Backpack

SUMMER'S STING

A monthly report on personal health, life and leisure

SCOTT STEELE June 26 1995
Backpack

SUMMER'S STING

A monthly report on personal health, life and leisure

SCOTT STEELE June 26 1995

SUMMER'S STING

Backpack

HEALTHWATCH

A monthly report on personal health, life and leisure

SCOTT STEELE

They’re back. Along with summer comes a bevy of blood-sucking bugs: blackflies, deerflies and horseflies, tiny midges—popularly known as “no-see-ums”—and, of course, ubiquitous mosquitoes. Anyone who has ever waded into the great outdoors at this time of year knows what a nuisance those pests can be. And in the weeks ahead, as city dwellers troop off to cottages, campgrounds and backyard barbecues, most will be armed with some form of protection from the bothersome vampires—from cockamamy home remedies to scientifically proven methods of defence.

It is a summertime tradition born of necessity. Canada is home to more than 70 species of

mosquitoes alone. As with other biting flies, only the females are a problem, requiring a blood meal to produce their eggs. Is there any place Canadians can go to escape their probing proboscises? “Maybe the North Pole,” deadpans Gordon Surgeoner, an entomologist at Ontario’s University of Guelph who is one of the world’s leading experts on mosquitoes.

Still, some parts of Canada do suffer from significantly higher concentrations of the winged predators. “Mosquitoes tend to breed any place where the drainage is really poor,” says Aylward Downe, retired head of biology at Queen’s University in Kingston, Ont. For more than 30 years,

Downe has studied the creatures in their natural habitat—from Ellesmere Island to the southern United States. “There are big populations in some parts of the North, but some of the worst areas I have encountered are in southern Saskatchewan,” he says. “Parts of Prince Edward Island, too, have intense concentrations at various times of the year.” Winnipeg’s mosquito problem is legendary—and is only made bearable by what Surgeoner calls “the best mosquito-control program in the country,” which includes occasional insecticide spraying. Downtown Toronto, on the other hand, is relatively skeeter-free.

In addition to drainage—females lay their eggs in stagnant water and moist soil—climate is a significant factor. “If it is a cool but very wet spring, mosquitoes build up in temporary pools and you can get a very severe summer,” says

Downe. “Alternatively, a hot and dry spring usually cuts down on the population, because the breeding areas dry up.” But despite being home to a colossal mosquito population—both Downe and Surgeoner say it is impossible to estimate their numbers—Canada is thankfully free of most mosquito-borne diseases such as dengue, yellow fever and malaria. One variety of mosquitoes, the genus Culex, can carry a bacterium that causes encephalitis, an infection of the brain. But outbreaks, largely confined to southern Alberta, Saskatchewan and Manitoba, are sporadic. A more widespread problem is canine heartworm, a mosquito-spread parasite that can be fatal to dogs. Dog

owners should consult a veterinarian for preventive medication.

What can potential human hosts do to protect themselves from bites? Over the years, people have tried everything imaginable, from dousing themselves with urine to smearing on garlic and onion juice, mud and pork fat. Some avoid bananas, mistakenly believing that the fruit attracts bugs that feed on plant sugars. Other purported repellents include peppermint, bay leaves, cloves, sassafras, cedar, eucalyptus and pennyroyal. Some people swear by the essential oil of citronella, a fragrant lemonyscented plant native to Java and Sri Lanka.

While a few of those substances—particularly citronella—have some repellent qualities, most are of little or no value. But fear not: there are some simple steps that can be taken to ensure a relatively bite-free summer.

REPELLENTS: Insect repellents come in a wide array of lotions and creams, liquids, pump and aerosol sprays. But experts agree that the best formulations contain a compound called N,N-diethyl-3-meta-tolu-

than deet-based repellents, especially over time. Similarly, citronella candles and mosquito coils burned outdoors can ward off some bugs, but only if there is little wind and people are sitting in close range.

ELECTRONIC DEVICES: A number of electronic gadgets on the market purport to control biting insects. Among the most common are blue electric zappers that fry bugs with a distinctive crackle. But while they are effective under certain indoor conditions, outdoors the zappers tend to attract more bugs than they kill. And, says Surgeoner, only one per cent of the bugs they zap are actually mosquitoes. Another dubious device is the high-pitched sonic mosquito repellen “The female mosquito, the one who bites, doesn’t really hear at all,” says Downe. “She is just about deaf.” He adds that such devices “are not founded on scientific fact— and are a waste of money.”

TIMING: The feeding habits of mosquitoes are dictated by an internal biological clock, says Downe. In mosquito-infested areas at dusk and dawn, their appetites are at their peak. Research has also shown that feeding may actually increase during a full moon. And in most parts of Canada, with the notable exception of a few species in the Prairies, “mosquitoes do their thing mainly in the early part of the summer,” says Downe. “By the end of July, they are no longer really a big problem at all.”

CLOTHING AND GROOMING: While it may offend fashion sensibilities, tucking long pants into socks and attaching strings to the brim of a hat can discourage bugs from attacking the ankles and face. Head screens and stylish new “bug shirts” are also gaining in popularity. At one outdoor equipment store in Toronto, sales staff have been

A few simple steps can reduce the number of bites

amide, better known as “deet.” Developed by researchers at the U.S. department of agriculture in 1953 to protect soldiers in the tropics, the repellent has proved powerful against a wide range of biting insects— including flies, mosquitoes, gnats, fleas, ticks and midges. “Deet is far and away the best repellent going,” says Downe.

Scientists are not sure exactly how deet works, beyond theorizing that it somehow overrides the biological factors that cause biting insects to land. Deet repellents come in a variety of concentrations—as low as seven per cent by volume in Skintastic, a pleasant-smelling lotion produced by S. C. Johnson Ltd. for the consumer market, to more heavy-duty versions in excess of 90 per cent. The Canadian Forces often use a 75-per-cent deet solution called Nero.

Although there have been cases of allergic reactions and deet toxicity, most experts agree that deet is safe if properly used. They advise against using deet on infants, or putting it on broken skin or sunburns. And they suggest rubbing it on the face with the palms of the hands, avoiding the eyes and mouth. As a further precaution, Surgeoner recommends washing deet off with soap and water when it is no longer required.

There is also no need for overkill. Surgeoner and others say that higher concentrations of deet generally result in longer, rather than better, protection. Some formulations containing concentrations higher than 35 per cent, for instance, have been shown to be highly effective for periods up to eight hours. For canoe trips in the deep woods, stronger repellents are suggested. For walking the dog or a backyard barbecue, weaker ones are usually fine. One of deet’s unpleasant properties, however, is that the repellent is a solvent and can dissolve plastic and nylon, including eyeglasses and nylon camping gear.

Another product that has a wide following is Avon’s Skin-So-Soft, a fragrant bath oil that is not actually a registered repellent. It contains diisopropyl adipate benzophenome, which does have some repellent qualities. But research has shown that it is significantly less effective

unable to keep up with demand for the meshed and hooded shirts, which retail for $54.

Researchers say that mosquitoes are less attracted to drab colors— such as khaki green—and lighter hues. Avoid wearing navy and bright colors: they may actually attract not only mosquitoes but also stinging insects like hornets and wasps.

Also worth avoiding are strongly scented hair sprays, perfumes and lotions, all of which may attract bugs. Bathing frequently can help as well, since components of human sweat have been shown to lure many pests.

DEFENSIVE ACTION: Keeping in mind that mosquitoes breed in standing water, it is a good idea to inspect backyards and cottage lots for potential egg-laying pools. Driveway puddles, eaves troughs, birdbaths (if the water is not changed regularly) and discarded cans are just a few examples of the sorts of things that can send mosquito populations soaring. Keep bushes and shrubs well trimmed and cut long grass where mosquitoes and other biting insects like to congregate.

Some people, of course, claim that they are never bitten by mosquitoes and other pests. They may be right mosquitoes are attracted by a combination of things, including carbon dioxide, body heat and lactic acid found in breath and perspiration, and some people do appear to attract fewer insects than others. But Surgeoner says there is another factor at play. As mosquitoes bite, they inject a saliva that keeps the blood from clotting as it is sucked up. Certain individuals are less allergic to the saliva than others, and may not realize that they have been attacked.

Those who are bitten or stung by insects should avoid scratching, which can spread toxins deeper into the skin. Instead, experts recommend disinfecting bites with soap and water or alcohol, then applying calamine lotion or a simple paste of baking soda and water. If nothing else, that should take away some of the itch—at least until the next bite. □