Beyond the Bite

How to Fight the West Nile Virus

Susan Sheldon’s husband thrashed wildly about the kitchen trying to kill the one mosquito that, he believed, bit him four times. "You have to keep the door closed," he growled as he finally managed to swat the insect in mid-air. Sheldon, who was worried about the West Nile virus, argued that her husband should have put up the screens.

The truth is that it’s very unlikely that this particular mosquito was infected. According to the Centers for Disease Control and Prevention (CDC), even in areas where mosquitoes do carry West Nile virus, only about one in 500 are carriers. If Sheldon’s husband were actually infected, he probably would not even know it. Most people who do contract the disease experience very mild symptoms—or none at all.

Over the five- to 15-day incubation period, Sheldon would watch for high fever, disorientation, muscle weakness, headache or nausea. Only about one infected person in 150 becomes seriously ill with a central nervous system infection such as encephalitis (inflammation of the brain) or meningitis (inflammation of the membrane surrounding the brain). If a serious West Nile-related infection does occur, it is fatal in only eight percent of cases, mostly among seniors.

Unfortunately, for 4,156 people nationwide in 2002, West Nile was a serious proposition, and for 284 it was a killer. In 2003, West Nile spread far and wide. By September, 1,764 Americans had contracted West Nile, and 31 died.

West Nile virus has taken an even greater toll on a variety of animals. In 2002, the CDC reported more than 9,000 cases of West Nile virus-related illness among horses and more than 14,000 deaths among crows, blue jays and 92 other bird species. While scientists do not know the actual number of bird deaths, they are learning other things from the studies launched in response. In New York, where 80,000 dead birds were collected, it was found that more died from exposure to common lawn pesticides such as Diaznon and Dursban than from West Nile virus, according to the National Audubon Society.

Reducing Your Risk

Even though most people won’t get sick from West Nile virus, we owe it to our families, neighbors, pets and wildlife to reduce the incidence of this mosquito-borne disease. It’s not too early to begin thinking about next year’s mosquito season.

One of the most effective, cheapest and environmentally benign ways to reduce the chance of infection is to eliminate mosquito-breeding grounds around your home. The West Nile virus has been found in 36 different varieties of mosquito, but the CDC still considers the Culex variety to be its primary vector. The Culex mosquito lays its eggs in murky, standing water such as in puddles, birdbaths and discarded tires.

Leaving standing water around your home may mean a new batch of adult mosquitoes emerging daily. Empty accumulated water from tire swings and outdoor toys. Drill holes in the bottom of outdoor recycling containers. Clean clogged roof gutters regularly. Turn over plastic children’s pools and wheelbarrows, and change water in birdbaths every seven days. Keep swimming pools chlorinated (or use a natural alternative), and aerate ornamental pools or stock them with larva-eating fish that are indigenous to your area. If you notice standing water on another person’s property, you may report it to your local health department, which can order it removed.

Try treating very wet areas with the biological larvicide Bacillus thuringiensis israelensis, or BTI, available in many hardware stores. According to the National Coalition Against the Misuse of Pesticides, BTI is proven to be effective and has low levels of toxicity.

If you own an ultraviolet bug zapper, you might as well throw it out. Research shows that bug zappers kill plenty of insects, such as June bugs and moths, but not many mosquitoes. The $295 Mosquito Magnet Defender or $495 Mosquito Magnet Liberty by American Biophysics are more effective, although Consumer Reports tests showed them to have only moderate success against Culex mosquitoes.

You may also want additional protection for hiking, camping or other outdoor activities. To fight the bite, wear protective clothes. Apply a natural soybean oil-based repellent such as Bite Blocker. According to an independent study, Bite Blocker provides one to four hours of protection, as much as products with a 4.75 percent concentration of N,N-diethyl-m-toluamide, commonly known as DEET. Natrapel, a citronella-based product, and Avon Skin-So-Soft provided little to no protection in the same study.

The CDC claims DEET is the most effective and best-studied insect repellent available and is safe when used as directed. However, DEET has been found to cause allergic responses, seizures, dermatitis, confusion, irritability and insomnia among a small number of frequent users. "I live in a swamp. I have more mosquitoes per acre than anyone in Louisiana and I will not use DEET," says Bill Cooke, coordinator of the National Audubon Society Pesticide Project. David Pimentel, professor of entomology at Cornell University, agrees. "In most cases, the risk of using DEET is greater than the risk of disease," he says.

Recent research at Iowa State University suggests that catnip may be about 10 times more effective at repelling mosquitoes than DEET. Other all-natural repellants can be purchased from such companies as Aubrey, Kiss My Face, Burt’s Bees and All Terrain. Many of these herbal concoctions are also purported to rival DEET in repelling power.

Chemical Control

In an attempt to control mosquito populations and disease outbreaks, many communities will resort to chemical sprays. The most commonly used are methoprene (a chemical hormone), malathion (an organophosphate) and synthetic pyrethroids. Besides being costly, there are many downsides to these chemicals. Overuse can lead to resistance in mosquitoes, ultimately leading to the need for more pesticides. These chemicals can kill wildlife, birds and beneficial insects such as bees, butterflies and dragonflies, which prey on mosquitoes.

According to the Journal of Pesticide Reform, malathion has been implicated in vision loss, and can cause headaches, sore throats, respiratory problems, dizziness and behavioral disorders. A 2000 federal review of malathion found "suggestive evidence" that high doses may cause cancer in laboratory animals.

Unfortunately, officials may feel obligated to respond to a West Nile outbreak with an arsenal of pesticides. Despite such pressures, Fort Worth, Texas has issued a mandate not to spray under any circumstances. Brian Rogers of the Fort Worth Health Authority says spraying for mosquitoes would harm more people than it would help. "I’ve never seen it work," he says. "Spraying is always followed by more human cases."

Even if West Nile has not yet reached your community, it may not be long before it does. Call your local health department and suggest that they establish a pest management advisory board comprised of residents, entomologists and pesticide experts to develop a plan that mitigates, and if possible, eliminates the need for chemical sprays.

ALYSSA ISRAEL is a Connecticut-based consultant specializ

ing in community health.

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