Fort Worth officials will begin ground-level spraying of insecticide to attack mosquitoes for the first time since the 1990s as the city steps up efforts to deal with the spread of West Nile virus.
The move comes as officials in Dallas County get set to begin aerial spraying, perhaps as early as Thursday.
But Tarrant County Public Health officials said they have no plans for aerial spraying. They continue to urge residents to use insect repellent.
As of Tuesday, 171 people in Tarrant County have been infected with West Nile virus and two have died.
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In Dallas County, 10 people have died and 207 have been sickened.
Fort Worth has not done any targeted spraying this year, which has been characterized as the worst for West Nile since the disease migrated to the United States in 1999, according to Brandon Bennett, the city's code compliance director.
The city decided to begin spraying in certain neighborhoods because of the growing number of cases in more locations, Bennett said.
Mosquito activity appears to have increased from dawn to dusk and at dawn during days when temperatures are highest, Bennett said.
Fort Worth residents received calls via the city's emergency notification system warning them to continue using personal protection methods to avoid being infected, Bennett said.
"Even if we drained all the breeding areas, there would still be adult mosquitoes flying around carrying the virus," Bennett said. "We're finding multiple cases near susceptible populations. And school will be starting in a couple of weeks and we wanted to be sensitive to that also."
Decisions on where to spray could be made late today or early Thursday based on an analysis of mosquito pools, Bennett said. Once the city decides, it will begin notifying residents in and near those areas.
Officials will try to identify residents with respiratory or other conditions that might be sensitive to the insecticide, Bennett said. Other cities in Tarrant County doing ground-level spraying include Benbrook, Euless, Grand Prairie, Hurst, North Richland Hills and Westover Hills.
Officials with Tarrant County Public Health have identified 48 human cases of West Nile infection in Fort Worth.
The virus killed an individual in his 80s who lived in the 76131 ZIP code in far north Fort Worth, west of Park Glen but east of North Saginaw Boulevard. The other Tarrant County resident who died was a woman in her 60s who had underlying health conditions.
The virus causes two forms of illness. The milder West Nile fever has flu-like symptoms such as headache, fatigue and body aches with possible rashes or swollen lymph nodes.
The more serious illnesses are neuroinvasive infections, including meningitis and encephalitis. Those symptoms include disorientation, stupor, tremors, convulsions and muscle weakness. Young children, the elderly and people with compromised immune systems are the most vulnerable.
Lou Brewer, Tarrant County's public health director, said both deaths in Tarrant County have been from the neuroinvasive form and occurred in people with underlying conditions.
"Two-thirds of our cases are fever instead of neuroinvasive," Brewer said.
A presentation to Tarrant County commissioners Tuesday showed that up to 73 percent of residents infected with the virus in Tarrant County never used insect repellent while outdoors and that 16 percent used insect repellent only one-quarter to one-half of the time.
About 11 percent of those infected used insect repellent three-quarters of the time or always, the documents showed.
The figures were culled from epidemiological surveys of the infected in Tarrant County, according to a public health official.
Those who became sick were most often gardening or engaging in recreational water activities, such as fishing, boating or attending a pool party, according to officials with Tarrant County Public Health.
Mitch Mitchell, 817-390-7752