The USDA’s Animal and Plant Health Inspection Service has identified a new vesicular stomatitis (VSV)-positive equine premises in Montezuma County, Colorado.
Since October 2025, VSV has been found in 15 equine premises in Arizona. This is the first case outside of Arizona, and all confirmed cases have been of the vesicular stomatitis New Jersey virus (VSNJV) serotype.
The most recent outbreak of VSV in the U.S. occurred from May 2023 to January 2024, affecting 319 premises across California, Nevada, and Texas. VSV typically circulates between livestock and insect vectors in southern Mexico and occasionally enters the U.S.
EDCC Health Watch is an Equine Network marketing program that uses information from the Equine Disease Communication Center (EDCC) to create and distribute verified equine disease reports. The EDCC is an independent nonprofit organization supported by industry donations to provide open access to infectious disease information.
About Vesicular Stomatitis
Vesicular stomatitis is a viral disease affecting horses, donkeys, mules, cattle, swine, and New World camelids in the Western Hemisphere. It causes vesicular lesions in the form of blisters, crusts, and ulcers on various parts of the body. The virus is transmitted by biting midges and is seasonal.
Clinical signs of vesicular stomatitis include:
- Vesicle formation leading to ulcerative lesions on the lips, muzzle, nostrils, and tongue.
- Ulceration of the inner surface of the lips.
- Crusting of the muzzle, nostrils, and ears.
- Excessive salivation.
- Difficulty eating and chewing.
- Lameness due to erosions on the coronary band.
- Lesions on the udder, sheath, and ears.
- Potential secondary infections.
- Increased risk for animals on pastures.
Diagnosis is based on recognizing vesicular lesions, confirmed through laboratory testing. Treatment involves pain relief, anti-inflammatories, and supportive care. Quarantine and biosecurity measures are crucial until all animals have recovered.