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West Nile Virus, IL

Investigators
Solter, Leellen
Institutions
University of Illinois - Urbana-Champaign
Start date
2005
End date
2008
Objective
  1. Quantify seasonal and regional variation in vector abundance, predicting transmission cycles with simulation modeling;
  2. Correlate trends in vector populations with spatial and temporal population dynamics of bird and mammal hosts;
  3. Develop a database on the prescence of and exposure to West Nile virus and other flaviviruses in mosquitoes, birds and mammals.
More information
NON-TECHNICAL SUMMARY: WNV first entered Illinois in 2001 and was detected primarily in northern Illinois from about 140 corvids and raptors, 20 pools of mosquitoes, and 2 horses. By October 2002, Illinois had the highest number of human cases (over 700) and deaths (56) in the United States, exceeding the 1975 St. Louis encephalitis epidemic. West Nile virus transmission was detected in 98 of 102 counties in Illinois, based on data from mosquitoes (528 WNV-positive pools), birds (513 WNV-positive dead birds) and horses (807). Human cases were distributed among 46 counties, although Cook County, which encompasses about 40% of Illinois' population, had 501 cases and 24 fatalities. Numbers of human cases dropped dramatically in 2003, with only 2 deaths reported in the state from WNV. Reasons for the change from one year to the next are not known, but understanding those changes is one of the goals of this research proposal.

APPROACH: Our investigations will address two areas of applied research: 1) the population dynamics and feeding behavior of potential vectors of WNV, and 2) the seasonal interactions of vector mosquitoes and avian hosts. The long-term goals are to develop descriptive and quantitative models to predict spatial and temporal interactions of key vector and host populations that influence virus transmission in the state. Illinois represents a unique area for these studies because it has a history of SLEV outbreaks, major bird migration corridors, large crow wintering and breeding sites, a major metropolitan transportation center, and distinct latitudinal variation in temperature, rainfall, and vector and host dynamics. We will compare seasonal population dynamics of key species (Cx. pipiens, Cx. restuans, Cx. salinarius, Culex quinquefasiciatus, and Aedes albopictus) by collecting adult mosquitoes at selected sites using 5 different methods. At each site, mosquito collections will be conducted for 1-3 days before and during the bird collections in the same general area. Collection data will be used to determine seasonal trends in regional abundance, indices of mosquito species association, and correlation of key events and temporal events to environmental variables. We will determine the relative abundance of mourning doves, house sparrows, American crows, blue jays, and European starlings during May to September. Data will be based on encounter surveys conducted in conjunction with bird and mosquito trapping. We will analyze temporal overlap in host and mosquito abundance and key developmental stages. We will survey birds from northern to southern Illinois every 3 weeks from May through mid-September. Results from the mosquito and host sampling and serology will be entered into a database. The real-time, statewide database will provide temporal and spatial data to allow predicting outbreaks of disease based on positive samples of mosquitoes and hosts, as well as evidence of human cases of WNV. The database will allow us to geocode data points, manage spatial data, and allow user-generated maps and tables of all data via the internet. The database on spread and management of WNV will be critical to extension of the models to be developed.

PROGRESS: 2005/06 TO 2008/06
OUTPUTS: This special grant provided the basis for bringing together scientists, graduate and undergraduate students, and mosquito abatement and public health personnel. Several topics were studied from different perspectives, particularly the interaction of the mosquito vector and the avian reservoir hosts. In Illinois, a system was devised by which field research funded by the Special Grant, "West Nile Virus, Illinois", was uploaded via Excel spreadsheet to the Illinois Department of Public Health (IDPH), including GIS database information for monitoring West Nile virus activity in mosquitoes, birds, horses, and humans. This consisted of samples from three mosquito abatement districts (MAD) in Cook County (Northwest MAD, North Shore MAD, and DesPlaines River Valley MAD), a mosquito abatement district in Macon County, an intense surveillance program in Champaign and Urbana in central Illinois, and biweekly transects in southern and western Illinois. The results of all field-collected mosquitoes in various research projects that were tested for WNV-RNA were reported to IDPH to be added to the state-wide surveillance by MADs and local health departments. The mosquito samples were tested in the Medical Entomology Laboratory by Real Time-PCR for WNV-RNA, and within 48 hours the results were provided to IDPH (http://www.idph.state.il.us/envhealth/wnv.htm). The results were used by the MAD centers to make decisions on treatment locations, and by IDPH and local public health departments to make risk assessments. From 2005-2007, approximately 30,000 sample sets of mosquitoes were tested, a total of approximately one million individual mosquitoes. Nearly 14% of all sample sets were positive over this time period. As part of this process, infection rates were routinely calculated and supplied to the mosquito abatement groups. The research demonstrated how different testing methods could improve estimation of risk without testing all of the mosquito pools. Email discussions of these results were conducted with the mosquito abatement directors and IDPH personnel. Presentations were made to Audubon Society chapters, University of Illinois entomology students, Green City in the Chicago Department of Environment, and a forum of city commissioners in northern Cook County. Temperature models for mosquito species abundance were placed on the world-wide web. One of the main goals of the output program was to present the results at major conventions related to vector borne diseases, mosquito ecology and behavior, and avian flight behavior and selection by mosquitoes as bloodmeals. Data were also submitted to scientific journals for publication and critical feedback from peers regarding new findings. Oral and poster presentations were made at the American Ornithologist's Union, the Society of Vector Ecologists, American Society of Tropical Medicine and Hygiene, and the American Mosquito Control Association.
PARTICIPANTS: The core research group for this project included a principal scientist (Dr. Robert Novak), research scientists (Dr. Richard Lampman and Dr. Weidong Gu), postdoctoral research associates (Dr. Mike Ward and Dr. Osee Sanogo), doctoral collaborators (Dr. Ken Kunkel) and master's level technical scientist (Nina Krasavin). Additional research collaborators included individuals within the Illinois Natural History Survey (Dr. Nohra Mateus) and those from outside academic institutions (see publications). In addition, funds provided summer support for 8 undergraduate students, 8 Master's or Ph.D. level students, and 10 post-baccalaureate students. Undergraduate students, minority students and visiting students from Latin America (Pan American School of Agriculture) were trained. Over the course of this grant, about 30 individuals participated directly in mosquito, avian, virus, and diagnostic research projects. Four individuals conducted their Master's or doctoral research on West Nile virus and an additional four graduate students were funded to do summer work with this program. Several mosquito abatement districts collaborated, sharing their collections to address temporal and spatial questions regarding the distribution of infected mosquito species. These included the directors or field supervisors of Northwest MAD (Mike Szyska), North Shore MAD (Robert Berry), and Des Plaines Valley MAD (Paul Geery) in Cook County and from central Illinois Macon MAD (Robert Millington). Results of all WNV detection tests were provided to the Illinois Department of Public Health with participation by Dr. Linn Haramis, Dr. Curt Colwell, and Ken McCann. Two additional IDPH individuals, Sam Davis and Barb O'Meara, provided assistance in collection of mosquitoes above and below ground in Cook County. They also provided samples for testing from various health departments. Personnel in the environmental section of the local health department in our area, Champaign-Urbana Public Health Department were also collaborators. Presentations at the local meetings provided continuing education credits for IDPH personnel.
TARGET AUDIENCES: This special grant brought together researchers and students from different disciplines (entomology, ornithology, climatology, molecular biology, statistical ecology, and landscape ecology) to study the basics aspects of West Nile virus transmission in Illinois. The goals were to define the major vectors and hosts, improve sampling methods for estimation of infection rates and risk, better understand the patterns of interaction between vectors and hosts, and to identify meteorological and biological drivers that regulate the intensity of transmission. The target audiences for these studies include those agencies responsible for vector management (mosquito abatement districts and local public health departments) and disease surveillance (Illinois Department of Public Health and the Centers for Disease Control and Prevention). The data also added to the body of knowledge regarding transmission of arboviruses and the potential risks to members of the general public and other disciplines were explained. Results improved abatement district surveillance systems, as well as provided temporal and spatial estimates of risk (density of infected vectors). Surveillance helped notify the general public about the level of WNV transmission and importance of personal protection measures. Results were shared at various technical society meetings, as well as public forums and with radio, television, and print new media. The results of these efforts helped form a communication network within the state and provided for one of the most widespread collection networks.

IMPACT: 2005/06 TO 2008/06
The effects of WNV on humans and wildlife first became evident when westward movement of the virus extended into the Midwest in 2002, resulting in the first largest arbovirus epidemic in North America and the largest WNV outbreak worldwide. Illinois is relatively unique in the northeastern U.S., enzootic transmission remained high from 2002-2007 and epidemic rebounds occurred in 2005 and 2006. Lower outbreak intensities in other years appeared related to weather. Collaboration with mosquito abatement districts in Cook County revealed spatial and temporal variation in infection rates for Culex mosquitoes. In one study, the proximity of traps to the Des Plaines River Valley Forest Preserve was related to the intensity of transmission (abundance of infected Culex). The forest preserve sites, surrounded by residential and industrial habitats, may act as focal points for bird and mosquito interactions. The prevalence of infected mosquitoes in Cook County was high for extended periods, typically between 5-14% for 3-5 weeks, thus an intense enzootic transmission even in years with low human cases. Stormwater tunnels in the area contained almost exclusively Cx. pipiens during the winter possibly leading to their rapid increase as compared to central Illinois. Some of the spatial variability of infections rates was due to rainfall and landscape factors. A weekly study of infection rates of individual mosquitoes at one site in Cook County suggested the natural competency of Cx. pipiens in the field was less than 50%. Seroprevence studies (by epitope blocking ELISA) and bloodmeal analyses (GenBank sequences) indicated northern cardinals, mourning doves, house sparrows, and American robins were the most commonly infected species. A late season shift in Culex feeding behavior was not observed. Based on research projects throughout the state, there is a 100-fold difference in infection rates in mosquitoes between southern and northern Illinois, but no corresponding stratification in human incidence rates. Bloodmeal analyses are attempting to address whether this is due to geographic variation in the feeding behavior. Molecular methods developed for identification of cryptic Culex species, detected hybrids in the Culex pipiens complex in central Illinois, which is well above the normal hybrid zone. The population trends of 16 urban bird species were estimated before and after the arrival of West Nile virus (WNV) in Illinois and four species showed post-WNV arrival declines (black-capped chickadee, tufted titmouse, blue jay, and American crow) in areas with known high transmission activity.The invasive mosquito species, Aedes (Oc.) japonicus was found in central Illinois and is an active human biter. Studies in central Illinois developed temperature models for predicting Culex pipiens and Cx. restuans abundance (http://mcc.sws.uiuc.edu/research/westnile/background.htm.).

Funding Source
Nat'l. Inst. of Food and Agriculture
Project source
View this project
Project number
ILLU-371-660
Accession number
203221
Categories
Sanitation and Quality Standards
Risk Assessment, Management, and Communication
Viruses and Prions
Bacterial Pathogens