Wednesday, April 16, 2008

Fly and Diseases

Some of the most serious diseases among humans is Dengue Fever, viral encephalitis, filariasis, malaria, and yellow fever, that is transmitted by mosquitoes. Many hundreds of thousands of people living along Africa's river are permanently blinded by small roundworms introduced by the bite of the black-fly.

In much of the world to day, poor sanitation, domestic flies, and intestinal diseases are constant and related problems. In Latin America, Africa and India, blowflies and houseflies are especially abundant; they shuttle between faces and human food, carrying the agents of cholera, dysentery, diarrhea disease, and gastroenteritis. Some species prefer the eye and transfer the microbes of pinkeye, conjunctivitis, and trachoma from diseased to healthy eyes; others spread yaws, a skin disease, when they feed on cuts and stores.

Some adult flies are harmless but deposit their eggs in wounds or body openings of livestock and humans. The larval flies, or maggots, consume living tissue, and the wound enlarges as more females are attracted to the site for oviposition. Such maggot infestations are called myiasis. Agricultural crops, such as wheat and onions, are also attacked.

Beneficial Roles

Beneficial activities of flies include pollination, the reduction and recycling of plant and animals wastes, and the unique contributions of the fruit fly, Drosophila, to genetics and our understanding of heredity. In 1930s, before the advent of antibiotics and sulfa drugs, doctors cured stubborn cases of osteomyelitis with sterile blowfly maggots. The maggots ate only the dead and decaying tissue, cleaning out the wound, suppressing harmful bacteria with their secretions, and encouraging growth of healthy tissue.

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