Overview of West Nile Virus (WNV)
West Nile encephalitis, a mosquito-transmitted disease, was first documented in North America during the summer of 1999, when an outbreak occurred in New York City. Since that time, cases of West Nile virus (WNV) infection have been confirmed in northeastern, north central, and southern regions of the United States, and the virus is expected to spread throughout North America. As of December, 2001, there were 149 confirmed human cases of WNV, including 18 fatalities in the United States.
Of 738 cases of clinical WNV infection reported in horses (from 130 counties in 20 states), 651 cases were verified through diagnostic testing at the National Veterinary Services Laboratories of the U.S. Department of Agriculture–Animal and Plant Health Inspection Service, and 156 horses have died or were euthanized. An equine vaccine is available in some states through licensed veterinarians.
The strain of WNV circulating in the United States causes significant mortality in exotic and native bird species, especially in the American crow (Corvus brachyrhynchos). Dead birds serve as an early warning that the virus may be active in your area, report these to your local health department.
Origin of WNV
WNV was first isolated in 1937 in the West Nile province of Uganda, Africa, and can adversely affect humans, birds, and other animals in Africa, Eastern Europe, western Asia, and the Middle East. Epidemics have occurred in Africa, Europe, and the Middle East, most recently in Israel during 2000.
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.
Symptoms of West Nile Encephalitis
Fever
Headache
Body aches
Swollen lymph glands
Body rash
Most humans infected with WNV have no symptoms.
Encephalitis develops in less than 1 percent 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.
Mosquito Prevention and Control - WHAT YOU CAN DO
OTHER RESOURCES & LINKS:
The American Mosquito Control Association (AMCA) has published their position on mosquito traps and this can be viewed at: mosquito.org
For more information about WNV and mosquito control recommendations visit the Center for Disease Control Web Site at www.cdc.gov/ncidod/dvbid/westnile/index.htm
North Dakota Department of Health – www.health.state.nd.us/disease/arbovirus
North Dakota Department of Agriculture – www.agdepartment.com
USDA Animal and Plant Inspection Service – www.aphis.usda.gov/oa/wnv
USGS West Nile Virus Maps - http://cindi.usgs.gov/hazard/event/west_nile/west_nile.html
Works Cited: http://www.cdc.gov/ncidod/dvbid/westnile/qa/overview.htm
JUST FOR FUN:
http://www.mosquitoweb.nl/ |
