State Veterinarian Dr. Keith Roehr, says nearly one of every three horses with advanced symptoms such as muscle tremors, stumbling, lack of coordination must be euthanized or do not recover.
Roehr says this is a mostly preventable disease, with vaccinations.
And Dr. Roehr says Rabies is another constant threat to animals.
Authorities have recently confirmed a human case of West Nile Virus in Clear Creek County. The 12th case of the virus in humans in Colorado in 2018, including six in Larimer County. There's also been three in Weld County, and one each in Delta and Washington counties.
The transmission of the disease varies from year to year and depends on a number of factors including mosquito numbers. The WNV can carried by infected birds and then spread locally by mosquitoes that bite those birds. The mosquitoes can then pass the virus to humans and animals.