malaria: Treatment and Control
The bark of the cinchona and its product, quinine, have been used in the treatment of malaria for centuries. After World War II, they were largely replaced by the synthetic analog chloroquine. The use of chloroquine, in addition to the use of DDT for mosquito control, was expected to eradicate the disease, but a World Health Organization campaign (1955–69) to eradicate the disease globally (by controlling mosquitoes long enough to allow the human population to become disease free) proved unsuccessful. Despite that, spraying successfully eradicated the disease in some areas (Sardinia, Japan, and Taiwan). In the United States, the disease, which had been endemic in many SE states, was eradicated in 1951.
In the 1960s several strains of the malarial parasite developed resistance to chloroquine. This, plus the growing immunity of mosquitoes to insecticides, caused malaria to become one the of world's leading re-emerging infectious diseases, infecting some 225 million people a year and killing more than 650,000 in 2010. Those numbers may be significant underestimates. By 2010, however, the number of infections was again falling due to improved malaria control in Africa.
Mefloquine may be used in areas where the disease has become highly resistant to chloroquine, but some strains are now resistant to it and other drugs. Artemisinin (derived from sweet wormwood) or a derivative such as artesunate or dihydroartemisinin in combination with other drugs is now in many cases the first-line treatment in many cases, but resistance to artemisinins also has developed, in parts of SE Asia and sub-Saharan Africa. Dihydroartemisinin in combination with piperaquine is now a common treatment, but resistance to that combination has developed in parts of SE Asia. Amodiaquine in combination with sulfadoxine and pyrimethamine has also been shown to be effective, and malarone (atovaquone and proguanil) also is used for resistant strains. The use of combinations of drugs with different modes of actions increases the effectiveness of treatment and helps reduce the development of drug resistance.
Vaccines against malaria remain experimental. Spraying is still used to control malaria-transmitting mosquitoes, and more recently the use of mosquito nets treated with a long-lasting insecticide has become widespread. Fish that feed on mosquito larvae also have been employed to control mosquitoes.
The Columbia Electronic Encyclopedia, 6th ed. Copyright © 2012, Columbia University Press. All rights reserved.
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