But the threat alone was enough to force Disney World to close its swimming pools and provoke statewide pesticide overkill, drenching the state in malathion. And encephalitis may not be the greatest threat. Worldwide, malaria, once thought under control, is on a deadly rebound. If we're not careful, this disease, that caused more casualties than gunfire during the Civil War, may re-emerge as a major hazard in America. Second, malarial protozoa and insects that carry it have become resistant to the drugs and pesticides used to control.
Malaria is spread by the bite of Anopheles mosquitoes.
Early in this century, the only effective control was to eliminate stagnant water, where these creatures reproduced, such as swamps and landfills. Then in 1939, the organochlorine pesticide DDT was discovered. This compound proved a godsend in the Third World, curtailing the disease dramatically. Soon, this organochloride was replaced by less persistent organophosphates, such as parathion and malathion. This was ironic.