Mosquitoes aplenty this July Fourth bring disease concerns for North Florida

July 1, 2009

GAINESVILLE, Fla. — Recent weeks of heavy rain have left conditions statewide ripe for a Fourth of July rife with mosquitoes. For some North Florida areas, however, the pests are more than a holiday annoyance — they bring the threat of the eastern equine encephalitis virus, known as EEEV.

“This year doesn’t look like it’s going to be tremendously unusual in terms of overall cases of mosquito-borne diseases,” said Jonathan Day, a professor of medical entomology with the University of Florida’s Institute of Food and Agricultural Sciences. “But transmission of [EEEV] tends to be very focal, and there are some areas that are looking risky.”

EEEV is best known for being deadly in horses, but humans can contract the virus as well.

According to the national Centers for Disease Control and Prevention, the virus can cause a severe infection of the central nervous system in humans, and is fatal for nearly a third of those afflicted.

So far this year, 26 horses have been found to be infected in North Florida, with five more in the state’s Panhandle.

These cases, along with analysis of weather conditions and other indicators, have led UF entomologists to believe that a band of counties beginning at Volusia County and stretching northwest into the Florida Panhandle carry a moderate to high risk of mosquitoes carrying the virus.

For an up-to-date risk map, please visit http://eis.ifas.ufl.edu/eis1.htm.

“July is usually the peak for EEEV transmission,” said Roxanne Connelly, an IFAS professor of medical entomology. “We’ve had the type of weather patterns that can make the problem worse in some areas.”

The disease is spread via mosquitoes that have fed on birds. Humans and horses cannot spread the virus to other humans and horses.

Connelly advises that people in risk areas avoid being outside during peak feeding times for mosquitoes that carry the disease — calm, humid periods from dusk to dawn.

If you are outside during these times, you should cover as much skin as possible. Bare skin should be treated with a repellent that carries DEET or Picaridin.

“There are all sorts of traps and tools out there like bug lights and citronella candles,” Connelly said. “None of them keeps mosquitoes from biting you — only a repellent applied directly on your body can do that.”

Pet birds should be kept inside and, while it is very rare for dogs and cats to contract EEEV, Connelly suggests being aware that pets aren’t immune to pesky mosquito bites.

Spraying dogs and cats with repellents labeled for use on humans can be dangerous because they can lick the repellent while grooming. There are products made for dogs that do not contain DEET, but make sure to read and follow the directions.

Pets are best kept inside away from mosquitoes during peak feeding times. And, any dog that is at risk of being bitten should be on a monthly heartworm prevention treatment. Prevention treatments formulated for cats are also available.