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The Sudbury Star
Saturday, September 1, 2001
OTTAWA -- Concerned health officials would do better to unleash tens of thousands of dragonflies against potential West Nile virus-carrier mosquitoes than resort to pesticides, say environmental and citizens groups.
The natural method of mosquito control has been used in Wells, Me., for the last 26 years. The tiny seaboard tourist town unleashed 17,000 of the natural predators at the end of May this year. And since West Nile virus cropped up 40 kilometres south in New Hampshire on Aug. 17, their neighbours have been coming up to check out their program.
With 11 confirmed cases of the virus in Ontario birds this week, Dr. Colin D'Cunha, Ontario's chief medical officer, announced that local health officials would consider using pesticides if there were evidence of an imminent risk to human health. Quebec passed a bill in the national assembly in June that overrides municipal pesticide bans (there are 37 in the province) to allow the aerial spraying of pesticides again West Nile.
But Canadian doctors and others are warning health officials that spraying pesticides to control West Nile virus might actually increase the chances of people dying.
"Exposure to chemical pesticides leads to subsequent weakening of the immune system and actually increases the risk of developing West Nile virus encephalitis," said Dr. Libuse Gilka, an Ottawa member of Physicians and Scientists for a Healthy World.
The virus, which first emerged in North America in New York in 1999, is rarely fatal, usually causing flu-like symptoms including fever, headaches and swollen glands. However, it can be fatal for people with weak immune systems. It has killed 12 people across the United States.
Ontario Ministry of Health spokesman John Letherby says pressure has been mounting from the public for health officials on the front lines to do something to forestall human infection.
"They have a problem and they want to be able to say they've done something for it," says Michel Gaudet, vice-president of the Montreal-based Coalition for Alternatives to Pesticides. "But they are not being rational. ... West Nile virus will affect maybe one per cent of 5,000 people. On the other hand, if you start massively spraying pesticides, you will affect the health of thousands of people."
The New York Health Department has been using pesticides since 1999, in an effort to kill off the mosquitoes that can transmit the virus to humans from infected birds.
The unannounced ground spraying of pesticides at a park in Moreau, N.Y., on June 25, landed almost 40 teen softball players and spectators in hospital with headaches, wheezing, coughing and nausea. One woman fainted.
Westchester County physician Lucy Waletzky says people without asthma have even developed the respiratory condition as a result of the spraying. She said recent studies by the New York State Department also show more birds have died as a result of pesticides than West Nile.
She said authorities should explore biological methods of killing mosquitoes, such as the Wells dragonfly program.
"Some people tell me they can't believe the difference," said Wendy Griffiths, part-time bookkeeper for the Wells Chamber of Commerce. "Plus, dragonflies are so friendly and so beautiful and inquisitive."
Every year, scores of residents and local businesses buy new dragonfly nymphs and place them around ponds or standing water. The chamber picks up dragonfly larvae from a hatchery in West Hampton, Mass., in the spring. Bags of 500 cost $175 US.
DOZENS OF CALLS
Hatchery employees say they have been receiving dozens of phone calls since West Nile began spreading.
The only catch for Canadians is that they don't ship across the border, and it may be hard for border-hoppers to clear guidelines on importing foreign species. The fear is that predators may become pests, as occurred recently with Asian lady beetles brought in to attack soybean-eating aphids.
The "mosquito fish" is another natural predator, but the larvae-devouring American fish has been known to displace other species.
However, Steve Marshall, an environmental biology professor at the University of Guelph, says he has never heard of dragonflies becoming a pest themselves.
"I find it difficult to imagine dragonflies having any negative effect," he said.
The Canadian Food Inspection Agency regulates the use of biological pest control. Spokesman Alain Charette said an environmental and efficiency assessment would have to be undertaken before they could import mass quantities of dragonflies.