July 11, 2008

As we move into mid to late summer, be alert to potential mosquito breeding grounds to reduce the risk of West Nile Virus. The following information from the USDA National Pest Alert: West Nile Virus in North America offers information on the virus and its symptoms, how it's transmitted and how to control the mosquitoes that carry it from birds to humans, horses and other animals. West Nile encephalitis was first documented in North America during the summer of 1999 but now can be found throughout much of the U.S.

Virus Transmission

WNV is transmitted by infected mosquitoes, primarily Culex, Aedes, and Ochlerotatus spp. C. pipiens, the northern house mosquito, is a common household mosquito and the primary vector of WNV. Mosquitoes become infected after biting infected wild birds that serve as the primary host of the virus. The virus undergoes a reproductive cycle inside the mosquito, in which it must pass through the midgut wall, multiply in many tissues, and accumulate in the salivary glands of the mosquito. Mosquitoes salivate every time they bite, and they are capable of transmitting the virus 10 to 14 days after feeding on an infected bird, so bites after that time are infectious.

Mosquito Prevention and Control

Homeowners can most effectively reduce the number of mosquitoes around their homes and neighborhoods by eliminating the standing water where mosquitoes grow and breed.

• Dispose of any refuse that can hold water, such as tin cans, containers, and in particular, used tires. Tires have become the most important mosquito-breeding sites in the country. Drill holes in the bottoms of recycling containers and check uncovered junk piles.
• Clean clogged roof gutters every year, and check storm drains, leaky outdoor faucets, and window wells.
• Empty accumulated water from wheelbarrows, boats, cargo trailers, pet dishes, toys, and ceramic pots. If possible, turn these items over when not in use.
• Do not allow water to stagnate in birdbaths, ornamental pools, water gardens, and swimming pools or their covers. Ornamental pools can be aerated orstocked with fish.
• Swimming pools should be cleaned and chlorinated when not in use.
• Alter the landscape of your property to eliminate standing water.
• Keep in mind that during warm weather, mosquitoes can breed in any puddle of water.
• Larvicides are highly effective in controlling immature mosquitoes and should be considered when standing water cannot be eliminated.

Protect Yourself from Bites

Even though your property may lack mosquito-breeding sites,mosquitoes can travel 2 to 3 miles from their breeding site in searchof a blood meal. Therefore, it may be necessary to supplement larvalcontrol with other control measures directed at adult mosquitoes.

The following tips can help to reduce your risk of being bitten by a mosquito: 

• Make sure window and door screens are "bug tight."
• Use the proper type of light outside: incandescent lights attractmosquitoes, whereas fluorescent lights neither attract nor repelmosquitoes.
• Stay indoors at dawn, dusk, and in the early evening whenmosquitoes are most active. If you must go outdoors, wear along-sleeved shirt and long pants.
• Insect repellents when applied (sparingly) to exposed skin determosquitoes from biting. Spray thin clothing with repellentbecause mosquitoes can bite through thin clothing. TheAmerican Academy of Pediatrics recommends that repellentsused on children contain no more than 10% DEET, theactive ingredient in mosquito repellents. Be sure to follow alldirections on product labels.

Symptoms of West Nile Encephalitis

Most humans infected with WNV have no symptoms. A small percentage of individuals infected develop mild symptoms that include fever, headaches, body aches, swollen lymph glands, and a body rash. Encephalitis develops in less than 1% of infected people, with severe symptoms that include headache, high fever, neck stiffness, disorientation, tremors, convulsions, paralysis, and coma. If you experience these symptoms, contact a physician or hospital immediately. Occasionally, death can occur. The elderly are most at risk of death due to encephalitis.

The U.S. Geological Survey and the Centers for Disease Control andPrevention are tracking the distribution of the virus in birds,mosquitoes, humans, and other animals.