| Spatial Analysis of West Nile Virus: Rapid Risk Assessment of an Introduced Vector-Borne Zoonosis | Brownstein, John S. | 2002 |
KeywordsWNV AbstractThe distribution of human risk for West Nile virus was determined by spatial analysis of the initial case distribution for the New York City area in 1999 using remote sensing and geographic information system technologies. Cluster analysis revealed the presence of a statistically significant grouping of cases, which also indicates the area of probable virus introduction. Within the cluster, habitat suitability for potentially infective adult mosquitoes was measured by the amount of vegetation cover using satellite imagery. Logistic regression analysis revealed satellite-derived vegetation abundance to be significantly and positively associated with the presence of human cases. The logistic model was used to estimate the spatial distribution of human risk for West Nile virus throughout New York City. Accuracy of the resulting risk map was cross-validated using virus-positive mosquito sample sites. These new epidemiological methods aid in rapid entry point identification and spatial prediction of human risk of infection for introduced vector-borne pathogens. AuthorsMiller, James R., Brownstein, John S., Rosen, Hilary, Purdy, Dianne, Merlino, Mario, Mostashari, Farzad and Fish, Durland Year Published2002 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/15303660260613729 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/12737545 |
| Early Season Crow Mortality as a Sentinel for West Nile Virus Disease in Humans, Northeastern United States | Julian, Kathleen G. | 2002 |
KeywordsWNV AbstractThe 1999 New York epidemic of human West Nile virus (WN) encephalitis and meningitis was preceded by a crow die-off also caused by WN infection. As one component of the subsequently developed national surveillance system, crow mortality data were collected to detect WN activity before humans might become infected. However, predicting areas at risk for human WN disease likely requires assessment of multiple factors, including the intensity and timing of crow epizootics. To identify early season measures of WN activity in crows associated with subsequent WN disease in humans, county-level crow mortality data from seven northeastern states were analyzed. A predictive model was developed based on analysis of 2000 surveillance data and then assessed for 2001. To characterize the intensity of early season WN activity in crows, 15 variables were constructed from surveillance data of 52 counties that tested at least four crows during the early season (defined as June 17-July 28, 2000). County values for each variable were dichotomized at the 75th percentile into "high" and "low" activity. Multivariate analysis indicated that "high" early season activity of two variables - density of reported dead crow sightings (reported dead crows/area) and [(WN-infected crows/tested crows) × (human population)] - were associated with report of at least one human WN disease case (for each variable: adjusted odds ratio, 6.9; 95% confidence interval, 1.2-40.6). An assessment of this model using 2001 surveillance data from 61 counties yielded similar findings. With emphasis on early season WN activity, crow surveillance may allow timely targeting of interventions to protect the public health. AuthorsMiller, James R., Julian, Kathleen G., Eidson, Millicent, Kipp, Aaron M., Weiss, Erin, Petersen, Lyle R., Hinten, Steven R. and Marfin, Anthony A. Year Published2002 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/15303660260613710 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/12737544 |
| Effect of Environmental Temperature on the Ability of Culex pipiens (Diptera: Culicidae) to Transmit West Nile Virus | Dohm, David J. | 2002 |
KeywordsWest Nile virus, Culex pipiens, environmental temperature, WNV AbstractEnvironmental temperature can affect the ability of mosquitoes to transmit an arbovirus. However, results of various studies indicate that these effects are not consistent among viruses or mosquito species, and there is no information available on the effect of environmental temperature on the ability of North American mosquito species to transmit West Nile (WN) virus. We evaluated the effect of incubation temperature (18, 20, 26, or 30°C) on the ability of Culex pipiens L. derived from specimens collected during the outbreak in New York in 1999 to transmit a strain of WN virus obtained from a crow that died during this outbreak. Although mosquitoes fed on the same viremic chickens, infection rates were directly related to subsequent incubation temperatures. In mosquitoes held at 30°C, virus was recovered from nearly all mosquitoes tested, disseminated infections were detected as early as 4 d after the infectious blood meal, and >90% of all mosquitoes had a disseminated infection 12 or more days after the infectious blood meal. In contrast, for mosquitoes held at 18°C, disseminated infections were not detected until 25 d after the infectious blood meal, and even after 28 d, <30% contained a disseminated infection. Results for mosquitoes held at 20 and 26°C were intermediate for both infection and dissemination rates. The effect of environmental temperature should to be considered when evaluating the vector competence of these mosquitoes and modeling risk of WN virus transmission in nature. AuthorsDohm, David J., Turell, Michael J. and O’Guinn, Monica L. Year Published2002 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-39.1.221 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/11931261 |
| West nile virus-associated optic neuritis and chorioretinitis | Anninger, William V. | 2003 |
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| West Nile Virus Infection Rates in Culex nigripalpus (Diptera: Culicidae) Do Not Reflect Transmission Rates in Florida | Rutledge, C. Roxanne | 2003 |
KeywordsWest Nile virus, infection rate, field transmission, arbovirus, WNV AbstractWe describe the first documented field transmission of West Nile (WN) virus by a North American mosquito. WN was first detected in northern Florida in 2001. An intensive mosquito trapping and surveillance program was conducted in this region for four nights to assess mosquito transmission of WN. Four mosquito traps, each with a single sentinel chicken, were placed at five different locations on each of four nights. A total of 11,948 mosquitoes was collected, and 14 mosquito pools were found to contain WN, giving a minimum infection rate between 1.08 and 7.54 per 1,000. Only one of the 80 sentinel chickens seroconverted to WN, demonstrating a single mosquito transmission event during the study and a mosquito transmission rate of between 0.8 and 1 per 1,000. Culex nigripalpus Theobald was responsible for WN transmission to the sentinel chicken, although both Cx. nigripalpus and Culex quinquefasciatus Say were found infected with WN. Mosquito transmission rates are reported in this study for the first time for a WN outbreak. This information is essential to determine risk of human and animal infection. AuthorsLord, Cynthia C., Day, Jonathan F., Rutledge, C. Roxanne, Stark, Lillian M. and Tabachnick, Walter J. Year Published2003 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-40.3.253 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/12943101 |
| Wicking Assays for the Rapid Detection of West Nile and St. Louis Encephalitis Viral Antigens in Mosquitoes (Diptera: Culicidae) | Ryan, J. | 2003 |
Keywordsarbovirus, West Nile virus, St. Louis encephalitis, rapid detection, wicking assay, surveillance, WNV AbstractThe recent outbreaks of West Nile (WN) encephalitis and St. Louis encephalitis (SLE) in the United States have highlighted the need for rapid and specific methods of detecting arboviral antigens in mosquitoes. We evaluated rapid, field-usable assays for detecting and differentiating WN and SLE viruses in mosquito pools, based on a patent-pending, immunochromatographic technology (VecTest) formatted on a dipstick. The device provides results in less than 20 min and can be used in laboratories with adequate containment facilities. In laboratory assessments, both the SLE and WN virus tests demonstrated sensitivity comparable with that of an antigen capture ELISA, but less than can be achieved with Vero cell plaque or reverse-transcriptase polymerase chain reaction assays. There was no evidence of cross-reaction when tested with high concentrations of heterologous flavivirus antigens or with Eastern equine encephalitis or Western equine encephalitis viruses. Both the WN and SLE dipstick tests delivered a clear positive result with a single positive specimen in a pool of 50 mosquitoes. This virus assay technology reduces the time required to obtain test results and will allow rapid medical threat assessment and effective targeting of vector control measures. AuthorsRyan, J., Davé, K., Emmerich, É., Fernández, B., Turell, M., Johnson, J., Gottfried, K., Burkhalter, K., Kerst, A., Hunt, A., Wirtz, R. and Nasci, R. Year Published2003 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-40.1.95 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/12597660 |
| West Nile virus: pending crisis for greater sage-grouse | Naugle, DE | 2004 |
KeywordsCentrocercus urophasianus, emerging infectious disease, endangered species; greater sage-grouse; mosquito; population decline; survival; vector surveillance; West Nile virus AbstractScientists have feared that emerging infectious diseases could complicate efforts to conserve rare and endangered species, but quantifying impacts has proven difficult until now. We report unexpected impacts of West Nile virus (WNv) on radio-marked greater sage-grouse (Centrocercus urophasianus), a species that has declined 45-80% and is endangered in Canada and under current consideration for federal listing in the US. We show that WNv reduced late-summer survival an average of 25% in four radio-marked populations in the western US and Canada. Serum from 112 sage-grouse collected after the outbreak show that none had antibodies, suggesting that they lack resistance. The spread of WNv represents a significant new stressor on sage-grouse and probably other at-risk species. While managing habitat might lessen its impact on sage-grouse populations, WNv has left wildlife and public health officials scrambling to address surface water and vector control issues in western North America. AuthorsNaugle, DE; Aldridge, CL; Walker, BL; Cornish, TE; Moynahan, BJ; Holloran, MJ; Brown, K; Johnson, GD; Schmidtmann, ET; Mayer, RT; Kato, CY; Matchett, MR; Christiansen, TJ; Cook, WE; Creekmore, T; Falise, RD; Rinkes, ET; Boyce, MS Year Published2004 PublicationEcology Letters LocationsDOI10.1111/j.1461-0248.2004.00631.x |
| From the field: Outbreak of West Nile virus in greater sage-grouse and guidelines for monitoring, handling, and submitting dead birds | Walker, BL | 2004 |
KeywordsCentrocercus urophasianus, emerging infectious disease, greater sage-grouse, lek count, Montana, population decline, Powder River Basin, survival, West Nile virus, Wyoming AbstractWest Nile virus (WNV) resulted in a 25% decline in survival in four populations of radiomarked greater sage-grouse (Centrocercus urophasianus) across Alberta, Wyoming, and Montana in 2003. Unexpected impacts of WNV are disturbing because range-wide habitat loss and degradation already threaten sage-grouse populations. In the Powder River Basin of Wyoming and Montana, late-summer survival of sage-grouse was lower at a site with confirmed WNV mortalities (20%) than at two sites without (76%). Dramatic declines in both male and female lek attendance at the WNV site the following spring suggest that outbreaks may threaten some local populations with extirpation. The key to understanding broader impacts of WNV on sage-grouse is to monitor additional populations and to determine whether populations infected in 2003 are again impacted this year. To facilitate this process, we describe a strategy for monitoring WNV mortality in the field and provide information on how to handle, store, and submit dead birds for testing. AuthorsWalker, BL; Naugle, DE; Doherty, KE; Cornish, TE Year Published2004 PublicationWildlife Society Bulletin LocationsDOI10.2193/0091-7648(2004)032[1000:FTFOOW]2.0.CO;2 |
| Nutrient-Dependent Reduced Growth and Survival of Larval Culex restuans (Diptera: Culicidae): Laboratory and Field Experiments in Michigan | Reiskind, Michael H. | 2004 |
Keywordsdensity dependence, population regulation, larval habitat, West Nile virus AbstractCulex 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. AuthorsReiskind, Michael H., Walton, Emily T. and Wilson, Mark L. Year Published2004 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-41.4.650 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 Michigan | Reiskind, Michael H. | 2004 |
Keywords mosquito oviposition, larval habitat, landscape ecology, density dependence, West Nile virus, WNV AbstractOviposition 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. AuthorsReiskind, Michael H. and Wilson, Mark L. Year Published2004 PublicationJournal of Medical Entomology LocationsDOI10.1603/0022-2585-41.2.179 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15061276 |
