Fifty-nine horses were infected with West Nile virus in 2000, including a 4-month-old colt, the youngest horse ever known in the United States to become ill because of the often-fatal encephalitis virus, according to a government summary.
In the summary, the USDA-APHIS stated that 143 counties in 12 states have reported findings of West Nile virus in mosquitoes, birds, or mammals. The virus has spread as far south as North Carolina, where an infected crow was found.
Of the 59 horses, 23 died or were euthanatized. The 4-month-old colt did recover, however.
West Nile virus is a flavivirus commonly found in Africa, West Asia, and the Middle East. It is closely related to St Louis encephalitis virus found in the United States. It is not known how long the virus has been in the United States, but scientists believe it has probably been in the eastern part of the country since the early summer of 1999, possibly longer.
A total of 20 human cases of West Nile encephalitis were reported in 2000, including one death. The year before, 62 cases were reported, including seven deaths, all in the New York area.
The APHIS summary states that infections have been confirmed in five more species: a skunk in Connecticut, and two bats, a squirrel, a rabbit, and a chipmunk in New York. Birds continue to be the species most susceptible to the virus, especially crows, with deaths numbering in the thousands.