Larvicide enlisted in mosquito fight

Hitting mosquitoes where they breed will be a major part of Toronto's efforts to control West Nile virus, the city's chief medical officer of health said Wednesday.

• INDEPTH: West Nile Virus
  

Dr. Sheela Basrur

Sheela Basrur said the city would target areas such as catch basins with a larvicide.

Toronto is hiring 24 temporary staff to survey catch basins to see how many virus-infected mosquitoes are there now, and to determine a schedule for applying the larvicide called methoprene.

One reason the city is hitting catch basins is because the Culex pipiens, the mosquito most responsible for transmitting the virus, likes breeding in standing water.

"I want to reassure Torontonians that the risk of contracting West Nile virus remains extremely low," she said.

While neither the virus nor the mosquito can be eliminated, the city's measures combined with personal protective ones should reduce the risk substantially, she said.

Controlling standing water on private property is another concern.

Basrur and Joe Mihevc, chair of Toronto's Board of Health, said there are sufficient laws available to deal with that issue. Windsor passed a bylaw Tuesday making it illegal to have standing water on private property for more than four days.

Toronto has no plans to do aerial spraying or fogging to control adult mosquitoes.

And that's a good thing, according to the Canadian Council for Health and the Environment. It says spraying and fogging could harm birds which are natural predators of mosquitoes.

A dead crow was found in the Toronto area in April, sparking fears there would be an early start to West Nile season.

Basrur said it was impossible to predict how hard West Nile would hit Toronto.

• FROM MAY 7, 2003: West Nile more virulent than predicted: study
  

Dr. Harvey Artsob of Health Canada told CBC Newsworld on Wednesday that he expected West Nile would spread further across the country this summer.