Cities take offensive on mosquito eradication

By Thomas Wilson
STAR STAFF
twilson@starhq.com

   A dry summer means fewer mosquitos to harass gardeners, hikers and outdoors enthusiasts.
   "There hasn't been a lot of complaints about mosquitos this year since we've had such dry weather," said Mike Potter, who is charged with eradicating mosquitos for the city of Elizabethton Department of Public Works. "The more rain you have the more mosquito problems you have."
   That's good news for East Tennessee residents, considering the fatalities occurring in Louisiana linked to the West Nile virus (WNV) -- one of several mosquito-borne viruses in the United States that can infect humans.
   Five people in Louisiana have died this summer after contracting West Nile, a virus that can cause flu-like symptoms and a potentially fatal swelling of the brain. Most victims have been older people or those with weak immune systems.
   The virus exists in nature primarily through a transmission cycle involving mosquitoes and birds. Mosquitoes become infected with WNV when they feed on infected birds, according to local and state health officials.
   "We are testing the blue jays and crows," said Kathy Bowman, a registered nurse with the Carter County Health Department.
   Bowman said citizens who found dead birds or crows could bring the carcass to the health department where it would be sent to the state health department lab in Knoxville for testing.
   She urged citizens not to handle a dead bird with bare hands. Use rubber gloves or a plastic bag when grasping the animal.
   One of the riskiest mosquitos in Northeast Tennessee is an exotic species called the Asian tiger, according to a local city official charged with eradicating mosquitos.
   "It's habit is different than other species," explained Bill Potter, general supervisor of the Street Department for the city of Johnson City. "After it hatches into the adult stage, it's tendency is to harbor in grass and shrubbery like a flea."
   The Asian tiger is a small black mosquito very quick of flight, and extremely aggressive. Distinct striping on their hind legs corroborate their names.
   Bill Potter, who oversees Johnson City's mosquito eradication program, said the Asian tiger was a "container breeder" that could lay eggs in very small amounts of standing water -- a characteristic that made the species very difficult to control.
   "If the container -- a bottle cap to a swimming pool -- is not emptied or cleaned out within three days, a mosquito can lay her eggs in it and they will hatch in six days," he said. "I've found them in as small as a bottle cap or a Styrofoam cup. I've found them in garbage cans and wheelbarrows that are not turned over."
   According to the Tennessee Department of Health's (TDOH) Web site information of 2002 testing results, 102 birds have tested positive for the West Nile virus. One horse out of 45 horses tested also was found positive for the virus, according to the TDOH.
   Since the 1930s, West Nile virus has been commonly reported to cause asymptotic infection and fevers in humans in Africa, West Asia and the Middle East, according to the U.S. Geological Survey.
   In 1999 and 2000, 83 human cases of West Nile illness including encephalitis (inflammation of the brain) were reported in the New York City area. Nine of those infected with the virus died.
   Bill Potter said scientists at the University of Tennessee at Knoxville were trying to do tests to determine whether the Asian tiger was a carrier of the West Nile virus. He added that Johnson City used an ultra-low volume cold aerosol generator or ULV to disperse an insecticide called Permethrin, which is derived from the chrysanthemum plant.
   "The Asian tiger is very firmly planted in all our areas of Tennessee right now," said Bill Potter. "It is by far the worst one we've seen. It poses the biggest health risk to the general public."
   Both Potters said their cities usually conducted the mosquito spraying program in mid- or late May and until mid-October. Both also said one of the worst breeding areas for mosquitos was in old tires and junked automobiles.
   "Most people can help by emptying any water containers around their house such as cans, flowers pots and old tires in their back yard," said Mike Potter. "They need to get rid of those."