With the West Nile virus present in Alachua County

Staff are struggling to determine how best to control the mosquitoes carrying it.

The Alachua County Health Department has seen far higher numbers of culex nigripalpus mosquitoes West Nile's primary carrier this year than in the past five, said health department administrator Paul Myers.

With several flocks of sentinel chickens and a horse testing positive for West Nile virus, the county was placed under a mosquito-borne illness advisory on Sept. 27. The virus was discovered in the area on Sept. 20.

The county also has found non-human cases of eastern equine encephalitis, which is transmitted to people less than West Nile virus but is more lethal.

If virus transmission intensifies or human cases are recorded, the county will be given alert status, Myers said at a Tuesday County Commission meeting.

The county health department's surveillance system for mosquito-borne illnesses includes regular testing of sentinel chickens, which are often the first to show the presence of such diseases.

Myers said the county must reduce its mosquito population, which bloomed after Tropical Storm Debby this summer.

"From Pensacola all the way to Jacksonville, they continue to see human cases, and it's not going to be a surprise to me if we see them in Alachua County," he said.

But culex nigripalpus mosquitoes are tricky to eliminate.

They breed in standing water, from retention ponds to empty flower pots.

Spraying can have mixed results because even at peak flight times like dusk, up to 80 percent of the adult females that bite humans are resting and thus not susceptible to spray, Myers said.

In humans, West Nile virus can cause West Nile fever, which causes flu-like symptoms that can last months and may induce depression, Myers said.

But the biggest danger is West Nile virus neuroinvasive disease, which can cause severe, irreparable neurological damage or even death. People over 50 years old or who have underlying health problems are most at risk.

No human cases have been detected in the county yet, and the last reported human case in the county was in 2003.

The virus incubates for two to 14 days in humans, so people could soon show symptoms.

"I'm not trying to be Chicken Little here, an alarmist, but the potential is there," Myers told commissioners.

But the cost of spraying and uncertainty of its effectiveness made commissioners hesitant to authorize it at Tuesday's meeting.

It would cost $33,000 to spray four key county zones with the highest observed numbers of culex nigripalpus mosquitoes, Myers said. These zones are the city of Waldo, the city of Hawthorne and the northwest and southwest urban fringes of Gainesville.

It would need to be done from trucks because the areas are too small for aerial spraying to be effective, he said. The zones would likely need to be sprayed more than once.

The health risks of spraying are theoretical, while the risk of mosquito-borne diseases are documented and should be weighed more heavily, he said.

Commissioner Mike Byerly questioned whether funding is better used on spraying than, for example, the FluMist immunization program.

The mosquito population could be more of a nuisance issue than a public health one, he said.

Myers said he would give an emergency situation like the presence of West Nile virus higher priority.

This fiscal year's county budget does not provide funding for mosquito spraying. Myers suggested at the meeting looking for sustainable funding alternatives, but said in a later interview that such options are scarce.

The city of Gainesville's mosquito control program does spraying to control adult populations and uses mosquitofish and bacteria to manage larvae numbers, according to its website. It inspects more than 350 breeding sites monthly.

For now, the county will continue its current mosquito plan, which includes surveillance, larvaciding mosquito eggs in the county's 200-plus retention basins, and public education.

The county has warned doctors to watch for potential West Nile virus cases in patients.

Byerly suggested the county focus on public education instead of spraying.

People can best prevent the transmission of West Nile virus by taking personal precautions, such as staying inside at dusk, Myers said.

By Morgan Watkins