June 14, 2010, 8:55 a.m.
Environment Canada is predicting a summer of sunny, warm temperatures with a bit of rainfall, creating perfect weather for most Canadians. But the pleasant forecast is also the perfect climate for a season plagued by virus-carrying mosquitoes.
So specialists are warning regions across Canada — which have been abandoning their mosquito-control programs in recent years — that the anticipated summer heat could be accompanied by an outbreak of West Nile virus.
This spring had a premature start, meaning mosquitoes emerged from hibernation early and will multiply, live longer, and feed more — or, in short, infect more humans and small animals, said Christian Back, a medical entomologist and biologist.
"In principle, this combination favours the transmission of the West Nile virus," Back conceded.
Back is also vice-president of GDG Environment Group Ltd., a Quebec-based company that has been monitoring mosquitoes and their transmitting of infectious diseases in several cities across Canada for the past decade.
"In last few years, West Nile virus has not been very active, but it's an issue of adjustment between risk of disease and preventative control measures. Programs have to be maintained because this could be that special year West Nile virus would pop up again. The prospect, as we speak, is extremely favourable," he said.
Studies in California showed that about 109 days of above 14 C weather would equal "optimal development" of the West Nile virus and, as temperatures climb, multiplication of virus-carrying mosquitoes will accelerate, Back said.
Environment Canada's official long-term summer forecast predicts above normal temperatures, exceeding 20 C for most of the country, excluding Vancouver, which should sound warning bells for a potential outbreak.
However, experts say they've noticed a decline in monitoring and tracking.
"The funding looks like it went down by 80 per cent this year, but it was a sign of the economy and what our province wanted to spend," said Cheryl Phippen, a biologist and owner of BWP Consulting, a mosquito-control agency monitoring most of British Columbia.
Initially, the province allocated enough funding for surveillance of only its four highest-risk regions — the Fraser Valley, Metro Vancouver, the Central Okanagan and Okanagan-Similkameen.
Phippen said more funding was later released in early June to cover additional areas, including the North Okanagan and some of the Kootenay area.
Back said most of Quebec quit mosquito-monitoring programs in 2006, and only conducts "passive surveillance."
Since then, other provinces have followed suit.
In 2007, residents in Saskatchewan, the province with the most infections recorded so far, had a 1 in 10 chance of getting bitten and infected by a mosquito carrying the virus. Nearly 1,300 people were infected, resulting in six deaths and 113 severe cases.
But Saskatchewan dismantled its provincial shared mosquito-control program this spring, which had poured $6 million into monitoring since 2003, leaving the onus on cities to track the issue on their own.
Regina, already plagued with wet, mosquito-friendly weather conditions, is running programs with 50 per cent less funding this year, a $290,000 difference.
"We're convinced our municipalities can control their mosquito-control programs and assured them that should the human health risk increase, we'll step in," said Philip Curry, the province's West Nile co-ordinator.
In Ontario, a City of Ottawa spokesman said funding for mosquito-control programs remained the same this year, but Windsor reported $126,000 will be spent, a substantial decrease from the $300,000 invested last year.
Cities in Manitoba will combat the West Nile virus "the same way we do every year," said Dr. Joel Kettner, the province's public health officer.
"We're not scaling back. We have to put it into perspective and we know the potential to cause severe illness is there, so we take this disease seriously," he said.
Back said the Prairies, Ontario and Quebec are the regions most at risk of epidemics. The risk peaks in July and into August. Urban and suburban regions will encounter the virus most because there are more catch basins, where mosquito larvae are found, and more humans to infect.
West Nile virus was first reported in Canada in 2001. By 2003, 1,481 human infections were recorded. Reports in the following years wavered from the dozens to the hundreds across the country, but the virus peaked again in 2007 with 2,215 cases.
The West Nile virus is transmitted to mosquitoes when they feed on an infected bird. There is evidence that some female mosquitoes transfer the virus to their offspring.
Mild cases of human infection result in flu-like symptoms, including fever, headache and body aches. Some people also develop a mild rash, or swollen lymph glands.
Others, who have weak immune systems, are at risk of fatal sicknesses, including meningitis or encephalitis, which cause inflammation of the brain or spinal cord.