Sunday, April 20, 2003
Copyright © Las Vegas Review-Journal

Nevada game officials on the lookout for West Nile Virus

Just as the Exotic Newcastle Disease outbreak has eased in southern Nevada, health officials are bracing for another bird-related disease, West Nile Virus. Nevada is one of just four states that have not reported the virus, and some officials believe the state may identify its first case this spring or summer.

While Newcastle is an extremely contagious and fatal disease affecting all species of birds, particularly domestic poultry, it doesn't have human health implications. West Nile, on the other hand, which is also naturally hosted by many species of birds often with little or no ill effects to the host, can be passed on to people by the bite of a mosquito that has been infected from biting a bird that carried the virus.

Human illness is rare even in areas where the virus has been reported and the chance that anyone will become ill from a mosquito bite is low. Most humans infected with West Nile have no symptoms. A small proportion develop mild symptoms that include fever, headache, body aches, skin rash and swollen lymph glands. Less than 1 percent of infected people develop a more severe illness that includes encephalitis or meningitis.

West Nile, never previously reported in the Western hemisphere, has spread rapidly across the United States since it was first identified in the New York City area in 1999. By January 2003, only Nevada, Oregon, Utah and Arizona had not reported the virus.

Broad partnerships of governmental organizations are working on the distribution, prevention and control and treatment of the virus. The Centers for Disease Control, U.S. Geological Survey, U.S. Fish and Wildlife Service, National Wildlife Health Center, U.S. departments of agriculture and defense, and the National Park Service are cooperating nationally in this effort.

In Nevada, public health authorities are monitoring human health for clinical evidence of West Nile. The Nevada Department of Agriculture is monitoring sentinel chicken flocks distributed widely in the state. NDOA also samples mosquitoes and wild birds trapped by USDA Wildlife Services, as well as wild horses. The Nevada Division of Wildlife, along with other agencies, is monitoring wild birds for any unusual mortality.

To date, more than 110 species of birds have been either naturally or experimentally infected with the virus in North America. The virus affects different species and groups of birds differently. Many species of birds once infected, develop antibodies and show no clinical symptoms of the disease.

Other species, particularly hawks, falcons and owls, show symptoms of the disease, and if they survive, show chronic neurological dysfunction. Many crows, magpies, ravens and jays suffer acutely from the disease. These birds often do not survive the disease after infection. Bird-mortality events can be an important indicator of the presence of the virus.

Dead birds in an area may mean that West Nile is circulating between the birds and the mosquitoes in that area. Although birds, particularly crows, ravens, magpies and jays, infected with the virus can die or become ill, most infected birds do survive.

The public can play an important role in monitoring West Nile through reporting dead birds to the Nevada State Veterinarian at (775) 688-1180 or NDOW at (775) 688-1180.

To learn more about West Nile Virus, visit the Centers for Disease Control Web site at www.cdc.gov/ncidod/dvbid/ westnile/index.htm.