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The species, which originates in Japan, was discovered in the storm sewers and a rock-based ornamental outdoor pond in Wedgewood Valley.
It is the first time the species has been found in western Wisconsin, except for Fort McCoy. Last year the species was found in Madison.
“This could have greater ramifications potentially than West Nile,” said Dave Geske, director of the La Crosse County Health Department mosquito control program.
“It has awakened us because it’s new mosquito and another disease vector that has been brought to a highly endemic area for La Crosse encephalitis — and carries four kinds of encephalitis,” he said.
Geske said the species isn’t just a mosquito that feeds on animals and birds, hibernates during the winter and leaves egg residual for the following spring. The mosquitoes also thrive later in the fall, he said.
He said fewer of these mosquitoes die than Aedes triseriatus, the original vector for La Crosse encephalitis, which causes a disease of the nervous system.
“It’s an opportunistic biter and a strong flyer,” said Jessica Hulberg Southwick, who has studied the species and has been looking for it the past two summers.
Southwick, a West Salem, Wis., native who has a biology degree from Luther College, identified the mosquito a week ago after Jim Boland, a former biologist with the state Department of Natural Resources and former mosquito control worker, found it in the Shelby neighborhood.
She had been working on a grant from the health department and the Centers for Disease Control to monitor the species in the area, especially near Fort McCoy where the U.S. Army identified the species in 2005 after pools of West Nile virus were found.
Southwick never found the mosquito in nine counties in western Wisconsin and southeastern Minnesota until a week ago. “Even though I didn’t find it at Fort McCoy, it’s probably still there,” Southwick said.
The mosquito — ochlerotatus japonicus — was first discovered in the United States in Suffolk County, N.Y., 10 years ago. It has been identified in several states including Iowa and has been moving westward, Geske said.
“It was inevitable that we would find it here,” Southwick said.
Geske said he and his staff are monitoring the town of Shelby and killing the breeding mosquitoes with bacterial treatment.
“We don’t know where the mosquito is and how it got here,” Geske said. “We’re eliminating the mosquitoes as we find them.
“But we want to find them before they are established in the area so we don’t have to put out fires later,” he said.
Southwick said ochlerotatus japonicus is known as a rock pool mosquito, and breeds in artificial containers such as bird baths, buckets, plastic milk jugs, wheelbarrows, rock pools and tires.
“The last place I expected to find it was in the storm sewers in Shelby,” Southwick said.
She said the species colonizes better in tires than the encephalitis-carrying mosquito, Aedes triseriatus.
Geske said the areas near Wedgewood Valley and State Road Elementary School were the first locations monitored for La Crosse encephalitis after 17 cases were reported in the area more than 30 years ago.
“This species is a big deal for public health, and it will be a high priority for us,” Geske said.
“We knew sooner or later, we’d find it here, but as money is drying up for mosquito control, we will have to reallocate our resources and take a step back and cut control measures for nuisance mosquitoes,” he said.
Who to call
Terry Rindfleisch can be reached at (608) 791-8227 or trindfleisch@lacrossetribune.com.
