The reality is that the American ban on DDT did not extend to other nations, although some later enacted their own prohibitions. For that matter, the pesticide was not completely banished in the United States or elsewhere; the E.P.A. declared it acceptable if public health was at risk. And despite a decline in its effectiveness because of overuse, it remains a valued anti-malaria tool in many countries, principally for spraying indoors, where its potency is enhanced and its impact on nature is kept low.
Then, too, the notion that Carson advocated a ban on pest-killing chemicals is a fiction. It was not her contention, she said, that “chemical insecticides must never be used.”
“No responsible person contends that insect-borne disease should be ignored,” she wrote in “Silent Spring.” The trouble, in her view, was that DDT and other chemicals were employed so liberally that “the insect enemy” developed resistance to them in fairly short order and was thus “made actually stronger by our efforts.”
In their adaptability, mosquitoes can be quite clever creatures, Raymond John St. Leger, an entomologist at the University of Maryland, told Retro Report. “Some mosquito populations can actually recognize the silhouette of a door, and go for people when they come in and out of doorways,” he said. “That’s how sophisticated evolution can be in changing behavior.”
Insect resistance to DDT, many scientists say, was a major reason for a sharp decline in its use around the world: Why bother spraying if the bugs would just shrug it off? Experts also blamed reduced spending on anti-malaria projects by governments and international organizations — not Carson — for a resurgence of the disease after 1972.
But the tide may have turned. Mortality rates have dropped by about 50 percent over the last decade and a half, according to the World Health Organization. Where malaria once killed several million people a year, the organization’s estimated toll for 2015 was 429,000, the principal victims being children under 5 in sub-Saharan Africa.
Notwithstanding such gains, the battle is far from over. W.H.O. says that 3.2 billion people in 97 countries, nearly half of the world’s population, remain at risk. In Burkina Faso, a focus of the Retro Report video, roughly 40 percent of the people get malaria each year.
To keep the disease on the run, experts say new methods are needed. Some that are under study now go beyond blitzing insects with chemicals. Scientists have experimented with ways to manipulate the mosquito’s genome to make it resistant to malaria and perhaps other diseases as well, like dengue fever, yellow fever and the latest global scourge, the Zika virus. There have been successes in the laboratory. But spreading the desired traits among wild insect populations has thus far proved elusive (not to mention that concerns about genetic modification’s unintended consequences are ever lurking).
Dr. St. Leger has experimented with fungi that, when absorbed by a mosquito, will inject deadly spider venom directly into its blood. Still, he cautioned that a combination of approaches was necessary.
“The solution,” he said, “isn’t going to be relying on any single technology as the silver bullet.”
For now, the weapons of choice remain what they have been for a while: diligently covering beds with nets infused with pyrethroids, synthetic versions of organic pesticides; judiciously coating the interiors of houses with DDT and other chemicals; and carefully mopping up pools of stagnant water where mosquitoes breed. That last one requires arduous and often fruitless labor. But it is a challenge that ought to be familiar to the Trump administration. To borrow a phrase it has popularized, it means draining the swamp.
CLYDE HABERMAN, a regular contributor to Retro Report, has been a reporter, columnist and editorial writer for The New York Times, where he spent nearly 13 years based in Tokyo, Rome and Jerusalem. Subscribe to our newsletter here and follow us on Twitter @RetroReport.
This article first appeared in The New York Times.