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District outlines program to target one species of disease-carrying mosquito

April 13, 2018
By TIFFANY REPECKI ( , Island Reporter, Captiva Current, Sanibel-Captiva Islander

The Lee County Mosquito Control District is preparing to implement a new program on Captiva, as well as the north end of Sanibel, aimed at reducing the population of one disease-carrying insect.

At the Captiva Community Panel meeting on April 10, representatives from the district provided information on its Sterile Insect Technique, or SIT, program. The program will target the Aedes aegypti mosquito, which is an invasive exotic species that is a transmitting carrier for a variety of viruses.

The list includes yellow fever, dengue fever, the chikungunya virus and the Zika virus.

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Dr. David Hoel, assistant director of Lee County Mosquito Control District, discusses at Captiva Community Panel meeting on April 10 the SIT program, expected to be operational in 2019.

"Which is why we're targeting just them," Assistant Director Dr. David Hoel said.

If successfully implemented, the program will greatly reduce the population of the species, which currently poses a serious public health risk. He noted that the insect has few natural predators due to its preferred breeding habitat, so reducing the population will not significantly impact the food chain.

"There's no benefits to the population," Hoel said, explaining that other species of mosquitoes such as the salt water mosquito are sources of food for fish and other wildlife. "Not so with these guys."

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Introduced to America by way of slave ships from North Africa, the Aedes aegypti mosquito is an "urban mosquito," meaning that is breeds around homes - inside water-holding containers, tires, bird baths, potted plants, gutters, cans and bottles, even storm drains - and prefers to feed on humans.

The species is difficult to control by conventional means, like insecticide applications and source reduction, due to its cryptic behavior and daytime biting habits, which only the females take part in.

"These are hard mosquitoes to control," he said.

SIT is a technique used to sterilize insects to reduce or eradicate their populations. It involves the release of lab-reared sterilized males, which mate with the wild population. Female mosquitoes mate once in their lifetime. If she mates with a sterilized one, she will not produce any viable offspring.

"The girl's chance of mating with a viable male is greatly reduce," Hoel said.

The process for sterilization requires no genetic manipulation, only gamma rays or X-rays.

"There's no radioactive reside," he said. "It's perfectly safe."

The district began trapping the species in June across Captiva and on part of Sanibel.

"We have an idea of the mosquito density for the island because of the trappings," Hoel said.

Eric Jackson, spokesman for the district, explained that the initial figures will be used as a baseline to analyze the effectiveness of the program once the releases begin, which are set for winter of 2019.

Captiva is a prime location because of the species' size and abundance on the island.

The trapped mosquitoes are also being harvested for their eggs. Once the lab-grown mosquitoes reach the pupae stage in their life, X-rays will be used to render them sterile for when they hit adulthood.

The sterile males will then be released to mate with the wild population.

"The (lab-reared) females won't be released," Jackson said.

Any female mosquitoes accidentally released will also be sterile, so of little concern.

According to Hoel, SIT is not a new technology. Its first use in the United States took place on Sanibel in 1951 to eliminate the screwworm fly. Recently, sterile screwworm flies were released successfully in the Florida Keys to control one outbreak. SIT is used in agriculture to control fruit flies and tsetse flies.

The district noted that is is only trapping mosquitoes now, not releasing any of them.

"It's not operational yet," Hoel said of the program.

Jackson added that district will set up educational talks, classroom presentations in local schools and town hall meetings to answer questions and explain the program before any of the releases occur.

"This is just the beginning," he said of the presentation for the panel.

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