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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
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

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

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

Association of West Nile virus illness and urban landscapes in Chicago and DetroitRuiz, Marilyn O2007

Association of West Nile virus illness and urban landscapes in Chicago and Detroit

Keywords

WNV

Abstract

Background West Nile virus infection in humans in urban areas of the Midwestern United States has exhibited strong spatial clustering during epidemic years. We derived urban landscape classes from the physical and socio-economic factors hypothesized to be associated with West Nile Virus (WNV) transmission and compared those to human cases of illness in 2002 in Chicago and Detroit. The objectives were to improve understanding of human exposure to virus-infected mosquitoes in the urban context, and to assess the degree to which environmental factors found to be important in Chicago were also found in Detroit. Results Five urban classes that partitioned the urban space were developed for each city region. The classes had many similarities in the two settings. In both regions, the WNV case rate was considerably higher in the urban class associated with the Inner Suburbs, where 1940–1960 era housing dominates, vegetation cover is moderate, and population density is moderate. The land cover mapping approach played an important role in the successful and consistent classification of the urban areas. Conclusion The analysis demonstrates how urban form and past land use decisions can influence transmission of a vector-borne virus. In addition, the results are helpful to develop hypotheses regarding urban landscape features and WNV transmission, they provide a structured method to stratify the urban areas to locate representative field study sites specifically for WNV, and this analysis contributes to the question of how the urban environment affects human health.

Authors

Ruiz, Marilyn O, Walker, Edward D, Foster, Erik S, Haramis, Linn D and Kitron, Uriel D

Year Published

2007

Publication

International Journal of Health Geographics

Locations
DOI

10.1186/1476-072X-6-10

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17352825

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

Salt Marsh as Culex salinarius Larval Habitat in Coastal New YorkRochlin, Ilia2008

Salt Marsh as Culex salinarius Larval Habitat in Coastal New York

Keywords

WNV

Abstract

Culex salinarius is considered one of the most likely bridge vectors involved in the human transmission cycle of West Nile virus (WNV) and eastern equine encephalomyelitis virus (EEEV) in the northeastern USA. The larval habitats of this species in the coastal region of New York State are currently poorly known. Between 2005 and 2007, a larval survey was carried out to identify and characterize possible larval habitats in Suffolk County, encompassing natural and man-made freshwater wetlands, artificial containers, and salt marshes. Only relatively undisturbed salt marsh yielded Cx. salinarius larvae in considerable numbers from several sites over a period of 2 years. The immature stages of this species were found associated with Spartina patens and S. alterniflora of the upper marsh at salinities ranging from 4.3 to 18.8 parts per thousand. Both heavily impacted and relatively undisturbed salt marshes produced several hundreds of adult Cx. salinarius per Centers for Disease Control and Prevention (CDC) light trap per night, an order of magnitude higher than CDC light traps deployed at upland sites. The ability of Cx. salinarius to use both heavily impacted and relatively undisturbed salt marshes for reproduction has significant repercussions for marsh restoration and vector control practices.

Authors

Rochlin, Ilia, Dempsey, Mary E., Campbell, Scott R. and Ninivaggi, Dominick V.

Year Published

2008

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/5748.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18939687

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

Comparative Analysis of Distribution and Abundance of West Nile and Eastern Equine Encephalomyelitis Virus Vectors in Suffolk County, New York, Using Human Population Density and Land Use/Cover DataRochlin, I.2008

Comparative Analysis of Distribution and Abundance of West Nile and Eastern Equine Encephalomyelitis Virus Vectors in Suffolk County, New York, Using Human Population Density and Land Use/Cover Data

Keywords

mosquito vectors, urban, rural, GIS, West Nile virus, WNV

Abstract

Five years of CDC light trap data from Suffolk County, NY, were analyzed to compare the applicability of human population density (HPD) and land use/cover (LUC) classification systems to describe mosquito abundance and to determine whether certain mosquito species of medical importance tend to be more common in urban (defined by HPD) or residential (defined by LUC) areas. Eleven study sites were categorized as urban or rural using U.S. Census Bureau data and by LUC types using geographic information systems (GISs). Abundance and percent composition of nine mosquito taxa, all known or potential vectors of arboviruses, were analyzed to determine spatial patterns. By HPD definitions, three mosquito species, Aedes canadensis (Theobald), Coquillettidia perturbans (Walker), and Culiseta melanura (Coquillett), differed significantly between habitat types, with higher abundance and percent composition in rural areas. Abundance and percent composition of these three species also increased with freshwater wetland, natural vegetation areas, or a combination when using LUC definitions. Additionally, two species, Ae. canadensis and Cs. melanura, were negatively affected by increased residential area. One species, Aedes vexans (Meigen), had higher percent composition in urban areas. Two medically important taxa, Culex spp. and Aedes triseriatus (Say), were proportionally more prevalent in residential areas by LUC classification, as was Aedes trivittatus (Coquillett). Although HPD classification was readily available and had some predictive value, LUC classification resulted in higher spatial resolution and better ability to develop location specific predictive models.

Authors

Rochlin, I., Harding, K., Ginsberg, H. S. and Campbell, S. R.

Year Published

2008

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2008)45[563:CAODAA]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18533453

Environmental risk factors associated with West Nile virus clinical disease in Florida horsesRIOS, L. M. V.2009

Environmental risk factors associated with West Nile virus clinical disease in Florida horses

Keywords

WNV

Abstract

The objective of this study was to examine the extrinsic risk factors of West Nile virus (WNV) clinical disease in Florida horses as established from confirmed and negative horses tested within the state from 2001 to 2003. An Arboviral Case Information Form (ACF) was submitted by a referring veterinarian at the time of testing to the Florida Department of Agriculture and Consumer Services on every horse suspected of a viral encephalitis in Florida. A follow-up survey that focused on arbovirus prevention and farm ecology was created and mailed to the owner of each tested horse. Data from the follow-up survey indicated peak WNV prevalence in the late summer months in Florida. Quarter horses were the most commonly affected breed. The WNV vaccine was highly protective and natural water on the property also had a protective association. Factors that increased the risk of WNV to horses were the use of fans and a stable construction of solid wood or cement. Some risk indicators were dead birds on the property and other ill animals on the property. Data from this retrospective study have helped identify factors associated with WNV transmission in equines in Florida. Horses that have not been vaccinated and show clinical signs of arboviral infection from June to November should be tested for WNV. Horses that have been vaccinated and show clinical signs should be tested when the vaccination was administered within 1 month or greater than 6 months prior to the onset of clinical symptoms associated with WN infection.

Authors

RIOS, L. M. V., SHEU, J.-J., DAY, J. F., MARUNIAK, J. E., SEINO, K., ZARETSKY, H. and LONG, M. T.

Year Published

2009

Publication

Medical and Veterinary Entomology

Locations
DOI

10.1111/j.1365-2915.2009.00821.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19941601

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