| Use of Scented Sugar Bait Stations to Track Mosquito-Borne Arbovirus Transmission in California | Lothrop, Hugh D. | 2012 |
Keywordssurveillance, West Nile virus, sugar feeding, bait station, Culex larsalis, WNV AbstractLaboratory and field research was conducted to determine if Culex tarsalis Coquillett expectorated West Nile virus (WNV) during sugar feeding and if a lure or bait station could be developed to exploit this behavior for WNV surveillance. Experimentally infected Cx. tarsalis repeatedly expectorated WNV onto filter paper strips and into vials with wicks containing sucrose that was readily detectable by a quantitative reverse transcriptase-polymerase chain reaction assay. Few females (33%, n = 27) became infected by imbibing sugar solutions spiked with high concentrations (107 plaque forming units/ml) of WNV, indicating sugar feeding stations probably would not be a source of WNV infection. In nature, sugar bait stations scented with the floral attractant phenyl acetaldehyde tracked WNV transmission activity in desert but not urban or agricultural landscapes in California. When deployed in areas of the Coachella Valley with WNV activity during the summer of 2011, 27 of 400 weekly sugar samples (6.8%) tested positive for WNV RN A by reverse transcriptase-polymerase chain reaction. Prevalence of positives varied spatially, but positive sugar stations were detected before concurrent surveillance measures of infection (mosquito pools) or transmission (sentinel chicken seroconversions). In contrast, sugar bait stations deployed in urban settings in Los Angeles or agricultural habits near Bakersfield in Kern County supporting WNV activity produced 1 of 90 and 0 of 60 positive weekly sugar samples, respectively. These results with sugar bait stations will require additional research to enhance bait attractancy and to understand the relationship between positive sugar stations and standard metrics of arbovirus surveillance. AuthorsLothrop, Hugh D., Wheeler, Sarah S., Fang, Ying and Reisen, William K. Year Published2012 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME12117 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/23270177 |
| Landscape-Level Spatial Patterns of West Nile Virus Risk in the Northern Great Plains | Chuang, T.-W. | 2012 |
KeywordsWNV AbstractUnderstanding the landscape-level determinants of West Nile virus (WNV) can aid in mapping high-risk areas and enhance disease control and prevention efforts. This study analyzed the spatial patterns of human WNV cases in three areas in South Dakota during 2003–2007 and investigated the influences of land cover, hydrology, soils, irrigation, and elevation by using case–control models. Land cover, hydrology, soils, and elevation all influenced WNV risk, although the main drivers were different in each study area. Risk for WNV was generally higher in areas with rural land cover than in developed areas, and higher close to wetlands or soils with a high ponding frequency. In western South Dakota, WNV risk also decreased with increasing elevation and was higher in forested areas. Our results showed that the spatial patterns of human WNV risk were associated with landscape-level features that likely reflect variability in mosquito ecology, avian host communities, and human activity. AuthorsChuang, T.-W., Hockett, C. W., Kightlinger, L. and Wimberly, M. C. Year Published2012 PublicationAmerican Journal of Tropical Medicine and Hygiene LocationsDOI10.4269/ajtmh.2012.11-0515 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/22492161 |
| Rainfall Influences Survival of Culex pipiens (Diptera: Culicidae) in a Residential Neighborhood in the Mid-Atlantic United States | Jones, Christy E. | 2012 |
KeywordsCulex pipiens, dispersal, mosquito, survival, West Nile virus, WNV AbstractMeasurement of the survival and dispersal rates of mosquito vectors is an important step in designing and implementing control strategies. Vector survival plays a key role in determining the intensity of pathogen transmission, and vector movement determines the spatial scale on which control efforts must operate to be effective. We provide the first estimates of field survival and dispersal rates for Culex pipiens L. in North America, an important enzootic and bridge vector for West Nile virus (WNV). We conducted mark-release-recapture studies in a residential area near Washington, DC, in two consecutive years and fit nonlinear regression models to the recapture data that incorporate weather information into survival and recapture probabilities. We found that daily survival rates were not significantly different between the 2 yr but were negatively affected by rainfall. The daily survival rate was 0.904 ± 0.037 (SE), which implies an average longevity of 10.4 d. As with other vector-borne pathogens, the measured survival rate suggests that at our site the majority of WNV-infected Cx. pipiens mosquitoes may perish before becoming infectious (being able to transmit WNV to hosts). We found relatively little evidence of dispersal after the initial night after release. Our results suggest that transmission of WNV and other pathogens transmitted by Cx. pipiens may be highly local and they highlight the importance of factors that influence survival of mosquito vectors. AuthorsJones, Christy E., Lounibos, L. Philip, Marra, Peter P. and Kilpatrick, A. Marm Year Published2012 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME11191 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/22679852 |
| Remote Sensing of Climatic Anomalies and West Nile Virus Incidence in the Northern Great Plains of the United States | Chuang, Ting-Wu | 2012 |
KeywordsWNV AbstractThe northern Great Plains (NGP) of the United States has been a hotspot of West Nile virus (WNV) incidence since 2002. Mosquito ecology and the transmission of vector-borne disease are influenced by multiple environmental factors, and climatic variability is an important driver of inter-annual variation in WNV transmission risk. This study applied multiple environmental predictors including land surface temperature (LST), the normalized difference vegetation index (NDVI) and actual evapotranspiration (ETa) derived from Moderate-Resolution Imaging Spectroradiometer (MODIS) products to establish prediction models for WNV risk in the NGP. These environmental metrics are sensitive to seasonal and inter-annual fluctuations in temperature and precipitation, and are hypothesized to influence mosquito population dynamics and WNV transmission. Non-linear generalized additive models (GAMs) were used to evaluate the influences of deviations of cumulative LST, NDVI, and ETa on inter-annual variations of WNV incidence from 2004-2010. The models were sensitive to the timing of spring green up (measured with NDVI), temperature variability in early spring and summer (measured with LST), and moisture availability from late spring through early summer (measured with ETa), highlighting seasonal changes in the influences of climatic fluctuations on WNV transmission. Predictions based on these variables indicated a low WNV risk across the NGP in 2011, which is concordant with the low case reports in this year. Environmental monitoring using remote-sensed data can contribute to surveillance of WNV risk and prediction of future WNV outbreaks in space and time. AuthorsChuang, Ting-Wu and Wimberly, Michael C. Year Published2012 PublicationPLOS One LocationsDOI10.1371/journal.pone.0046882 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/23071656 |
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West Nile virus cluster analysis and vertical transmission in
Culex pipiens
complex mosquitoes in Sacramento and Yolo Counties, California, 2011
| Fechter-Leggett, Ethan | 2012 |
KeywordsCalifornia, California: epidemiology, Culex, West Nile virus: pathogenicity, West Nile virus, West Nile Fever: transmission, West Nile Fever, Infectious Disease Transmission, Vertical, Female, Culex: virology, Animals AbstractWest Nile virus (WNV) is now endemic in California, with annual transmission documented by the statewide surveillance system. Although much is known about the horizontal avian-mosquito transmission cycle, less is known about vertical transmission under field conditions, which may supplement virus amplification during summer and provide a mechanism to infect overwintering female mosquitoes during fall. The current study identified clusters of WNV-infected mosquitoes in Sacramento and Yolo Counties, CA, during late summer 2011 and tested field-captured ovipositing female mosquitoes and their progeny for WNV RNA to estimate the frequency of vertical transmission. Space-time clustering of WNV-positive Culex pipiens complex pools was detected in the northern Elk Grove area of Sacramento County between July 18 and September 18, 2011 (5.22 km radius; p<0.001 and RR=7.80). Vertical transmission by WNV-infected females to egg rafts was 50% and to larvae was 40%. The estimated minimal filial infection rate from WNV-positive, ovipositing females was 2.0 infected females/1,000. The potential contribution of vertical transmission to WNV maintenance and amplification are discussed. AuthorsFechter-Leggett, Ethan, Nelms, Brittany M., Barker, Christopher M. and Reisen, William K. Year Published2012 PublicationJournal of Vector Ecology LocationsDOI10.1111/j.1948-7134.2012.00248.x Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/23181869 |
