WNV

Abstract

Oviposition activity and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection rates were assessed for members of the Culex pipiens complex from July through December 2002 by using gravid traps placed at four ecologically different sites in the southern portion of the hybrid zone in Shelby County, TN. Molecular assays identified three members of the Cx. pipiens complex: Cx. pipiens pipiens L., Cx. p. quinquefasciatus Say, and Cx. p. pipiens–Cx. p. quinquefasciatus hybrids (hybrids). The Cx. pipiens complex accounted for 90% of mosquitoes collected in gravid traps. All 285 WNV-positive mosquitoes were Culex mosquitoes, and 277 (97%) were Cx. pipiens complex mosquitoes. Infection rates among members of the Cx. pipiens complex were not significantly different. Infection rates were significantly higher at two urban sites than at a rural site, and WNV was not detected at a forested site. At urban sites, abundances of members of the Cx. pipiens complex corresponded to a simple latitude model of the hybrid zone. Cx. p. quinquefasciatus was most abundant (46.4%), followed by hybrids (34.1%) and Cx. p. pipiens (19.5%). The relative abundances at a rural site were reversed with Cx. p. pipiens (48.4%) being most abundant. This demonstrates that spatial habitat variation may profoundly influence the distribution of members of the Cx. pipiens complex within the hybrid zone. Members of the Cx. pipiens complex did not display different oviposition patterns. However, oviposition patterns assessed hourly at urban and rural sites were significantly different. At urban sites, oviposition activity of Cx. pipiens complex mosquitoes was bimodal with an evening peak associated with sunset and a morning peak associated with sunrise. At the rural site, the evening peak was pronounced and the morning peak weak and similar to nighttime activity.

Authors

Savage, Harry M., Anderson, Michael, Gordon, Emily, McMillen, Larry, Colton, Leah, Charnetzky, Dawn, Delorey, Mark, Aspen, Stephen, Burkhalter, Kristen, Biggerstaff, Brad J. and Godsey, Marvin

Year Published

2006

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2006)43[1227:OAPAWN]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17162958

Host-Seeking Heights, Host-Seeking Activity Patterns, and West Nile Virus Infection Rates for Members of the Culex pipiens Complex at Different Habitat Types Within the Hybrid Zone, Shelby County, TN, 2002 (Diptera: Culicidae)Savage, Harry M.2008

Host-Seeking Heights, Host-Seeking Activity Patterns, and West Nile Virus Infection Rates for Members of the Culex pipiens Complex at Different Habitat Types Within the Hybrid Zone, Shelby County, TN, 2002 (Diptera: Culicidae)

Keywords

Culex pipiens complex, host-seeking activity period, host-seeking height, West Nile virus, pipiens, WNV

Abstract

Host-seeking heights, host-seeking activity patterns, and West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection rates were assessed for members of the Culex pipiens complex from July to December 2002, by using chicken-baited can traps (CT) at four ecologically different sites in Shelby County, TN. Host-seeking height was assessed by CT placed at elevations of 3.1, 4.6, and 7.6 m during one 24-h period per month. Host-seeking activity was assessed by paired CT placed at an elevation of 4.6 m. Can traps were sampled at one 10-h daytime interval and at seven 2-h intervals during the evening, night, and morning. Cx. pipiens complex mosquitoes accounted for 87.1% of collected mosquitoes. Culex (Melanoconion) erraticus (Dyar & Knab) accounted for 11.9% of specimens. The average number of Cx. pipiens complex mosquitoes collected per 24-h CT period from July to September was lowest at a rural middle income site (1.7), intermediate at an urban middle income site (11.3), and highest at an urban low income site (47.4). Can traps at the forested site failed to collect Cx. pipiens complex mosquitoes. From July to September at urban sites, Culex pipiens pipiens L. was the rarest of the three complex members accounting for 11.1–25.6% of specimens. At the rural site, Culex pipiens quinquefasciatus Say was the rarest member of the complex. Cx. p. pipiens was not collected after September. Mean abundance of Cx. pipiens complex mosquitoes was higher in traps at 7.6 m than in traps at 4.6 m. Abundances at 3.1 m were intermediate and not significantly different from abundances at the other heights. Initiation of host-seeking activity was associated with the end of civil twilight and activity occurred over an extended nighttime period lasting 8–10 h. All 11 WNV-positive mosquitoes were Cx. pipiens complex mosquitoes collected from urban sites in traps placed at elevations of 4.6 and 7.6 m. Infection rates were marginally nonsignificant by height. Infection rates, host-seeking heights, and activity patterns were not significantly different among members of the Cx. pipiens complex.

Authors

Savage, Harry M., Anderson, Michael, Gordon, Emily, McMillen, Larry, Colton, Leah, Delorey, Mark, Sutherland, Genevieve, Aspen, Stephen, Charnetzky, Dawn, Burkhalter, Kristen and Godsey, Marvin

Year Published

2008

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2008)45[276:HHHAPA]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18402144

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

Drought-Induced Amplification and Epidemic Transmission of West Nile Virus in Southern FloridaShaman, Jeffrey2005

Drought-Induced Amplification and Epidemic Transmission of West Nile Virus in Southern Florida

Keywords

West Nile virus, amplification, transmission, Culex nigripalpus, drought, WNV

Abstract

We show that the spatial-temporal variability of human West Nile (WN) cases and the transmission of West Nile virus (WNV) to sentinel chickens are associated with the spatial-temporal variability of drought and wetting in southern Florida. Land surface wetness conditions at 52 sites in 31 counties in southern Florida for 2001–2003 were simulated and compared with the occurrence of human WN cases and the transmission of WNV to sentinel chickens within these counties. Both WNV transmission to sentinel chickens and the occurrence of human WN cases were associated with drought 2–6 mo prior and land surface wetting 0.5–1.5 mo prior. These dynamics are similar to the amplification and transmission patterns found in southern Florida for the closely related St. Louis encephalitis virus. Drought brings avian hosts and vector mosquitoes into close contact and facilitates the epizootic cycling and amplification of the arboviruses within these populations. Southern Florida has not recorded a severe, widespread drought since the introduction of WNV into the state in 2001. Our results indicate that widespread drought in the spring followed by wetting during summer greatly increase the probability of a WNV epidemic in southern Florida.

Authors

Day, Jonathan F., Shaman, Jeffrey and Stieglitz, Marc

Year Published

2005

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2005)042[0134:DAAETO]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15799522

Achieving Operational Hydrologic Monitoring of Mosquitoborne DiseaseShaman, Jeffrey2005

Achieving Operational Hydrologic Monitoring of Mosquitoborne Disease

Keywords

WNV

Abstract

Mosquitoes and mosquitoborne disease transmission are sensitive to hydrologic variability. If local hydrologic conditions can be monitored or modeled at the scales at which these conditions affect the population dynamics of vector mosquitoes and the diseases they transmit, a means for monitoring or modeling mosquito populations and mosquitoborne disease transmission may be realized. We review how hydrologic conditions have been associated with mosquito abundances and mosquitoborne disease transmission and discuss the advantages of different measures of hydrologic variability. We propose that the useful application of any measure of hydrologic conditions requires additional consideration of the scales for both the hydrologic measurement and the vector control interventions that will be used to mitigate an outbreak of vectorborne disease. Our efforts to establish operational monitoring of St. Louis encephalitis virus and West Nile virus transmission in Florida are also reviewed.

Authors

Day, Jonathan F. and Shaman, Jeffrey

Year Published

2005

Publication

Emerging Infectious Diseases

Locations
DOI

10.3201/eid1109.050340

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16229760

Hydrologic Conditions Describe West Nile Virus Risk in ColoradoShaman, Jeffrey2010

Hydrologic Conditions Describe West Nile Virus Risk in Colorado

Keywords

WNV

Abstract

We examine the relationship between hydrologic variability and the incidence of human disease associated with West Nile virus (WNV; family Flaviviridae, genus Flavivirus) infection (hereafter termed "human WN cases") in Colorado from 2002 to 2007. We find that local hydrologic conditions, as simulated by the Mosaic hydrology model, are associated with differences in human WN cases. In Colorado's eastern plains, wetter spring conditions and drier summer conditions predict human WN cases. In Colorado's western mountains, drier spring and summer conditions weakly predict human WN cases. These findings support two working hypotheses: (1) wet spring conditions increase the abundance of Culex tarsalis vectors in the plains, and (2) dry summer conditions, and respondent irrigational practices during such droughts, favor Cx. pipiens and Cx. tarsalis abundance throughout Colorado. Both of these processes potentially increase the local vector-to-host ratio, favoring WNV amplification among competent avian hosts and bridging to humans.

Authors

Shaman, Jeffrey, Day, Jonathan F. and Komar, Nicholas

Year Published

2010

Publication

International Journal of Environmental Research and Public Health

Locations
DOI

10.3390/ijerph7020494

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20616987

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

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