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.

A 20 year fight against deadly mosquitos

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.

LISTEN | Keeping London's mosquito population down:

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.

No cases of West Nile in the region so far this year

The MLHU keeps a close eye on cases of West Nile Virus in the area and, so far, Hogeveen said that while they haven't detected any this year, it is still early in the season.

"The transmission cycle starts with birds and then we start to see positive adult mosquito traps. In August and September is when the virus is high enough in the population that we start to see some human cases," said Hogeveen.

While the MLHU has many programs in place to cull the mosquito population, he stresses there are still areas they need help with from the community.

"We can't go onto private property and start getting every puddle and flip over every bird bath, but what we're hoping is that people will recognize these locations and get rid of that water if it's there for longer than a week," said Hogeveen.

"We're never going to eliminate [vector mosquitos] completely, nor would we want to, but if we're able to manage this, that definitely keeps the population down, which, in turn, can keep the virus transmission down."