• By Lynne Mitchell
• Posted Monday, July 25, 2011

First N.C. Case of La Crosse Encephalitis

On July 22nd, State public health officials announced the season’s first case of the mosquito-borne illness La Crosse viral encephalitis (LAC). The patient – a child from Macon County – is recovering.

“This case is an important reminder that we all need to take precautions to prevent mosquito bites,” State Epidemiologist Megan Davies said. “In addition to La Crosse, mosquitoes may carry other viruses such as those causing eastern equine encephalitis, West Nile virus infection and other diseases.”

You can protect yourself against mosquito-borne illness in a number of ways:

• Use repellent: When outdoors, use insect repellent containing DEET, picaridin, IR3535 or oil of lemon eucalyptus on exposed skin as well as on clothing (mosquitoes will bite through thin cloth). Remember always to follow the manufacturer’s recommendations.
  - Permethrin is a repellent/insecticide that can be applied to clothing and will provide excellent protection through multiple washes. You can treat clothing yourself or purchase pre-treated clothing. For best protection it is still necessary to apply other repellent to exposed skin.
• Wear protective clothing: Wear long sleeves, pants and socks when weather permits.
• Avoid peak biting hours: Avoid outdoor activity or use protective measures when mosquitoes are active, typically from dawn until dusk.
• Install and repair screens: Have secure, intact screens on windows and doors to keep mosquitoes out.
• Eliminate breeding areas from your home and yard: Mosquitoes can lay eggs even in small amounts of standing water. Fill tree holes in/around your yard with soil and empty standing water from flower pots, buckets, barrels, children’s wading pools and tires. Drill holes in tire swings so water drains out. Change the water in pet dishes and replace the water in bird baths weekly.

La Crosse viral infection symptoms occur from a few days to a couple of weeks after being bitten. Symptoms include fever, headache, nausea and vomiting. In more severe cases, convulsions, tremors and coma can occur. Children under 16 years of age and the elderly are the most susceptible to the disease.

While other mosquito-borne diseases like West Nile virus infection are found across the state, LaCrosse encephalitis is largely confined to western North Carolina and is the state’s most common mosquito-borne disease. Most cases in North Carolina are recorded in late summer and early fall. State officials recorded 21 LAC cases in 2010. The U.S. Centers for Disease Control and Prevention records about 70 cases each year. The disease is rarely fatal, but a Swain County child died as a result of infection in 2009.

There is no vaccine against La Crosse encephalitis virus (LACV), so reducing exposure to mosquito bites is the best defense against getting infected with LACV or other mosquito-borne viruses. For additional information regarding mosquitoes and ticks, visit the N.C. Public Health website. For more information on insect repellent use in children, see the Healthy Children website. For specific information on the use of DEET on children see the American Academy of Pediatrics.