Although tiny sandflies are its only vector, vesicular stomatitis can travel hundreds of miles or disappear for years at a time, only to pop back up in a different location, with no known explanation.

“Its unpredictability is the only predictable thing about it,” said Dr. Max Coats, the deputy director for Animal Health Programs for the Texas Animal Health Commission. Coats has spent much of 2004 dealing with this most recent outbreak of VSV, which turned up in Texas in May.

VSV is a viral disease that is seldom fatal. The symptoms include painful blister-like lesions on the tongue, lips, nostrils and hooves, and it mainly affects horses, cattle and sheep.

“It causes severe pain and discomfort,” explained Coats. “The animals will oftentimes refuse to eat and drink, only as much they have to to survive, until these bare spots in the mouth heal over.”

Once the viral infection shows up in a herd, it can be spread by contact with infected animals. Humans too can contract the disease, although symptoms are similar to the flu and don’t include blisters in the mouth. Not all affected animals show clinical symptoms, and there is nothing to be done but try and make the animal comfortable with the symptoms once they have contracted VSV, until it’s run its course. And that usually takes about two weeks.

The real aggravation comes from the fact that the symptoms are identical to foot-and-mouth disease. FMD hasn’t appeared in the United States since 1929, but it can be fatal and often leaves animals debilitated.

It causes severe losses in the production of meat and milk, spreads very rapidly, and basically shut down horse sports in Great Britain in 2001.

Since VSV mimics the more deadly FMD, and VSV is only found on the American continents, the OIE, a French-based international organization created to help control animal diseases, has put VSV on its “List A.” That list is reserved for transmissible diseases that have the most serious impact on public health and international trade.

Europeans cannot afford to have VSV cross the ocean because it would be mistaken for FMD. “Nobody really needs that kind of diagnostic confusion factor in their country,” explained Coats.

That’s why this relatively harmless disease causes major hassles whenever it appears. It’s why European officials immediately impose restrictions, which vary from establishing prohibitions of entry for animals that have been in proximity ofanimals that test positive for VSV to prohibiting animals that have been in the same state as a positive blood test. Kentucky, Florida and other states that have a significant international horse trade also prevent entry of animals that come from the states with VSV cases to protect their own trade.

Breeders’ Cup Concerns

Although entry restrictions are frustrating under the best of circumstances, this year they caused particular concern because the Breeders’ Cup World Thoroughbred Championships was scheduled at Lone Star Park in Grand Prairie, Texas, on Oct. 30. One of the most prestigious days of racing in the world, the Breeders’ Cup draws horses from all over the country and the world.

The outbreak of VSV in May left organizers feeling concerned that strict entry restrictions might force the Breeders’ Cup to change location. During the last outbreak of VSV in 1998, the European Union prohibited entry for all horses that had been in a state in which VSV had appeared or had been in contact with horses that had come from a state with VSV.

If such strict limitations had been issued, it would have made it impossible for foreign or Kentucky-based horses to run in the Breeders’ Cup for fear that they wouldn’t be able to return home.

Following the initial diagnosis of VSV, Breeders’ Cup officials immediately went into action.

“We immediately contacted the USDA and the administrator to try and explain to them the importance of trying to get a decision out of the E.U. so that we could have the free movement of horses into and out of Texas,” said Pamela Blatz-Murff, senior vice president of Breeder’s Cup operations.

“In addition, we also started a protocol to show the USDA that we were monitoring the situation so that we could declare Lone Star Park free of the disease and maintain that it is a disease-free zone,” Blatz-Murff added.

When the E.U. declared more relaxed restrictions, prohibiting only horses that had been on a VSV-positive premise, officials decided to go on with the show. They went through an extensive process to insure that the grounds and the surrounding areas would remain VSV free.

“We have been doing physical inspections of all resident horses on the backside of Lone Star Park since May,” said Blatz-Murff. “Every horse that has come onto the backside of the race track has had to provide negative VSV cELISA testing in addition to statements on their health papers and physical inspections indicating that they have been inspected and have no signs, that they’ve not come from an area that has been under quarantine.”

More than 1,000 horses at the Texas track have had blood drawn and tested by the U.S. Department of Agriculture’s laboratory. In addition to inspecting and testing horses, measures have been taken to prevent the spread of the disease.

“They’re going into extensive vector-control procedures and have been doing so all summer,” said Coats. “Area spraying, keeping water away, doing the fogging in the area of the track and the barns, on the grounds.”

An End In Sight

And all that attention to keeping Lone Star Park VSV free has paid off. The Breeders’ Cup ran as planned, and the state of Texas was actually declared free of the disease just two weeks before the meet.

“It wanes quickly,” explained Coats. “The disease goes away historically oncethe weather turns cold and the vectors disappear.”

The first case in Texas was confirmed on May 18 at a roping facility in Balmorhea, just south of the New Mexico state line. The premises were immediately put under quarantine, but the disease’s unpredictable nature meant that it was anyone’s guess where it might show up next.

On June 4 a positive case was confirmed in Carlsbad, N.M., and by July 2 it had cropped up in Colorado. As of Oct. 21 there had been 236 positive equine cases across the three states, as well as a smaller number of cattle and swine. Although Texas no longer has any quarantined premises, VSV remains in New Mexico and Colorado as of Nov. 1.

Because VSV appears for no apparent reason, it’s impossible to predict when or where it will show up next.

“The principal access seems to be up through New Mexico into Colorado,” said Coats. “Occasionally it spills into Texas, occasionally it spills into Arizona, or it may even get into Utah and Wyoming. One year it went all the way to Idaho.”

Clearly, VSV makes its way into the United States via Mexico, where they have cases every year. USDA officials inspect horses at the border, but blood tests aren’t very useful since a horse that has been exposed to the disease may have antibodies in his blood even though he isn’t sick or contagious.

“It’s so imperfectly understood, we don’t know exactly where it comes from or if it’s hanging around someplace in a grasshopper or a cricket or something. We just don’t know,” admitted Coats.

“Some of these diseases seem to be able to disappear at least from view for very long periods of time, and they’re harbored somewhere else in something we haven’t suspected. And vesicular stomatitis is one of those kinds of conditions that has the propensity for emerging from nobody knows where or why,” he added.

False-Positive VSV Test Leaves Richards Scrambling

Jim Richards doesn’t live in Texas, and he wasn’t planning on visiting the Southwest, but vesicular stomatitis still caused headache and anxiety for him.

A newcomer to the world of competitive driving, Richards, of Douglasville, Ga., was invited to compete as an individual in the World Four-In-Hand Driving Championships, but he needed to do one more competition at the CAI-A Nebanice (Czech Republic).

“I had to finish the event and do well in the marathon,” explained Richards. “I had to use young horses because they weren’t qualified. It was a bar that I had to clear that was tricky.”

The plan was to ship the horses to Europe on the Saturday before the competition. Three days prior to leaving, blood work was done on the horses to test for a number of things, including VSV.

When Richards’ best and most experienced horse, Chack, tested positive for VSV, panic ensued. “We knew it was a false positive because he was not symptomatic. There are frequent false positives, and the disease has never occurred east of the Mississippi!” said Richards.

Nevertheless, the positive test meant that Richards’ farm (where the Foxhall Cup CCI*** is held in April) was put under quarantine, and it looked like he wouldn’t be able to ship any of his horses to Europe.

So they immediately air-freighted more blood to the U.S. Department of Agriculture lab Ames, Iowa, to be tested again. At the last possible moment, the quarantine was released and all the horses but Chack, who tested negative in the next five blood tests, were allowed to go. Chack was finally cleared too, but not until it was too late to send him.

“There was a half day there where I thought my World Championships were over,” said Richards.

He had to replace Chack with an inexperienced 6-year-old mare, although he still managed to finish seventh overall and second in the marathon at the competition at Nebanice. And then that mare tied up before the World Championships and couldn’t compete, forcing Richards to purchase another qualified horse at the last minute. His mix-and-match team ended up 40th at the World Championships.