Emily Nietrzeba, DVM, MPH, addresses the current isses with vesicular Stomatitis in horses in California and throughout the nation in the Summer Sonoma 2020 Journal. Vesicular stomatitis (VS) is a viral infection that can affect horses, cattle, and pigs, and can also but rarely be seen in goats, sheep, and llamas.
Horse isolated in stall
The 2020 Vesicular Stomatitis outbreak began on April 13, 2020, when the National Veterinary Services Laboratories in Ames, Iowa confirmed the first VS-positive premises in Dona Ana County.
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Vesicular stomatitis is a reportable disease in most states, including California, not only because of rapid transmission but because clinical signs of this disease are identical to those caused by foot and mouth disease in cattle and swine, swine vesicular disease, and vesicular exanthema of swine.
According to the Merck Veterinary Manual, excessive drooling is often the first sign of disease. Ulcers and erosions of the mouth linings, shedding of the surface of the tongue, and ulcers at the junctions of the lips are commonly seen. Inflammation and erosions at the coronary band of the hoof are sometimes observed; lameness soon follows.
Crusting lesions of the muzzle, lower abdomen, the covering of the penis, and udder of horses are typical during outbreaks in the southwestern US. Loss of appetite due to mouth ulcers and lameness due to foot ulcers are normally of short duration, as the disease generally resolves within 2 weeks. However, reinfection can occur following a second exposure. Both noninfectious and infectious causes of mouth sores must be considered as other possible diagnoses.
VS transmission occurs via direct contact with sores of infected animals or vector-borne blood transmission. Known vectors for VS transmission include black flies, sand flies, and biting midges (Culicoides spp.), which have been implicated as the likely source of infection in most recent positive premises.
Infected animals must be promptly isolated to reduce intra-herd transmission, and positive premises are quarantined for 14 days following the onset of lesions of the last affected animal.
Biosecurity measures and vector mitigation efforts are frequently implemented on infected premises to reduce within-herd spread of the virus. No specific treatment for VS is indicated aside from supportive care, usually consisting of pain management and soft feeds in the presence of perioral lesions.
The 2020 VS outbreak began on April 13, 2020, when the National Veterinary Services Laboratories (NVSL) in Ames, Iowa confirmed the first VS-positive premises in Dona Ana County, New Mexico. Arizona, Texas, Kansas, Nebraska, and Oklahoma subsequently broke with VS cases which were confirmed by NVSL on April 22, 2020 (Cochise County, Arizona, April 23, 2020 (Starr County, Texas), June 16, 2020 (Butler County, Kansas), June 24, 2020 (Buffalo County, Nebraska), and July 7, 2020 (Washington County, Oklahoma).
See somplete list of states with confirmed cases of vesicular stomatitis here.
For import into California, all horses, cattle, sheep, goat and swine originating from any state where vesicular stomatitis has been diagnosed (except cattle and swine transported directly to slaughter) must be accompanied by a health certificate (Certificate of Veterinary Inspection) signed by an accredited veterinarian that includes the following statement:
“I have examined all the animals identified on this certificate within 7 days of shipment date and found them to be free from signs of Vesicular Stomatitis (VS). During the last fourteen (14) days, these animals have not been exposed to VS nor located on a VS confirmed or a VS suspected premises.”
Press release Sonoma Horse Council