The New Mexico Livestock Board (NMLB) and New Mexico’s state veterinarian are urging livestock owners in New Mexico, particularly those along the Rio Grande River, to exercise caution so their animals don’t contract or spread vesicular stomatitis (VS).

On Thursday, July 29, three additional equine were confirmed with VS on different premises than the 19 other VS cases that surfaced earlier this year, raising the number of VS infected equine this year to 22 this year spread across six counties.

Vesicular stomatitis is a virus that can affect horses, cattle, sheep, goats, and pigs. It causes blister-like lesions in the mouth and on the tongue, which are often painful enough to limit the animal’s appetite. The virus can also cause lesions just above the hooves that can limit the animal’s mobility.

“This particular strain of VS appears to be virulent,” said Dr. Dave Fly, state veterinarian for New Mexico. “Lesions in most of the affected animals we’ve seen this year have been pretty severe.”

Last week San Miguel and Socorro became the latest counties in New Mexico to report and quarantine suspected VS cases. Earlier this month the virus was found in Valencia County where a total of nine premises remain under quarantine for suspected or confirmed cases of VS. The first confirmed case in New Mexico this year was in April in Otero County, but no additional cases have been confirmed there. All 2012 VS cases have been New Jersey serotype.

Since VS has a tendency to appear near waterways, Fly said counties along the Rio Grande River are considered at elevated risk. The virus is spread by many types of biting insects. It can also spread from animal to animal if they share a water or feed bucket or if owners use the same pieces of tack on more than one animal.

VS is problematic because of the restrictions other states and countries impose on livestock entering from states in which the virus is confirmed. That can make traveling to and from events such as rodeos very cumbersome for livestock owners. Once it appears, VS generally remains active until hard freezes occur in the late fall or winter. Dr. Fly said his office will update recommendations periodically in accordance with any movement of the virus.

In the past decade, the Southwestern and Western United States experienced a number of vesicular stomatitis outbreaks. Outbreaks usually occur during the warmer months, often along waterways. In some years, only a few premises in a single state have been affected. However, in other years, multiple states and many premises have been involved.

Since there could be a vesicular stomatitis outbreak in any given year, it is essential that veterinarians and livestock owners be on the alert for animals displaying clinical signs of the disease. For current information on vesicular stomatitis outbreaks or summaries of the most recent past outbreaks, please visit the APHIS Web site at www.aphis.gov/vs/nahss/equine/vsv

Economic Impacts

According to the USDA/APHIS Web site about VS, 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 vesicular stomatitis 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.

Clinical Signs

In affected livestock, the incubation period for vesicular stomatitis ranges from two to eight days. Often, excessive salivation is the first symptom. Close examination of the mouth initially reveals blanched and raised vesicles or blister-like lesions on the inner surfaces of the lips, gums, tongue, and/or dental pad.

In addition, these blister-like lesions can form on the lips, nostrils, coronary band, prepuce, vulva, and teats. The blisters swell and break, which causes oral pain and discomfort and reluctance to eat or drink. Lameness and severe weight loss may follow. Body temperature may rise immediately before or at the same time lesions first appear.

Texas Animal Health Rules
TAHC veterinarians have conducted numerous investigations for vesicular lesions in horses and vesicular stomatitis has not been diagnosed in Texas so far in 2012. TAHC is encouraging Texas horse owners and veterinarians to continue to report suspicious symptoms in susceptible species.