Super mosquito set to invade Florida

Discovered by accident, DDT became one of the greatest public health tools of the 20th century. Overuse harmed its efficacy -- and made it politically unpopular.


Dichloro-diphenyl-trichloroethane (DDT) was first synthesized, for no purpose, in 1874 by German chemist Othmar Zeidler. In 1939, Dr. Paul Müller independently produced DDT. Müller found that DDT quickly killed flies, aphids, mosquitoes, walking sticks and Colorado potato beetles. Müller and the Geigy corporation patented DDT in Switzerland (1940), England (1942) and U.S. (1943).

The first large-scale use of DDT occurred in 1943 when 500 gallons of DDT were produced by Merck & Company and delivered to Italy to help squelch a rapidly spreading epidemic of louse-borne typhus. Later in 1943, the U.S. Army issued small tin boxes of 10 percent DDT dust to its soldiers around the world who used it to kill body lice, head lice and crab lice.

Müller won the Nobel Prize in 1948 for his work on DDT.

Peak usage occurred in 1962, when 80 million kilograms of DDT were used and 82 million kilograms produced.

"In May 1955 the Eighth World Health Assembly adopted a Global Malaria Eradication Campaign based on the widespread use of DDT against mosquitos and of antimalarial drugs to treat malaria and to eliminate the parasite in humans. As a result of the Campaign, malaria was eradicated by 1967 from all developed countries where the disease was endemic and large areas of tropical Asia and Latin America were freed from the risk of infection. The Malaria Eradication Campaign was only launched in three countries of tropical Africa since it was not considered feasible in the others. Despite these achievements, improvements in the malaria situation could not be maintained indefinitely by time-limited, highly prescriptive and centralized programmes."

[Bull World Health Organ 1998;76(1):11-6]

"To only a few chemicals does man owe as great a debt as to DDT... In little more than two decades, DDT has prevented 500 million human deaths, due to malaria, that otherwise would have been inevitable."

[National Academy of Sciences, Committee on Research in the Life Sciences of the Committee on Science and Public Policy. 1970. The Life Sciences; Recent Progress and Application to Human Affairs; The World of Biological Research; Requirements for the Future.]

It is believed that [malaria] afflicts between 300 and 500 million every year, causing up to 2.7 million deaths, mainly among children under five years.

[Africa News, January 27, 1999]

Some mosquitoes became "resistant" to DDT. "There is persuasive evidence that antimalarial operations did not produce mosquito resistance to DDT. That crime, and in a very real sense it was a crime, can be laid to the intemperate and inappropriate use of DDT by farmers, espeially cotton growers. They used the insecticide at levels that would accelerate, if not actually induce, the selection of a resistant population of mosquitoes."

[Desowitz, RS. 1992. Malaria Capers, W.W. Norton & Company]

"Resistance" may be a misleading term when discussing DDT and mosquitoes. While some mosquitoes develop biochemical/physiological mechanisms of resistance to the chemical, DDT also can provoke strong avoidance behavior in some mosquitoes so they spend less time in areas where DDT has been applied -- this still reduces mosquito-human contact. "This avoidance behavior, exhibited when malaria vectors avoid insecticides by not entering or by rapidly exiting sprayed houses, should raise serious questions about the overall value of current physiological and biochemical resistance tests. The continued efficacy of DDT in Africa, India, Brazil, and Mexico, where 69% of all reported cases of malaria occur and where vectors are physiologically resistant to DDT (excluding Brazil), serves as one indicator that repellency is very important in preventing indoor transmission of malaria."

[See, e.g., J Am Mosq Control Assoc 1998 Dec;14(4):410-20; and Am J Trop Med Hyg 1994;50(6 Suppl):21-34]

II. Advocacy against DDT

....Under threat of trade sanctions from the West, African nations have been forced to use less effective and more expensive methods to fight the malaria epidemic, such as mosquito-repellent bed nets—which, according to World Health Organization estimates, have about a 50 percent success rate. (Countries that have reintroduced DDT, such as South Africa, have found it has a 90 percent success rate.) In any event, the DDT alternatives don’t seem to be doing much good: Every year, up to 300 million Africans get malaria, and it costs the continent’s economies billions in medical expenses and lost work days.

The situation was so dire that, in 2006, the World Health Organization announced its support for indoor DDT spraying in countries ravaged by malaria, saying the chemical had “a clean bill of health” and any possible negative effects of DDT did not outweigh its benefits. The usual suspects went nuts. As the environmentalist group the Sierra Club whined, “Studies have linked widespread reproductive disorders in animals to DDT exposure—including reproductive failure in the American Bald Eagle.” This is what happens when people start rating wildlife more worthwhile than human life.

As for DDT’s effect on humans, the claim that it causes cancer has never been proven. Some studies show a link, especially in agricultural workers who were exposed to large amounts of DDT as well as other chemicals. Others, such as one conducted by Dr. David J. Hunter of the Harvard Medical School, have found none at all. One study by the National Cancer Institute found that DDT actually reduced tumors in animals.

Others, such as writer Paul Driessen, describe the fear of DDT as a “country club anxiety,” a luxury of rich Westerners who can afford organic foods and all-natural cosmetics and clothing. They will never contract malaria. Meanwhile, Africans—many of whom are lucky to afford any food at all—have made it clear that they’re willing to accept the risk of potential side effects if it means avoiding the very real threat of malaria. Two weeks ago, Uganda initiated a program to spray houses with DDT, even though it will probably hurt their trade with the U.S. and the European Union. As Ugandan businesswoman Fiona Kobusingye told reporters, “I lost my son, two sisters and two nephews to malaria. Don’t talk to me about birds. And don’t tell me a little DDT in our bodies is worse than the risk of losing more children to this disease. African mothers would be overjoyed if that were their biggest worry.”.....