Control

Dengue control is dependent on control of Ae. aegypti because there is no licensed vaccine for dengue, which will need to be tetravalent because of the phenomena of immune enhancement, and no clinical cure has been found. Despite a history of detailed study of Ae. aegypti, vector control programs for dengue control are often nonexistent or ineffective. Outdoor applications of aerosol insecticides to kill adults have in most instances not been effective because the majority of females rest indoors where they avoid contact with the insecticide. Over any considerable period of time, control of immatures using chemicals, biological control, or community-based source reduction has been effective only in authoritative systems in which negative consequences are associated with noncompliance. Disease control based on genetic manipulation of mosquito vectors, rendering them incapable of transmitting virus, is currently being investigated but this method will require extensive evaluation before it can be deployed. Of great concern is the observation that explosive dengue epidemics occur even when Ae. aegypti population densities are low. This apparent paradox illustrates that aspects of Ae. aegypti biology other than population density, such as their blood-feeding behavior, duration of extrinsic incubation, and female survival, play an important role in defining virus transmission dynamics. Control of dengue constitutes a formidable challenge for public health officials.

See Also the Following Articles

Medical Entomology • Mosquitoes • Zoonoses

Further Reading

Gubler, D. J., and Kuno, G. (1997). "Dengue and Dengue Hemorrhagic Fever," p. 462. CAB Int., Wallingford, U.K.

Halstead, S. B., Rojanasuphot, S., and Sangkawibha, N. (1983). Original antigenic sin in dengue. Am. J. Trop. Med. Hyg. 32, 154-156.

Harrington, L. C., Edman, J. D., and Scott, T. W. (2001). Why do female Aedes aegypti (Diptera: Culicidae) feed preferentially and frequently on human blood? J. Med. Entomol. 38, 411-422.

Kuno, G. (1995). Review of the factors modulating dengue transmission. Epidemiol. Rev. 17, 321-335.

Monath, T. P. (1994). Dengue: The risk to developed and developing countries. Proc. Natl. Acad. Sci. USA. 91, 2395-2400.

Rigau-Perez, J., Clark, G. G., Gubler, D. J., Reiter, P., Sanders, E. J., and Vordam, A. V., (1998). Dengue and dengue haemorrhagic fever. Lancet 352,971-977.

Scott, T. W., Amerasinghe, P. H., Morrison, A. C., Lorenz, L. H., Clark, G. G., Strickman, D., Kittayapong, P., and Edman, J. D., (2000). Longitudinal studies of Aedes aegypti (L.) (Diperta: Culicidae) in Thailand and Puerto Rico: Blood feeding frequency. J. Med Entomol. 37, 89-101.

Watts, D. M., Porter, K. R., Putvatana, P., Vasquez, B., Calampa, C., Hayes, C. G., and Halstead, S. B. (1999). Failure of secondary infection with American genotype dengue 2 to cause dengue haemorrhagic fever. Lancet 354, 1431-1434.

FIGURE 1 European earwig (Forficula auricularia): (A) adult male and (B) his right hind wing. [Reprinted with the permission of Scribner, a Division of Simon & Schuster, from "College Entomology" by E. O. Essig (Macmillan, New York, 1942).]

male genitalia. Earwigs are not of medical importance; they do not crawl in people's ears (occasional anecdotal accounts notwithstanding), and they do not bite, although some may pinch with their forcepslike cerci. Some earwigs may be pests of gardens or households; alternatively, some species are important biocontrol agents, feeding on agricultural pests, such as aphids, armyworms, mites, and scale insects.

0 0

Post a comment