| Geographic incidence of human West Nile virus in northern Virginia, USA, in relation to incidence in birds and variations in urban environment | Liu, Hua | 2011 |
KeywordsWNV AbstractPrevious studies have analyzed the number and location of bird infections with human incidence of West Nile virus (WNV) as well as the effects of environmental and socioeconomic factors on WNV propagation. However, such associations require more quantitative analyses. This study is intended to quantitatively analyze the relationship in eight counties/independent cities in the northern Virginia, based on an integrated analysis of spatially explicit information on precipitation, land cover, infrastructure, and demographic data using Geographical Information Systems, remote sensing, and statistics. Results show that bird infections in years 2002–2003 were closely associated with low to medium level of impervious surface with certain percentage of canopy and precipitation. Environmental and socioeconomic factors such as percentages of impervious surface, canopy, senior population (65 and older), old houses, bird risk areas, and low-income population were important indicators of human WNV risk in 2002. Limited impervious surface with some canopy provides suitable habitats for WNV transmission, where bird-feeding mosquitoes can forage for blood meals from nesting/roosting birds. Certain socioeconomic conditions such as old houses were linked with human infections by providing favorable environmental conditions, i.e., mature trees with abundant canopy and settled storm sewer systems. It should be noted that the current results may be biased toward urban environments, where dead birds were more likely found, and because the sampling efforts for the bird mortality were rather based on local residents' reports than a designed random sampling method. This geospatial study contributes toward better targeting of WNV prevention within the study area. It also provides an example of how geospatial methods and variables may be used in understanding the ecology of human WNV risk for other areas. AuthorsLiu, Hua, Weng, Qihao and Gaines, David Year Published2011 PublicationScience of The Total Environment LocationsDOI10.1016/j.scitotenv.2011.07.012 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21802710 |
| Climate-based models for West Nile Culex mosquito vectors in the Northeastern US | Gong, Hongfei | 2011 |
KeywordsWNV AbstractClimate-based models simulating Culex mosquito population abundance in the Northeastern US were developed. Two West Nile vector species, Culex pipiens and Culex restuans, were included in model simulations. The model was optimized by a parameter-space search within biological bounds. Mosquito population dynamics were driven by major environmental factors including temperature, rainfall, evaporation rate and photoperiod. The results show a strong correlation between the timing of early population increases (as early warning of West Nile virus risk) and decreases in late summer. Simulated abundance was highly correlated with actual mosquito capture in New Jersey light traps and validated with field data. This climate-based model simulates the population dynamics of both the adult and immature mosquito life stage of Culex arbovirus vectors in the Northeastern US. It is expected to have direct and practical application for mosquito control and West Nile prevention programs. AuthorsGong, Hongfei, DeGaetano, Arthur T. and Harrington, Laura C. Year Published2011 PublicationInternational Journal of Biometeorology Locations- Site 1, North Brunswick, Middlesex County, New Jersey (40.4°N,74.5°W) 1990–1993, 1997, 1999, 2001 (40.4, -74.5)
- Site 2, near Cambridge, Dorchester County, Maryland (38.56°N, 76.07°W ) (38.56, -76.07)
DOI10.1007/s00484-010-0354-9 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/20821026 |
| The Effect of Spatial and Temporal Subsetting on Culex tarsalis Abundance Models—a Design for Sensible Reduction of Vector Surveillance | Brown, Heidi E. | 2011 |
KeywordsWNV AbstractEarly identification of increasing mosquito activity is critical to effective mosquito control, particularly when increasing host-seeking behavior may be associated with increased risk of mosquito-borne disease. In this paper, we analyzed the temporal abundance pattern of the West Nile Virus vector, Culex tarsalis, in Fort Collins, CO, using an autoregressive integrated moving average model. We determined that an autoregressive model order 5 with lagged minimum temperatures was best at describing the seasonal abundance of Cx. tarsalis. We then tested the effect of using both temporal and spatial subsets of the data to determine the effect of reduced sampling effort on abundance predictions. We found that, if reduced trapping is necessary due to limited resources, removal of the least productive 1/3 or 1/4 of the traps produced the least erroneous predictions of seasonality represented in the observed data. We show that this productivity-based subset scheme performs better than other sampling effort reductions in generating the best estimate of Cx. tarsalis abundance per trap-night. AuthorsBrown, Heidi E., Doyle, Michael S., Cox, Jonathan, Eisen, Rebecca J. and Nasci, Roger S. Year Published2011 PublicationJournal of the American Mosquito Control Association LocationsDOI10.2987/10-6077.1 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21805843 |
| Using a neural network for mining interpretable relationships of West Nile risk factors | Ghosh, Debarchana | 2011 |
KeywordsWest Nile virus; Risk factors; Nonlinear; Neural network; Urban morphology; USA, WNV AbstractThe West Nile Virus (WNV) is an infectious disease spreading rapidly throughout the United States, causing illness among thousands of birds, animals, and humans. Yet, we only have a rudimentary understanding of how the mosquito-borne virus operates in complex avian–human environmental systems. The four broad categories of risk factors underlying WNV incidences are: environmental (temperature, precipitation, wetlands), socioeconomic (housing age), built-environment (catch basins, ditches), and existing mosquito abatement policies.
This research first built a model incorporating the non-linear relationship between WNV incidences and hypothesized risk factors and second, identified important factor(s) whose management would result in effective disease prevention and containment. The research was conducted in the Metropolitan area of Minnesota, which had experienced significant WNV outbreaks from 2002.
Computational neural network (CNN) modeling was used to understand the occurrence of WNV infected dead birds because of their ability to capture complex relationships with higher accuracy than linear models. Further a detailed interpretation technique, based on weights and biases of the network, provided a means for extracting relationships between risk factors and disease occurrence.
Five risk factors: proximity to bogs, lakes, temperature, housing age, and developed medium density land cover class, were selected by the model. The detailed interpretation indicated that temperature, age of houses, and developed medium density land cover were positively related, and distance to bogs and lakes were negatively related to the incidence of WNV.
This paper provides both applied and methodological contributions to the field of health geography. The relationships between the risk factors and disease occurrence could contribute to vector control strategies such as targeted insecticide spraying near bogs and lakes, mosquito control treatments for older houses, and extensive mapping, inspection, and treatments of catch basins. The proposed interpretation technique expanded the role of CNN models in health sciences as both predictive and explanatory tools. AuthorsGhosh, Debarchana and Guha, Rajarshi Year Published2011 PublicationSocial Science & Medicine LocationsDOI10.1016/j.socscimed.2010.09.014 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/20950908 |
| Blood-Feeding Patterns of the Culex pipiens Complex in Sacramento and Yolo Counties, California | Montgomery, Matthew J. | 2011 |
KeywordsCulex pipiens, mosquito feeding, West Nile virus, WNV AbstractMosquitoes in the Culex pipiens complex are competent vectors of West Nile virus (WNV; family Flaviviridae, genus Flavivirus) in the laboratory, and field-collected mosquitoes have tested positive for the virus in California and elsewhere. A better understanding of Cx. pipiens complex blood-feeding patterns will help define the threat that these mosquitoes pose to human health and their role in WNV amplification in northern California. We collected blood-engorged Cx. pipiens complex mosquitoes from resting sites near and away from human habitation in Sacramento and Yolo Counties. Cytochrome c oxidase 1 gene sequences were used to identify the vertebrate species from which blood meals were taken. Of 330 engorged mosquitoes collected at 28 sites from June through August 2007 and May through August 2008, >99% fed on an avian host. Three mosquitoes contained bovine blood and none had fed on a human. American Robins (Turdus migratorius) were bitten most often, and the proportion of American Robin blood meals increased significantly over the summer. Other important avian hosts included House Finches (Carpodacus mexicanus), Barn Swallows (Hirundo rustica), Western Meadowlarks (Sturnella neglecta), and Mourning Doves (Zenaida macroura). In rural areas, Barn Swallows, Brewer's Blackbirds (Euphagus cyanocephalus), and House Sparrows (Passer domesticus) were frequent hosts. In settings near human habitation, Mourning Doves and Western Meadowlarks were common hosts. Our data indicate that in north central California mosquitoes in the Cx. pipiens complex may be more important as epiornitic than epidemic vectors of WNV. AuthorsMontgomery, Matthew J., Thiemann, Tara, Macedo, Paula, Brown, David A. and Scott, Thomas W. Year Published2011 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME10067 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21485380 |
| Abundance of West Nile virus mosquito vectors in relation to climate and landscape variables | Deichmeister, Jayne M. | 2011 |
KeywordsWNV AbstractIt is currently unclear if the potential for West Nile virus transmission by mosquito vectors in the eastern United States is related to landscape or climate factors or both. We compared abundance of vector species between urban and suburban neighborhoods of Henrico County, VA, in relation to the following factors: temperature, precipitation, canopy cover, building footprint, and proximity to drainage infrastructure. Mosquitoes were collected throughout the 2005, 2006, and 2007 seasons and tested for West Nile virus (WNV) in pools of 10-50. Test results of mosquito pools were compared to average site abundance from 37 sites in Henrico County, VA; abundance was then examined in relation to ecological variables. Urban infrastructure was positively correlated with the abundance of Culex pipiens L./Cx. restuans, and our findings implicate combined sewer overflow systems as large contributors to Culex vector populations. No measure of urbanization examined in our study was correlated with Aedes albopictus abundance. Our study showed that certain landscape variables identified using Geographic Information Systems are valuable for predicting primary WNV vector abundance in Virginia, and that temperature along with low precipitation are strong predictors of population growth. Our results support other regional studies that found WNV proliferates under drought conditions. AuthorsDeichmeister, Jayne M. and Telang, Aparna Year Published2011 PublicationJournal of Vector Ecology LocationsDOI10.1111/j.1948-7134.2011.00143.x Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21635644 |
| The fog of war: Why the environmental crusade for anadromous fish species in California could disarm the State’s local vector control districts in their war against mosquitoes | Siptroth, Stephen M. | 2011 |
KeywordsClean Water Act; Vector control district; Mosquito; Malaria; West Nile virus; California, WNV AbstractIn California, local mosquito and vector control districts have successfully controlled mosquito and vector-borne diseases by improving drainage patterns and applying pesticides. The Bay-Delta Conservation Plan, which is a proposed habitat conservation plan for the Sacramento-San Joaquin Bay-Delta estuary, proposes to add over 70,000 acres of habitat in the Delta to improve conditions for threatened and endangered aquatic and terrestrial species. This habitat could also be a suitable mosquito breeding habitat, which will be located in close proximity to urban and suburban communities. Wetland management practices and continued pesticide applications in the Delta could mitigate the effects of a new mosquito breeding habitat. Recent legal developments, however, require districts to obtain and comply with Clean Water Act permits, which restrict the application of pesticides in or near waters of the United States. Moreover, the U.S. Environmental Protection Agency has taken the first step in a rulemaking process that could further limit or prohibit the use of certain vector control pesticides in the Delta. In the near term and until less harmful methods for mosquito control are available, local vector control districts’ application of mosquito control pesticides should be exempt from Clean Water Act permit requirements. AuthorsSiptroth, Stephen M. and Shanahan, Richard P. Year Published2011 PublicationJournal of Epidemiology and Global Health LocationsDOI10.1016/j.jegh.2011.06.001 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/23856372 |
| Winter Biology of Wetland Mosquitoes at a Focus of Eastern Equine Encephalomyelitis Virus Transmission in Alabama, USA | Burkett-Cadena, Nathan D. | 2011 |
Keywordsoverwintering, mosquito, winter emergence, eastern equine encephalitis, WNV AbstractAt temperate latitudes, vectors and pathogens must possess biological mechanisms for coping with cold temperatures and surviving from one transmission season to the next. Mosquitoes that overwinter in the adult stage have been proposed as winter maintenance hosts for certain arboviruses. In the cases of West Nile virus (family Flaviviridae, genus Flavivirus) and St. Louis encephalitis virus (family Flaviviridae, genus Flavivirus), discovery of infected overwintering females lends support to this hypothesis, but for other arboviruses, in particular Eastern equine encephalomyelitis virus (family Togaviridae, genus Alphavirus, EEEV), overwintering of the virus in mosquito hosts as not been demonstrated. In the current study, we collected overwintering mosquitoes from a focus of EEEV transmission in the southeastern United States to determine whether mosquitoes serve as winter maintenance hosts for EEEV and to document overwintering biologies of suspected vectors. No virus was detected via reverse transcription-polymerase chain reaction of >500 female mosquitoes collected during three winters. Investigation into the winter biologies indicated that Anopheles punctipennis (Say), Culex erraticus (Dyar & Knab), Culex peccator Dyar & Knab, and Uranotaenia sapphirina (Osten Sacken) overwinter as females. Females of these species were collected from hollow trees and emergence traps placed over ground holes. Southern magnolia, Magnolia grandiflora L., trees were preferred overwintering sites of culicine mosquitoes. Emergence from underground overwintering sites peaked in mid-March, when air temperatures reached 18–22°C, and the first bloodengorged females of Cx. erraticus and Cx. peccator were collected during this same period. Blood-fed Culex territans Walker females were collected as early as mid-February. This work provides insight into the overwintering biologies of suspected virus vectors at a site of active EEEV transmission and provides limited evidence against the hypothesis that EEEV persists through intertransmission periods in overwintering mosquitoes. AuthorsBurkett-Cadena, Nathan D., White, Gregory S., Eubanks, Micky D. and UNNASCH, THOMAS R. Year Published2011 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME10265 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21936314 |
| Temporal and Spatial Patterns of West Nile Virus Transmission in Saginaw County, Michigan, 2003-2006 | Chuang, Ting-Wu | 2011 |
KeywordsWest Nile virus, Aedes vexans, Culex pipiens, Culex restuans, sentinel pheasants, WNV AbstractThe dynamics of West Nile virus (family Flaviviridae, genus Flavivirus, WNV) infection in mosquitoes, sentinel pheasants, and wild dead birds were evaluated during 2003–2006 in Saginaw Co., MI. Mosquitoes were collected by New Jersey Light Traps at 22 sites during May–September, pooled by species and sample location, and tested for presence of WNV RNA by using a real-time reverse transcription-polymerase chain reaction assay. Oral swabs from wild dead birds submitted by the public were tested by Vec-Test assay. Sentinel pheasants were bled weekly, and serum was tested for antibodies with an inhibition enzyme immunoassay. In total, 37,225 mosquitoes [Aedes vexans (Meigen), Culex pipiens L., and Culex restuans Theobald] were tested in 5,429 pools, of which 59 (1.1%) were positive. Ae. vexans was most abundant but had a comparatively low infection rate (0.06–2.11) compared with Cx. pipiens (1.75–4.59) and Cx. restuans (1.22–15.67). Mosquito abundances were temporally related to variations in 2-wk average weather variables. Infected dead crows appeared earlier each transmission season than blue jays, but infection prevalence for both peaked approximately mid-August. Space-time clusters were found in different locations each year. Sentinel pheasant seroprevalence was 19.3% (16/83), 12.7% (10/79), and 7.7% (5/65) during 2003–2005, respectively. We demonstrated temporal patterns of WNV activity in corvid birds and Culex spp. mosquitoes during the study period, suggesting virus transmission within an enzootic cycle. Despite the absence of human case reports nearby, this surveillance system demonstrated WNV transmission and possible human risk. Maintained surveillance using more appropriate gravid traps and CDC CO2 light traps could improve sensitivity of vector collection and virus detection. AuthorsChuang, Ting-Wu, Knepper, Randall G., Stanuszek, William W., Walker, Edward D. and Wilson, Mark L. Year Published2011 PublicationJournal of Medical Entomology LocationsDOI10.1603/ME10138 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21936324 |
|
Surveillance for West Nile Virus and Vaccination of Free-Ranging Island Scrub-Jays (
Aphelocoma insularis
) on Santa Cruz Island, California
| BOYCE, WALTER M. | 2011 |
KeywordsWNV AbstractAbstract Transmission of West Nile virus (WNV) on mainland California poses an ongoing threat to the island scrub-jay (ISSJ, Aphelocoma insularis), a species that occurs only on Santa Cruz Island, California, and whose total population numbers 750 migrating and resident birds on the island from 2006 to 2009 indicated that WNV had not become established by the end of 2009. Several species of competent mosquito vectors were collected at very low abundance on the island, including the important mainland vectors Culex tarsalis and Culex quinquefasciatus. However, the island was generally cooler than areas of mainland California that experienced intense WNV transmission, and these lower temperatures may have reduced the likelihood of WNV becoming established because they do not support efficient virus replication in mosquitoes. A vaccination program was initiated in 2008 to create a rescue population of ISSJ that would be more likely to survive a catastrophic outbreak. To further that goal, we recommend managers vaccinate >100 ISSJ each year as part of ongoing research and monitoring efforts. AuthorsBOYCE, WALTER M., Vickers, Winston, Morrison, Scott A., Sillett, T. Scott, Caldwell, Luke, Wheeler, Sarah S., Barker, Christopher M., Cummings, Robert and Reisen, William K. Year Published2011 PublicationVector-Borne and Zoonotic Diseases LocationsDOI10.1089/vbz.2010.0171 Additional Information:http://www.ncbi.nlm.nih.gov/pubmed/21438695 |
