On July 17, the National Veterinary Services Laboratory reported that four horses on two Weld County, Colo., premises tested positive for vesicular stomatitis. The initial investigation was performed by one of the field veterinarians from the State Veterinarian’s Office at the Colorado Department of Agriculture. The diagnosed horses have no history of travel, according to the CDA.

On July 21, the CDA reported that a premise in Boulder County, Colo., has another confirmed diagnosis.

All cases have been placed under quarantine and a number of other premises in the surrounding areas are being investigated. 

Vesicular stomatitis is a highly contagious virus and is known to cause blisters and sores in the mouth, on the tongue, muzzle, teats or hooves of horses, cattle, swine, sheep, goats and llamas. The virus is thought to be spread by insects, saliva and open wounds with an incubation period of two to eight days. 

Livestock with clinical signs of vesicular stomatitis are isolated until they are “determined to be of no further threat for disease spread,” according to the CDA. There are currently no United States Department of Agriculture-approved vaccines for vesicular stomatitis. 

Colorado is the second state in the country to have a confirmed case of vesicular stomatitis. Previous confirmed cases in 2014 have been diagnosed in the southern area of Texas near the Mexico border and more recently in Bastrop and Travis Counties just south of Austin, Texas. 

Many states have placed restrictions on horses crossing state lines, with most requiring a newer health certificate and prohibiting any horses that have been on quarantined properties within the last 30 days.