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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
DEMOGRAPHIC AND SPATIAL ANALYSIS OF WEST NILE VIRUS AND ST. LOUIS ENCEPHALITIS IN HOUSTON, TEXASRIOS, JANELLE2006

DEMOGRAPHIC AND SPATIAL ANALYSIS OF WEST NILE VIRUS AND ST. LOUIS ENCEPHALITIS IN HOUSTON, TEXAS

Keywords

West Nile virus, St. Louis encephalitis, geospatial analysis, environment, demographics, WNV

Abstract

This descriptive prevalence study describes the relationships between mosquito density and the presence of arboviruses (in mosquitoes and humans) with various socioeconomic and environmental factors present near the time of the arbovirus outbreak in Harris County, Texas, in 2002. This study suggests that mosquito density increased if the trap was located in an area with a large number of containers that may inadvertently retain rainwater (P = 0.056). When considering only virus-positive mosquitoes, significant relationships were observed if the trap was located near waste materials (P < 0.001) or near containers that may inadvertently retain rainwater (P = 0.037). Furthermore, the presence of arbovirus activity (in mosquitoes or humans) in a geographic area tended to be associated with the socioeconomic status of the local community. Although the results of the socioeconomic comparisons were not significant, they were suggestive, demonstrating an interesting trend. Compared with communities where virus activity was not observed, the socioeconomic status of the arbovirus-positive community was consistently lower. Specifically, results showed that the populations residing in virus-positive census tracts attained less education, earned less income per household, and were more likely to be below the poverty level. In addition, this study found that virus-positive mosquitoes were randomly distributed throughout the study area, whereas severe human infection cases were clustered. Based on the results of this study, we conclude that the health outcome of a local community as it relates to West Nile virus and St. Louis encephalitis is dependent on many factors, including the socioeconomic and environmental characteristics of the community.

Authors

RIOS, JANELLE, HACKER, CARL S., HAILEY, CHRISTINA A. and PARSONS, RAY E.

Year Published

2006

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/8756-971X(2006)22[254:DASAOW]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17019771

Antibody Prevalence of West Nile Virus in Birds, Illinois, 2002Ringia, Adam M.2004

Antibody Prevalence of West Nile Virus in Birds, Illinois, 2002

Keywords

WNV

Abstract

Antibodies to West Nile virus were detected in 94 of 1,784 Illinois birds during 2002. Captive and urban birds had higher seropositivity than did birds from natural areas, and northern and central Illinois birds’ seropositivity was greater than that from birds from the southern sites. Adult and hatch-year exposure rates did not differ significantly.

Authors

Ringia, Adam M., Blitvich, Bradley J., Koo, Hyun-Young, Van de Wyngaerde, Marshall, Brawn, Jeff D. and Novak, Robert J.

Year Published

2004

Publication

Emerging Infectious Diseases

Locations
DOI

10.3201/eid1006.030644

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15207067

Juvenile Dogs as Potential Sentinels for West Nile Virus SurveillanceResnick, M. P.2008

Juvenile Dogs as Potential Sentinels for West Nile Virus Surveillance

Keywords

West Nile virus;surveillance;canines;seroconversion;sentinels;enzyme-linked immunosorbant assay, WNV

Abstract

We conducted a study to determine whether juvenile stray dogs could be sentinels for West Nile virus (WNV) surveillance. Seroconversion was detected 6 weeks before the first reported human case. Our findings provide evidence that dogs could be useful sentinels for monitoring areas for evidence of WNV during transmission seasons.

Authors

Resnick, M. P., Grunenwald, P., Blackmar, D., Hailey, C., Bueno, R. and Murray, K. O.

Year Published

2008

Publication

Zoonoses and Public Health

Locations
DOI

10.1111/j.1863-2378.2008.01116.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18399945

SYNERGISTIC IMPACTS OF MALATHION AND PREDATORY STRESS ON SIX SPECIES OF NORTH AMERICAN TADPOLESRelyea, Rick A.2004

SYNERGISTIC IMPACTS OF MALATHION AND PREDATORY STRESS ON SIX SPECIES OF NORTH AMERICAN TADPOLES

Keywords

Predation;Stress;Synergy;Frog;Toad, WNV

Abstract

The decline of many amphibian populations is associated with pesticides, but for most pesticides we know little about their toxicity to amphibians. Malathion is a classic example; it is sprayed over aquatic habitats to control mosquitoes that carry malaria and the West Nile virus, yet we know little about its effect on amphibians. I examined the survival of six species of tadpoles (wood frogs, Rana sylvatica; leopard frogs, R. pipiens; green frogs, R. clamitans; bullfrogs, R. catesbeiana; American toads, Bufo americanus; and gray tree frogs, Hyla versicolor) for 16 d in the presence or absence of predatory stress and six concentrations of malathion. Malathion was moderately toxic to all species of tadpoles (median lethal concentration [LC50] values, the concentration estimated to kill 50% of a test population, ranged from 1.25–5.9 mg/L). These values are within the range of values reported for the few amphibians that have been tested (0.2–42 mg/L). In one of the six species, malathion became twice as lethal when combined with predatory stress. Similar synergistic interactions have been found with the insecticide carbaryl, suggesting that the synergy may occur in many carbamate and organophosphate insecticides. While malathion has the potential to kill amphibians and its presence is correlated with habitats containing declining populations, its actual role in amphibian declines is uncertain given the relatively low concentration in aquatic habitats.

Authors

Relyea, Rick A.

Year Published

2004

Publication

Environmental Toxicology and Chemistry

Locations
DOI

10.1897/03-259

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15095908

Nutrient-Dependent Reduced Growth and Survival of Larval Culex restuans (Diptera: Culicidae): Laboratory and Field Experiments in MichiganReiskind, Michael H.2004

Nutrient-Dependent Reduced Growth and Survival of Larval Culex restuans (Diptera: Culicidae): Laboratory and Field Experiments in Michigan

Keywords

density dependence, population regulation, larval habitat, West Nile virus

Abstract

Culex restuans Theobold, a putative vector of West Nile virus among birds in northern North America, also may serve as a bridge vector to mammals. Despite its potential public health importance, little is known about what regulates populations of this species. Mosquitoes generally are subject to both density-dependent reductions in survival and growth and to density-independent limitations on their population abundances. The mechanisms by which density dependence may occur in this species were examined in both field and laboratory studies. Nutrient-dependent reductions in growth were found in field studies. Under laboratory conditions, nutrient levels in larval habitats and total water volume per container contributed to survival and growth of larvae. We related these findings to density-independent changes in available habitat for larval development observed in other studies. These results may suggest a mechanism for patterns of mosquito abundance.

Authors

Reiskind, Michael H., Walton, Emily T. and Wilson, Mark L.

Year Published

2004

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585-41.4.650

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15311456

Culex restuans (Diptera: Culicidae) Oviposition Behavior Determined by Larval Habitat Quality and Quantity in Southeastern MichiganReiskind, Michael H.2004

Culex restuans (Diptera: Culicidae) Oviposition Behavior Determined by Larval Habitat Quality and Quantity in Southeastern Michigan

Keywords

mosquito oviposition, larval habitat, landscape ecology, density dependence, West Nile virus, WNV

Abstract

Oviposition is a critical stage in the mosquito lifecycle, and may determine population levels, distribution, biting behavior, and pathogen transmission. Knowledge of the oviposition behavior of Culex restuans Theobald has become particularly important with the emergence of West Nile virus (WNV) in North America. Laboratory and field studies have examined some factors that contribute to oviposition choice in Culex spp., but few studies have investigated responses to cues of future competition and breeding habitat availability in the field. We hypothesized that female Cx. restuans mosquitoes avoid laying eggs in habitats containing cues of larval competition, and that increased availability of larval habitat decreases egg density. To test these hypotheses, a series of field experiments were conducted in southeastern Michigan during summer 2002. We found that female mosquitoes prefer nutrient-enriched containers and decrease ovipositing in containers with conspecific larvae. In addition, greater habitat abundance decreased egg clutch density per container, although there was considerable aggregation of egg clutches. These results support our hypotheses and have potentially important implications for pathogen transmission by mosquitoes.

Authors

Reiskind, Michael H. and Wilson, Mark L.

Year Published

2004

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585-41.2.179

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15061276

Effects of Temperature on the Transmission of West Nile Virus by Culex tarsalis (Diptera: Culicidae)Reisen, William K.2006

Effects of Temperature on the Transmission of West Nile Virus by Culex tarsalis (Diptera: Culicidae)

Keywords

Culex tarsalis, West Nile virus, transmission, temperature, degree-days, WNV

Abstract

Culex tarsalis Coquillett females were infected with the NY99 strain of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) and then incubated under constant temperatures of 10–30°C. At selected time intervals, transmission was attempted using an in vitro capillary tube assay. The median time from imbibing an infectious bloodmeal until infected females transmitted WNV (median extrinsic incubation period, EIP50) was estimated by probit analysis. By regressing the EIP rate (inverse of EIP50) as a function of temperature from 14 to 30°C, the EIP was estimated to require 109 degree-days (DD) and the point of zero virus development (x-intercept) was estimated to be 14.3°C. The resulting degree-day model showed that the NY99 WNV strain responded to temperature differently than a lineage II strain of WNV from South Africa and approximated our previous estimates for St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus, SLEV). The invading NY99 WNV strain therefore required warm temperatures for efficient transmission. The time for completion of the EIP was estimated monthly from temperatures recorded at Coachella Valley, Los Angeles, and Kern County, California, during the 2004 epidemic year and related to the duration of the Cx. tarsalis gonotrophic cycle and measures of WNV activity. Enzootic WNV activity commenced after temperatures increased, the duration of the EIP decreased, and virus potentially was transmitted in two or less gonotrophic cycles. Temperatures in the United States during the epidemic summers of 2002–2004 indicated that WNV dispersal and resulting epicenters were linked closely to above-average summer temperatures.

Authors

Reisen, William K., Fang, Ying and Martinez, Vincent M.

Year Published

2006

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2006)043[0309:EOTOTT]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16619616

VECTOR COMPETENCE OF CULISETA INCIDENS AND CULEX THRIAMBUS FOR WEST NILE VIRUS 1 Reisen, William K.2006

VECTOR COMPETENCE OF CULISETA INCIDENS AND CULEX THRIAMBUS FOR WEST NILE VIRUS 1

Keywords

Culiseta incidens (Thomson), Culex thriambus Dyar, West Nile virus, California, vector competence, WNV

Abstract

The vector competence of Culiseta incidens (Thomson) and Culex thriambus Dyar for West Nile virus (WNV) were compared to Cx. quinquefasciatus Say or Cx. tarsalis Coquillett and Cx. stigmatasoma Dyar collected concurrently in California. Culiseta incidens were less susceptible to oral infection than Cx. quinquefasciatus, but transmitted virus at a significantly higher rate, thereby yielding comparable population transmission rates. Culex thriambus was equally susceptible to oral infection and transmitted virus at rates comparable to Cx. tarsalis or Cx. stigmatosoma. A mammalian host selection pattern most likely precluded detection of natural infection in Cs. incidens, a fairly abundant peridomestic species. In contrast, an avian host selection pattern and efficient vector competence resulted in repeated detection of WNV in Cx. thriambus; however, limited abundance and restrictive riparian larval habitat requirements would seem to limit the involvement of Cx. thriambus in WNV epidemiology.

Authors

Reisen, William K., Fang, Ying and Martinez, Vincent M.

Year Published

2006

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/8756-971X(2006)22[662:VCOCIA]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17304934

Overwintering of West Nile Virus in Southern CaliforniaReisen, William K.2006

Overwintering of West Nile Virus in Southern California

Keywords

West Nile virus, overwintering, southern California, Culex tarsalis, Culex pipiens quinquefasciatus, WNV

Abstract

West Nile virus (family Flaviviridae, genus Flavivirus, WNV) invaded southern California during 2003, successfully overwintered, amplified to epidemic levels, and then dispersed to every county in the state. Although surveillance programs successfully tracked and measured these events, mechanisms that allowed the efficient overwintering and subsequent amplification of WNV have not been elucidated. Our current research provided evidence for three mechanisms whereby WNV may have persisted in southern California during the winters of 2003–2004 and 2004–2005: 1) continued enzootic transmission, 2) vertical transmission by Culex mosquitoes, and 3) chronic infection in birds. WNV was detected in 140 dead birds comprising 32 species, including 60 dead American crows, thereby verifying transmission during the November–March winter period. Dead American crows provide evidence of recent transmission because this species always succumbs rapidly after infection. However, WNV RNA was not detected concurrently in 43,043 reproductively active female mosquitoes comprising 11 species and tested in 1,258 pools or antibody in sera from 190 sentinel chickens maintained in 19 flocks. Although efficient vertical transmission by WNV was demonstrated experimentally for Culex tarsalis Coquillett infected per os, 369 females collected diapausing in Kern County and tested in 32 pools were negative for WNV. Vertical transmission was detected in Culex pipiens quinquefasciatus Say adults reared from field-collected immatures collected from Kern County and Los Angeles during the summer transmission period. Chronic infection was detected by finding WNV RNA in 34 of 82 birds that were inoculated with WNV experimentally, held for >6 wk after infection, and then necropsied. Frequent detection of WNV RNA in kidney tissue in experimentally infected birds >6 wk postinfection may explain, in part, the repeated detection of WNV RNA in dead birds recovered during winter, especially in species such as mourning doves that typically do not die after experimental infection. In summary, our study provides limited evidence to support multiple modes of WNV persistence in southern California. Continued transmission and vertical transmission by Culex p. quinquefasciatus Say seem likely candidates for further study.

Authors

Reisen, William K., Fang, Ying, Martinez, Vincent M., Cahoon-Young, Barbara, Carney, Ryan, Lothrop, Hugh D., Wilson, Jennifer, O’Connor, Paul, Shafii, Marzieh and Brault, Aaron C.

Year Published

2006

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2006)043[0344:OOWNVI]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16619621

Does Feeding on Infected Mosquitoes (Diptera: Culicidae) Enhance the Role of Song Sparrows in the Transmission of Arboviruses in California?Reisen, William K.2007

Does Feeding on Infected Mosquitoes (Diptera: Culicidae) Enhance the Role of Song Sparrows in the Transmission of Arboviruses in California?

Keywords

mosquito, song sparrow, West Nile virus, western equine encephalomyelitis virus, oral infection, WNV

Abstract

Song sparrows, Melopiza melodia, inoculated subcutaneously with either western equine encephalomyelitis virus (family Togaviridae, genus Alphavirus, WEEV) or West Nile virus (family Flaviviridae, genus Flavivirus, WNV) developed elevated viremias, and they were considered to be competent experimental hosts for both viruses. However, birds that ingested from three to 20 mosquitoes containing comparable amounts of either WEEV or WNV failed to become infected, indicating limited oral susceptibility. Comparatively few field-collected birds had antibodies against either WEEV or WNV, indicating that this species was infrequently bitten by infectious mosquitoes in nature and probably was of limited importance in viral amplification.

Authors

Reisen, William K. and Fang, Ying

Year Published

2007

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2007)44[316:DFOIMD]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/17427703

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