Progress 10/01/05 to 09/30/09
Outputs
OUTPUTS: This is a final report covering a four year period of investigation of West Nile virus and mosquito dynamics in southern Wisconsin. The first major output included identification of characteristics of the urban and public water sources that generate West Nile virus vectors (Culex species). As a result of these detailed studies, we tested biological control strategies for a subset of these sites that were resistant to treatment with Bacillus sphaericus. After examining notonectids, turbellarians, and fish as potential predators in laboratory studies, we selected fathead minnows for field testing. Field collected adult mosquitoes were tested for the presence of the West Nile virus pathogen and for co-occurrence of avian malaria parasites because these pathogens can interact in both the bird reservoir species and in the mosquito host. A subset of field -collected adults were examined to determine the source of the blood meal using DNA-based methods. The efficacy of trap methods was compared to determine whether these traps accurately predict the risk of human exposure to West Nile virus vectors and to examine the community of mosquito species that occur in southern Wisconsin. PARTICIPANTS: Two graduate students, Patrick Irwin and Tony Hughes, worked on this project and received training in mosquito management practices. A large number of undergraduates also participated in summer field collections, mosquito identifications and West Nile virus testing of pooled mosquito samples. Partner organizations included the State of Wisconsin Department of Public Health (Diep Hoang Johnson), the La Crosse county public health department (David Geske), Dane County Public Health (John Hausbeck) and Milwaukee Public Health (Dave Campbell). TARGET AUDIENCES: Target audiences included public health departments that monitor mosquito populations and West Nile virus at the county, state and federal levels. Major efforts were to provide advance knowledge of changes in mosquito populations and in vector infection status. WNV test results were reported weekly to the counties, state and to the national Centers for Disease Control. Dane County Public Health continues to support investigations of biological control in stormwater systems. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
The results of detailed studies of mosquito larval habitats demonstrated that the sources of West Nile virus vectors were overwhelmingly dominated by ditches and catch basins, constructed systems used for managing rain water runoff. The presence of predatory species was correlated with reduction of or absence of mosquito larvae. Tests of the fathead minnow indicated that these fish can survive in ditches and can dramatically reduce the need for treatment with other chemicals. Fathead minnows are native fish that are frequently used as bait and are readily available for use in mosquito control programs. The results of pathogen testing demonstrated that West Nile virus is circulating in Culex mosquitoes but could not be detected in the most abundant human-feeding species, Aedes vexans and Aedes trivittatus. Culex mosquitoes also harbored avian malaria species at a high level, suggesting that interactions may be affecting pathogen transmission with potential effects on bird health and on vector efficacy. Surprisingly, blood meal analysis suggested that white-tailed deer serve as the most important blood source for both of the major nuisance Aedes species in Madison. Culex mosquitoes were relatively low in all trap collections (gravid, CO2 light, Mosquito Magnet)when compared with other urban areas, suggesting that climate and stormwater management practices may reduce the risk of West Nile transmission here. Mosquito collections revealed a new species for Wisconsin, Aedes japonicus, which has been identified as a potential vector of La Crosse virus and of West Nile virus.
Publications
- Irwin P. and Paskewitz S.M. Investigation of fathead minnows (Pimephales promelas) as a biological control agent of Culex mosquitoes under laboratory and field conditions. Journal of the American Mosquito Control Association. 2009. 25:301-309.
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Progress 01/01/08 to 12/31/08
Outputs
OUTPUTS: The specific aims of the project are to identify the vectors of West Nile virus in southern Wisconsin. During 2008, we identified WNV infections in mosquitoes that were collected in 2007 and 2008. We also sampled adult and larval mosquitoes within the cities of Madison, Sun Prairie, and Middleton. We identified the blood meal source for common human feeding mosquitoes to determine whether they are likely to switch between birds and humans. We characterized the aquatic habitats that generate Culex mosquitoes as these are the most important vectors of WNV between birds. We identified ditches as common sources of these mosquitoes and initiated field trials of a biological control strategy using fish that are suited to these habitats. We began investigation of an additional possible biocontrol agent, predaceous copepods, which can feed on early instars of larval mosquitoes. Dissemination of these results occurred through multiple avenues, including direct conversations with stakeholders in the Wisconsin Division of Health and within county Health or Environmental Health departments (Milwaukee, LaCrosse). Results were also disseminated via a newly designed website and through multiple media outlets. Finally, I presented a summary of these results on July 2, 2008 entitled "Integrated mosquito management for West Nile Virus Control" to the National Livestock Resources Research Institute in Tororo, Uganda. PARTICIPANTS: One student, Tony Hughes, received a Master's Degree in 2008. Mr. Hughes received a Navy fellowship and worked on surveillance and diagnosis of WNV and avian Plasmodium in Culex mosquitoes and other human-feeding species in Madison. A second student, Patrick Irwin, is in the last year of his doctoral program and was supported by this project. The project relied heavily on partner organizations including the Health Departments of the City of Madison and Dane County, the State Division of Health, and the National Wildlife Health Center. As a result of our surveillance efforts, we contributed training for City of Milwaukee Environmental Health staff in identification of mosquitoes. We also trained City of Madison staff in sampling, identification, and chemical control methods for larval mosquitoes. TARGET AUDIENCES: The following media and public contacts were intended to inform the general public about various aspects of mosquito biology and disease transmission by these vectors. Interview with Janesville Gazette April 23, 2008; Interview with Wisconsin State Journal, May 15, 2008; Creation and promotion of website "Integrated mosquito management" which resulted in ca. 50 direct contacts from the public; Interview with Channel 3 News, May 16, 2008; Interview with Wisconsin State Journal May 21, 2008; Interview with Newsweek; Interview with Madeline Fisher for Wisconsin Idea; Cited in New York Times blog; Cited in Steamboat; Interview for GROW (CALS magazine for alums); Wisconsin State Journal cover, Saturday June 28, 2008; Interview for Indiana Public Radio, July 23; Presentation to a Madison Kiwanis group, November 2008. PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
The most important results of these studies were 1) the identification of new species of mosquitoes for the State of Wisconsin, including Aedes japonicus and Psorophora cyanescens. We determined that Aedes japonicus, a potential vector of several viruses including La Crosse and WNV, is now widely distributed in the southern 1/3 of the state, although populations are not yet large. Future changes in the populations may impact disease transmission. 2)the identification of blood meal sources for the two most common human-feeding mosquitoes, Aedes vexans and Aedes trivittatus. In each case, white tailed deer are the most common hosts and no bird feeding was detected. This may suggest that nuisance mosquitoes could be reduced by reducing the deer herd in urban areas. 3) We successfully piloted the implementation of fathead minnows for larval Culex mosquito control. These fish are cheap and hardy and provided complete control (elimination of need for chemical control) in 3 pilot ditches. These studies will be expanded to determine whether fish can become established after wintering and whether additional habitat types can be treated successfully. 4) We continued surveillance and diagnosis for WNV in adult mosquitoes which resulted in measuring the highest populations of nuisance species yet seen in Madison and triggered additional public health warnings during periods of major human outdoor activity (July 4th). 5) For the second year, we identified a population of human-feeding mosquitoes that tested positive for WNV by a commonly used protein-based method but not by RNA-based diagnostics. Although we had established a collaboration to isolate viruses from these mosquitoes should the need arise, populations declined too quickly after the initial positive test for us to attempt the isolation. 6) We continued to refine a model of the catch basin system in Madison as this underground storm water system also generates significant numbers of Culex during dry years. The model suggests features of catch basins that may favor larval mosquito development and should help to identify which basins may need surveillance and treatment. 7) We sampled above and below-ground sites for copepod predators and identified 3 species that may be useful for biocontrol. We initiated culture of these local isolates for further study.
Publications
- Irwin P., Arcari C., Hausbeck J., and Paskewitz S.M. The urban wet landscape as mosquito habitat in the upper Midwest. Ecohealth. 5:49-57. 2008.
- Hughes T.H., Irwin P.M., Kaufman A., Sage H., and Paskewitz S.M. First records of Aedes japonicus japonicus in Wisconsin. Journal of the American Mosquito Control Association. 24:583-584. 2008.
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Progress 01/01/07 to 12/31/07
Outputs
OUTPUTS: Outputs that contribute to the goals and objectives of the project included 1) collection of mosquitoes that were attracted to humans at various times of the day over the 2007 season; 2) collection of mosquitoes by gravid trap (collects likely vectors of West Nile virus and mosquitoes that have already taken at least one blood meal); 3)collection of mosquitoes by light/CO2 traps; 4) identification of WNV in gravid-trapped mosquitoes; 5) collections of larval mosquitoes and comparisons across habitat and multiple seasons. The results of these studies were disseminated through discussions with personnel involved in mosquito management in the City of Madison, Fitchburg, Sun Prairie and Middleton. Results were presented at committee meetings (committee on the Environment) at the City of Madison, the State West Nile Virus Task Force, and at two professional meetings (one regional, one national) as follows: Irwin, P., Arcari C., Hausbeck J., and Paskewitz S. American Mosquito
Control Association. Seasonal weather patterns and production of mosquito larvae in the Upper Midwest. April 1-5, 2007, Orlando, Fla. Irwin P. Arcari C. Hausbeck J. and Paskewitz S. Annual Midwestern Conference on Parasitology. Seasonal weather patterns and production of mosquito larvae in the Upper Midwest. June 14-16, 2007. Oshkosh, Wisconsin.
PARTICIPANTS: Susan Paskewitz, PI. Patrick Irwin, graduate student. This student was responsible for working with the City of Madison to train new staff in larval collections and for analyzing larval collection data and ecological associations. This student also participated in all adult mosquito collections and mosquito identifications. Tony Hughes, graduate student. This student participated in all adult mosquito collections and was responsible for identification of WNV in gravid-trapped mosquitoes. A team of four undergraduates helped with identification of mosquitoes from traps as well as collections.
TARGET AUDIENCES: The target audiences include City personnel involved in mosquito abatement for the purpose of reducing exposure to West Nile virus, state officals involved in coordinating, collecting and disseminating information about WNV in Wisconsin,and the research community on mosquito ecology and WNV transmission.
PROJECT MODIFICATIONS: There were no major changes in approach.
Impacts
Results of these studies indicated that 1) West Nile virus vectors do not occur in high numbers in the Madison area but focal spots of high populations are identifiable and a subset are consistent superproducers between years; 2) both above and below-ground wet sites generate mosquitoes but the relative contribution varies according to rainfall; 3) a new species, Ochlerotatus japonicus, has been introduced into Wisconsin; 4) Culex pipiens/restuans mosquitoes are extremely rare in human landing collections, suggesting that other bridge vectors may be more important in disease transmission; 5) natural wet sites do not generate high numbers of larval Culex mosquitoes in comparison with sites constructed for storm water management. These findings are being used to predict which wet sites should be priority targets for mosquito surveillance and to provide information about storm water management to local city engineers. These findings further suggest significant differences
occur between mosquito communities in Wisconsin and those in other urban areas with higher WNV transmission and are serving as the basis for additional collaborative studies. Resources were used to provide a stipend for one graduate student and to provide supplies and transport for this student and a second student funded by the US Navy.
Publications
- No publications reported this period
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Progress 01/01/06 to 12/31/06
Outputs
During 2006, the project completed the following research projects: 1) collection of human biting mosquitoes at four locations in southern Wisconsin, correlating these collections with those obtained in carbon-dioxide baited light traps and gravid traps for each week between June and October; 2) collection of human biting mosquitoes on an hourly basis during times of peak human outdoor activity and mosquito biting (5-10 p.m.); 3) collection of larval mosquitoes and sampling of water quality in 14 catch basins on a weekly basis and in 80 catch basins on a monthly basis; 4) collection of blood fed mosquitoes from natural resting sites for determination of blood meal sources; and 5) monitoring of newly installed rain gardens for the presence of mosquito larvae. Mosquitoes that were collected during this summer were frozen for detection of the presence of West Nile virus and other pathogens during the winter of 2007. Nuisance mosquitoes, including Aedes vexans and
Ochlerotatus trivittatus were the most abundant species collected. Human landing catches resulted in different profiles of mosquito species complexity and abundance when compared with other trap methods. Results indicated that Culex mosquito species that are thought to be involved in transmission of West Nile virus on the east coast of the United States were not attracted to humans in southern Wisconsin although they were found in gravid and light traps taken at the same locations. Catch basins and rain gardens served as sources of larvae of Culex pipiens and Cx. restuans. Physical properties of catch basins and chemical properties of the water contained therein affected larval abundance.
Impacts
This work will provide information about the prevalence and human biting habits of mosquitoes in southern Wisconsin. We will also determine whether current methods of surveillance through light and CO2 trapping are efficient indicators of human annoyance and risk. Finally, we will be able to suggest measures for personal protection in relation to mosquito population, peak biting periods, and risk of infection.
Publications
- No publications reported this period
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Progress 10/01/05 to 12/31/05
Outputs
The project has 3 aims: 1) characterize the circadian rhythm of mosquitoes that feed on humans in southern Wisconsin; 2) identify the natural sources of blood in mosquitoes that can feed on humans; 3) determine whether the human landing catches produce similar profiles of mosquitoes as carbon-dioxide or light baited traps. During the first 2 months of the project, we found and hired a student with substantial experience in mosquito collection in southern Wisconsin. With his help, we identified a number of sites in Madison where Culex pipiens, a major vector of West Nile virus, breed. We also identified sites in Madison where mosquitoes do not occur, although conditions look appropriate for mosquito breeding. We looked for resting sites where adult Culex mosquitoes might be overwintering in the UW arboretum and found Anopheles adult mosquitoes. Finally, we began discussions with city and state personnel with responsibilities for West Nile virus surveillance about
combining surveillance efforts for greater impact.
Impacts
This work will provide information about the prevalence and human biting habits of mosquitoes in southern Wisconsin. We will also determine whether current methods of surveillance through light and CO2 trapping are efficient indicators of human annoyance and risk. Finally, we will be able to suggest measures for personal protection in relation to mosquito population, peak biting periods, and risk of infection.
Publications
- No publications reported this period
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