TCS Daily


How Many Must Die?

By Henry I. Miller - August 14, 2003 12:00 AM

The four-year old U.S. outbreak of West Nile virus is a significant threat to public health. With the peak season just beginning, the mosquito-borne virus has been found in animal hosts (primarily birds and horses) in 40 states, and has caused 367 serious infections and nine deaths in humans in 20 states.


Last year, there were more than four thousand cases and almost 300 deaths. We may be on the verge of a major epidemic, but there is no treatment and a vaccine is at least a decade away.

Federal public health officials have recognized the seriousness of the problem, but their response has been tepid and politically correct. The web-site of the Centers for Disease Control suggests: "avoid mosquito bites," by wearing clothes that expose little skin, using insect repellent, and staying indoors during peak mosquito hours (dusk to dawn); "mosquito-proof your home," by removing standing water, and installing and maintaining screens; and "help your community," by reporting dead birds and checking to see whether there are local mosquito-control programs.

Conspicuously absent from its list of suggestions -- and also from CDC Director Julie Gerberding's remarks at public appearances -- is any mention of insecticides or widespread spraying. Anyone curious about the role of pesticides in battling mosquitoes and West Nile is directed to a maze of other Web sites.

Perhaps the Atlanta-based CDC officials don't get out much. Residents of areas such as coastal Maine, Texas, Florida and the Carolinas, the cotton-growing regions of the Deep South, the lake country of the Northern Midwest, and the marshlands of the Delaware Valley and Chesapeake Bay could tell the bureaucrats that they're on the wrong track: Emptying birdbaths and the saucers under flower pots is not going to get rid of a zillion hungry mosquitoes.

In the absence of a vaccine (the development of which has public policy problems of its own), elimination of the vehicle that spreads the disease -- in this case, the mosquito -- ought to be the key to preventing epidemics, but fundamental shortcomings in public policy limit the weapons that are available.

In 1972, on the basis of data on toxicity to fish and migrating birds (but not to humans), the Environmental Protection Agency banned virtually all uses of the pesticide DDT, an inexpensive and effective pesticide once widely deployed to kill disease-carrying insects. Allowing green politics to trump science, regulators also cited the possibility that DDT posed a cancer risk for humans an assertion based on studies showing an increased incidence of the illness in mice that were fed extremely high doses of the pesticide. (The validity of extrapolating these high-dose animal studies to minuscule exposures in humans was and remains in doubt.)

Not only did government regulators minimize scientific evidence of the effectiveness and relative safety of DDT, they also failed to appreciate the distinction between its large-scale use in agriculture and more limited application for controlling carriers of human disease. Although DDT is a (modestly) toxic substance, there is a big difference between applying large amounts of it in the environment -- as American farmers did before it was banned -- and applying it carefully and sparingly to fight mosquitoes and other disease-carrying insects. A basic principle of toxicology is that the dose makes the poison.

The regulators who banned DDT also failed to take into consideration the inadequacy of alternatives. Because it persists after spraying, DDT works far better than many pesticides now in use, some of which are toxic to fish and other aquatic organisms. Also, the need to spray other insecticides repeatedly -- especially in marshlands and forests, where mosquito-breeding areas are large -- drives up costs and depletes public coffers. Budgetary limitations compelled Maryland this summer to turn down requests for spraying from communities that were badly infested with mosquitoes. And Caddo Parish, Louisiana, which currently spends more than $360,000 a year on mosquito control (yet has the most human cases of West Nile virus infections in the state), uses much of its mosquito-control budget for spraying with pyrethroid pesticides, but these products can't keep up; they are inactivated within an hour or two.

Even without DDT, currently approved pesticides controlled mosquitoes moderately well last year in much of the eastern and southern United States, in spite of near-hysterical resistance to spraying by environmental activists, who have attacked the killing of mosquitoes as "disrupting the food chain." And New York's Green Party literature declared, "These diseases only kill the old and people whose health is already poor." These activists seem to regard epidemics of infectious diseases as a valid method of human population control. (Interestingly, Illinois led the nation in both West Nile infections and deaths in 2002 because government officials, bullied by radical environmentalists, rejected the widespread spraying of insecticides.)

Since the banning of DDT, insect-borne diseases such as malaria and dengue -- and now West Nile virus -- have been on the rise. (Had they been declining, activists would probably have demanded that we protect the infectious agents as endangered species.) The World Health Organization estimates that malaria kills about a million people annually, and that there are between 300 million and 500 million new cases each year.

There are some recent success stories to be found, however; countries that have continued to use DDT have lower death rates and lower economic losses than those that have instituted bans. For example, India reduced the number of cases of malaria from approximately 75 million in 1951 to around 50,000 in 1961; the incidence remains low today because India continues to use DDT. And during the six years following Ecuador's 1993 decision to increase DDT use, there was a 60 per cent decrease in malaria cases. By contrast, the number of new cases rose 90 per cent during the same period in Bolivia, Paraguay, and Peru, all of which stopped spraying DDT altogether in 1993.

How can we drain the public policy swamp? First, the government should undertake a re-evaluation of the voluminous data on DDT that has been compiled since the 1970's. It should also make DDT available for mosquito control in the United States.

Second, the United States should oppose international strictures on DDT. This includes retracting American support for the heinous United Nations Persistent Organic Pollutants Convention, which severely stigmatizes DDT and makes it exceedingly difficult for developing countries -- many of which are plagued by malaria -- to use the chemical.

Finally, federal officials should embark on a campaign to educate local authorities and citizens about the safety and potential importance of DDT. Right now, most of what people hear is the reflexively anti-pesticide drumbeat of the environmental movement. In order to accomplish this, however, a senior public health official will need to come forth and champion the issue. CDC Director Gerberding's unwillingness even to mention the p-word -- pesticide -- makes her a non-starter. The U.S. Surgeon General, Richard Carmona, seems a likely candidate -- or at least he would be if he weren't completely invisible.

Because DDT gets such a bad rap, it will be politically difficult to resurrect its use. But we should begin the process now. In the meantime, we'll just slather on the insect repellent, slap, scratch -- and occasionally become infected with a life-threatening but preventable disease.

Henry I. Miller, a physician, is a fellow at the Hoover Institution. He was an official at the NIH and FDA from 1977-1994. E-mail: miller@hoover.stanford.edu.

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