| 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 |
| 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 |
| West Nile Virus Antibodies in Bats from New Jersey and New York | Pilipski, Jacob D. | 2004 |
KeywordsAntibodies, bats, New Jersey, survey, West Nile virus, WNV AbstractEighty-three serum samples were obtained from big brown (Eptesicus fuscus), little brown (Myotis lucifugus), and northern long-eared (Myotis septentrionalis) bats (Chiroptera: Vespertilionidae), from New Jersey and New York (USA) between July and October 2002. Samples were analyzed for neutralizing antibodies to West Nile virus (WNV) and St. Louis encephalitis (SLE) virus. One little brown bat and one northern long-eared bat tested positive for WNV neutralizing antibodies. No bats had antibodies to SLE virus. This was the first large-scale investigation of WNV infection in bats in New Jersey. Additional work is needed to determine the effects of WNV on bat populations. AuthorsPilipski, Jacob D., Pilipski, Lucas M. and Risley, Lance S. Year Published2004 PublicationJournal of Wildlife Diseases Locations- Atlantic (39.5ºN, 74.3ºW), Morris (40.7ºN, 74.4ºW), and Passaic (41.1ºN, 74.2ºW) counties in New Jersey and Orange County (41.3ºN, 74.6ºW) in New York. (41.3, -74.6)
- Atlantic (39.5ºN, 74.3ºW), Morris (40.7ºN, 74.4ºW), and Passaic (41.1ºN, 74.2ºW) counties in New Jersey and Orange County (41.3ºN, 74.6ºW) in New York. (41.1, -74.2)
- Atlantic (39.5ºN, 74.3ºW), Morris (40.7ºN, 74.4ºW), and Passaic (41.1ºN, 74.2ºW) counties in New Jersey and Orange County (41.3ºN, 74.6ºW) in New York. (40.7, -74.4)
- Atlantic (39.5ºN, 74.3ºW), Morris (40.7ºN, 74.4ºW), and Passaic (41.1ºN, 74.2ºW) counties in New Jersey and Orange County (41.3ºN, 74.6ºW) in New York. (39.5, -74.3)
DOI10.7589/0090-3558-40.2.335 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15362837 |
| West Nile Virus in California | Reisen, William | 2004 |
KeywordsWNV AbstractWest Nile virus (WNV) was first detected in California during July 2003 by isolation from a pool of Culex tarsalis collected near El Centro, Imperial County. WNV then amplified and dispersed in Imperial and Coachella Valleys, where it was tracked by isolation from pools of Cx. tarsalis, seroconversions in sentinel chickens, and seroprevalence in free-ranging birds. WNV then dispersed to the city of Riverside, Riverside County, and to the Whittier Dam area of Los Angeles County, where it was detected in dead birds and pools of Cx. pipiens quinquefasciatus. By October, WNV was detected in dead birds collected from riparian corridors in Los Angeles, west to Long Beach, and through inland valleys south from Riverside and to San Diego County. WNV was reported concurrently from Arizona in mid-August but not from Baja, Mexico, until mid-November. Possible mechanisms for virus introduction, amplification, and dispersal are discussed. AuthorsReisen, William, Lothrop, Hugh, Chiles, Robert, Madon, Minoo, Cossen, Cynthia, Woods, Leslie, Husted, Stan, Kramer, Vicki and Edman, John Year Published2004 PublicationEmerging Infectious Diseases LocationsDOI10.3201/eid1008.040077 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15496236 |
| Assessment of arbovirus vector infection rates using variable size pooling | Gu, W. | 2004 |
KeywordsCulex pipiens;Cx. restuans;arbovirus vector;maximum likelihood estimation;minimum infection rate;pool testing;variable size pooling;West Nile virus;Chicago;U.S.A, WNV AbstractPool testing of vector samples for arboviruses is widely used in surveillance programmes. The proportion of infected mosquitoes (Diptera: Culicidae) is often estimated from the minimum infection rate (MIR), based on the assumption of only one infected mosquito per positive pool. This assumption becomes problematic when pool size is large and/or infection rate is high. By relaxing this constraint, maximum likelihood estimation (MLE) is more useful for a wide range of infection levels that may be encountered in the field. We demonstrate the difference between these two estimation approaches using West Nile virus (WNV) surveillance data from vectors collected by gravid traps in Chicago during 2002. MLE of infection rates of Culex mosquitoes was as high as 60 per 1000 at the peak of transmission in August, whereas MIR was less than 30 per 1000. More importantly, we demonstrate roles of various pooling strategies for better estimation of infection rates based on simulation studies with hypothetical mosquito samples of 18 pools. Variable size pooling (with a serial pool sizes of 5, 10, 20, 30, 40 and 50 individuals) performed consistently better than a constant size pooling of 50 individuals. We conclude that variable pool size coupled with MLE is critical for accurate estimates of mosquito infection rates in WNV epidemic seasons. AuthorsGu, W., Lampman, R. and Novak, R. J. Year Published2004 PublicationMedical and Veterinary Entomology LocationsDOI10.1111/j.0269-283X.2004.00482.x Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/15189246 |
