The arrival of the West Nile virus in Dallas has proceeded with all the panicked fanfare that typically comes with public health scares: News reports announce the "deadly" virus' arrival; residents begin to worry, and city officials respond, in this case, by spraying neighborhoods with pesticides in an attempt to wipe out the mosquitoes that carry the disease.
"It's a gigantic overreaction," says Dallas radio personality Howard Garrett, an organic horticulturist and co-author of the Texas Bug Book, a gardener's guide to using "beneficial insects" to control plant-eating pests.
Garrett is a member of a small but growing number of critics who argue that the blanket spraying of toxic pesticides is an ineffective and outdated practice, particularly in reaction to the West Nile virus, a disease that presents a small public health threat. The policy, they argue, amounts to little more than a public relations effort, which helps ease public fears but may wind up doing more harm than good.
City officials argue that the nighttime spraying, which began in July and will continue for the foreseeable future, is needed because the presence of the virus within city limits has been confirmed.
"If there is evidence of disease-bearing mosquitoes in an area, then it is not irresponsible to try and kill those mosquitoes," says Mary Vaughn, the director of the city's environment and health services department. She says the spraying is effective at carrying out its primary objective: "It does what it does. It kills adult mosquitoes."
At the same time, however, Vaughn concedes that the city has no idea how effective the chemicals are. Her employees don't know whether the neighborhoods they are spraying are the breeding grounds of virus-toting mosquitoes, and they have no way of tracking what effect, if any, the chemicals are having in reducing the mosquito population.
So why is the city spraying? Moreover, what chemical is the city using and what effect does it have on the environment? Those are questions pesticide critics like Garrett say the city needs to answer, and the sooner the better. Although current fears about the West Nile virus will subside as the summer passes, the health threats posed by it and other mosquito-borne diseases, including St. Louis encephalitis, will only grow as these once-foreign diseases become a permanent part of the local ecology.
In lieu of spraying, critics say, the city should revamp its overall mosquito-control program by expanding the use of prevention programs, including wide-scale public education efforts that are considered to be more effective at keeping the mosquito population down. Vaughn, for one, agrees that spraying is not a long-term solution to the problem, but with more than 200 Dallas residents calling her office a day, she doesn't have the time or the money to make any drastic changes.
"We're really doing the best we can just to answer the phone," Vaughn says.
By now, most Dallas residents should know that their chances of being sickened by the West Nile virus are extremely remote. In areas where the disease is present, less than 1 percent of the mosquitoes living there carry the disease. When those mosquitoes bite people, less than 1 percent of those bites will transmit the disease. What's more, most people who contract the disease never experience any symptoms.
There are about 3,000 species of mosquitoes, but it is the culex mosquito that is causing all the current trouble. The culex, also known as the Southern house mosquito, is only active at night, and it can only breed in standing pools of water--bird baths, wading pools, gutters, water-filled glasses and even dripping outdoor faucets are a few examples.
That means the most effective and inexpensive way to combat the bug is to get rid of the water, a simple task residents can carry out in their own yards. All this takes is a little public education. The problem is, the city does not have a public education program to speak of, Vaughn says. Instead, it waits for an outbreak to become news and then relies on the news media to pass the information on to the public.
The city does have some prevention programs. It regularly traps mosquitoes at various locations throughout the city and has them tested for disease. If disease is found, the city will go to those areas, locate any breeding grounds that can't be eliminated and use larvicides to kill the mosquito eggs before they hatch. (Although the West Nile virus is new to Dallas this summer, the area has for years been home to more troublesome mosquito-borne diseases, including St. Louis encephalitis.)
Primarily, though, Vaughn says, the city won't take any action unless it receives complaints--either about large numbers of mosquitoes in a neighborhood or, as is the case now, reports of dead crows or blue jays, two birds that commonly carry the West Nile virus.
Although Vaughn denies that the city's spraying program is a reaction to the current scare, the city only began spraying neighborhoods in July, after the presence of the West Nile virus in the city was officially confirmed. Since then, the city has carried out a policy of spraying neighborhoods in which the dead birds are found.
Critics say that policy is misguided for one simple reason: The dead birds may not have contracted the disease in the area where they died. The culex mosquito is a pest that stays close to home. At most, if the wind is strong, they can travel two miles away from their breeding grounds. Birds, however, can be miles away from the infected breeding grounds before the virus kills them.
Dallas, like many other cities, is now spraying an insecticide called "Scourge," a neurotoxin that kills adult mosquitoes only when it comes in direct contact with them. The product can cause minor health problems in people, namely allergic-like reactions. (Ironically, the people most likely to have those reactions are the same people who are most susceptible to the West Nile virus, the elderly and those with weakened immune systems.)
Although Vaughn says the product is safe, the city is advising people to keep themselves and their pets indoors during the spraying, which is conducted between the hours of 2 a.m. and 7 a.m. But there are additional safety tips parents especially should know about the product, says Jessica Lunsford, a spokesman for Beyond Pesticides, a Washington-based organization that acts as a watchdog on pesticide issues.
Although Scourge breaks down after a few hours of exposure to the sun, Lunsford says the chemical may still be present in the early morning hours after it has been applied. That means parents are wise not to allow their children to play in the yard at that time or with toys that have been left out overnight.
But the real problem with the chemicals, Lunsford says, is they kill beneficial insects, such as insect-eating spiders and pollinating bees.
"You're killing the predators that would be feeding on the mosquitoes," Lunsford says. "So in the long run, you may be giving the mosquitoes the heads up."
Texas entomologist Roy Burton, the state's bug expert, says the debate over the use of chemical sprays is growing as the mosquito-borne diseases are spreading. This summer, Burton has been swamped by calls from city officials seeking advice about how they should combat mosquitoes.
Burton agrees that the use of sprays or adulticides isn't effective unless it targets the source of disease. And while the sprays are toxins that people should avoid, Burton says government agencies are obligated to take steps to protect the public health, including the use of chemicals. Ultimately, however, the process of devising a comprehensive mosquito-control strategy must be debated locally.
"It gets political real quick," Burton says. "Here in Central Texas there's a group that does not want any chemicals sprayed. Then you have people who want to be sprayed. How do you walk that fine line? It's a difficult choice. You're never going to make everyone happy."
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