LAWRENCEVILLE - Of more than 800 standing water pools in Gwinnett, Newton and Rockdale counties, seven have tested positive for West Nile virus, said Sid Kirkpatrick, Gwinnett County Environmental Health Services.
September and October are the peak months for mosquito activity, said Don Crouch, West Nile supervisor.
"We have documented a rise in the number of mosquitoes at our trap sites and this may continue due to minimal amounts of rainfall," Crouch said in a written statement. "Excessive rainfall lowers the amount of adult mosquitoes as the mosquito eggs are washed out of their breeding sites."
The good news is that Gwinnett County and most of its cities are fighting the virus by dropping larvicide pellets and brickets in standing water. Sugar Hill workers began a spraying program in August, in addition to larvicide, that treats every city street with chlorpyrifos, a pesticide often found on pets' flea and tick collars.
Four pools were found in or near Lawrenceville, and one each in or around Grayson, Lilburn and Norcross.
Since 2001, Gwinnett County's Environmental Health Department has supplied about $100,000 worth of larvicide treatments per year to local municipalities at no charge.
Fighting West Nile
West Nile virus is not as potentially deadly as people had feared. It first appeared in the Western Hemisphere in 1999, then spread into all 48 continental states, Canada and Mexico.
Since then, more than 15,000 people have tested positive for the infection, but only 500 have died, according to the Centers for Disease Control and Prevention.
Symptoms include fever, headache, tiredness and body aches, possibly accompanied by a rash on the trunk of the body and swollen lymph glands. For most of those sufferers, symptoms last a few days to a few weeks while the body heals itself of the virus. Less than 1 percent of those infected, mostly elderly people and those with lowered immune systems, develop serious illnesses such as West Nile encephalitis or West Nile poliomyelitis.
Environmental workers monitor 44 mosquito traps throughout Gwinnett, Newton and Rockdale counties from April until November, the mosquitoes' most active season.
"They don't fly in the winter like they do in the summertime, but they winter over," Kirkpatrick said.
Larvicide treatments begin in the early spring. Workers drop pellets or larger briquettes down street drains and into retention ponds.
"We go to any standing water, creek, birdbath, clogged gutters, anything we can find and we treat those with larvicide," Kirkpatrick said. "We notify the people at that address that we are treating and try to educate them about standing water. If you have a bottlecap full of water, mosquitoes will eventually breed in it."
West Nile virus showed up in dead birds in Georgia in 2001. The Environmental Health Division of Gwinnett County's Board of Health created a program at that time to collect and monitor data.
"Initially, our program was to pick up dead and sick birds," Kirkpatrick said. "The phone calls were incessant, about 1,200 to 1,500 phone calls during the first summer. In 2003 we started the mosquito-trapping program. A bird can fly 50 miles from where it got infected to where it fell dead. Mosquitoes give us a better location because they don't travel a far distance."
The Culex mosquito species is the predominant West Nile carrier in this area. The mosquito's life span is about two weeks, Kirkpatrick said.
Sugar Hill officials this summer invested $7,500 in a spray machine that allows them to spray every city street with chlorpyrifos.
The machine will pay for itself in savings in less than two years, after which Sugar Hill will spend about $2,500 per year for the pesticide, City Manager Bob Hail said. Workers sprayed the first week of August and the first two weeks of September - the mosquitoes' breeding season.
Eggs mature in October. Sugar Hill remains the only city in Gwinnett County that sprays in addition to using larvicide pellets and brickets.
"I'm all for it," said Jeanne Ferguson, local resident. "Anything they can do to fight the mosquitoes is fine with me."
Two residents who endure chemical sensitivities spoke against the spraying program when it was discussed in a recent City Council meeting.
Humans who breathe or ingest chlorpyrifos may experience a variety of reactions, such as headaches, blurred vision, nausea, diarrhea and increased salivation, depending on the dose and length of exposure, according to the Agency for Toxic Substances and Disease Registry, a division of the U. S. Department of Health and Human Services.
Chlorpyrifos is mixed with oil and clings tightly to soil particles. It mixes poorly with water, so it rarely enters local water systems, and breaks down with exposure to sunlight and bacteria.
Lilburn city workers use the larvicide briquettes supplied by the Environmental Health Division of Gwinnett County's Board of Health.
"We put them near drainage areas, in ponds and places where kids and pets can't get to them," said Marsha Hendrix, assistant to Lilburn's city manager. "We haven't considered spraying because we went along with what the environmental people said, feeling like they are the experts on the matter."
Kirkpatrick said the question of whether to spray comes up in meetings quite often.
"There's a big debate as to how effective they are compared to problems they could cause in the community," Kirkpatrick said. "Gwinnett does not spray and there are varying opinions. Larvicide brickets are effective, they're good for 150 days and have no side effects. We've used it in fish ponds, bird baths, anyplace with no ill effects to anything except mosquito larvae."
The best protection against mosquitoes is to wear long sleeves and use a mosquito repellent containing a high concentration of DEET. Pet water should be changed daily, Kirkpatrick said.