Last week, an older resident from the Idiot’s Hill neighborhood contacted the Denton Record-Chronicle to find out why the city of Denton wasn’t fogging for mosquitoes after several traps around the city returned positive tests for West Nile virus.
The Centers for Disease Control and Prevention warns that people over 60 are at greater risk for severe illness if they are infected with West Nile virus, as are people with certain medical conditions including cancer, diabetes, hypertension, kidney disease and those who have received an organ transplant.
“I talked with some friends, and we’re older but when we grew up, the city sprayed for things like that every summer and they would go up and down the streets and do it,” the resident said.
Currently at Risk Level 3, the city has identified 12 locations with traps that have tested positive for mosquitoes with West Nile virus since late June. At Risk Level 3, human outbreak of the virus is considered low to moderate.
Despite the positive traps, the city hasn’t treated the areas using ground-fogging or spraying and won’t be doing so until someone from Denton contracts the virus, said Dustin Sternbeck, the city’s chief spokesperson.
“A single human case of WNV reported within the corporate limits of Denton would trigger a move to Risk Level 4,” Sternbeck said.
Sternbeck referred to the Mosquito Surveillance Response Plan, which the City Council approved in 2019.
As the 2019 plan points out, spraying for adult mosquitoes, also known as “adulticiding,” is only considered by city officials when evidence of West Nile activity shows that it is at a level suggesting a high probability of human infection.
“In general, finding an isolated WNV-positive mosquito pool does not by itself constitute evidence of an imminent threat to human health and does not warrant adulticiding,” according to the 2019 plan.
The plan recommends spraying at dusk and dawn and to consider the weather and the terrain when spraying.
The city also considers human population density in Denton in the response plan. According to the plan, “If the area in question is rural and does not contain many people, the cost and potential risk associated with spraying may not justify its use. If the area in question is densely populated, adult mosquito control may be more justified as long as adequate precautionary measures are taken.”
Population density could explain why the county doesn’t wait for a transmission to humans before it begins treatment after a positive trap is identified, since some of the unincorporated areas in Denton County aren’t as populated.
Jenica Bates, a public information officer for Denton County, said that Denton County Public Health is still fogging the locations that have tested positive within the past week in unincorporated areas.
“Only one trap needs to be positive for West Nile virus for fogging to occur in the surrounding area,” Bates said.
But the problem with treating for mosquitoes over a large area is that the chemicals used don’t just harm adult mosquitoes.
The most widely used residential mosquito sprays are also toxic to native pollinators, such as bees and butterflies and other aquatic organisms and can pose a risk to pets and people, according to the National Wildlife Federation.
It’s a concern also highlighted in the city’s response plan.
“Routine mosquito spraying, for example, has the potential to expose the public to pesticides. Depending upon the pesticide used, effects on humans are possible and may be more likely for people who already suffer from asthma or other respiratory problems,” the plan states.
Instead, Sternbeck pointed out that the city’s response plan targets known breeding sources with larvicide application, such as BTi briquettes or dunks, on publicly maintained property.
“We encourage residents to do the same on private property,” Sternbeck said. “This type of application does reduce mosquito population growth and poses the least risk to the environment.”
Sternbeck said that any future action by the city will be driven by mosquito trapping and disease testing results, combined with human case information provided by public health officials.
The city owns spray equipment that it will utilize if needed.
“In the event that spraying is necessary, a comprehensive community notification process will occur,” Sternbeck said.