Progress 08/01/07 to 10/01/09
Outputs
OUTPUTS: In 2009, we conducted field work on understudied aspects of feeding behavior of three potential mosquito vectors of West Nile virus (WNV). The mosquitoes were Culex pipiens, Cx. restuans, and Ochlerotatus japonicus. Cx. pipiens is a known vector, while the other two species are suspect vectors that were found infected with WNV in field collections. Ochlerotatus japonicus is of special interest because it was recently introduced from Japan. We sought a better understanding of the host feeding behavior of these species, including possible host-switching behavior, as well as potential environmental and biological cues for changes in behavior. We collected mosquitoes throughout the 2009 season using host-baited traps (hamster and Japanese quail) at four different study sites that were previously characterized as areas with good populations of Cx. pipiens and Cx. restuans over a period of years. Three of these sites had also been characterized in terms of their WNV activity. We also collected larval Oc. japonicus from rock pools along the Brandywine River in Wilmington, a known habitat of this species. The field tests were backed up in two ways: 1) By performing blood meal analyses of mosquitoes caught in gravid traps at the same four sites above; and 2) testing host choice of lab-reared mosquitoes exposed to three different daylength regimens. These regimens mimicked natural light conditions in the field. The host choice lab tests provided backup data for the field-collected data, as did the blood meal analyses. In order to perform the field studies, we modified a standard CDC mosquito trap to allow odor emanations from the quail or hamster to be diffused around the top of the trap intake. We also developed a host choice chamber that allowed mosquitoes to choose between a hamster and a quail. Numerous replications were performed to allow statistical analyses. In order to see if there were a relationship between bird species present and mosquito feeding activity on birds, we performed bird point counts at each field collection period. PARTICIPANTS: Jack B. Gingrich, Ph.D., Department of Entomology and Wildlife Ecology; Angela T. Caranci, Master of Science Candidate, Department of Entomology and Wildlife Ecology; Hyeji Kim, Independent study student, Department of Biology. Formal training and professional opportunities were afforded to both students above. Angela Caranci reported her preliminary results to a scientific conference, and is now analyzing her data. Hyeji Kim is writing a paper that will be published when the work is complete. TARGET AUDIENCES: Public health entomologists, epidemiologists, and mosquito control professionals; collaborators of the Multistate project on Mosquitoes, Diseases, and Public Health PROJECT MODIFICATIONS: Nothing significant to report during this reporting period.
Impacts
Results to date are preliminary. However, some important information was obtained that did not require quantitation: 1) The modified CDC mosquito traps performed erratically, and did not collect as many mosquitoes as a CO2-baited CDC trap; and 2) the host choice chamber provided replicable data from test to test, and is considered a good design. Two trends are emerging from initial evaluations of the host choice data: 1) Older mosquitoes (>5 days old) feed at higher rates than mosquitoes 3-5 days old; 2)Mosquitoes exposed to 14:10 daylight feed at higher rates than the other two groups. A third trend is that all three species seem to have a greater attraction to mammals than was predicted by earlier studies, and were somewhat more opportunistic than expected. This feeding behavior information will be very important in determining why it appears that transmission of WNV to humans always occurs in late summer, and for a relatively short period of a few weeks, just before the mosquito feeding season ends. All of this work is subject to further elaboration, with special emphasis on analyzing and writing up the data for publication in the coming year. The work will also be presented at professional conferences.
Publications
- No publications reported this period
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