Quarantines have been imposed in the state of Colorado due to an outbreak of vesicular stomatitis in horses.

Vesicular stomatitis virus causes painful blisters in the mouth, muzzle, and hoof areas of horses and other livestock animals. This season, cases of the disease have been confirmed in Montezuma, Montrose, La Plata, and Archuleta counties. According to the latest federal reports, since the beginning of the current outbreak on October 31, 2025, 39 affected facilities housing horses have been identified in the states of Arizona, Colorado, and New Mexico. In each confirmed case, the New Jersey serotype was identified.

The primary vectors of the virus are insects: black flies, biting midges, and sand flies. The infection is also transmitted through direct contact of animals with saliva or fluid from ruptured blisters, or via contaminated equipment, clothing, and footwear of personnel. In rare cases, the disease can be transmitted to humans when working with sick animals. Symptoms in humans usually resemble the flu: fever, headache, and muscle pain. Treatment is supportive; no specific vaccine exists.

Quarantine measures are implemented not because of a threat to human health, but to eliminate the risk of spreading foot-and-mouth disease—a dangerous illness capable of causing significant damage to agriculture. Since the lesions of these two diseases are visually almost identical, the quarantine at facilities remains in effect until laboratory test results are received and restrictions are lifted, usually no earlier than 14 days after the recovery of the last animal.

Colorado State Veterinarian Maggie Baldwin has recommended that animal owners remain vigilant when inspecting their livestock. If clinical signs of vesicular stomatitis are detected, it is necessary to immediately contact a veterinary specialist, who will coordinate further actions with the State Veterinarian's Office.

Disease prevention is based on controlling insects and following biosecurity measures: using gloves, regular hand washing, and avoiding the use of shared feeding and watering containers. Animal owners planning to move livestock between states should check current requirements at destinations in advance, as the current situation regarding the spread of the virus affects livestock transportation rules and the holding of mass events.