Malaria Makes a Comeback

Resistant mosquitoes are defying DDT and infecting millions

"We are in a strategic withdrawal. The days of euphoria are over." With those words, a World Health Organization official last week gloomily characterized the current state of man's long battle against an ancient scourge: malaria. As recently as 15 years ago, health authorities were confident that they were well on the way to the total conquest of malaria. The dread disease, which afflicted as many as 300 million people at a time in the 1940s, was being swept away by the clouds of DDT spray that killed the malaria-transmitting Anopheles mosquitoes. Now, in Asia, Africa and Latin America, malaria is again on the rampage; the number of cases around the world has risen to an estimated 120 million.

The resurgence of malaria has been most dramatic in India, where the number of reported cases has soared from an alltime low of 40,000 in 1966 to 1,430,000 in 1972 and 5.8 million last year. One day last week 9,000 new cases were recorded in New Delhi alone. Sri Lanka, Pakistan and African countries south of the Sahara have also reported spectacular rises in the disease. Central America has been extremely hard hit; in Honduras, for example, malaria cases rose from 7,503 in 1974 to 30,289 in 1975 and 48,804 in 1976. El Salvador, poorest and most densely populated of the Central American republics, was stricken with a rise from 66,691 cases in 1974 to 83,290 in 1976. Nicaragua and Guatemala have also reported significant numbers of new cases.

To some extent, malaria's comeback results from overconfidence bred by the success of antimalaria drives in the 1950s and 1960s. From the southern U.S. to northern Argentina in South America, the Pan American Health Organization (a branch of WHO), UNICEF and the U.S. Agency for International Development had cooperated with national governments in financing a massive extermination operation. In hundreds of yellow-painted Jeeps and trucks equipped with tanks of insecticides, crews traveled everywhere, spraying pools of stagnant water, obvious breeding areas for mosquitoes. Helmeted personnel entered millions of houses and shacks to spray the walls, on the rationale that the oily DDT residue would knock out any disease-carrying mosquito that alighted there.* The campaign succeeded so well that malaria was reduced in many countries to a minor public-health problem. Similar success was achieved under World Health Organization auspices in Asia and parts--but by no means all--of Africa.

But then, lulled into a false sense of security and hindered by oil price hikes, many governments cut back on their eradication programs. At the same time, Anopheles mosquitoes became increasingly resistant to DDT. As the mosquitoes swarmed, malaria made its maleficent comeback.

In an effort to stem the tide of new cases, health authorities are now using more of other insecticides, such as Malathion and propoxur to kill DDT-resistant mosquitoes--but the insects are already showing signs of developing resistance to the newer chemicals. Thus the most practical response now to malaria's new challenge, says Dr. Robert Kaiser, of the Center for Disease Control in Atlanta, is a return to the pre-DDT approaches: draining mosquito-breeding areas and monitoring water supplies. In addition, several drugs can be used both to prevent and to treat human malarial infections. Says Kaiser: "We are going back to the basic malariology abandoned in the 1950s with the advent of the broad-brush chemical approach." The great hope, he says, is for an antimalarial vaccine. But that, he concedes, is at least a decade away.

* In Mexico, where the technique is still used, poor campesinos in the steamy coastal state of Oaxaca call the exterminators los matagatos (the cat killers). Reason: their cats lick the DDT residue off their paws and die of a disease of the nervous system. So rats multiply, eat more human food and leave the peasants hungrier than ever.

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