A horse in Grand Forks County, ND, has been confirmed as positive for West Nile virus (WNV). This is the first-ever detection of WNV in North Dakota.

The horse was an approximately 2-year-old Quarterhorse gelding that became ill on June 30, 2002, and had to be euthanized on July 2. The horse had never been out of the Grand Forks County area and was not vaccinated against WNV.

WNV infection was confirmed at the National Veterinary Services Laboratories (NVSL) in Ames, IA, through positive results on a WNV IgM-capture enzyme-linked immunosorbent assay (ELISA) and a WNV plaque-reduction neutralization test (PRNT) of a serum sample, plus a positive WNV reverse transcriptase nested polymerase chain reaction (RT-nPCR) on brain tissue. Virus isolation attempts are underway.

No WNV has ever been detected in humans, birds, or mosquitoes in North Dakota, but the infection of a horse with no history of travel indicates that WNV is present in the local bird and mosquito populations