Medicine: The War on Anopheles

"We now have it within our power to eradicate from the face of the earth that age-old scourge of mankind: malaria." So said President Eisenhower last week in his State of the Union speech (see NATIONAL AFFAIRS). By latest estimates, two-fifths of the world's 2.6 billion people are subject to the disease; each year 200 million suffer from malaria, and 2,000,000 to 2,500,000 die of it. In the 60 years since the discovery that the disease is transmitted by mosquitoes of the genus Anopheles, men of medicine have had periodic fevers of hope about wiping out malaria—with the old drug quinine, with new drugs such as quinacrine, or with mosquito-killing DDT. But malaria proved to be an unexpectedly formidable foe.

The tiny, disease-causing parasite, conveyed from mosquito to men and back again, has such an incredibly complicated life cycle that no one drug can kill its various forms, lodged in hideouts in different parts of the body. Area spraying (from Airplanes or trucks) is expensive, inefficient and may be self-defeating: some of the Anopheles develop resistance to DDT, thereafter thrive in its presence.

The Pause That Destroys. Fortunately, the female Anopheles (only the female sucks blood, transmits malaria) is a shy creature of habit. Except in a few areas, she does no hunting outdoors, seeks her victims in their homes. She slips unobtrusively into a hut, rests a while on a wall, buzzes down to gorge herself on a drop of blood (often, in the process, infecting her victim with the parasites in her saliva), then rests on a wall before heading out. In a dwelling whose walls have been sprayed with DDT, these pauses are her undoing. As long as six months after a spraying, there is enough DDT left to kill her soon after contact.

It is on this detail of mosquito behavior that the World Health Organization and other international bodies, plus 60 governments, are now basing a $500 million blitz campaign to wipe malaria off the world's disease map within ten years.

From House to House. The shift in goals—from mere "malaria control" to complete and quick eradication—was dictated partly by the success of early campaigns in Sardinia, Italy, Greece and Chile, partly by the danger that unless the attack is promptly pushed, the DDT-resistant strains of Anopheles may get out of hand. Abandoning area spraying, the malaria fighters are tackling the huge job of spraying every dwelling in malarial regions. Walls are saturated with DDT as fast as possible; scheduled are at least three more annual sprayings. This way, doctors believe, the cycle of mosquito-man-mosquito renewal can be broken.

The Anopheles should be prevented from starting any new infections, and old ones will eventually burn out because the parasites lose their reproductive powers after two or three years. In areas where the mosquitoes are resistant to DDT, another insecticide, dieldrin, will be used. Where the mosquitoes bite in the open, preventive drugs will be used in addition to spraying. Example: the entire table-salt supply for the Amazon Valley is now being laced with chloroquine to build up the inhabitants' resistance.