[Mosquito Control Supplement] Dengue in Florida: An Update

Clean-up efforts around the home can prevent spread of mosquito-borne ‘break-bone’ fever. Many Key West Floridians unknowingly create a ripe breeding ground in their own backyards and homes for dengue-infected mosquitoes: containers left outside that collect water. Indoors, even refrigerator drain pans coated with condensation are culprits.
“People who live in the Key West area leave their doors and windows open to let in the sea breeze, so mosquitoes are free to go inside the home,” says Roxanne Connelly, Ph.D., associate professor and extension medical entomology specialist at UF/IFAS/FMEL in Vero Beach, Fla.

Sixty-three cases were reported in Key West in 2010, up from 20-some cases in 2009, Connelly says. “Dengue is more abundant in Key West than anywhere else—it’s pretty rare in other parts of Florida,” she says. But there is not enough information about the mosquito carrying that disease or whether the disease was “local.”

In Key West, dengue is generally home-grown, meaning reported cases are not people who traveled to tropical countries where the viral disease is sometimes experienced in pandemic proportions. No one can say yet whether Key West will see even more cases of dengue in 2011. There are currently four strains of mosquitoes that cause dengue. The strain in Key West is referenced as “strain 1,” Connelly says. “This is going to be one of those test years,” she says. “In general, we feel like [dengue] is not over and we’ll see more cases coming out of the Keys. But now, we don’t have indications from the two years we’ve seen cases that it’s going to spread [beyond the Keys].”

The Aedes aegypti vector is not prevalent in other areas of Florida. And the mosquito vector common to the entire state and southern U.S. — Aedes albopictus, or the Asian tiger mosquito — has not presented in Key West cases.

The good news: Preventing dengue fever simply involves adopting a few habits around the home, and education is a pest management professional’s greatest tool, Connelly emphasizes. “Where PMPs can be very helpful is by communicating the importance of getting rid of those containers of water and cleaning up around the home,” she says.

What’s interesting about the Key West dengue strain is that the mosquito actually prefers to live indoors, so PMPs need preventive strategies beyond using insecticide, which can be applied to outdoor areas, such as on shrubs and around homes.

Connelly recommends a good old-fashioned yard cleanup that includes dumping out and securing containers that collect water; treating ponds, rain barrel systems and other outdoor water sources with larvicide to prevent mosquito larvae; and cleaning out gutters bogged with leaves. “These can collect water and you can have larvae on the roof,” Connelly says.

Additionally, PMPs should advise homeowners to repair window and door screens that welcome mosquitoes into the house. Not all mosquitoes carry dengue, but everyone who lives in a southern climate should take steps to avoid attracting mosquitoes, including wearing repellent.

For more information on dengue fever in Florida, visit http://entnemdept.ifas.ufl.edu/pestalert/arbovirus/arbovirus.htm.

— Kristen Hampshire