Michelle DaCruz
Northern News Services

Yellowknife (June 03/02) - Using common sense, a little bit of science and a healthy dose of chemicals to fend off the little bloodsuckers is the advice most bug experts provide.

Products containing DEET at concentrations above 30 per cent will no longer be registered in Canada under the Pest Control Products Act. However, it is legal to sell them until Dec. 31, 2004. This product, containing 95 per cent DEET, is available in most sporting goods stores in the territory. - Robert Dall/NNSL photo

There is good news and bad news when it comes to developing an immunity to mosquito bites, said Doug Currie, curator of entomology at the Royal Ontario Museum.

The positive side is as you are bitten by the 27 species of mosquito in the North -- there are a total of 75 species -- your reaction will dissipate, said Currie.

On the other hand, you have to be bitten by all 27 to be in the clear. Also, the immunity will not last for the next summer. And remember, only the female mosquitoes bite.

"Initially people may have huge welts, but toward the end of the bug season they have less reaction, or none at all. Unfortunately, next summer you have to start again," said Currie.

The lowdown on DEET

Of all the insect repellents on the market, those containing DEET seem to be the most effective, since it works on a number different bugs and provides hours of protection.

The U.S. government developed DEET, or diethyl-m-toluamide, in the 1940s for the military. The first time it was widely used was during the Vietnam War.

Andre Corriveau, NWT chief medical officer, said using insect repellents containing DEET is still safe in his studied opinion.

Health Canada issued safety tips on using products containing DEET in April. They warn against using DEET on infants, and advise using only low-dose products, 10 per cent or less, on children under 12. The agency recommends adults use only a 30 per cent concentration of DEET, but points out products with a higher amount, up to 99 per cent, will still be available for sale in Canada until December 2004.

Corriveau said the warnings for children are based on their tender skin's ability to be more absorbent, but added, there has been no scientific evidence of prolonged use leading to dangerous effects, unless ingested.

High concentrations of the product, Corriveau said, could have neuro-toxic effects, like insomnia, mood disturbances, and impaired cognitive functions. Other reactions can include skin allergies, in the form of rashes or blisters.

"Reducing the concentration of the product to 30 per cent also reduces the product's effectiveness," said Corriveau. "You will have to apply it more often, especially when out on the land because it evaporates with sweat."

Scratching bites, especially for children, said Corriveau is dangerous, because bacteria on skin and under fingernails can cause infections, like impetigo, or clusters of infected lesions.

Mosquito forecast

Predicting the severity of the mosquito season is a task even entomologists cannot accurately forecast.

The North has the highest population of mosquitoes on earth, with Siberia running a close second, according to Currie.

"There is a lot of water and geography that has not been developed. Coupled with permafrost, this leads to a particular capacity for them to breed in large numbers," said Currie.

Predictions for the upcoming season are difficult since breeding is based on rainfall patterns over a number of years, said Hugh V. Danks, entomologist of the Canadian Museum of Nature in Ottawa.

"It's tricky to predict because there are too many variables. Factors during winter, for instance how fast the snow melts, and during spring like the amount of rainfall are important," said Danks, who was the editor of Arctic Insect News, which was published for 11 years in the Yukon.

Randy Wedell, client services of the Water Survey of Canada, said that is true for most years, but the greatest influence this year has been temperature.

"We had the first hatch of winter bugs and they have died because of the freezing temperatures in the last two weeks of May," said Wedell.