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VOL. 124 | NO. 117 | Wednesday, June 17, 2009

Mosquito Season Calls for Disease Prevention Efforts

By Tom Wilemon

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MOSQUITO CONTROL: Demetrius Johnson, an employee of the Memphis and Shelby County Health Department’s vector control division, prepares a solution for mosquito control in the New Chicago neighborhood. -- PHOTO BY TOM WILEMON

As the number of foreclosed and abandoned properties increases with the stagnating economy, so do the breeding grounds for mosquitoes.

The tiny insects that almost eradicated Memphis are still a health concern more than a hundred years after the Yellow Fever epidemics. All the factors are in place for plentiful broods of mosquitoes this summer: ample rainfall, warm weather and a multitude of hatching spots.

The National Pest Management Association, an organization that represents the pest control industry, issued a statement earlier this month linking the high number of foreclosed properties nationwide to potential outbreaks of West Nile virus.

Although no cases of the virus have been reported in Tennessee so far this year, the disease is established in the United States, according to the U.S. Centers for Disease Control and Prevention.

Last year, there were 19 cases of reported human infections in Tennessee, 65 in Mississippi and nine in Arkansas. St. Louis encephalitis is another disease carried by mosquitoes, which is endemic in the Memphis area, with the last large outbreak in the mid-1970s, according to the CDC.

Widespread problem

Now is a good time to identify and eliminate breeding areas for the disease-carrying species of “house” mosquitoes, which bite primarily at night and use open containers, such as old tires and other vessels, as habitats, said Daniel Sprenger, an entomologist at the Memphis and Shelby County Health Department.

“We’ve gone house to house,” Sprenger said. “I can tell you that roughly 15 percent of residents on any given block are raising mosquitoes.”

DAY’S WORK: Charles Watkins, a foreman for the Memphis and Shelby County Health Department’s vector control division, walks down a slope in the New Chicago neighborhood to take mosquito samples as Lashawn Greer, another employee, follows. -- PHOTO BY TOM WILEMON

One option homeowners have to control mosquito populations is to install an automated misting system. Mike Wilburn, the owner of Yard Guard Inc., said that sales of the automated systems are down slightly from last year, which he attributes to the economy.

“It’s a system that we put in around people’s homes outside with small tubing and there is a misting nozzle approximately every 10 feet. On a predetermined schedule, on a digital control, we program this and it mists out this product for durations of 30 seconds, whatever we wet it for so many times a day,” Wilburn said.

The pyrethrum-based insecticide also controls flies, fleas, ticks and wasps.

An automated misting system is luxury for most households with a 20-nozzle system costing $1,900-$2,400 depending on the size of a lot and other factors, so Sprenger is proposing a pilot program that would recruit volunteers to trap mosquitoes.

Do-it-yourself project

All it takes to make a trap is an old dish pan, water, some blades of grass and black spray paint. Mix the grass blades with water and let it sit for a week, then pour the infusion into the black container and leave it out for about five days. Then dump the container and start over again.

“If you dump that water at the end of the five days, you will be destroying all the eggs and all the larvae that have hatched in the pan,” Sprenger said.

For another type of mosquito that can spread disease, the Asian tiger, simply switch out the dish pan with a black plastic cup.

However, people who make traps and don’t maintain them will end up breeding more mosquitoes. Sprenger plans to set up a registry for volunteers to monitor the program.

Samples are taken from mosquitoes and birds then tested to check for the presence of West Nile virus. The virus has not yet been detected this year, said Shelley Walker, a representative at the office of communications for the Tennessee Department of Health.

However, Sprenger said the virus will recur. Workers set traps for mosquitoes in 163 locations throughout the county and test them.

“From the beginning of June to the end of June, we have virus over most of the county,” he said. “By July, it’s virtually border to border. Most of the human cases occur in August and September.

“Since the house mosquitoes only come out at night, the best advice to people is if you are going to sit outdoors at the end of July, August or September, you really should wear repellant.”

It’s out there

The virus was detected earlier last year.

“We are about a month behind,” Sprenger said. “Last year, we found the virus on a collection on May 15. It’s not predictable when it is going to pop up. It hasn’t. I don’t know if that’s a factor of the cooler weather we’ve had.”

“Pest” mosquitoes, which bite during the day and lay their eggs adjacent to bodies of water, have not been identified as vectors for diseases, such as West Nile virus and encephalitis, Sprenger said.

He also advised that abandoned swimming pools do not present as much of a health concern for mosquito breeding as smaller containers.

“Swimming pools have gotten a lot of attention, and I really don’t know why,” he said. “It’s rare that we find mosquitoes in a swimming pool. Most of the time, people are complaining because of the algae.”

To file a complaint or volunteer, call the health department’s vector control division at 324-5547.

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