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Local municipalities see significant mosquito reduction
According to a report released by the Denton County Health Department on Wednesday, the county saw a 60-percent reduction in the mosquitoes known to carry West Nile virus, Culex tarsalis and Culex quinquefasciatus, following aerial spraying that took place Sept. 1 and Sept. 2.
Specifically, Southlake saw a 75-percent reduction of those mosquitoes.
Other municipalities that participated in aerial spraying included Flower Mound, which had a reduction of 67 percent, and Lewisville, which saw a 53-percent reduction.
Overall mosquito reduction county-wide was 56 percent, according to the report.
Four airplanes sprayed 565,629 acres in the county with 0.8 ounces per acre of Duet, a dual-action adulticide composed of Prallethrin and Sumithrin. Both ingredients are pyrethroids, or synthetic chemical insecticides.
Cities that opted to participate in aerial spraying set out traps before and after spraying to record mosquito populations.
Southlake set out traps before and after spraying for a comparison.
“Seventy-five percent bodes well for spraying to reduce mosquitoes in our city,” said Pilar Schank, city spokesperson.
County officials, too, were pleased with the county-wide numbers.
“That’s a good number because that’s basically six out of 10 mosquitoes that are no longer here,” said Bob Martinez, public health preparedness coordinator for the Denton County Health Department. “Sixty percent is about average. Some areas saw 94 percent or better. A good number of Culex mosquitoes were knocked down.”
Southlake was one of three municipalities that also performed a quality assurance test. One cage of mosquitoes was placed outdoors 30 minutes before aerial spraying began and then brought indoors. Another cage was placed in the same location during aerial spraying. Afterward, both cages were examined.
In the cage with mosquitoes not exposed to the aerial spraying, none of the mosquitoes were killed. In the cage with mosquitoes that were exposed, 95 percent of the mosquitoes were killed.
Throughout the summer, West Nile virus became a growing concern. Humans who are bit by infected mosquitoes can, but not always do, show West Nile virus symptoms. Non-severe symptoms include fever, headache, nausea and vomiting. The severe version of the disease includes severe headache, high fever, stiff neck, confusion, loss of consciousness or muscle weakness. The severe form of the disease can be fatal.
Southlake has had eight human cases of West Nile virus to date.
While many people supported the city’s decision to conduct aerial spraying, some people opposed it, fearing the pesticides would hurt various aspects of the ecosystem, such as bees, as well as fish, birds and plants.
Schank said the city received a few calls from concerned residents immediately following spraying activities, but she said those calls have tapered off during the last two weeks.
Going forward, Martinez said he does not expect more aerial spraying this year, especially since the mosquito season tends to taper off in September.
Schank said the city will continue to monitor the situation.
“We are continuing to trap and look to see if there are positive results of West Nile virus,” Schank said. “So far, we have not seen a positive result since August.”
Cities will also continue with education efforts to remind residents how to reduce the number of mosquitoes around their home, as well as how to prevent being bit by mosquitoes.
Martinez said the county is looking to establish guidelines that will help officials respond to the virus next year if it happens.
“Hopefully the cycle will be better next year,” Martinez said. “But there is no way of knowing. If we have the same type of winter that we had this year, I expect the mosquitoes to be bad then, too.”