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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
Factors Associated With the Risk of West Nile Virus Among Crows in New York StateDeCarlo, C. H.2011

Factors Associated With the Risk of West Nile Virus Among Crows in New York State

Keywords

WNV

Abstract

West Nile virus (WNV) is transmitted between avian hosts in enzootic cycles by a mosquito vector. The virus has significant disease effects on humans and equines when it bridges into an epizootic cycle. As the initial epidemic of WNV in 1999, perennial outbreaks in New York State suggest the local establishment of natural foci with perpetuation of the virus among susceptible hosts rather than reintroduction of the virus. The factors that play a role in the perpetuation of the virus are not fully understood. American crows (Corvus brachyrhynchos) are known to be highly susceptible to infection with the virus. We investigate the factors that put crows at risk of infection in Tompkins County, New York during the period of 2000-2008 in a case-control study. Cases were crow carcasses that were found dead and tested positive for WNV using real time reverse transcription or VecTest. Data on putative risk factors were collected and assessed for significance of association with the presence of WNV using logistic regression analysis to evaluate the significance of each factor while simultaneously controlling for the effect of others. The risk of a crow carcass testing WNV positive varied with age, season of the year and ecological area where the carcass was found. Crows that were more than 1-year-old were four times more likely to be WNV positive in comparison to birds that were less than 1 year of age. It was three times more likely to find WNV positive carcasses in residential areas in comparison to rural areas. The risk of testing WNV positive did not vary by sex of the crow carcasses.

Authors

DeCarlo, C. H., Clark, A. B., McGowan, K. J., Ziegler, P. E., Glaser, A. L., Szonyi, B. and Mohammed, H. O.

Year Published

2011

Publication

Zoonoses and Public Health

Locations
DOI

10.1111/j.1863-2378.2010.01346.x

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/20707862

Using Hydrologic Conditions to Forecast the Risk of Focal and Epidemic Arboviral Transmission in Peninsular FloridaDay, Jonathan F.2008

Using Hydrologic Conditions to Forecast the Risk of Focal and Epidemic Arboviral Transmission in Peninsular Florida

Keywords

arboviral epidemics, water table depth, hydrologic monitoring, St. Louis encephalitis virus, West Nile virus, WNV

Abstract

The accurate forecasting and tracking of arboviral transmission is becoming increasingly critical for the early recognition and management of arboviral epidemics. Meteorological factors, especially rainfall and temperature, drive arboviral epidemics, but monitoring rainfall and temperature alone is not predictive of increased levels of vector-borne disease transmission. In Florida, model simulations of water table depth (WTD) provide a measure of drought, and they have been shown to provide an accurate forecast of arboviral transmission. Here, we tracked WTD in two peninsular Florida regions where focal West Nile virus (family Flaviviridae, genus Flavivirus, WNV) transmission was reported during 2004 and 2005. We compared the resulting WTD profiles with historical WTD simulations for Indian River County (IRC), FL, where two peninsular Florida St. Louis encephalitis virus epidemics had their epicenters in 1977 and 1990. In both of the regions where focal WNV transmission was reported during 2004 and 2005, the local WTD profiles approached the 1977 and 1990 IRC WTD profiles; however, differences in the local temporal sequence of hydrologic conditions were observed. These differences seem in part to explain why the focal WNV transmission during 2004 and 2005 failed to reach epidemic levels in peninsular Florida. These findings suggest that hydrologic monitoring, specifically WTD, may help determine the geographic extent, timing, and intensity of WNV transmission. We speculate that a more precise sequence of drought and wetting, including a secondary summer drying and wetting cycle, as occurred in IRC during 1977 and 1990, may provide the optimal hydrologic conditions for the expansion of an arbovirus outbreak from focal to epidemic. This study documents that monitoring hydrologic conditions, along with vector, avian amplification host, and virus population data, increases our ability to track and predict significant levels of arboviral transmission.

Authors

Day, Jonathan F. and Shaman, Jeffrey

Year Published

2008

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2008)45[458:UHCTFT]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18533440

Severe Winter Freezes Enhance St. Louis Encephalitis Virus Amplification and Epidemic Transmission in Peninsular FloridaDay, Jonathan F.2009

Severe Winter Freezes Enhance St. Louis Encephalitis Virus Amplification and Epidemic Transmission in Peninsular Florida

Keywords

WNV

Abstract

Mosquito-borne arboviral epidemics tend to strike without warning. The driving force for these epidemics is a combination of biotic (vector, amplification host, and virus) and abiotic (meteorological conditions, especially rainfall and temperature) factors. Abiotic factors that facilitate the synchronization and interaction of vector and amplification host populations favor epidemic amplification and transmission. In Florida, epidemics of St. Louis encephalitis (SLE) virus (family Flaviviridae, genus Flavivirus, SLEV) have been preceded by major freezes one or two winters before the onset of human cases. Here, we analyze the relationship between severe winter freezes and epidemic SLEV transmission in peninsular Florida and show that there is a significant relationship between the transmission of SLEV and these severe freezes. We propose that by killing cold-sensitive understory vegetation in the mid-peninsular region of Florida, freezes enhance the reproductive success of ground-feeding avian amplification hosts, especially mourning doves and common grackles. In conjunction with other appropriate environmental signals, increased avian reproductive success may enhance SLEV and West Nile (WN) virus amplification and result in SLE and WN epidemics during years when all of the biological cycles are properly synchronized. The knowledge that winter freezes in Florida may enhance the amplification and epidemic transmission of SLE and WN viruses facilitates arboviral tracking and prediction of human risk of SLE and WN infection during the transmission season.

Authors

Day, Jonathan F. and Shaman, Jeffrey

Year Published

2009

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/033.046.0638

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/19960704

Crow Deaths Caused by West Nile Virus during WinterDawson, Jennifer R.2007

Crow Deaths Caused by West Nile Virus during Winter

Keywords

WNV

Abstract

In New York, an epizootic of American crow (Corvus brachyrhynchos) deaths from West Nile virus (WNV) infection occurred during winter 2004–2005, a cold season when mosquitoes are not active. Detection of WNV in feces collected at the roost suggests lateral transmission through contact or fecal contamination.

Authors

Eidson, Millicent, Ebel, Gregory D., Kramer, Laura D., Dawson, Jennifer R., Stone, Ward B., Young, David S., Galinski, David S., Pensabene, Jason P. and Franke, Mary A.

Year Published

2007

Publication

Emerging Infectious Diseases

Locations
DOI

10.3201/eid1312.070413

Effects of Single and Multiple Applications of Mosquito Insecticides on Nontarget ArthropodsDavis, Ryan S.2008

Effects of Single and Multiple Applications of Mosquito Insecticides on Nontarget Arthropods

Keywords

Mosquito control, adulticide, larvicide, ecological risk, nontarget organisms, West Nile virus, WNV

Abstract

Mosquito management plans have been implemented in the United States and globally to manage mosquito vectors of West Nile virus and many other diseases. However, there is public concern about ecological risks from using insecticides to manage mosquitoes. Two studies were conducted during the late summers of 2004 through 2006 at Benton Lake National Wildlife Refuge near Great Falls, MT. The first experiment was conducted in 2004 and 2005 to assess acute impacts of mosquito adulticides (permethrin and d-phenothrin) and larvicides (Bacillus thuringiensis israelensis and methoprene) on nontarget aquatic and terrestrial arthropods after a single application. The second experiment was conducted in 2005 and 2006 to assess longer-term impacts of permethrin on nontarget terrestrial arthropods after multiple repeated applications. For aquatic samples, in the first study, no overall treatment effects were observed despite a potentially deleterious effect on amphipods on sample date 1 in 2004. During the same study, 1 of 54 responses had a significant overall treatment effect for sticky-card samples. Many of the responses for sticky-card samples suggested significant time effects and time × treatment effects. Three response variables were associated with fewer individuals present in the insecticide-treated plots in a multivariate analysis. For the multiple-spray study conducted in 2005 and 2006, 6 of the response variables collected via sticky cards exhibited significant overall treatment effects, but none was associated with fewer individuals in the insecticide-treated plots. None of the responses collected using sweep-net sampling suggested overall treatment effects. Time and time × treatment effects were prevalent in 2005, but no discernable pattern was evident. In general, nearly all of the responses evaluated for either study indicated few, if any, deleterious effects from insecticide application.

Authors

Davis, Ryan S. and Peterson, Robert K. D.

Year Published

2008

Publication

Journal of the American Mosquito Control Association

Locations
DOI

10.2987/5654.1

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/18666536

Bird-Baited Traps for Surveillance of West Nile Mosquito Vectors: Effect of Bird Species, Trap Height, and Mosquito Escape RatesDarbro, Jonathan M.2006

Bird-Baited Traps for Surveillance of West Nile Mosquito Vectors: Effect of Bird Species, Trap Height, and Mosquito Escape Rates

Keywords

West Nile virus, house sparrow, chicken, Culex p. pipiens, Culex restuans, WNV

Abstract

Host-seeking mosquitoes were sampled in bird-baited traps at four sites in New York state in 2003–2004. Trap placement and efficacy of chickens, Gallus gallus domesticus L., as bait compared with house sparrows, Passer domesticus L., an important reservoir of West Nile virus (family Flaviviridae, genus Flavivirus, WNV), was evaluated. Each site had a chicken-baited trap near ground level (≈1.5 m) and in the tree canopy (≈9 m), and a house sparrow-baited trap at ground level and canopy level. Each trap allowed mosquito access to birds on one end, and an inner mesh screen blocked bird access on the other end. The two most abundant mosquitoes, Culex restuans Theobald and Culex pipiens pipiens L., were differentiated using molecular characters. In 2003, Cx. restuans and Cx. p. pipiens made up 88% of total mosquito catch. In 2004, Cx. restuans comprised 43% of total catch and Cx. p. pipiens comprised 33%. The remaining species representing at least 1% of total catch were Ochlerotatus trivittatus (Coquillett), Coquilletidia perturbans (Walker), and Culiseta morsitans (Theobald). Capture rates were similar for chicken and house sparrow-baited traps; however, significantly more mosquitoes were captured in the canopy for both bird species. Cx. restuans preferred canopy traps, whereas equal numbers of Cx. p. pipiens were captured at ground and canopy levels. Mosquitoes were more likely to escape (74%) when excluded from birds than when allowed free access to birds (54%). Sentinel bird surveillance for WNV can be improved by trapping in the tree canopy in addition to ground level to capture the most important avian vectors.

Authors

Darbro, Jonathan M. and Harrington, Laura C.

Year Published

2006

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585(2006)043[0083:BTFSOW]2.0.CO;2

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16506452

Liver metal concentrations in Greater Sage-grouse (Centrocercus urophasianus)Dailey, Rebecca N.2008

Liver metal concentrations in Greater Sage-grouse (Centrocercus urophasianus)

Keywords

Centrocercus urophasianus, ICP-MS, liver, metals, sage-grouse

Abstract

Greater Sage-grouse (Centrocercus urophasianus) are a species of concern due to shrinking populations associated with habitat fragmentation and loss. Baseline health parameters for this species are limited or lacking, especially with regard to tissue metal concentrations. To obtain a range of tissue metal concentrations, livers were collected from 71 Greater Sage-grouse from Wyoming and Montana. Mean SE metal concentrations (mg/kg wet weight) in liver were determined for vanadium (V) (0.12 +/- 0.01), chromium (Cr) (0.50 +/- 0.02), manganese (Mn) (2.68 +/- 0.11), iron (Fe) (1,019 +/- 103), nickel (Ni) (0.40 +/- 0.04), cobalt (Co) (0.08 +/- 0.02), copper (Cu) (6.43 +/- 0.40), mercury (Hg) (0.30 +/- 0.09), selenium (Se) (1.45 +/- 0.64), zinc (Zn) (59.2 +/- 4.70), molybdenum (Mo) (0.93 +/- 0.07), cadmium (Cd) (1.44 +/- 0.14), barium (Ba) (0.20 +/- 0.03), and lead (Pb) (0.17 +/- 0.03). In addition to providing baseline data, metal concentrations were compared between sex, age (juvenile/adult), and West Nile virus (WNv) groups (positive/negative). Adult birds had higher concentrations of Ni and Cd compared to juveniles. In addition, Zn and Cu concentrations were significantly elevated in WNv-positive birds.

Authors

Dailey, Rebecca N.; Raisbeck, Merl F.; Slemion, Roger S.; Cornish, Todd E.

Year Published

2008

Publication

Journal of Wildlife Diseases

Locations
Mosquito and Arbovirus Activity During 1997–2002 in a Wetland in Northeastern MississippiCupp, E. W.2004

Mosquito and Arbovirus Activity During 1997–2002 in a Wetland in Northeastern Mississippi

Keywords

Saint Louis encephalitis, eastern equine encephalomyelitis virus, Culex erraticus, Culiseta melanura, blood meal identification, WNV

Abstract

The species composition and population dynamics of adult mosquitoes in a wetland near Iuka, MS, were analyzed over a 6-yr period (1997–2002) and reverse transcription-polymerase chain reaction (PCR) detection rates of arboviruses determined during five of those years. Blood meals of three likely vector species were identified using a PCR-based method that allows identification of the host to species. Culex erraticus (Dyar & Knab) composed 51.9% of the population during the 6-yr period with 295 females collected per trap night. Eastern equine encephalomyelitis (EEE) virus was detected in six genera of mosquitoes [Coquillettidia perturbans (Walker), Culex restuans Theobald, Culex salinarius Coquillett, Culex erraticus (Dyar & Knab), Anopheles crucians Wiedemann, Anopheles quadrimaculatus Say, Aedes vexans (Meigen), Ochlerotatus triseriatus Say, and Psorophora ferox Humboldt) with positive pools occurring in 1998, 1999, and 2002. Culiseta melanura Coquillett occurred at a low level (<1%) and was not infected. Saint Louis encephalitis virus was detected once in a single pool of Cx. erraticus in 1998. Neither West Nile virus nor LaCrosse virus was found. Minimum infection rates per 1000 females tested of competent vectors of EEE virus were variable and ranged from 0.14 for Cx. erraticus to 40.0 for Oc. triseriatus. Thirty-nine species of birds were identified in the focus with blood-engorged mosquitoes found to contain meals (n = 29) from eight avian species. The majority of meals was from the great blue heron, Ardea herodias L. (n = 55%), but when bird abundance data were adjusted for avian mass, the brown-headed cowbird, Molothrus ater (Boddaert); blue jay, Cyanocitta cristata (L.); and northern mockingbird, Mimus polyglottos (L.), were overrepresented as hosts.

Authors

Cupp, E. W., Tennessen, K. J., Oldland, W. K., Hassan, H. K., Hill, G. E., Katholi, C. R. and Unnasch, T. R.

Year Published

2004

Publication

Journal of Medical Entomology

Locations
DOI

10.1603/0022-2585-41.3.495

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/15185956

SUSCEPTIBILITY OF GREATER SAGE-GROUSE TO EXPERIMENTAL INFECTION WITH WEST NILE VIRUSClark, Larry2006

SUSCEPTIBILITY OF GREATER SAGE-GROUSE TO EXPERIMENTAL INFECTION WITH WEST NILE VIRUS

Keywords

Centrocercus urophasianus, experimental infection, greater sage-grouse, vaccine, West Nile virus, WNV

Abstract

Populations of greater sage-grouse (Centrocercus urophasianus) have declined 45– 80% in North America since 1950. Although much of this decline has been attributed to habitat loss, recent field studies have indicated that West Nile virus (WNV) has had a significant negative impact on local populations of grouse. We confirm the susceptibility of greater sage-grouse to WNV infection in laboratory experimental studies. Grouse were challenged by subcutaneous injection of WNV (103.2 plaque-forming units [PFUs]). All grouse died within 6 days of infection. The Kaplan-Meier estimate for 50% survival was 4.5 days. Mean peak viremia for nonvaccinated birds was 106.4 PFUs/ml (±100.2 PFUs/ml, standard error of the mean [SEM]). Virus was shed cloacally and orally. Four of the five vaccinated grouse died, but survival time was increased (50% survival=9.5 days), with 1 grouse surviving to the end-point of the experiment (14 days) with no signs of illness. Mean peak viremia for the vaccinated birds was 102.3 PFUs/ml (±100.6 PFUs/ml, SEM). Two birds cleared the virus from their blood before death or euthanasia. These data emphasize the high susceptibility of greater sage-grouse to infection with WNV.

Authors

Klenk, Kaci, Bowen, Richard, Clark, Larry, Hall, Jeffrey, McLean, Robert, Dunbar, Michael and Smeraski, Cynthia A.

Year Published

2006

Publication

Journal of Wildlife Diseases

Locations
DOI

10.7589/0090-3558-42.1.14

Additional Information:

http://www.ncbi.nlm.nih.gov/pubmed/16699144

Susceptibility of greater sage-grouse to experimental infection with West Nile virusClark, L2006

Susceptibility of greater sage-grouse to experimental infection with West Nile virus

Keywords

Centrocercus urophasianus experimental infection greater sage-grouse vaccine West Nile virus

Abstract

Populations of greater sage-grouse (Centrocercus urophasianus) have declined 45-80% in North America since 1950. Although much of this decline has been attributed to habitat loss, recent field studies have indicated that West Nile virus (WNV) has had a significant negative impact on local populations of grouse. We confirm the susceptibility of greater sage-grouse to WNV infection in laboratory experimental studies. Grouse were challenged by subcutaneous injection of WNV (10(3.2) plaque-forming units [PFUs]). All grouse died within 6 days of infection. The Kaplan-Meier estimate for 50% survival was 4.5 days. Mean peak viremia for nonvaccinated birds was 10(6.4) PFUs/ml (+/- 10(0.2) PFUs/ml, standard error of the mean [SEM]). Virus was shed cloacally and orally. Four of the five vaccinated grouse died, but survival tune was increased (50% survival = 9.5 days), with 1 grouse surviving to the end-point of the experiment (14 days) kith no signs of illness. Mean peak viremia for the vaccinated birds was 10(2.3) PFUs/ml (+/- 10(0.6) PFUs/ml, SEM). Two birds cleared the virus from their blood before death or euthanasia. These data emphasize the high susceptibility of greater sage-grouse to infection with WNV.

Authors

Clark, L; Hall, J; McLean, R; Dunbar, M; Klenk, K; Bowen, R; Smeraski, CA

Year Published

2006

Publication

Journal of Wildlife Diseases

Locations

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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...

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