Experts say it's unusual....but it appears that a horse near Brainerd is the first case of West Nile virus in Minnesota this year. The horse, a pregnant mare, was euthanized April 19th. State officials say the early emergence of the disease doesn't necessarily mean Minnesota will see a big spike in West Nile cases this year.. West Nile arrived in Minnesota for the first time last year. Nearly one thousand horses tested positive for the virus, and about 38 percent of them died. New research from the University of Minnesota indicates many of the surviving horses seem to have residual effects...even six months after being diagnosed.. Julie Wilson is a veterinarian at the U of M. She says she was surprised by the number of horses still having trouble.