Last year, Texas was at the epicenter of what turned out to be the worst outbreak of West Nile virus since the disease first appeared in the United States in 1999. Of the 5,387 cases of West Nile — with 243 deaths — reported in 2012, one-third occurred in Texas. Of the cases reported in Texas, half were in the Dallas-Fort Worth area.
In Burleson, three human cases were reported and five mosquito traps tested positive.
“It was incredible,” Lisa Duello, director of neighborhood services, told Burleson City Council on Monday night. “Even the scientists don’t really know what went on last year” to lead to such an extensive West Nile outbreak.
Duello said that last year the city was “in kind of a reactive mode” when it came to dealing with the swarms of mosquitoes that carry West Nile. This year, she said, her department is ready to move ahead with a more proactive approach.
“We had been setting traps on an ad hoc basis as we received complaints,” Duello said, but as the situation worsened, the city was forced to spend more than $11,000 in emergency funds to spray twice for adult mosquitoes.
Each spray was conducted over three consecutive nights, the first triggered by human cases being reported within close proximity of each other, and the second triggered by a positive trap test.
Duello said that over a three-and-a-half-week period, 27 city employees were involved in battling the mosquitoes, and the city sprayed about 47 miles of streets covering 5,200 addresses.
This year, Duello said, she recommends that the city start out by following guidelines issued by the Centers for Disease Control, the Texas Department of Health and Human Services and the Tarrant County health department. The guidelines, she said, call for increased surveillance and quicker reaction to potential trouble areas.
“Last year, people were spraying in response to human cases,” Duello said. But the problem with that is by the time the human cases are reported, it is too late to curtail other infections.
According to guidelines from the CDC and other experts, “we’ve got to spray when we have a positive trap. And one of the big things that has changed is the number of traps the CDC and the others are recommending,” Duello said. “We need to have strategically placed traps that are out there on a weekly basis.
“These mosquitoes are not traveling more than a mile. So we’ve laid out an area on the map where we’ve got a trap in a one-mile radius, another trap in a one-mile radius [overlapping] in the most densely populated area of town. Six to eight traps should cover that, and we will have a couple of traps left that we can set out on a complaint basis.”
The plan, Duello said, calls for a more comprehensive surveillance effort, with more traps out more frequently, stepped up spraying for the mosquito larvae and quicker spraying for adult mosquitoes when there are positive trap results rather than waiting for reports of human cases.
To meet CDC and state health department guidelines, surveillance will take an estimated 352 employee hours, because, “They want us counting mosquitoes this year in the traps which will be a little time-consuming,” Duello said. Completing the recommended larvacide spraying will take about 330 hours, for a total of 682 hours.
Duello said her department recommends the city hire a part-time employee to work from May through October at a cost of about $13,000. Other options were more expensive Duello said, noting that a third-party company had quoted a cost of $39,000 to do that work.
The second step of the prevention efforts, spraying for adult mosquitoes after a positive trap, will require bringing in someone equipped to do the job, Duello said.
“Again, it is very difficult to predict what will happen this year, but based on what we known, we’re predicting maybe three spray events [for adult mosquitoes] for a cost of approximately $15,750,” she said.
Total cost of the recommended mosquito control plan, Duello said, is predicted to be just under $30,000.
“We really need to consider our future options. Emergency response is, obviously, not the most economical way to go. What we spent last year in a three-and-a-half-week period was quite a bit,” Duello said. “In the upcoming year, we’d like to consider a sustainable mosquito surveillance program with a dedicated staff and consider in-house adulticiding. It costs quite a bit to contract spray. You can buy a low-volume sprayer for about $8,000 and of course, you have to get someone out there to spray.”
She added that the city should also consider, in the future, purchasing equipment to test the mosquito traps in-house. The equipment is expensive, but in-house testing can save valuable time between finding a positive test and carrying out the necessary spraying.
Mayor Ken Shetter and other council members agreed that the staff’s recommended plan appears to be the best approach.
“Spraying for positive traps makes a lot more sense to me,” Shetter said. “If we’ve got positive traps, that means we’ve got positive mosquitoes. Why wait for them to infect somebody. This makes a lot of sense to me.”
City Manager Dale Cheatham said that the city can pay for the recommended plan through a budget amendment to draw down funds from the general fund balance, “ and we certainly have the ability to do that.”
Because the presentation was delivered during the council’s workshop session and not included as an action item on the regular council meeting agenda, the council will have to wait to vote on the recommendations until a future meeting.