The six-year-old U.S. outbreak of West Nile virus is a significant threat to public health and shows no signs of abating. Last year, there were more than 2,500 serious cases and 100 deaths. Though still early in the West Nile virus season (there is a time lag during which animals are infected, mosquitoes convey the virus to humans, and the virus incubates until symptoms occur), this year the mosquito-borne virus has been found in animal hosts (primarily birds) in 39 states, and has caused more than a hundred serious infections and three human deaths in 18 states.
Typical of local developments around the country, the desire to prevent West Nile virus induced property owners in two California counties on August 2 to approve fees to fund the fight against the mosquitoes that spread the disease. In Santa Clara County, property owners voted to raise yearly assessments more than 160 percent. However, thanks to politically correct but preposterous decisions by federal regulators, the tools available to local officials are limited — and largely ineffective.
The website of the Centers for Disease Control suggests several measures to escape West Nile virus infection: "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.
Conspicuously absent from its list of suggestions 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 websites.
Perhaps the Atlanta-based CDC officials don't get out much. You don't have to be a rocket entomologist to know that 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 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. (How ironic that regulators banned DDT largely for its toxicity to birds, for now it's unavailable to combat a mosquito-borne disease that killing birds by the hundreds of thousands!)
Allowing green politics to trump science, regulators also cited the possibility that DDT posed a cancer risk for humans, an assertion based on studies 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 underplay 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 mosquitoes tend to breed — drives up costs and depletes public coffers. Pyrethroid pesticides, the most common alternative to DDT, are inactivated within an hour or two.
The spraying of any pesticides — let alone DDT — has been greeted by near-hysterical resistance from environmental activists, who have attacked the killing of mosquitoes as "disrupting the food chain." New York's Green-party literature declares that "These diseases only kill the old and people whose health is already poor."
Since the banning of DDT, insect-borne diseases such as malaria and dengue — and now West Nile virus — have been on the rise. 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.
How can we drain the public-policy swamp? First, the government should undertake a reevaluation of the voluminous data on DDT that has been compiled since the 1970s, and regulators should make DDT available immediately 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, senior public-health officials will need to come forth and champion the issue.
Because DDT has 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 and occasionally become infected with a life-threatening but preventable disease.