West Nile virus also has been found in horses in Wyoming, Colorado, New Mexico, Arizona, Nevada, California and Idaho. A third of horses that show symptoms die.

The horse was a 5-year-old quarter horse gelding in the Ogden area. The horse, which had not traveled outside the area in the past year, was not vaccinated against West Nile.

The horse was euthanized because of the severity of the symptoms, the Utah Department of Agriculture and Food said in a statement.

No Humans Infected

The most common sign of West Nile virus in horses is extreme weakness, usually in the hindquarters. Weakness may be indicated by a widened stance, stumbling, leaning to one side and hoof dragging. In extreme cases, paralysis may follow.

Ag department officials said a third of horses that show symptoms of the illness die. The virus has also been found in horses in Wyoming, Colorado, New Mexico, Arizona, Nevada, California and Idaho.

West Nile virus cannot be transmitted from horses to humans.

Health officials also have found the West Nile virus in the last week in mosquitoes Salt Lake, Utah, Duchesne and Uintah counties.

Last year, 11 people were infected with the virus in Utah. This year, officials said no humans have been infected.