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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
Detection of West Nile Virus RNA in Mosquitoes and Identification of Mosquito Blood Meals Collected at Alligator Farms in LouisianaUnlu, Isik2010

Detection of West Nile Virus RNA in Mosquitoes and Identification of Mosquito Blood Meals Collected at Alligator Farms in Louisiana

Keywords

mosquitoes, Alligator mississippiensis, Culex quinquefasciatus, Culex nigripalpus, cytochrome B, WNV

Abstract

Since 2001, alligator farms in the United States have sustained substantial economic losses because of West Nile virus (WNV) outbreaks in American alligators (Alligator mississippiensis). Once an initial infection is introduced into captive alligators, WNV can spread among animals by contaminative transmission. Some outbreaks have been linked to feeding on infected meat or the introduction of infected hatchlings, but the initial source of WNV infection has been uncertain in other outbreaks. We conducted a study to identify species composition and presence of WNV in mosquito populations associated with alligator farms in Louisiana. A second objective of this study was to identify the origin of mosquito blood meals collected at commercial alligator farms. Mosquitoes were collected from 2004 to 2006, using Centers for Disease Control light traps, gravid traps, backpack aspirators, and resting boxes. We collected a total of 58,975 mosquitoes representing 24 species. WNV was detected in 41 pools of females from 11 mosquito species: Anopheles crucians, Anopheles quadrimaculatus, Coquillettidia perturbons, Culex coronator, Culex erraticus, Culex nigripalpus, Culex quinquefasciatus, Mansonia titillans, Aedes sollicitans, Psorophora columbiae, and Uranotaenia lowii. The blood meal origins of 213 field-collected mosquitoes were identified based on cytochrome B sequence identity. Alligator blood was detected in 21 mosquitoes representing six species of mosquitoes, including Cx. quinquefasciatus and Cx. nigripalpus. Our results showed that mosquitoes of species that are known to be competent vectors of WNV fed regularly on captive alligators. Therefore, mosquitoes probably are important in the role of transmission of WNV at alligator farms.

Authors

Unlu, Isik, Kramer, Wayne L., Roy, Alma F. and Foil, Lane D.

Year Published

2010

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME09087

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20695278

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

Ecological Niche Modeling of Potential West Nile Virus Vector Mosquito Species in IowaLarson, Scott R.2010

Ecological Niche Modeling of Potential West Nile Virus Vector Mosquito Species in Iowa

Keywords

WNV

Abstract

Ecological niche modeling (ENM) algorithms, Maximum Entropy Species Distribution Modeling (Maxent) and Genetic Algorithm for Rule-set Prediction (GARP), were used to develop models in Iowa for three species of mosquito - two significant, extant West Nile virus (WNV) vectors (Culex pipiens L and Culex tarsalis Coquillett (Diptera: Culicidae)), and the nuisance mosquito, Aedes vexans Meigen (Diptera: Culicidae), a potential WNV bridge vector. Occurrence data for the three mosquito species from a state-wide arbovirus surveillance program were used in combination with climatic and landscape layers. Maxent successfully created more appropriate niche models with greater accuracy than GARP. The three Maxent species' models were combined and the average values were statistically compared to human WNV incidence at the census block group level. The results showed that the Maxent-modeled species' niches averaged together were a useful indicator of WNV human incidence in the state of Iowa. This simple method for creating probability distribution maps proved useful for understanding WNV dynamics and could be applied to the study of other vector-borne diseases.

Authors

Larson, Scott R., DeGroote, John P., Bartholomay, Lyric C. and Sugumaran, Ramanathan

Year Published

2010

Publication

Journal of Insect Science

Locations
DOI

10.1673/031.010.11001

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20874412

Irrigated Agriculture Is an Important Risk Factor for West Nile Virus Disease in the Hyperendemic Larimer-Boulder-Weld Area of North Central ColoradoEisen, Lars2010

Irrigated Agriculture Is an Important Risk Factor for West Nile Virus Disease in the Hyperendemic Larimer-Boulder-Weld Area of North Central Colorado

Keywords

Colorado, Culex, irrigated agriculture, mosquito larval habitat, West Nile virus disease, WNV

Abstract

This study focused on two West Nile virus (WNV) disease outbreak years, 2003 and 2007, and included a three-county area (Larimer, Boulder, and Weld) in North Central Colorado that is hyperendemic for WNV disease. We used epidemiological data for reported WNV disease cases at the census tract scale to: 1) elucidate whether WNV disease incidence differs between census tracts classified as having high versus lower human population density (based on a threshold value of 580 persons/km2) and 2) determine associations between WNV disease incidence and habitat types suitable as development sites for the larval stage of Culex mosquito vectors. WNV disease incidence was significantly elevated in census tracts with lower human population density, compared with those with high density of human population, in both 2003 (median per census tract of 223 and 143 cases per 100,000 population, respectively) and 2007 (median per census tract of 46 and 19 cases per 100,000 population). This is most likely related, in large part, to greater percentages of coverage in less densely populated census tracts by habitats suitable as development sites for Culex larvae (open water, developed open space, pasture/hay, cultivated crops, woody wetlands, and emergent herbaceous wetlands) and, especially, for the subset of these habitats made up by irrigated agricultural land (pasture/hay and cultivated crops) that presumably serve as major producers of the locally most important vector of WNV to humans: Culex tarsalis. A series of analyses produced significant positive associations between greater coverage of or shorter distance to irrigated agricultural land and elevated WNV disease incidence. As an exercise to produce data with potential to inform spatial implementation schemes for prevention and control measures within the study area, we mapped the spatial patterns, by census tract, of WNV disease incidence in 2003 and 2007 as well as the locations of census tracts that had either low (75th percentile) WNV disease incidence in both outbreak years (relative to the incidence for each year). This revealed substantial changes from 2003 to 2007 in the spatial pattern for census tracts within the study area with high WNV disease incidence and suggests a dynamic and evolving scenario of WNV transmission to humans that needs to be taken into account for prevention and control measures to stay current and represent the most effective use of available resources.

Authors

Eisen, Lars, Barker, Christopher M., Moore, Chester G., Pape, W. John, Winters, Anna M. and Cheronis, Nicholas

Year Published

2010

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/ME10036

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20939393

The Effects of West Nile Virus on the Reproductive Success and Overwinter Survival of Eastern Bluebirds in AlabamaHill, Geoffrey E.2010

The Effects of West Nile Virus on the Reproductive Success and Overwinter Survival of Eastern Bluebirds in Alabama

Keywords

WNV

Abstract

We tested for negative effects of West Nile virus (WNV) on a breeding population of eastern bluebirds in Alabama by comparing fecundity and reproductive success in years before and after the arrival of WNV and by comparing fecundity, reproductive success, and overwinter survival of seropositive and seronegative individuals within the same population in the same years. We found that female bluebirds were more likely to be seropositive than male bluebirds. Age and individual condition did not affect likelihood of being seropositive. Being seropositive for WNV was not associated with any negative effects on reproduction or survival. However, female fecundity was higher in years after WNV compared to years before the arrival of WNV. The reproductive success of males who tested positive for WNV exposure was higher than that of males that were seronegative. Overall, we found no negative effects on reproduction or survival after exposure to WNV.

Authors

Hill, Geoffrey E., Siefferman, Lynn, Liu, Mark, Hassan, Hassan and UNNASCH, THOMAS R.

Year Published

2010

Publication

Vector-Borne and Zoonotic Diseases

Locations
DOI

10.1089/vbz.2008.0211

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19589058

West Nile Virus Emergence and Persistence in Los Angeles, California, 2003-2008Kwan, J. L.2010

West Nile Virus Emergence and Persistence in Los Angeles, California, 2003-2008

Keywords

WNV

Abstract

West Nile virus (WNV) invaded Los Angeles in September 2003, and during the subsequent five-year period followed a pattern of amplification, subsidence, and resurgence. Enzootic transmission was tracked by abundance and infection incidence in Culex pipiens quinquefasciatus and Cx. tarsalis and by seroprevalence in peridomestic passerine birds, infection in dead birds, and seroconversions in sentinel chickens. Culex p. quinquefasciatus served as the primary vector of WNV, with gravid traps serving as the best sampling method and the most consistent indicator of viral activity. Spatial scan statistics applied to mosquito infection and positive dead bird data delimited three major clusters of WNV transmission, with introduction occurring in the Los Angeles Basin, and amplification and dispersal events carrying transmission to the San Fernando and Santa Clarita valleys. Los Angeles experienced major epidemics in 2004 and 2008, providing a unique opportunity to investigate specific patterns of enzootic amplification preceding epidemics.

Authors

Kwan, J. L., Kluh, S., Madon, M. B. and Reisen, W. K.

Year Published

2010

Publication

American Journal of Tropical Medicine and Hygiene

Locations
DOI

10.4269/ajtmh.2010.10-0076

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20682890

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

Dry weather induces outbreaks of human West Nile virus infectionsWang, Guiming2010

Dry weather induces outbreaks of human West Nile virus infections

Keywords

WNV

Abstract

BACKGROUND: Since its first occurrence in the New York City area during 1999, West Nile virus (WNV) has spread rapidly across North America and has become a major public health concern in North America. By 2002, WNV was reported in 40 states and the District of Columbia with 4,156 human and 14,539 equine cases of infection. Mississippi had the highest human incidence rate of WNV during the 2002 epidemic in the United States. Epidemics of WNV can impose enormous impacts on local economies. Therefore, it is advantageous to predict human WNV risks for cost-effective controls of the disease and optimal allocations of limited resources. Understanding relationships between precipitation and WNV transmission is crucial for predicting the risk of the human WNV disease outbreaks under predicted global climate change scenarios. METHODS: We analyzed data on the human WNV incidences in the 82 counties of Mississippi in 2002, using standard morbidity ratio (SMR) and Bayesian hierarchical models, to determine relationships between precipitation and human WNV risks. We also entertained spatial autocorrelations of human WNV risks with conditional autocorrelative (CAR) models, implemented in WinBUGS 1.4.3. RESULTS: We observed an inverse relationship between county-level human WNV incidence risk and total annual rainfall during the previous year. Parameters representing spatial heterogeneity in the risk of human exposure to WNV improved model fit. Annual precipitation of the previous year was a predictor of spatial variation of WNV risk. CONCLUSIONS: Our results have broad implications for risk assessment of WNV and forecasting WNV outbreaks. Assessing risk of vector-born infectious diseases will require understanding of complex ecological relationships. Based on the climatologically characteristic drought occurrence in the past and on climate model predictions for climate change and potentially greater drought occurrence in the future, we suggest that the frequency and relative risk of WNV outbreaks could increase.

Authors

Wang, Guiming, Minnis, Richard B, Belant, Jerrold L and Wax, Charles L

Year Published

2010

Publication

BMC Infectious Diseases

Locations
DOI

10.1186/1471-2334-10-38

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20181272

Migratory Birds and the Dispersal of Arboviruses in CaliforniaReisen, W. K.2010

Migratory Birds and the Dispersal of Arboviruses in California

Keywords

WNV

Abstract

Each spring large numbers of neotropical migrants traversing the Pacific flyway pass through the Coachella Valley enroute to northern destinations, providing an opportunity to test the hypothesis that mosquito-borne encephalitis viruses are introduced annually into California by migratory birds. A total of 5,632 sera were collected from 43 species of migrants during spring (April-June), of which 34 (0.61%) comprised of 14 species tested positive by enzyme immunoassay; only 10 were confirmed by plaque reduction neutralization tests (PRNT). In addition, of 1,109 migrants comprised of 76 species that were reported dead by the public and necropsied, 126 (11%) were positive for West Nile virus (WNV) RNA; however, only three (0.7%) of 428 birds tested during the spring were positive. Limited experimental infection studies with WNV showed that Orange-crowned Warblers were highly susceptible and frequently died, whereas most Yellow Warblers survived. Our results indicated that birds entering California rarely exhibited a history of infection and that most birds probably became infected after entering California.

Authors

Reisen, W. K., Wheeler, S. S., Garcia, S. and Fang, Y.

Year Published

2010

Publication

American Journal of Tropical Medicine and Hygiene

Locations
DOI

10.4269/ajtmh.2010.10-0200

Evaluation of a New Formulation of Adulticide, Duet™, Against West Nile Virus Vector MosquitoesQualls, Whitney A.2010

Evaluation of a New Formulation of Adulticide, Duet™, Against West Nile Virus Vector Mosquitoes

Keywords

WNV

Abstract

DUET was evaluated against field-collected mosquito populations in St. John's County, FL, under laboratory and field conditions. Ten serial dilutions ranging from 22 to 2.2E-08 microg/ml of the product were tested against Aedes albopictus, Ae. taeniorhynchus, Culex quinquefasciatus, and Psorophora columbiae. At 0.0022 microg/ml, 100% mortality was recorded for all species except for Cx. quinquefasciatus. The 50% lethal concentration value for Cx. quinquefasciatus was 0.0029 microg/ml (CI = 0.00069 to 0.013). At the lowest dilution (2.2E-08 microg/ml) evaluated, Ae. albopictus, Ae. taeniorhynchus, and Ps. columbiae showed > 50% mortality. Ground ultralow-volume application of DUET resulted in overall average mortality of 87% of field-collected Cx. quinquefasciatus mosquitoes. There was a significant difference in mortality based on the distance of the caged mosquitoes (P < 0.05). However, mortality was > 70% at the farthest distance from the application (106 m).

Authors

Qualls, Whitney A. and Xue, Rui-De

Year Published

2010

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/10-5993.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20649133

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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...

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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