|Kline, Daniel - Dan|
Submitted to: Journal of Chemical Ecology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 1/9/2006
Publication Date: 7/26/2006
Citation: Williams, C.R., Scott, R.A., Russell, R.C., Eiras, A.E., Kline, D.L., Geier, M. 2006. Geographic Variation in Attraction to Human Odor Compounds by Aedes Aegypti Mosquitoes (Diptera: Culicidae): A Laboratory Study.. Journal of Chemical Ecology. Interpretive Summary: The yellow fever mosquito, Aedes aegypti, is the most important worldwide vector of dengue viruses, which cause human illnesses ranging from mild fever to fatal hemorrhagic disease. This study was part of an ongoing international project (a collaborative project among scientists from Australia, Brazil, Germany and the United States [USDA-ARS, CMAVE, Gainesville, FL]) to develop a standard sampling technique to capture adult Ae. aegypti, utilizing odor-baited traps, to replace currently used methods, such as human-biting catches and aspiration samples, which expose human collectors to the risk of contracting dengue. The major objective of this laboratory y-olfactometer study was to determine the response of host-seeking Ae. aegypti from four populations of distinct geographic origin (Australia, Brazil, Singapore and the United States) to host kairomones (odors). Experiments were to determine the responses of these geographically distinct populations to lactic acid, ammonia and caproic acid, alone and in combination. Results obtained from these experiments indicated there was behavioral variability among the populations to individual odors and the combinations of odors. For example, although all four populations were attracted to lactic acid, the U.S. population was the most sensitive (0.03 µg/min), followed by populations from Singapore and Brazil (0.17µg/min) and distantly by the Australian population (1.92 µg/min). These results indicate that the development of trapping lures for host-seeking Ae. aegypti may require some specialization depending upon the region of origin.
Technical Abstract: Previous investigations of Aedes aegypti response to human odor components have revealed a number of compounds that attract host-seeking females. However, such studies have utilized only a small number of long-term laboratory Ae. aegypti colonies. Using laboratory y-olfactometers, we studied the attraction of four different Ae. aegypti populations (North Queensland Australia, Florida USA, Singapore, and Minas Gerais Brazil) to a key attractant compound from human skin, lactic acid. Combinations of lactic acid with ammonia and a fatty acid (caproic acid) were also investigated. The aims were to determine the extent of variation in lactic acid dose response between populations, and to see whether all four populations responded equally to combinations of human odor components. Although all Ae. aegypti populations were attracted to lactic acid, there were differences in the threshold dose required for attraction: Florida 0.03 µg/min, Singapore and Brazil 0.17 µg/min, North Queensland 1.92 µg/min. Attraction to lactic acid alone (maximum ca. 37%, Singapore Ae. aegypti) was significantly lower than for human odor (over 87% for all populations). Brazil Ae. aegypti showed a poor attractive response to lactic acid (maximum ca. 12%). Significant increases in attraction were observed when lactic acid was combined with both ammonia and caproic acid, although not for all populations. In addition, the highest doses of caproic acid tested decreased attraction when combined with lactic acid. The divergent responses to host kairomones seen here may be evidence of adaptation to locally available hosts in different parts of the geographic range of Ae. aegypti.