May 21, 2004

Vesicular Stomatitis Confirmed In US West Texas

The U.S.'s first case of vesicular stomatitis since 1998 was confirmed Wednesday near Balmorhea, in Reeves County in west Texas, the Texas Animal Health Commission said in a press release.
 
VS is a viral disease that occurs sporadically in the U.S., usually in southwestern states. The disease can affect horses, cattle and pigs, and occasionally, sheep, goats and deer, causing blisters to form in the animals' mouth, on teats or along the hooves, resulting in excessive salivation, lameness or oozing sores.
 
The premises where VS was found has nine horses and eight head of cattle, the TAHC said Wednesday in the release.
 
The clinical signs of VS can cause concern because they mimic those of foot-and-mouth disease, a highly contagious foreign animal disease, which has been eradicated in the U.S. since 1929, the TAHC said. Laboratory tests must be run to differentiate between the two diseases, when cattle, pigs, sheep or other cloven-hooved animals develop signs of the disease.
 
Unlike foot-and-mouth disease, VS also can affect horses and other members of the equine family, according to the TAHC. Although the disease does not affect food safety, infected livestock are withheld from slaughter until they recover.
 
"We always launch a disease investigation when blisters or sores are reported in livestock, to determine if foot-and-mouth disease has been introduced into the U.S.," said Max Coats, deputy director for Animal Health Programs for the TAHC, the state's livestock and poultry health regulatory agency, in the release. "Because horses are not susceptible to FMD, we knew, in this case, that the animals had vesicular stomatitis, or possibly had come in contact with poison or a toxic plant. The National Veterinary Services Laboratory in Ames, Iowa, has confirmed that the three horses in Reeves County have VS."
 
Coats said researchers have determined that VS outbreaks are started by a virus transmitted by arthropods, such as ticks, mites, biting midges, mosquitoes or house flies. Following an incubation period of two to eight days, infected animals may develop clinical signs of disease.
 
The outbreak can then be perpetuated by biting insects that carry the disease from infected to healthy livestock, Coats said. VS-infected animals also can spread the virus if their saliva or the fluid from ruptured blisters contaminates equipment or feed shared by herd mates.
 
Coats said all livestock on the affected ranch in Reeves County will remain quarantined for several weeks, until they no longer pose a health threat to other livestock. Prior to quarantine release, the animals will be re-examined by a state or federal regulatory veterinarian, to prevent the spread of disease to other premises.
 
"VS is rarely fatal, and infection usually runs its course in a couple of weeks," said Coats. "Infected livestock may need supportive care to prevent secondary infections where blisters have ruptured. The affected animals also may lose condition, because they will avoid eating as long as their mouth is sore. Lesions can also occur along hooves, resulting in temporary lameness.
 
"The only thing regular about VS is its irregularity," he said. "Thirteen years passed between a 1982-83 outbreak of VS and one in 1995 that involved infection on more than 365 ranches in five states. These affected states were New Mexico, Colorado, Arizona, Utah and Texas, where infection was confined to only one premise," he said.
 
"Texas was spared in May l997, when the disease was detected in Arizona in horses. By late fall, when the outbreak ended, infection had been detected on 380 ranches in four states; Arizona, Colorado, New Mexico and Utah," Coats said. Prior to the case announced Wednesday, VS was most recently confirmed in l998, in Reeves County, Texas, and in New Mexico.
 
"Humans reportedly may contract VS and develop flu-like symptoms that can last four to seven days," Coats said.
 
"Because VS has been confirmed in Texas, some states may require our shipments of livestock to undergo additional inspections or testing (before shipment)."