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Although variation in mortality is considered by virtually all vector-borne disease specialists to be one of the most important determinants of an arthropods capacity to transmit pathogens, the operational assumption often is that insect vector mortality is independent of age. Acceptance of the non-senescence assumption leads to the erroneous conclusion that mosquito age is unimportant, results in misleading predictions regarding disease reductions after vector control, and represses study of other aspects of mosquito biology that change with age. We brought large-scale laboratory life table techniques (N > 100,000) to bear on the question of age-dependent mortality in the mosquito vector of dengue virus, Aedes aegypti. Mortality was highly age dependent in both sexes. Mortality was low at young ages (< 10 days old), steadily increased at middle ages, and decelerated at older ages. A newly derived age-dependent model of pathogen transmission shows the importance of young mosquitoes and population age structure to transmission dynamics. Departure from the age-independent mortality paradigm encourages research on overlooked complexities in mosquito biology, the need for innovative methods to study mosquito population dynamics, and the need to study age-dependent changes for an accurate understanding of mosquito biology and pathogen transmission.
Received May 31, 2006. Accepted for publication September 6, 2006.
Acknowledgments: The authors thank Miriam Khaliqi, Beverly King, Sharon Minnick, Susie Turold, and Anthony Vo for assistance on this project.
Financial support: This work was supported by grants from the University of California Mosquito Research Program to T.W.S. and National Institutes of Health (AI22119 to T.W.S. and AG022500-01 and AG08761-10 to J.R.C.).
* Address correspondence to Thomas W. Scott, Department of Entomology, One Shields Avenue, Davis, CA 95616. E-mail: twscott{at}ucdavis.edu
Authors addresses: Linda M. Styer, Arbovirus Laboratories, Wadsworth Center, New York State Department of Health, 5668 State Farm Road, Slingerlands, NY 12159, Telephone: 518-862-4306, E-mail: lstyer{at}wadsworth.org. James R. Carey, Department of Entomology, One Shields Avenue, Davis, CA 95616, Telephone: 530-752-6217, E-mail: jrcarey{at}ucdavis.edu. Jane-Ling Wang, Department of Statistics, One Shields Avenue, Davis, CA 95616, Telephone: 530-752-7624, E-mail: janelwang{at}ucdavis.edu. Thomas W. Scott, Department of Entomology, One Shields Avenue, Davis, CA 95616, Telephone: 530-754-4196, Fax: 530-752-1537, E-mail: twscott{at}ucdavis.edu.
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