The resurrection of DDT

StoryImage( ‘/Images/Story//Auto-img-11581746572345.jpg’, ‘Photo provided’, ‘Hundreds of North Korean prisoners of war in 1951 are deloused with DDT to prevent the spread of epidemic typhus fever.’);

When the United States entered World War II in 1941, it was obvious that large numbers of troops would have to be deployed to the far corners of the globe, and a wide variety of insect-transmitted diseases would be encountered. The only insecticides available at that time were mainly of an inorganic nature (arsenic), and a few of organic origin, such as pyrethrum, rotenone, and nicotine, none of which was very effective. An exhaustive search was undertaken to find an insecticide that had a broad spectrum of kill, persisted for a considerable time, and was relatively safe to use.

In 1939, a Swiss chemist discovered that dichloro-diphenyl-trichloroethane (DDT) had the amazing ability to kill a large variety of insects when applied in small amounts, and it had a long-lasting or residual effect. The material was investigated by the U.S. Bureau of Entomology and Plant Quarantine and was found to live up to its stated capacities. It was quickly adopted by the armed forces as the primary insecticide of choice to protect our service men and women from “exotic” insect-borne diseases.

DDT was found to be especially effective against the Anopheles mosquito, which is the transmitter of human malaria. It was equally deadly for the human body louse, which transmits epidemic typhus fever. Thousands of lives were saved when an outbreak of typhus occurred in Naples, Italy, in 1944, but it was quickly curbed by the dusting of the civilian population with DDT dust.

Likewise, during the Korean War several thousand North Korean POWs were massed on the island of Koje off the southern tip of South Korea. As a rule of thumb, when 10 percent of a population is found to be infested with body lice, mass delousing is undertaken. Ninety-five percent of the prisoners on Koje were found to be lousy. Only mass delousing with 10 percent DDT dust prevented an outbreak of epidemic typhus that would have resulted in hundreds of deaths as none of the prisoners was immunized against this serious disease.

At the close of WWII, DDT became available for widespread civilian use and was touted as the “magic bullet” that would end the world’s insect problems: medical, agricultural and domestic. This prediction fell short because as early as 1947, resistance of certain insects to DDT was reported. Stronger concentrations were needed for control, and newer, more potent relatives of DDT were developed.

However, the widespread, indiscriminate broadcasting of these chlorinated hydrocarbons over the environment continued. Just one example of this was in the early 1950s. A100-square-mile area south of Fairbanks, Alaska, was treated with DDT by air in an attempt to abate pestiferous arctic mosquitoes.

When Rachel Carson published her best selling book Silent Spring in 1962, the world became aware of the inherent danger of the indiscriminate use of these insecticides, but it was not until 1972 that DDT and most of its relatives were banned for use in the United States.

Now, The World Health Organization (WHO) is advocating the use of a residual spray of DDT in parts of Africa and other undeveloped countries to combat malaria, which still kills more than 1 million people each year. The U.S. is assisting WHO by increasing its budget for residual spraying to $20,000,000 for next year. Though new therapeutic drugs and insecticide-impregnated bed nets are helping reduce the rate of infection, WHO believes the use of a residual DDT spray in households is necessary to successfully combat this killer.

Several environmentalists and some public health officials have decried WHO’s decision to use DDT to break the chain of infection while many others, including myself, believe the judicious use of DDT should be reincorporated in the fight against malaria.

The noted WHO epidemiologist, Dr. Shiva Murugasaspillay, has the following to say about the matter: “We want to prevent people from getting malaria, so the issue is prevention, and one of the best tools is residual house spraying, and the best insecticide we have is DDT.”

Though DDT has undoubtedly saved countless human lives in the past, its misuse has done considerable damage to the environment, but to insist it should not be carefully redeployed to alleviate the suffering and death brought on by malaria is nonsense.

Ask any medical expert, and they will tell you that preventive medicine is the best kind.

Dr. Robert Hedeen is a former resident of Maryland’s eastern shore and resided in the Chicago area from 1960 to 1971. He is a retired professor emeritus of biological sciences in the University of Maryland system. He has published more than 30 scientific papers, has written numerous magazine articles, and is the author of two books on the natural history of the Chesapeake Bay.

From the Sept. 13-19, 2006, issue

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