Fall still prime mosquito, West Nile virus season

By for CAES News

By Elmer Gray
University of Georgia

In football season, most folks don't think much about mosquitoes. But they should. They're still active, and it's important to remain vigilant against them and the West Nile virus they can carry.

Many mosquito species have tested positive for West Nile virus nationwide. But the primary carrier in Georgia is the southern house mosquito (Culex quinquefasciatus).

This species prefers to breed in polluted water and the storm drain systems of towns and cities. The recent drying trend makes conditions ideal for this species.

Many entomologists believe the heavy rains of earlier this summer helped to suppress this species by regularly flushing the storm drain systems.

Empty all water containers

Fortunately for Georgians, the Asian tiger mosquito, which is very common in many neighborhoods, hasn't proven a significant vector of West Nile virus.

This mosquito prefers to breed in containers (buckets, tires, pet dishes and anything else that will hold a little water). It can best be controlled if homeowners are vigilant about emptying anything that can hold water around their homes.

Coastal areas typically have a greater variety of mosquitoes than upstate areas because there are more places with standing water. But even in these areas, the southern house mosquito is still the primary vector of West Nile virus.

Bumper crop of bugs

Heavy early-summer rains produced a bumper crop of mosquitoes in the low-lying swamp areas so common in south Georgia.

These higher-than-usual populations of Culiseta melanura, the primary carrier of eastern equine encephalitis, produced an outbreak of this disease that hadn't been seen in several years.

Eastern equine encephalitis is much more deadly than West Nile virus with a case fatality rate near 50 percent as opposed to West Nile virus's 3 percent to 15 percent.

To date, Georgia has had two human cases of EEE, one of which was fatal, and 14 cases of West Nile virus, one of which was fatal.

Both of these diseases can cause encephalitis, an inflammation of the brain. Even if encephalitis isn't fatal, it can have long- lasting health implications.

Horses are also affected by both diseases, with 71 cases of EEE and 16 cases of WNV in horses in Georgia this year.

Beat the bite

The best way to prevent any mosquito-borne diseases is to prevent bites. Avoid areas of intense mosquito activity if you can. Wear loose-fitting, long-sleeved shirts and pants. And use insect repellent containing DEET.

With the opening of hunting season, hunters should be vigilant when spending extended times in mosquito-infested areas.

Enlist neighbors in the fight

Homeowners, particularly those living in neighborhoods, often face nuisance mosquito populations despite their best efforts to prevent mosquito breeding.

Most mosquitoes can easily fly a quarter-mile. So it takes only a few negligent people for an entire neighborhood to be infested. Communication and education are the best tools in these situations.

Make property less attractive to mosquitoes by trimming grass and plants as short as possible around your home. Mosquitoes like dense vegetation to rest in during the heat of the day and to break wind currents. So the more open your property is, the less suitable it is for mosquitoes.

Adult mosquitoes often prefer to rest in low-lying areas, which have slightly higher humidity level and denser vegetation, during the heat of the day.

Like other insects, mosquitoes typically survive longer if it's more humid. The cooler days of early fall also extend their lives, since they don't dry out as fast. However, they do develop slower when it's cooler outside.

The bottom line: stay vigilant a little longer. Avoid as many mosquito bites as possible, and eliminate any standing water around your home and neighborhood. Soon the leaves will be turning and mosquitoes will be a distant memory.

Elmer Gray is a Cooperative Extension entomologist with the University of Georgia College of Agricultural and Environmental Sciences.