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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
Emergence of Culex pipiens from Overwintering HibernaculaCiota, Alexander T.2011

Emergence of Culex pipiens from Overwintering Hibernacula

Keywords

Culex pipiens, overwintering, mark–recapture, West Nile virus, WNV

Abstract

Overwintering populations of Culex pipiens, the principal enzootic vector of West Nile virus in the northeastern USA, were studied over 3 consecutive winters from 2006 to 2008, using mark–recapture techniques to determine when Cx. pipiens females began to disperse from overwintering hibernacula and how their survival influenced early season populations. In February of each year, Cx. pipiens were aspirated and marked using fluorescent powder; 4,067, 752, and 3,070 diapausing Cx. pipiens were marked in each successive year. Mosquitoes were then trapped from mid-April to early May of each year using 19 Centers for Disease Control and Prevention (CDC) light traps and 16 CDC gravid traps. A total of 348, 39, and 111 Culex mosquitoes were captured in the spring of 2006, 2007, and 2008, respectively. The number of mosquitoes marked in overwintering habitats is generally positively correlated with the number of mosquitoes recaptured in the early spring (linear regression, R2  =  0.79, P  =  0.04), yet results also suggest that seasonal variations beyond overwintering population size are likely important in determining the success of emergent populations. A single marked Cx. pipiens was captured in both 2006 and 2008. In 2006, the mosquito was captured 0.5 km from its overwintering site while in 2008 the mosquito was captured 0.3 km from its overwintering site. In all study years, mosquitoes consistently began exiting overwintering hibernacula the 3rd week of April, yet evidence of earlier exodus was observed in 2007, when outside temperatures were significantly higher in preceding days and months.

Authors

Ciota, Alexander T., Drummond, Cori L., Drobnack, Jason, Ruby, Meghan A., Kramer, Laura D. and Ebel, Gregory D.

Year Published

2011

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/8756-971X-27.1.21

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21476444

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

Weather and Land Cover Influences on Mosquito Populations in Sioux Falls, South DakotaChuang, Ting-Wu2011

Weather and Land Cover Influences on Mosquito Populations in Sioux Falls, South Dakota

Keywords

West Nile virus, Culex tarsalis, Aedes vexans, weather, land cover, WNV

Abstract

This study compared the spatial and temporal patterns of Culex tarsalis Coquillett and Aedes vexans Meigen populations and examined their relationships with land cover types and climatic variability in Sioux Falls, SD. Between 24 and 30 CDC CO2-baited light traps were set annually in Sioux Falls from May to September 2005–2008. Land cover data were acquired from the 2001 National Land Cover Dataset and the percentages of selected land cover types were calculated within a 600-m buffer zone around each trap. Meteorological information was summarized from local weather stations. Cx. tarsalis exhibited stronger spatial autocorrelation than Ae. vexans. Land cover analysis indicated that Cx. tarsalis was positively correlated with grass/hay, and Ae. vexans was positively correlated with wetlands. No associations were identified between irrigation and the host-seeking population of each species. Higher temperature in the current week and 2 wk prior and higher precipitation 3–4 wk before collection of host-seeking adult mosquitoes had positive influences on Cx. tarsalis abundance. Temperature in the current week and rainfall 2–3 wk before sampling had positive influences on Ae. vexans abundance. This study revealed the different influences of weather and land cover on important mosquito species in the Northern Great Plains region, which can be used to improve local vector control strategies and West Nile virus prevention efforts.

Authors

Chuang, Ting-Wu, Hildreth, Michael B., Vanroekel, Denise L. and Wimberly, Michael C.

Year Published

2011

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10246

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21661329

Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United StatesChuang, Ting-Wu2012

Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States

Keywords

WNV

Abstract

The northern Great Plains (NGP) of the United States has been a hotspot of West Nile virus (WNV) incidence since 2002. Mosquito ecology and the transmission of vector-borne disease are influenced by multiple environmental factors, and climatic variability is an important driver of inter-annual variation in WNV transmission risk. This study applied multiple environmental predictors including land surface temperature (LST), the normalized difference vegetation index (NDVI) and actual evapotranspiration (ETa) derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) products to establish prediction models for WNV risk in the NGP. These environmental metrics are sensitive to seasonal and inter-annual fluctuations in temperature and precipitation, and are hypothesized to influence mosquito population dynamics and WNV transmission. Non-linear generalized additive models (GAMs) were used to evaluate the influences of deviations of cumulative LST, NDVI, and ETa on inter-annual variations of WNV incidence from 2004-2010. The models were sensitive to the timing of spring green up (measured with NDVI), temperature variability in early spring and summer (measured with LST), and moisture availability from late spring through early summer (measured with ETa), highlighting seasonal changes in the influences of climatic fluctuations on WNV transmission. Predictions based on these variables indicated a low WNV risk across the NGP in 2011, which is concordant with the low case reports in this year. Environmental monitoring using remote-sensed data can contribute to surveillance of WNV risk and prediction of future WNV outbreaks in space and time.

Authors

Chuang, Ting-Wu and Wimberly, Michael C.

Year Published

2012

Publication

PLOS One

Locations
DOI

10.1371/journal.pone.0046882

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/23071656

Landscape-Level Spatial Patterns of West Nile Virus Risk in the Northern Great PlainsChuang, T.-W.2012

Landscape-Level Spatial Patterns of West Nile Virus Risk in the Northern Great Plains

Keywords

WNV

Abstract

Understanding the landscape-level determinants of West Nile virus (WNV) can aid in mapping high-risk areas and enhance disease control and prevention efforts. This study analyzed the spatial patterns of human WNV cases in three areas in South Dakota during 2003–2007 and investigated the influences of land cover, hydrology, soils, irrigation, and elevation by using case–control models. Land cover, hydrology, soils, and elevation all influenced WNV risk, although the main drivers were different in each study area. Risk for WNV was generally higher in areas with rural land cover than in developed areas, and higher close to wetlands or soils with a high ponding frequency. In western South Dakota, WNV risk also decreased with increasing elevation and was higher in forested areas. Our results showed that the spatial patterns of human WNV risk were associated with landscape-level features that likely reflect variability in mosquito ecology, avian host communities, and human activity.

Authors

Chuang, T.-W., Hockett, C. W., Kightlinger, L. and Wimberly, M. C.

Year Published

2012

Publication

American Journal of Tropical Medicine and Hygiene

Locations
DOI

10.4269/ajtmh.2012.11-0515

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/22492161

Factors associated with mosquito pool positivity and the characterization of the West Nile viruses found within Louisiana during 2007Christofferson, Rebecca C2010

Factors associated with mosquito pool positivity and the characterization of the West Nile viruses found within Louisiana during 2007

Keywords

WNV

Abstract

Background West Nile virus (WNV) is an arbovirus of public health importance in the genus Flavivirus, a group of positive sense RNA viruses. The NS3 gene has a high level of substitutions and is phylogenetically informative. Likewise, substitutions in the envelope region have been postulated to enable viruses to subvert immune responses. Analysis of these genes among isolates from positive mosquitoes collected in Louisiana illustrates the variation present in the regions and provides improved insight to a phylogenetic model. Employing a GIS eco-regionalization method, we hypothesized that WNV pool positivity was correlated with regional environmental characteristics. Further, we postulated that the phylogenetic delineations would be associated with variations in regional environmental conditions. Results Type of regional land cover was a significant effect (p < 0.0001) in the positive pool prediction, indicating that there is an ecological component driving WNV activity. Additionally, month of collection was significant (p < 0.0001); and thus there is a temporal component that contributes to the probability of getting a positive mosquito pool. All virus isolates are of the WNV 2002 lineage. There appears to be some diversity within both forested and wetland areas; and the possibility of a distinct clade in the wetland samples. Conclusions The phylogenetic analysis shows that there has been no reversion in Louisiana from the 2002 lineage which replaced the originally introduced strain. Our pool positivity model serves as a basis for future testing, and could direct mosquito control and surveillance efforts. Understanding how land cover and regional ecology effects mosquito pool positivity will greatly help focus mosquito abatement efforts. This would especially help in areas where abatement programs are limited due to either funding or man power. Moreover, understanding how regional environments drive phylogenetic variation will lead to a greater understanding of the interactions between ecology and disease prevalence.

Authors

Christofferson, Rebecca C, Roy, Alma F and Mores, Christopher N

Year Published

2010

Publication

Virology Journal

Locations
DOI

10.1186/1743-422X-7-139

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20579348

Parasites and Infectious Diseases of Greater Sage-Grouse.Christiansen, Thomas J.2011

Parasites and Infectious Diseases of Greater Sage-Grouse.

Keywords

Centrocercus urophasianus, disease, greater sage-grouse, parasite, pathogen

Abstract

We report the parasites, infectious diseases, and noninfectious diseases related to toxicants found in Greater Sage-Grouse (Centrocercus urophasianus) across its range. Documentation of population-level effects is rare, although researchers have responded to the recent emergence of West Nile virus with rigorous efforts. West Nile virus shows greater virulence and potential population-level effects than any infectious agent detected in Greater Sage-Grouse to date. Research has demonstrated that (1) parasites and diseases can have population-level effects on grouse species; (2) new infectious diseases are emerging; and (3) habitat fragmentation is increasing the number of small, isolated populations of Greater Sage-Grouse. Natural resource management agencies need to develop additional research and systematic monitoring programs for evaluating the role of micro-and macro parasites, especially West Nile virus, infectious bronchitis and other corona viruses, avian retroviruses, Mycoplasma spp., and Eimeria spp. and associated enteric bacteria affecting sage-grouse populations.

Authors

Christiansen, Thomas J.; Tate, Cynthia M.

Year Published

2011

Publication

Studies in Avian Biology

Locations
DOI

10.1525/california/9780520267114.001.0001

A Method to Increase Efficiency in Testing Pooled Field-Collected MosquitoesChisenhall, Daniel M.2008

A Method to Increase Efficiency in Testing Pooled Field-Collected Mosquitoes

Keywords

West Nile virus, mosquito pool, quantitative reverse transcriptase polymerase chain reaction, arbovirus testing, surveillance, WNV

Abstract

Testing field-caught mosquito collections can result in thousands of pools, and testing pools of 50 mosquitoes each can be both time consuming and cost prohibitive. Consequently, we have developed an alternative approach to testing mosquito pools for arboviruses, utilizing a superpool strategy. When mosquito samples are processed for extraction of viral RNA and subsequent virus testing via quantitative real-time polymerase chain reaction, each pool is tested individually. Using the method described here, 0.025 ml from each of 10 pools is combined into a superpool for RNA extraction and testing. When a virus-positive superpool sample is found, each of the original 10 pools that constitute this sample is tested individually in order to find the specific positive sample. By retesting the original samples after the initial superpool screen, we are still able to obtain reliable estimates for minimum infection rates or maximum likelihood estimations. To test this principle, we created controlled mosquito pools of known titer and subjected them to our superpool process. We were able to detect our entire range of laboratory-created pools as being West Nile virus (WNV) positive. In 2005, field surveillance efforts from our laboratory resulted in over 4,000 mosquito pools tested, with 8 resulting WNV-positive samples. We found that all of these field samples were detected as WNV positive using the superpool method and contained calculated virus titers from <0.1 to 4.1 log10 plaque-forming units/ml WNV, indicating that the limit of superpool detection of WNV is below this point. These results reveal that the superpool method could be accurately used to detect WNV in field-collected specimens.

Authors

Chisenhall, Daniel M., Vitek, Christopher J., Richards, Stephanie L. and Mores, Christopher N.

Year Published

2008

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/5671.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18666541

West Nile Virus in the New World: Appearance, Persistence, and Adaptation to a New Econiche—An Opportunity TakenCALISHER, CHARLES H.2000

West Nile Virus in the New World: Appearance, Persistence, and Adaptation to a New Econiche—An Opportunity Taken

Keywords

No keywords available

Abstract

No abstract available

Authors

CALISHER, CHARLES H.

Year Published

2000

Publication

Viral Immunology

Locations
    DOI

    10.1089/vim.2000.13.411

    Winter Biology of Wetland Mosquitoes at a Focus of Eastern Equine Encephalomyelitis Virus Transmission in Alabama, USABurkett-Cadena, Nathan D.2011

    Winter Biology of Wetland Mosquitoes at a Focus of Eastern Equine Encephalomyelitis Virus Transmission in Alabama, USA

    Keywords

    overwintering, mosquito, winter emergence, eastern equine encephalitis, WNV

    Abstract

    At temperate latitudes, vectors and pathogens must possess biological mechanisms for coping with cold temperatures and surviving from one transmission season to the next. Mosquitoes that overwinter in the adult stage have been proposed as winter maintenance hosts for certain arboviruses. In the cases of West Nile virus (family Flaviviridae, genus Flavivirus) and St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus), discovery of infected overwintering females lends support to this hypothesis, but for other arboviruses, in particular Eastern equine encephalomyelitis virus (family Togaviridae, genus Alphavirus, EEEV), overwintering of the virus in mosquito hosts as not been demonstrated. In the current study, we collected overwintering mosquitoes from a focus of EEEV transmission in the southeastern United States to determine whether mosquitoes serve as winter maintenance hosts for EEEV and to document overwintering biologies of suspected vectors. No virus was detected via reverse transcription-polymerase chain reaction of >500 female mosquitoes collected during three winters. Investigation into the winter biologies indicated that Anopheles punctipennis (Say), Culex erraticus (Dyar & Knab), Culex peccator Dyar & Knab, and Uranotaenia sapphirina (Osten Sacken) overwinter as females. Females of these species were collected from hollow trees and emergence traps placed over ground holes. Southern magnolia, Magnolia grandiflora L., trees were preferred overwintering sites of culicine mosquitoes. Emergence from underground overwintering sites peaked in mid-March, when air temperatures reached 18–22°C, and the first bloodengorged females of Cx. erraticus and Cx. peccator were collected during this same period. Blood-fed Culex territans Walker females were collected as early as mid-February. This work provides insight into the overwintering biologies of suspected virus vectors at a site of active EEEV transmission and provides limited evidence against the hypothesis that EEEV persists through intertransmission periods in overwintering mosquitoes.

    Authors

    Burkett-Cadena, Nathan D., White, Gregory S., Eubanks, Micky D. and UNNASCH, THOMAS R.

    Year Published

    2011

    Publication

    Journal of Medical Entomology

    Locations
    DOI

    10.1603/ME10265

    Additional Information:

    http://www.ncbi.nlm.nih.gov/pubmed/21936314

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