Dropping mosquito-repellant into London storm drains is keeping the pest population down

Scooter-riding mosquito busters have been travelling around London, Ont., dropping larvicide into roadside catch basins to keep the pest population down and fight the spread of the West Nile Virus.

The technicians work for the Canadian Centre for Mosquito Management, a company hired by the Middlesex-London Health Unit (MLHU) for the past several years.

"They drive by on the scooter, they drop [larvicide] in the catch basins and then they spray paint a little dot on it just to know that they were there," said Jeremy Hogeveen, the vector-borne disease coordinator with the MLHU.

The larvicide they use mainly targets the common house mosquito and white-dotted mosquito, which are both excellent vectors for the West Nile Virus, according to Hogeveen.

He said they do this across the city and surrounding counties three times a year starting in mid-June, and will target nearly 37,000 storm drains each time.

"The larvicide looks almost like hamster food. They only use .7 grams of it and it's strictly put in contained catch basins," he said, adding it doesn't pose a risk to public heath.

The city started the program in 2003 when the provincial and federal governments were looking for options to halt the spread of the West Nile Virus.

"Catch basins are a fantastic overwintering reservoir for the vector mosquitoes—those species of mosquitoes that can carry the virus," said Andrew Powell, the Manager of Safe Water, Rabies and Vector Borne Disease at the MLHU.

Powell said they can also treat backyard catch basins with the homeowner's permission.

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The health unit quickly discovered that killing larvae in this fashion was extremely effective in culling the mosquito population, so they've been maintaining the practice ever since, said Powell.

He also added that a program where the MLHU collects mosquitos in traps and then sends them off to labs to be identified is instrumental in keeping track of their numbers and identifying possible West Nile cases.

"The vector mosquitos get tested for West Nile Virus so that we can see if the virus is present within our community," he said.