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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
Use of Scented Sugar Bait Stations to Track Mosquito-Borne Arbovirus Transmission in CaliforniaLothrop, Hugh D.2012

Use of Scented Sugar Bait Stations to Track Mosquito-Borne Arbovirus Transmission in California

Keywords

surveillance, West Nile virus, sugar feeding, bait station, Culex larsalis, WNV

Abstract

Laboratory and field research was conducted to determine if Culex tarsalis Coquillett expectorated West Nile virus (WNV) during sugar feeding and if a lure or bait station could be developed to exploit this behavior for WNV surveillance. Experimentally infected Cx. tarsalis repeatedly expectorated WNV onto filter paper strips and into vials with wicks containing sucrose that was readily detectable by a quantitative reverse transcriptase-polymerase chain reaction assay. Few females (33%, n = 27) became infected by imbibing sugar solutions spiked with high concentrations (107 plaque forming units/ml) of WNV, indicating sugar feeding stations probably would not be a source of WNV infection. In nature, sugar bait stations scented with the floral attractant phenyl acetaldehyde tracked WNV transmission activity in desert but not urban or agricultural landscapes in California. When deployed in areas of the Coachella Valley with WNV activity during the summer of 2011, 27 of 400 weekly sugar samples (6.8%) tested positive for WNV RN A by reverse transcriptase-polymerase chain reaction. Prevalence of positives varied spatially, but positive sugar stations were detected before concurrent surveillance measures of infection (mosquito pools) or transmission (sentinel chicken seroconversions). In contrast, sugar bait stations deployed in urban settings in Los Angeles or agricultural habits near Bakersfield in Kern County supporting WNV activity produced 1 of 90 and 0 of 60 positive weekly sugar samples, respectively. These results with sugar bait stations will require additional research to enhance bait attractancy and to understand the relationship between positive sugar stations and standard metrics of arbovirus surveillance.

Authors

Lothrop, Hugh D., Wheeler, Sarah S., Fang, Ying and Reisen, William K.

Year Published

2012

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME12117

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/23270177

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

Rainfall Influences Survival of Culex pipiens (Diptera: Culicidae) in a Residential Neighborhood in the Mid-Atlantic United StatesJones, Christy E.2012

Rainfall Influences Survival of Culex pipiens (Diptera: Culicidae) in a Residential Neighborhood in the Mid-Atlantic United States

Keywords

Culex pipiens, dispersal, mosquito, survival, West Nile virus, WNV

Abstract

Measurement of the survival and dispersal rates of mosquito vectors is an important step in designing and implementing control strategies. Vector survival plays a key role in determining the intensity of pathogen transmission, and vector movement determines the spatial scale on which control efforts must operate to be effective. We provide the first estimates of field survival and dispersal rates for Culex pipiens L. in North America, an important enzootic and bridge vector for West Nile virus (WNV). We conducted mark-release-recapture studies in a residential area near Washington, DC, in two consecutive years and fit nonlinear regression models to the recapture data that incorporate weather information into survival and recapture probabilities. We found that daily survival rates were not significantly different between the 2 yr but were negatively affected by rainfall. The daily survival rate was 0.904 ± 0.037 (SE), which implies an average longevity of 10.4 d. As with other vector-borne pathogens, the measured survival rate suggests that at our site the majority of WNV-infected Cx. pipiens mosquitoes may perish before becoming infectious (being able to transmit WNV to hosts). We found relatively little evidence of dispersal after the initial night after release. Our results suggest that transmission of WNV and other pathogens transmitted by Cx. pipiens may be highly local and they highlight the importance of factors that influence survival of mosquito vectors.

Authors

Jones, Christy E., Lounibos, L. Philip, Marra, Peter P. and Kilpatrick, A. Marm

Year Published

2012

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME11191

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/22679852

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

West Nile virus cluster analysis and vertical transmission in Culex pipiens complex mosquitoes in Sacramento and Yolo Counties, California, 2011 Fechter-Leggett, Ethan2012

West Nile virus cluster analysis and vertical transmission in Culex pipiens complex mosquitoes in Sacramento and Yolo Counties, California, 2011

Keywords

California, California: epidemiology, Culex, West Nile virus: pathogenicity, West Nile virus, West Nile Fever: transmission, West Nile Fever, Infectious Disease Transmission, Vertical, Female, Culex: virology, Animals

Abstract

West Nile virus (WNV) is now endemic in California, with annual transmission documented by the statewide surveillance system. Although much is known about the horizontal avian-mosquito transmission cycle, less is known about vertical transmission under field conditions, which may supplement virus amplification during summer and provide a mechanism to infect overwintering female mosquitoes during fall. The current study identified clusters of WNV-infected mosquitoes in Sacramento and Yolo Counties, CA, during late summer 2011 and tested field-captured ovipositing female mosquitoes and their progeny for WNV RNA to estimate the frequency of vertical transmission. Space-time clustering of WNV-positive Culex pipiens complex pools was detected in the northern Elk Grove area of Sacramento County between July 18 and September 18, 2011 (5.22 km radius; p<0.001 and RR=7.80). Vertical transmission by WNV-infected females to egg rafts was 50% and to larvae was 40%. The estimated minimal filial infection rate from WNV-positive, ovipositing females was 2.0 infected females/1,000. The potential contribution of vertical transmission to WNV maintenance and amplification are discussed.

Authors

Fechter-Leggett, Ethan, Nelms, Brittany M., Barker, Christopher M. and Reisen, William K.

Year Published

2012

Publication

Journal of Vector Ecology

Locations
DOI

10.1111/j.1948-7134.2012.00248.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/23181869

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

Bloodmeal Host Congregation and Landscape Structure Impact the Estimation of Female Mosquito (Diptera: Culicidae) Abundance Using Dry Ice-Baited TrapsThiemann, Tara2011

Bloodmeal Host Congregation and Landscape Structure Impact the Estimation of Female Mosquito (Diptera: Culicidae) Abundance Using Dry Ice-Baited Traps

Keywords

Culex tarsalis, Anopheles freeborni, dry ice-baited traps, abundance, California, WNV

Abstract

Vegetation patterns and the presence of large numbers of nesting herons and egrets significantly altered the number of host-seeking Culex tarsalis Coquillett (Diptera: Culicidae) collected at dry ice-baited traps. The numbers of females collected per trap night at traps along the ecotone of Eucalyptus stands with and without a heron colony were always greater or equal to numbers collected at traps within or under canopy. No Cx. tarsalis were collected within or under Eucaplytus canopy during the peak heron nesting season, even though these birds frequently were infected with West Nile virus and large number of engorged females could be collected at resting boxes. These data indicate a diversion of host-seeking females from traps to nesting birds reducing sampling efficiency.

Authors

Thiemann, Tara, Nelms, Brittany and Reisen, William K.

Year Published

2011

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10273

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21661310

Simulation of the seasonal cycles of bird, equine and human West Nile virus casesLaperriere, Vincent2011

Simulation of the seasonal cycles of bird, equine and human West Nile virus cases

Keywords

Zoonosis; Arbovirus; Infectious disease; West Nile virus; Epidemic model; Climate forcing; Temperature dependent parameters; Seasons, WNV

Abstract

The West Nile virus (WNV) is an arthropod-borne virus (arbovirus) circulating in a natural transmission cycle between mosquitoes (enzootic vectors) and birds (amplifying hosts). Additionally, mainly horses and humans (dead-end hosts) may be infected by blood-feeding mosquitoes (bridge vectors). We developed an epidemic model for the simulation of the WNV dynamics of birds, horses and humans in the U.S., which we apply to the Minneapolis metropolitan area (Minnesota). The SEIR-type model comprises a total of 19 compartments, that are 4 compartments for mosquitoes and 5 compartments or health states for each of the 3 host species. It is the first WNV model that simulates the seasonal cycle by explicitly considering the environmental temperature. The latter determines model parameters responsible for the population dynamics of the mosquitoes and the extrinsic incubation period. Once initialized, our WNV model runs for the entire period 2002–2009, exclusively forced by environmental temperature. Simulated incidences are mainly determined by host and vector population dynamics, virus transmission and herd immunity, respectively. We adjusted our WNV model to fit monthly totals of reported bird, equine and human cases in the Minneapolis metropolitan area. From this process we estimated that the proportion of actually WNV-induced dead birds reported by the Centers for Disease Control and Prevention is about 0.8%, whereas 7.3% of equine and 10.7% of human cases were reported. This is consistent with referenced expert opinions whereby about 10% of equine and human cases are symptomatic (the other 90% of asymptomatic cases are usually not reported). Despite the restricted completeness of surveillance data and field observations, all major peaks in the observed time series were caught by the simulations. Correlation coefficients between observed and simulated time series were R = 0.75 for dead birds, R = 0.96 for symptomatic equine cases and R = 0.86 for human neuroinvasive cases, respectively.

Authors

Laperriere, Vincent, Brugger, Katharina and Rubel, Franz

Year Published

2011

Publication

Preventive Veterinary Medicine

Locations
DOI

10.1016/j.prevetmed.2010.10.013

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21093946

North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperatureAndrade, C. C.2011

North American West Nile virus genotype isolates demonstrate differential replicative capacities in response to temperature

Keywords

WNV

Abstract

The presence of West Nile virus (WNV) was first documented in California, USA, during the summer of 2003, and subsequently the virus has become endemic throughout the state. Sequence analysis has demonstrated that the circulating strains are representative of the North American (WN02) genotype that has displaced the East Coast genotype (NY99). A recent study has indicated that enhanced vector competence at elevated temperatures may have played a role in the displacement of the East Coast genotype by WN02. In the current study, four WN02 strains from California, including an initial 2003 isolate (COAV997), were compared to strain NY99 in growth curve assays in mosquito and duck embryonic fibroblast (DEF) cell lines at differing, biologically relevant temperatures to assess the relative temperature sensitivities of these natural isolates. COAV997 was significantly debilitated in viral replication in DEF cells at 44 °C. Full-length sequence comparison of COAV997 against the NY99 reference strain revealed non-synonymous mutations in the envelope glycoprotein (V159A), non-structural protein 1 (NS1) (K110N) and non-structural protein 4A (NS4A) (F92L), as well as two mutations in the 3' UTR: C→T at nt 10 772 and A→G at nt 10 851. These non-synonymous mutations were introduced into the NY99 viral backbone by site-directed mutagenesis. A mutant containing the NS1-K110N and NS4A-F92L mutations exhibited a debilitated growth phenotype in DEF cells at 44 °C, similar to that of COAV997. One explanation for the subsistence of this genotype is that COAV997 was obtained from an area of California where avian host species might not present elevated temperatures. These data indicate that the NS1 and NS4A mutations identified in some WN02 isolates could reduce thermal stability and impede replication of virus at temperatures observed in febrile avian hosts.

Authors

Andrade, C. C., Maharaj, P. D., Reisen, W. K. and Brault, A. C.

Year Published

2011

Publication

Journal of General Virology

Locations
DOI

10.1099/vir.0.032318-0

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21775581

The Impact of Adulticide Applications on Mosquito Density in Chicago, 2005Mutebi, John-Paul2011

The Impact of Adulticide Applications on Mosquito Density in Chicago, 2005

Keywords

WNV

Abstract

The city of Chicago used ground ultra-low volume treatments of sumithrin (ANVIL 10+10) in areas with high West Nile virus infection rates among Culex mosquitoes. Two sequential treatments in Morbidity and Mortality Weekly Reports wk 31 and 32 decreased mean mosquito density by 54% from 2.5 to 1.1 mosquitoes per trap-day, whereas mosquito density increased by 153% from 1.3 to 3.3 mosquitoes per trap-day at the nonsprayed sites. The difference between these changes in mosquito density was statistically significant (confidence intervals for the difference in change: -4.7 to -1.9). Sequential adulticide treatments in September (wk 34 and 35) had no effect on mosquito density, probably because it was late in the season and the mosquitoes were presumably entering diapause and less active. Overall, there was significant decrease in mosquito density at the trap sites treated in all 4 wk (wk 31, 32, 34, and 35), suggesting that sustained sequential treatments suppressed mosquito density. Maximum likelihood estimates (MLE) of infection rate estimates varied independently of adulticide treatments, suggesting that the adulticide treatments had no direct effect on MLE. Mosquito trap counts were low, which was probably due to large numbers of alternative oviposition sites, especially catch basins competing with the gravid traps.

Authors

Mutebi, John-Paul, Delorey, Mark J., Jones, Roderick C., Plate, David K., Gerber, Susan I., Gibbs, Kevin P., Sun, Gouhe, Cohen, Nicole J. and Paul, William S.

Year Published

2011

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/10-6045.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/21476450

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