True Flies

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.