Learning experience: Valdosta’s unique surveillance program is helping gather valuable information on mosquitoes that carry West Nile Virus, as well as a host of other dangerous conditions, says Mayor John Fretti
When the first documented case of the dangerous West Nile Virus in Georgia was discovered in a dead crow found near Valdosta during the summer of 2001, locals became far more serious about keeping track of mosquitoes, the carriers of the virus.
Since then, aided by biologists at Valdosta State University (VSU) and researchers at the South Georgia Rural Development Center (RDC), the city has launched the Geographic Information Systems Mosquito Surveil-lance Program (GIS) – the first of its kind in Georgia.
The GIS uses mosquito traps to snare the pesky biters so they can be tested for diseases such as West Nile Virus, Eastern Equine Encephalitis, and even malaria and yellow fever. “This partnership with VSU and the RDC has given us a great system for finding these viruses and protecting our citizens,” says John Whitehead, director of Valdosta’s Public Works Department. “We don’t have the resources and manpower to do this on our own, so the ability to use existing resources is important. And, by zeroing in on real threats, we put out chemicals only in specific areas and only at specific targets.”
That’s a big step away from the old practice of blanket spraying entire neighborhoods, Whitehead says. And Valdosta’s efforts to control the West Nile Virus have generated more than health benefits. By carefully focusing mosquito eradication practices on specific areas, the city reduces fuel and chemical costs, as well as labor expenses.
“Yes, we save money in the concentration of techniques in those areas where we have found mosquitoes that could pose a serious threat,” says Valdosta Mayor John Fretti, whose enthusiasm for GIS is well grounded – he holds a biology degree from VSU. “But my excitement is about the biology of it; the statistics of it and the protection of the citizens.”
To get the needed statistics, the mosquitoes must first be captured for lab testing. Under the GIS program, mosquito traps are set out in 25 locations around the city and even in outlying county sites, with particular interest given to populated areas such as those surrounding playgrounds, schools and nursing homes. The traps are watched most vigilantly during the high risk summer months.
“We have about 30 varieties of mosquitoes in the Valdosta area,” Whitehead says. “And there are four or five that are particularly aggressive and pose the most dangerous threat of being known carriers of diseases such as West Nile and Equine Encephalitis.”
Catching the most threatening mosquitoes is fairly easy. Traps are baited with rising plumes of carbon dioxide, just like that given off by all living animals, such as livestock and humans. The CO2 is an irresistible lure to a female mosquito looking to fill up on blood before depositing her eggs. Upon entering the trap for a meal, the mosquito is blown into a collection area by a fan.
When some two dozen mosquitoes have been trapped, they are removed, flash-frozen, placed in a vial on a bed of dry ice, and shipped to a lab at the University of Georgia School of Veterinary Medicine. Test results are sent to Valdosta officials and the Centers for Disease Control and Prevention.
When another case of West Nile was discovered in Valdosta in the fall of 2005, city workers quickly identified the source of the danger and responded with a controlled spraying program. “We were fast in detection and fast in response,” Whitehead says. “And that minimized the risk to humans and domestic animals in the surrounding neighborhood.”
No further evidence of West Nile Virus was discovered in 2006, giving proof of the effectiveness of the GIS, Whitehead says.
“In ’01, ’02 and ’03 we were very concerned about [West Nile Virus], and still are,” says mayor/ scientist Fretti. “As you look at the data over a period of four or five years, trends will start to emerge. During the hurricanes of ’05, we had 45- and 50-miles-per-hour winds, and do you know we captured two mosquitoes with the West Nile during those high wind times? Here’s my point: Trends start to emerge; trends of migration, trends of optimum conditions that we can share with the rest of country in the behavior of mosquitoes that carry West Nile Virus.”
Discoveries of mosquitoes carrying the virus are reported, but rarely generate much public notice. Concern rises when the virus is detected in an animal. “We have identified more mosquitoes that have carried West Nile than have been cases of it in horses, birds or people,” Mayor Fretti says. “I think we have prevented [animal infections] by these early captures of the mosquitoes.”
Public Works director Whitehead has a less scientific observation from an anonymous source that his fellow Valdostans can fully appreciate. “God did not create anything without a purpose,” he says. “But the mosquito comes pretty close.”