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True Flies

Flies As A Health Hazard

Some of the biting and blood-sucking flies are the vectors of important diseases of humans, domestic animals, and wild animals. The microorganisms that cause malaria, yellow fever, encephalitis, filariasis, dengue fever, sleeping sickness, typhoid fever, dysentery, and some other important diseases are all spread to humans by species of Diptera.

Malaria is one of the best-known cases of a disease that is spread by biting flies. Malaria is caused by the protozoan Plasmodium falciparum, and is spread to humans by a mosquito vector, especially species of Anopheles, which infect people when they bite them to obtain a blood meal. Malaria is an important disease in the tropics and subtropics. During the 1950s, about 5% of the world's population was infected with malaria, and during the early 1960s two to five million children died of malaria each year in Africa alone. The incidence of malaria has been greatly reduced by the use of insecticides to decrease the abundance of the Anopheles vectors, and by the use of prophylactic drugs that help to prevent infections in people exposed to the Plasmodium parasite. However, some of the pesticide-based control programs are becoming less effective, because many populations of Anopheles mosquitoes have developed a tolerance of the toxic effects of some insecticides.

The house fly (Musca domestica) is a non-biting fly, but it can carry some pathogens on its feet and body, and when it walks over food intended for consumption by humans, contamination can result. The house fly is known to be a contact vector of some deadly diseases, including typhoid fever, dysentery, yaws, anthrax, and conjunctivitis. House flies can be controlled using insecticides, although some populations of this insect have developed resistance to insecticides, rendering these chemicals increasing less effective as agents of control.


Resources

Books

Arnett, Ross H. American Insects. New York: CRC Publishing, 2000.

Borror, D.J., C.J. Triplehorn, and N. Johnson. An Introduction to the Study of Insects. New York: Saunders, 1989.

Carde, Ring, and Vincent H. Resh, eds. Encyclopedia of Insects. San Diego: Academic Press, 2003.

Lehane, M. Biology of Blood-sucking Insects. London: Unwin-Hyman, 1991.

Metcalf, R.L., and R.A. Metcalf. Destructive and Useful Insects. New York: McGraw-Hill, 1992.


Bill Freedman

KEY TERMS

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Complete metamorphosis

—This is an insect life history characterized by four stages: egg, larva, pupa, and adult.

Parasite

—An animal that derives its livelihood by feeding on another, usually much larger animal, but generally without causing the death of the host. For example, many bloodsucking species of flies are parasites of mammals or birds.

Vector

—Any agent, living or otherwise, that carries and transmits parasites and diseases.

Additional topics

Science EncyclopediaScience & Philosophy: Toxicology - Toxicology In Practice to TwinsTrue Flies - Biology Of True Flies, Common Families Of Terrestrial Flies In North America, Common Families Of Aquatic Flies In North America