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West Nile virus (WNV) first was detected in the United States in New York City, in 1999. In the years 2000 and 2001, WNV spread to 27 eastern and midwestern states. Many experts predict that WNV eventually will spread to all 48 states in the continental US, with the possibility that WNV may reach Wyoming in the summer of 2002.
WNV is transmitted by mosquitoes, and is maintained in a bird-mosquito cycle. Mosquitoes are infected by taking a blood meal from infected birds, and then can transmit the virus to humans, horses, and other animals. Many species of birds are susceptible to infection with WNV, with corvid species (crows, ravens, magpies, jays, and their relatives) serving as useful sentinels of WNV activity. Killing birds is not an effective means of controlling WNV.
West Nile virus infection can cause serious illness (encephalitis or inflammation of the brain) and death in humans, particularly the elderly, but the vast majority of people exposed to WNV develop inapparent infections or flu-like illness. WNV is not transmitted from person to person. Measures that reduce contact with mosquitoes are helpful in preventing human infections.
Horses may be infected with WNV, also resulting in serious illness (encephalitis) and death. The mortality rate following WNV infection in horses is variable, but again, most horses probably develop inapparent infections and survive. The virus is not transmitted from horse to horse or from horses to humans. A WNV vaccine is available for horses and horse owners should contact their veterinarians about use of this product.
In June of 2002, the state of Wyoming will institute a WNV Surveillance and Response plan to determine the distribution of the virus and to assist state and local agencies in reducing the impact of this disease on humans and horses. Questions about WNV should be directed to the following agencies involved in this program:
Bird/horse mortalities, Bird/horse testing, General WNV questions: Wyoming State Veterinary Laboratory
Terry Creekmore/Dr. Todd Cornish (307) 742-6638
Animal health regulatory questions:
Wyoming Livestock Board/State Veterinarian
Dr. Jim Logan (307) 777-6443;
and United States Department of Agriculture, APHIS, VS
Dr. Bret Combs (307) 772-2186
Human health and human testing:
Wyoming Department of Health
Dr. Karl Musgrave (307) 777-7172, (888) 996-9104
Wyoming Game and Fish Department
Dr. Walt Cook (307) 742-6638