Climbing in Ontario necessitates closer contact with biting bugs than I have ever desired. Black Flies and Mosquitoes are the main irritants in Ontario. But I never considered mosquitoes to be much of a problem, more of a nuisance. However, last year, the West Nile virus, transmitted to humans by mosquitoes, killed a number of people in New York City. While the virus has not been found in Ontario as of June2001, it has come close to our borders. It is likely to be here soon.

Female Mosquitoes are the biters; male mosquitoes are of no concern. The female searches for a blood meal from an animal to nourish her developing eggs. Mosquitoes find hosts by sight, by infrared radiation and by chemicals. She can sense carbon dioxide, amino acids, and sex hormones. Warm, perspiring humans are particularly attractive to mosquitoes.

There are over 60 different species of mosquitoes in the NorthEast. The Aedes japonicus species is the culprit, an Asian mosquito that somehow turned up in Eastern North America. Apparently, this mosquito bites birds that are infected with the disease and if the same mosquito subsequently bites a human, it can pass the virus to a human host.

Although most West Nile virus-positive birds have been American crows, infections also have been confirmed in other species, including the Blue Jay, Mallard Duck, American Robin, Sparrow, Canada Goose and various gulls and hawks, all of which live in Ontario.

The West Nile virus is a type of encephalitis. Encephalitis is a viral infection. Mild cases may include a slight fever and/or headache. More severe infections involve a rapid onset of a high fever with head aches and body aches. Muscle weakness, skin rash and swollen lymph glands have also been experienced. Occasionally, the illness may be more serious causing encephalitis (inflammation of the brain) and sometimes death. Usually symptoms occur from 5 to 15 days after exposure. There is no specific treatment for viral infections, other than to treat the symptoms and provide supportive care. Most people who get infected with West Nile virus do not get sick. Those most at risk include infants, persons over 50, and those persons with weakened immune systems

What to do?

In spite of relatively low risk to healthy climbers, it is probably wise that some precautions are taken to avoid being infected.

When in high-risk locations or during high-risk times, perfumed soaps, sprays or other sweet smelling formulas that might attract mosquitoes should not be worn. Light coloured clothing is rumored to be less attractive to mosquitoes. Covering skin with long-sleeved shirts and pants with fabric thick enough to prevent mosquitoes from biting would be useful, but probably impractical for climbing. Bug netting makes you look like a gumbie and hinders climbing.

Insect repellent containing DEET definitely deter the little monsters and is probably the best solution for most climbers. But there are precautions in using DEET. See the Health Canada website for tips on using insect repellants.

Various gadgets such as ultrasonic devices and bug zappers on the market that claim to deter mosquitoes are ineffective. Vitamin B and incense also have not been shown to be effective in preventing mosquito bites.

Mosquitoes lay their eggs in stagnant water. The eggs become larvae that remain in the water until they mature and fly off. Weeds, tall grass and shrubbery provide an outdoor home for adult mosquitoes. To reduce the mosquito population around your home and property, reduce or eliminate as much standing water as possible.

Bob Bennell
July 2001