Vesicular Stomatitis Identified at 15 California Premises
Four new cases of vesicular stomatitis have been confirmed in California, and 15 affected premises have been identified in Riverside and San Diego counties.
Four new cases of vesicular stomatitis have been confirmed in California, and 15 affected premises have been identified in Riverside and San Diego counties. | Wikimedia Commons

On May 17, a horse in San Diego County, California, was confirmed positive for vesicular stomatitis virus (VSV). Since the index case, there have been 15 new VSV-affected equine premises identified. The premises are located in San Diego and Riverside counties. Four new horses have been confirmed positive, and 11 horses are exposed.   

In Riverside County, there are two positive horses and two suspected premises. In San Diego County, there are two new positive cases and nine new suspected premises.

To date, all positive cases have been vesicular stomatitis New Jersey virus (VSNJV) serotype.

In response to the developing situation, Kentucky’s Administrative Regulations now prohibit entry of all livestock, wild and exotic animals into Kentucky originating from any California premises currently under quarantine as a result of confirmed or suspected cases of vesicular stomatitis. Additionally, any such animal that has been on premises currently quarantined for VS during the 30 days prior to entry is prohibited entry into Kentucky.

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Vesicular Stomatitis 

Vesicular stomatitis is a viral disease of horses, donkeys, mules, cattle, swine and New World camelids that occurs in the Western Hemisphere. It is named for the characteristic vesicular lesions it causes in the form of blisters, crusts and ulceration of the lips, muzzle, nose, tongue, ears, sheath, teats and/or coronary band. The virus is transmitted by biting midges and therefore is seasonal.

Clinical Signs for vesicular stomatitis include:

  • Vesicle formation leading to ulcerative lesions on the lips, muzzle, nostrils and tongue. The tongue is often the most severely affected area.
  • Ulceration of the inner surface of the lips.
  • Crusting of the muzzle, nostrils, and/or inside the ears.
  • Excessive salivation secondary to the oral lesions.
  • Difficulty picking up and chewing feed.
  • Lameness due to painful erosions on the coronary band.
  • Lesions can occur on the udder, sheath and inside of the ear.
  • Lesions can develop secondary infections resulting in slow-to-heal wounds.
  • Animals on pastures are at increased risk of vesicular stomatitis.

Initial diagnosis is based on recognition of characteristic vesicular lesions. Infection is confirmed via laboratory testing for serum antibodies and/or virus identification in fluid samples from active lesions. Veterinarians are required to report suspected cases to state/federal animal health officials who will direct sample submission to an approved regulatory laboratory for diagnostic testing. 

There is no specific treatment for vesicular stomatitis. Best practices include implementing good biosecurity and treating affected horses with pain relievers, anti-inflammatories and supportive care as recommended by a veterinarian.

Isolating all affected animals and placing the premise on immediate quarantine is required until all horses have fully recovered and no active lesions are present. The State Veterinarian will work with the local veterinarian to determine and implement necessary quarantine procedures.

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