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New Mexico State University

New Mexico State University

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NMSU Extension publication provides information about domestic livestock disease

Black flies are always bothersome around livestock animals. This year their presence is even more troublesome because of their transmission of vesicular stomatitis virus.

Man with horse
New Mexico State University Extension equine specialist Jason Turner inspects a horse for clinical signs of vesicular stomatitis virus. An Extension publication with the latest information about the virus is available at https://aces.nmsu.edu/pubs/_b/B717/. (NMSU photo by Jane Moorman)

“There is compelling evidence that insect vectors, primarily black flies, introduce VSV into populations of domestic animals,” said Jason Turner, New Mexico State University Extension equine specialist. “Last year we had a pretty bad outbreak. Because of the mild winter, and other conditions, black flies are already bothersome and reports of the virus are already being received.”

Outbreaks typically occur in the southwest United States beginning in late spring or early summer and normally continue through late fall, progressing northward along river ways and valleys.

Turner has edited a publication with the latest information about the virus, including photographs of clinical signs, treatment and preventive measures. The publication is available on the College of Agricultural, Consumer and Environmental Sciences website at https://aces.nmsu.edu/pubs/_b/B717/.

“It primarily affects equids, cattle and swine, but it can also occur in sheep, goats, llamas, alpacas and a variety of wild vertebrates,” Turner said. “As a zoonotic disease, VSV can infect humans and cause flu-like symptoms, so it is important that people handling infected horses practice proper biosecurity to protect themselves as well as other animals.”

The incubation period, or time from exposure to presence of clinical symptoms, usually ranges from two to eight days.

“Drooling and excess salivation are typically the first symptoms noticed,” Turner said. “Upon closer examination, there may be blanched areas and the characteristic vesicles or blisters in and around the mouth. These lesions are quite painful and can cause loss of appetite and/or refusal to drink water.”

Minimizing the risk of exposure for horses is the best preventative measure. The following suggestions can help reduce the incidence of vesicular stomatitis:
- Maintain an insect control program.
- Stable horses rather than leaving them on pasture.
- Routinely inspect for signs of VS and isolate suspected animals from the herd.
- Use individual rather than communal feeders, waterers, bits and tack.
- Isolate new horses for at least 21 days before turning them with other resident horses.

Because the clinical signs of VS are indistinguishable from those of foot and mouth disease, VS is a reportable disease, which means veterinarians have a duty to report suspect VS cases to state and federal animal health authorities. A veterinarian should be called to confirm the diagnosis of VS through laboratory testing of collected samples.

“If the horse is confirmed positive, then the premises will be quarantined with movement restrictions,” Turner said. “Quarantine periods may range from at least 14 days from the onset of lesions in the last affected animal on the premises to at least 21 days after all lesions are healed.”

Good communication with a veterinarian and animal health official is important in dealing with disease outbreaks such as VSV. For current recommendations and regulatory information on VS, visit the New Mexico Livestock Board web page at www.nmlbonline.com or contact the office of the state veterinarian at 505-841-6161.