COSTA MESA — State agriculture officials Wednesday blamed hay cubes contaminated with a botulism bacteria for the mystifying deaths of at least 15 horses in stables across Southern California over the past two weeks.
Laboratory tests confirmed that from two to three pounds of the candy bar-size cubes, collected at a San Bernardino County stable where three horses died, contained remains of a rabbit that may have carried the bacteria, officials confirmed during a news conference at the Orange County Fairgrounds Equestrian Center.
It was there that the puzzling malady came to light Oct. 28, and in the space of a few days claimed the lives of seven horses. Two other horses at the center have been stricken with similar symptoms--quivering muscles, difficulty breathing and dull eyes--but remained alive Wednesday night.
State officials and local veterinarians, encouraged that no new cases have been reported since Tuesday, expressed optimism that the crisis that had alarmed stable owners and equestrians throughout Southern California has ended.
"Each day that passes with no reports of new victims is a positive sign that we may have isolated the problem," said Irvine veterinarian John Byrd, who treated the sick horses at the Costa Mesa equestrian center. "For the first time in a week, we're feeling better."
In all, officials said that 15 horses have died; seven in Orange County, three in Chino, three in Los Angeles County and two in Ventura County. Los Angeles County veterinarians initially estimated that three other deaths had occurred, but on Wednesday said that they had been mistaken.
Investigators focused on the possibility of botulism after eliminating other potential culprits such as rabies, strychnine, heavy metals, pesticides or infectious viruses.
Dennis Thompson, a state Department of Food and Agriculture veterinarian, said hay cubes had been fed to each of the afflicted horses.
Early on, veterinarians had suspected botulism, a type of food poisoning. But it was not confirmed until cubes from the Prado Park Stables in Chino were analyzed and animal remains were found.
The tainted cubes, Thompson said, were processed in Utah, where the hay was cut and then compressed into pellets by a large harvesting combine. Thompson said the rabbit may have been caught in the harvesting machinery, then shredded and pressed into the cubes. The resulting toxin secreted by the animal parts may have produced the botulism bacteria that was then passed on to the horses. The toxin strikes the nervous system, usually within 48 hours after being ingested.
How many cubes have been tainted may never be known, Bryd said.
"Out of the 30,000 tons that they have sent down here (from Utah), maybe 16 or 17 are bad," he said. "We don't know if this is one load of cubes or an entire field of alfalfa."
The cubes were manufactured and distributed by Paramount Cubing, in southeast Los Angeles County. But Thompson said state officials have taken no action against the firm, except to quarantine those cubes delivered by the company to stables reporting sick horses.
To "firm up" the botulism theory, Thompson said testing of both the cubes and the stricken animals will continue. "Until proven otherwise, we believe that this is the cause," he said.
Thompson said the issue of whether the feed was prepared and shipped improperly has been turned over to the Feed, Fertilizer and Livestock Branch of the state agriculture department, the agency charged with regulating the animal feed industry. An spokesman said agency investigators have been dispatched to Utah to inspect the farms where the cubes are produced.
"At this point we have no reason to believe that anything improper has occurred," he said.
Byrd said the strain of botulism bacteria detected in the cubes is commonly found in dogs, cats and aquatic birds, but is extremely rare in horses. The last known occurrence of this type of botulism in a horse was 10 years ago in Florida. There is no cure for the illness, and the bacterium is considered one of the deadliest types known to man, officials said.
"One contaminated cube is enough to kill a horse," said Byrd, adding that he is awaiting the arrival of several types of experimental serums to treat those horses still suffering. "But nobody has had much experience with this, so there's no track record of how successful it might be."