The spread of vesicular stomatitis continues across the Southwest with a new case reported in a horse in Las Animas County Colorado, resulting in new Colorado travel rules to be issued for New Mexico horses, mules, cattle, bison, sheep, goats, swine and camelids entering the state.

As of July 25, more than 20 New Mexico premises have had horses test positive for VS. Counties with confirmed cases include Rio Arriba, San Miguel, Sandoval, Socorro, Valencia and Lincoln. In addition, other counties in the state are under observation.

The latest case in Colorado has animal health officials concerned as the horse had not recently traveled to or from New Mexico and is believed to have been infected by insect bite.

“While this is the first case diagnosed in Colorado in 2012, several cases have been  identified in the Rio Grande River Valley of New Mexico,” said Colorado State Veterinarian, Dr. Keith Roehr. “This Colorado case represents a northern movement of the virus that has been typical in past years.”

Travel requirements

A new emergency rule was approved Aug. 1 by Colorado animal health authorities related to livestock movement and vesicular stomatitis.

"New Mexico is currently experiencing a significant outbreak of vesicular stomatitis (VS). VS is classified as a Foreign Animal Disease (FAD), and, as such, cases are required to be reported nationally and internationally,” the published rule states. "To minimize the spread of the disease and to help avoid severe restrictions on future livestock movement, the following requirements and restrictions are being implemented. For livestock events held in N.M., the event coordinator is responsible for helping ensure livestock owners’ compliance with these and any other livestock movement requirements as it applies to animals admitted onto the premises of the event and will go away in 90 days."

In Texas, a similar rule applies to the movement of New Mexico livestock across state lines.

“Where out-of-state livestock are part of a public event such as roping, racing, breeding or other forms of public exhibition or traveling interstate, a health certificate (CVI) written within 5 days of entering the show will be required for all New Mexico origin livestock.

According to the published Texas rule, the following statement is to appear on the CVI:

"The animals represented on this certificate have not originated from a premises or area under quarantine for vesicular stomatitis (VS), or a premises on which VS has been diagnosed in the past 21 days. I have examined these animals and have not observed lesions or clinical signs of VS."

The Texas Animal Health Commission (TAHC) prohibits entry of animals from VS quarantined premises and also requires livestock to be accompanied by a valid certificate of veterinary inspection. After confirmation of VS in Colorado, TAHC officials encourage livestock owners to use the best means possible to limit exposure of their livestock to insect bites.

Similar rules have been issued by Arizona, Oklahoma and 31 other states and Canada.

Vesicular stomatitis is a viral disease that primarily affects horses and cattle and occasionally swine, sheep, goats, llamas, and alpacas. Humans can also become infected with the disease when handling affected animals, but this is a rare event. Vesicular stomatitis has been confirmed only in the Western Hemisphere. It is known to be an endemic disease in the warmer regions of North, Central, and South America, but outbreaks of the disease in other temperate geographic parts of the hemisphere occur sporadically.

In the past decade, the Southwestern and Western United States have experienced a number of VS outbreaks. Outbreaks usually occur during the warmer months, often along waterways.

Economic impacts

While vesicular stomatitis does not generally cause animals to die, it can still cause economic losses to livestock producers. The disease is particularly significant because its outward signs are similar to (although generally less severe than) those of foot-and-mouth

disease, a foreign animal disease of cloven-hoofed animals that was eradicated from the United States in 1929. The clinical signs of VS are also similar to those of swine vesicular disease, another foreign animal disease. The only way to tell these diseases apart is through laboratory tests.

How VS spreads is not fully known; insect vectors, mechanical transmission, and movement of animals are all factors. Once the disease is introduced into a herd, it may move from animal to animal by contact or exposure to saliva or fluid from ruptured vesicles. Humans rarely contract VS, but they can become infected.

Tips for Colorado livestock owners

The Colorado State Veterinarian’s Office is recommending that livestock events exercise extra precaution measures to minimize the transmission of vesicular stomatitis. Participants, regardless of origin should, when possible, arrive at the event with a Certificate of Veterinary Inspection that was issued within 48 hours of departure for the event and the Certificate of Veterinary Inspection should contain a statement from the issuing veterinarian certifying the animal(s) have tested free of VS. Any livestock that exhibit clinical signs of VS shall be immediately removed from the event and reported to a Colorado animal health official at 303-239-4161.