The Columbus Academy of Veterinary Medicine is an established local association of Central Ohio Veterinarians. Its members reflect all aspects of veterinary medicine from small and large animal veterinary practices to academics and research. All the members share the common goal of creating an organization to promote veterinary medicine and safeguard its interests on a local level. The Academy is a vital source of continuing education hours offered at no charge to its membership. It is an important link between the veterinary community and the public it serves.
A: West Nile virus is an arbovirus (short for arthropod-borne virus) that causes encephalitis (inflammation of the brain). Arboviruses, including West Nile virus, are transmitted by blood-feeding insects such as mosquitoes. Most infections with West Nile virus have been identified in wild birds, but the virus can also infect humans, horses, dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, and domestic birds.
A: West Nile virus was first identified in the West Nile district of Uganda in 1937 and has since been found in Africa, Eastern Europe, West Asia, the Middle East, and the United States. The strain of virus found in the United States most closely resembles that found in the Mediterranean and Middle East.
A: Mosquitoes draw the virus from infected birds and transmit it to animals and humans through bites. West Nile viral encephalitis develops in animals and humans when the virus multiplies and crosses the blood-brain barrier. West Nile virus is not transmitted directly from person to person, animal to person, person to animal, or animal to animal. Ticks infected with the virus have been found in Asia and Africa; however, there are no verified reports of ticks spreading the virus and their role in transmission has not been determined.
A: In areas where mosquitoes carry the virus, less than 1% are actually infected. Even if mosquitoes are infected, less than 1% of people bitten and infected by those mosquitoes become severely ill. The risk of becoming ill from a single mosquito bite is extremely low.
A: Horses - The most common sign is weakness, usually in the hindquarters. Weakness may be indicated by a widened stance, stumbling, leaning to one side, and toe dragging. In extreme cases, paralysis may follow. Fever is sometimes evident, as are depression and fearfulness. Approximately 40% of the cases of West Nile viral encephalitis in horses proved fatal during the 1999 outbreak.
Humans - Most infections in humans are relatively mild, with flu-like symptoms including fever, headache, body aches and, in some cases, skin rash and swollen lymph glands. Signs of more severe infections include high fever, neck stiffness, muscle weakness, convulsions and paralysis. Death rates associated with severe infection range from 3% to 15% and are highest among the elderly.
Other Animals - Wild birds infected with West Nile virus in the United States are most often found dead; therefore, descriptions of clinical signs in wild birds are not readily available. Nor have clinical signs associated with West Nile virus infection in dogs, cats, bats, chipmunks, skunks, squirrels, domestic rabbits, and domestic birds been well described. It appears that, although they may be infected, many of these latter species may not develop clinical signs of disease.
A: Diagnosis of West Nile viral encephalitis is based on a history of exposure, clinical signs, and results of diagnostic blood tests.
As for all viral diseases, treatment consists of providing support (e.g., hospitalization, intravenous fluids, respiratory support, prevention of secondary infections, and good nursing care) while the affected individual's immune system responds to the infection.
A: A vaccine is now available for horses. For other species, limiting exposure to mosquitoes is considered effective prevention. The following actions may reduce the risk of mosquito bites and possible exposure to West Nile virus: