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malaria
(mә-lar´e-ә)
a serious infectious disease seen in many warm regions of the world, caused by a protozoal infection; it is one of the world's leading causes of death, although the majority of patients recover. Malaria is caused
by the protozoal parasite Plasmodium, which is carried by mosquitoes of the genus Anopheles. When the mosquito bites an infected person, it sucks in the parasites residing in the person's blood, to be transmitted
to the bloodstream of the next person the mosquito bites. Inside the human host they first enter liver cells and later are released to enter
the bloodstream, where they penetrate the erythrocytes. There they mature, reproduce, and finally burst out of the blood cell. There are usually no symptoms until several cycles
have been completed. Then there is a simultaneous rupturing of erythrocytes by the entire brood, causing the characteristic chills and a fever that can go up to 40° to 40.5°C (104° to 105°F). As it
subsides, there is profuse sweating. Other symptoms are headache, nausea, body pains and, after the attack, exhaustion. The symptoms last from 4 to 6 hours and
recur at regular intervals, depending upon the parasitic species and its cycle. If the attack occurs every other day, the
disease is called tertian malaria, and if it occurs at 3 day intervals it is called quartan malaria. Bouts of malaria may last from 1 to 4 weeks; relapses are common, with attacks stopping and recurring at intervals for several
years. Malaria is not usually fatal; when it is, it is almost always caused by Plasmodium falciparum. Called also paludism. adj., malar´ial., adj.
Copyright 2007. An Elsevier publication. All rights reserved.
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