2023 Vesicular Stomatitis Virus

Current Outbreak Background

  • The United States Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed a finding of vesicular stomatitis New Jersey virus (VSNJV) on an equine premises in San Diego County, California on May 17, 2023. Since then, VSV has affected counties across California.
  • Cases of VSV have been reported in the northern Mexican states of Chihuahua and Sonora beginning in December 2022.
  • The first case of VSV in Texas was confirmed on June 15, 2023 in Maverick County.
  • VSV circulates annually between livestock and insect vectors in southern Mexico and only occasionally spreads to the U.S. when climatic and ecological factors support movement of VSV-infected insect vectors.
  • Susceptible species producers should practice strong biosecurity, watch for clinical signs, and call a private veterinarian immediately if VSV is suspected.
  • USDA Vesicular Stomatitis Webpage

Disease Information

Vesicular stomatitis virus (VSV) is a viral disease that primarily affects horses and cattle. VSV also can affect sheep, goats, llamas, alpacas, swine, deer and some other species, including bobcats, raccoons and monkeys. Humans can also become infected with the disease when handling affected animals, but this is a rare event.

Vesicular stomatitis virus has been confirmed only in the Western Hemisphere. The Southwestern and Western United States have experienced a number of VSV outbreaks. Outbreaks usually occur during the warmer months, often along waterways. The time from exposure to the onset of clinical signs is 2-8 days. VS is a state reportable disease.

2023 Texas VSV Situational Updates

Date Situation Report Total Currently Quarantined Premises*
8/22/2023 Shackelford County Premises Released 0
8/10/2023 Vesicular Stomatitis Virus Detected in Shackelford County Horse 1
6/27/2023 Maverick County Premises Released 0
6/16/2023 Vesicular Stomatitis Detected in a Maverick County Horse 1

*The total represents both laboratory confirmed cases of VSV and new premises presenting clinical signs of VSV located in a county that has a laboratory confirmed case as of the date listed.

Current Statewide Situation

2 = Total affected premises
2 = Total affected counties

Nationwide outbreak situational updates may be found on the USDA Vesicular Stomatitis webpage.

The Cycle of VSV

VSV normally has an incubation period of two to eight days before the infected animal develops blisters that swell and burst, leaving painful sores. The virus can be transmitted through direct contact with infected animals or by blood- feeding insects. Infected animals also can spread the virus when their saliva or the fluid from ruptured blisters contaminates feed, water or hay shared with herd mates.

Sick animals should be isolated and may need supportive care to prevent a secondary infection where blisters have broken. Painful lesions also can form around animals’ hooves, resulting in temporary lameness. Infected dairy cattle may have a dramatic drop in milk production.

In two or three weeks, VSV infection will usually run its course and animals will begin healing. VSV outbreaks usually, but not always, end with the fall or winter's first freeze.

Movement Restrictions

Confirmed cases of VSV must be reported to interstate and international trading partners, which may result in restrictions, additional inspections or testing requirements. Prior to shipping livestock during a VSV outbreak, check with the state of destination to ensure all entry requirements have been met.

According to the USDA states are no longer considered a VSV affected state 30 days after the last quarantine is released, with no new detections. Individual states may amend movement requirements after this time. However, timelines may vary. International movement requirements are specific to individual countries and may take 60 to 90 days or longer to ease restrictions.


  • Control biting flies (fly spray, fly traps, maintaining clean pens, etc.).
  • Keep equine animals stalled or under a roof to reduce exposure to flies.
  • Feed and water stock from their individual buckets.
  • Don't visit a ranch that’s under quarantine for VSV. Wait until the animals have healed.
  • Restrict nose-to-nose contact between horses from other premises.
  • Clean and disinfect tack and equipment between uses.