Vesicular Stomatitis Tracker
A reportable viral disease that causes painful blisters in horses and triggers premises quarantines. Track USDA APHIS-reported affected premises across the Southwest by county.
Affected premises by county
Orange markers are counties with premises currently quarantined; green markers are counties released from quarantine.
About the disease
What it is
A reportable viral disease of horses, cattle, and pigs that causes painful blisters (vesicles) and ulcers on the mouth, tongue, muzzle, teats, and coronary bands. It is significant because its lesions are nearly indistinguishable from foot-and-mouth disease, so every suspected case triggers a regulatory investigation and can halt animal movement. Outbreaks in the US recur in the Southwest, typically in warmer months.
Signs in horses
Excessive drooling or frothing, blisters and raw ulcers on the tongue, lips, muzzle, and gums, reluctance to eat or drink, and lameness when lesions form on the coronary band above the hoof. Fever may precede lesions. Most horses recover in about two weeks with supportive care.
How it spreads
Spread primarily by biting insects (black flies, sand flies, and midges) and by direct contact with saliva or fluid from ruptured blisters, or contaminated equipment, feed, and water. It is not typically fatal but is highly disruptive because of quarantine and movement rules.
Prevention
Use fly and insect control, isolate affected animals, avoid sharing water troughs, buckets, and equipment, and disinfect thoroughly. There is no widely used vaccine. Report any suspected case immediately to your state veterinarian or USDA APHIS — it is a reportable disease and affected premises are quarantined until lesions heal.
🚨 Report a suspected case
Vesicular Stomatitis is a reportable disease — its blisters look like foot-and-mouth disease, so any suspected case must be reported immediately.
- Call your state veterinarian or USDA APHIS Veterinary Services at once.
- Isolate affected animals; VSV spreads by biting insects and contact.
- Expect movement restrictions and premises quarantine if confirmed.
Affected counties (12)
| County | State | Status | Premises | Confirmed |
|---|---|---|---|---|
| Valencia | New Mexico | Quarantined | 5 | Jun 12, 2026 |
| Montrose | Colorado | Quarantined | 1 | Jun 30, 2026 |
| Rio Arriba | New Mexico | Quarantined | 1 | Jun 26, 2026 |
| Yavapai | Arizona | Released | 4 | Feb 25, 2026 |
| Maricopa | Arizona | Released | 4 | Dec 9, 2025 |
| Santa Cruz | Arizona | Released | 2 | Nov 25, 2025 |
| Gila | Arizona | Released | 2 | Nov 24, 2025 |
| Cochise | Arizona | Released | 2 | Oct 31, 2025 |
| Santa Fe | New Mexico | Released | 1 | Jun 9, 2026 |
| Sandoval | New Mexico | Released | 1 | May 22, 2026 |
| Montezuma | Colorado | Released | 1 | May 7, 2026 |
| Pinal | Arizona | Released | 1 | Jan 8, 2026 |
| Total premises | 25 | |||
Source: USDA APHIS Vesicular Stomatitis situation reports. Counts are affected premises aggregated by county and updated automatically. In this outbreak, all affected premises have been equine.