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Residents warned about West Nile virus The Charleston County Mosquito Control Division is responding to the threat posed by the West Nile virus (WNV), the agency said Aug. 2.   The S.C. Department of Environmental Control (DHEC) determined that mosquitoes in West Ashley, James Island and the in the city of Charleston peninsula; which would include the MUSC campus area; have tested positive for the virus.   Aiken, Charleston and Clarendon counties have the state’s first confirmed West Nile virus-positive mosquitoes this year, and York County has the first positive bird, DHEC reported July 31.   Charleston County Mosquito Control Division is helping to decrease the threat of the virus by: Treating catch basins in West Ashley, James Island and downtown Charleston for larval and adult mosquitoes. Catch basins are a significant source of the Southern House Mosquito, which is a major carrier of WNV. Increasing ground spraying for adult mosquitoes in West Ashley, James Island and downtown Charleston. Collecting mosquitoes from West Ashley, James Island, downtown Charleston, North Charleston and Mount Pleasant, and testing these insects for the presence of WNV. Other areas will be included if necessary. Monitoring the situation to determine when and where airplane spray missions will be required to reduce adult mosquito activity.   The public should take the following precautions to reduce their exposure to mosquitoes: Wear long sleeves and long pants when outdoors and use a repellent containing DEET, Picaridin or oil of lemon eucalyptus. Follow the label’s directions when using any repellent. Keep property clear of standing water where mosquitoes can breed. Stay inside during dawn and dusk hours when mosquitoes are most active. Keep screens on windows and doors in good repair. The public is requested to reduce mosquito breeding by doing the following: Flush birdbaths, potted saucers and other containers that hold water every three days because it can take as little as six days for mosquito eggs to hatch and become adults. Remove items from yard that hold water and are not needed outside such as wheel barrows, vehicle tires without rims, and tarps. Keep yard clean and cut to reduce areas where mosquitoes can hide. Fix leaky faucets. Keep gutters clean. Change pet water dishes regularly. Chlorinate swimming pools. Add fish to ponds. Chris Evans, Ph.D., entomologist with DHEC’s Bureau of Laboratories, said the public can help with WNV surveillance by submitting dead crows or blue jays to a local DHEC County Environmental Health office. Because dead birds may also indicate the presence of other diseases, do not touch a dead bird bare-handed. (For information about how to safely submit dead birds, go to http://www.DHEC.gov/health/envhlth/general_sanitation/bird_testing.htm.)   Each year, Charleston County Mosquito Control treats more than 90,000 acres by aircraft and 500,000 acres through ground spraying.   The week of June 24-30 was declared the Eighth Annual National Mosquito Control Awareness Week by the American Mosquito Control Association. In response, Charleston County staff distributed brochures at the five main county libraries, and at James Island County Park, Palmetto Islands County Park, and Wannamaker County Park. West Nile virus facts WNV was first isolated in 1937 from a human in the West Nile province of Uganda, Africa. Since then, WNVs have been reported from Africa, Europe, the Middle East, West and Central Asia, and, most recently, the United States and Canada. WNV was first found in the United States in New York City in September 1999.   West Nile infection was detected in mosquitoes, birds, horses, and a single human case in South Carolina for the first time during 2002.   The incubation period for the virus in humans (the time from infection to onset of disease symptoms) is usually three to 14 days. But most people who are infected with WNV will not have any type of illness.   An estimated 20 percent of the people who become infected will develop West Nile fever: mild symptoms, including fever, headache, and body aches, occasionally with a skin rash on the trunk of the body and swollen lymph glands. Symptoms of mild disease will generally last a few days.   Severe infection causes West Nile encephalitis (brain inflammation) or meningitis (inflammation of the membranes that surround the brain and spinal cord), and symptoms including headache, high fever, neck stiffness, stupor, disorientation, coma, tremors, convulsions, muscle weakness, and paralysis. Symptoms of severe disease may last several weeks, although effects on the nervous system might be permanent. An estimated one in 150 persons infected with the WNV will develop a more severe form of disease. Not infectious among humans, horses Clinical signs of WNV infection also have been observed in horses, even though most infected horses do not show symptoms.   Still, horses generally experience a 35-percent death rate from the virus. Like humans, virus levels in horses are generally too low to infect arthropod vectors like mosquitoes. For this reason, humans and horses are considered dead-end hosts incapable of continuing the virus transmission cycle. Birds, however, do experience virus levels capable of infecting mosquitoes, and they help to maintain the virus in nature.   Therefore, WNV exists primarily as an infection of birds, and it is transmitted from bird to bird by several species of mosquitoes. The principle route of human infection with WNV is through the bite of an infected mosquito. Mosquitoes become infected when they feed on infected birds, which may have the virus in their blood for a few days. The virus eventually finds its way into the mosquito’s salivary glands. When a mosquito bites, the virus may be injected into humans and animals where it can multiply and possibly cause illness. Mosquitoes are capable of transmitting the virus to another animal 10 to 14 days after feeding on an infected bird.   Of the many types of mosquitoes that can carry the virus, one of the main types is the Southern House Mosquito (Culex quinquefasciatus). This is the type that is prevelant in the Lowcountry. It breeds anywhere foul water (water with high organic content like marshes and wetlands) stands for more than a week, such as in rain barrels, tubs, catch basins, cesspools, ditches, ground pools, dairy drains, sewage lagoons, and other similar habitats. It bites at night and may enter homes. WNV also has been isolated from ticks, mites, and ked flies. Whether non-mosquito arthropods as potential human vectors is not known.   Song birds, shorebirds, owls, and hawks develop sufficient levels of virus to infect most feeding mosquitoes. Certain birds, including common grackles, various corvids (American crows, blue jays, magpies, and ravens), house finches, and house sparrows are highly infectious to mosquitoes. The corvids in North America are highly susceptible to infection and are thus useful as wild indicators for WNV surveillance. Infection is rarely fatal for several common bird species, including house sparrows, cardinals, catbirds, mourning doves, and rock doves. Bird species such as pigeons, woodpeckers, and ducks do not develop sufficient levels of virus to infect most feeding mosquitoes.   For information on Charleston County Mosquito Control activities, call 202-7880 or visit http://www.charlestoncounty.org.     Friday, Aug. 10, 2007 Catalyst Online is published weekly, updated as needed and improved from time to time by the MUSC Office of Public Relations for the faculty, employees and students of the Medical University of South Carolina. Catalyst Online editor, Kim Draughn, can be reached at 792-4107 or by email, catalyst@musc.edu. Editorial copy can be submitted to Catalyst Online and to The Catalyst in print by fax, 792-6723, or by email to catalyst@musc.edu. To place an ad in The Catalyst hardcopy, call Island Publications at 849-1778, ext. 201.