Sterile Mosquito Program Reducing Risk of Zika Virus In California

Every week for the last three months, 40,000 male mosquitoes have been released into a quiet neighborhood in Fresno County, California.

“You hear that distinctive buzz of the mosquito and you assume it is going to bite,” said Kathy Ramirez, vector biologist with the Consolidated Mosquito Abatement District in Fresno. “But the males don’t bite, which is good.”

These male mosquitoes, shipped from Kentucky, carry a naturally occurring bacteria called Wolbachia, not found in their California cousins, making reproduction impossible.

“We’re hoping that the males will find the females and they will mate with them, and then the eggs won’t be viable so they’ll reduce the population,” said Ramirez.

The Sterile Insect Program is aimed at reducing the number of Aedes aegypti mosquitoes, the type that can transmit the Zika virus.

Every week for the last three months, 40,000 male mosquitoes have been released into a California neighborhood to reduce the overall population of virus-carrying insects.

“When a male mosquito that has Wolbachia mates with a female that does not have Wolbachia, it basically renders the eggs nonviable,” said Jodi Holeman, scientific-technical services director for the Consolidated Mosquito Abatement District.

‘The eggs will not hatch, they will not develop into larvae and into adults,” said Holeman.

After just three months, the population of Aedes aegypti mosquitoes in the target neighborhood in Clovis, California has been cut by a third.

“I don’t see any reason why this type of control strategy wouldn’t work in Dallas or anywhere in the world,” said Holeman.

The mosquitoes are shipped overnight from MosquitoMate in Lexington, Kentucky.

“It’s fairly novel,” said MosquitoMate’s Senior Scientist Corey Brelsfoard. "We use this bacteria to basically sterilize the insect population or mosquito population.”

“This is a new tool that can be used to control those mosquitos that spread Zika as well as other diseases,” said Brelsfoard.

A leading entomologist at the University of Kentucky, Stephen Dobson began working on the technique 15 years ago.

“We’re cheating,” said Dobson. "We’re taking advantage of this naturally derived mechanism to control mosquito populations.”

Dobson’s previous tests on similar mosquitoes cut the target population by 80 percent.

40,000 Diseased Mosquitos Released to Curb Population

“This type of approach where you’re releasing using the insect against itself, has been used successfully in the past to eradicate insects from the U.S.,” said Dobson.

MosquitoMate just received government approval to expand the testing to other parts of California and the Florida Keys.

“This is probably not going to be a silver bullet,” said Dobson. “I think that we’re going to be integrating these approaches along with other approaches.”

Harris County, Texas is now scouting as many as three locations in Houston to join the testing program for releasing sterile mosquitoes.

Encouraged by the program’s success so far, Harris County is now scouting as many as three locations in Houston to join the testing program next spring.

“If you use this tool as its targeted to an area where you know the Aedes aegypti are, you’re going to get rid of them,” said Dr. Mustapha Debboun, director of mosquito control for Harris County Public Health.

“They certainly have the mosquitoes that we’re focusing on,” said MosquitoMate’s Jimmy Mains. “The strains that we’re producing here in our facility are incompatible with what they have in Houston.”

Harris County wants to begin releasing male mosquitoes from MosquitoMate before July 2017.

More about the Sterile Insect Technique can be found here.

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