Fayette County

UK scientists pit males vs. females to slow spread of tiger mosquitoes

University of Kentucky professor Stephen Dobson's research focuses on controlling the Asian tiger mosquito, which is in every Kentucky county.
University of Kentucky professor Stephen Dobson's research focuses on controlling the Asian tiger mosquito, which is in every Kentucky county. UK College of Agriculture

The Asian tiger mosquitoes have come to the United States, and they're spreading.

That's the bad news. The female tiger mosquitoes, in need of blood to support egg-bearing, have been chomping away in new territories over the past few years. (The male mosquitoes do not bite.)

A University of Kentucky study found that tiger mosquitoes were responsible for 90 to 95 percent of bites on Lexington test subjects during summer 2013.

At the University of Kentucky college of agriculture, scientists are working on a method to stop the spread of the pesky critters, which are now in every Kentucky county and are on the fly west — toward California — and north — toward New York and New Jersey. Developed at UK, the technology is licensed to the Kentucky company MosquitoMate.

UK professor Stephen Dobson and his colleague Jimmy Mains will soon be field-testing their method for controlling the voracious tiger female mosquitoes. The technology is non-toxic, non-GMO and selective — specific to the tiger mosquito's drive to reproduce.

The mosquitoes are a carrier of canine heartworm and transmit the Chikungunya virus, which produces symptoms similar to those of dengue fever — fever up to 106 degrees, headaches and muscle, bone and joint pain.

The key in the stable of MosquitoMate is the bacterium Wolbachia. Releasing males with a different strain of Wolbachia from that in the females in a targeted area results in males mating with females and producing — nothing. The eggs don't develop. The strain of Wolbachia used comes from Kentucky's common house mosquitoes.

"Once you infect one, all her children are infected," Dobson said. " ... Instead of spraying at mosquitoes, the male mosquitoes are the pesticide. ... this type of control approach is the first of its kind."

Growing the Wolbachia-infused males is simple, Dobson and Mains said: A diet of water and dog food works fine. "They're not picky eaters," Dobson said.

The release of the Wolbachia-bearing male mosquitoes puts a substantial dent in the biting Asian mosquito population, Dobson said. A mosquito tends to stay in a fairly small area during its life, probably roaming no more than the length of a football field.

Hence adding the MosquitoMate technology to an arsenal of mosquito-suppressing technologies may eventually be common.

Experts said in July that the big biter in the Lexington area was the Asian tiger, which likes to operate outdoors in daylight.

Chris Christensen, an entomologist who operates Urban Insect Solutions and Critter Control in Lexington, then called the tigers "vicious biters."

"These things come up out of the grass, they haul off and they bite and welt," Christensen said. "And everybody's breeding them in their backyards."

In 2014, the UK researchers will begin studies with the new-strain Wolbachia mosquitoes in neighborhoods around the university.

Dobson said that the proliferation of tiger mosquitoes also has a hidden health side effect — an increased risk of obesity: "People don't go outside and don't get as much exercise" when they are discouraged by biting insects, he said.