03/28/2005 12:00AM

Strangles is rarely fatal, but outbreak still scary


LEXINGTON, Ky. - The recent strangles outbreaks at the Trackside training center in Kentucky and Palm Meadows in Florida have raised awareness of this bacterial infection, which can spread quickly but is only occasionally fatal.

Churchill Downs, which operates Trackside, reported Friday that six horses tested positive for strangles last week, down from 19 the previous week. And Palm Meadows had reported five positives, with an additional suspected case that had not been confirmed by Monday.

Caused by the bacterium Streptococcus equi, the upper respiratory disease generally causes a sudden fever, nasal discharge, and swollen lymph nodes around the affected horse's throat area. The disease got the lurid popular name "strangles" because the lymph-node swelling can, in rare cases, become large enough to restrict a horse's breathing.

Most cases, veterinarians emphasize, do not become severe enough to kill a horse, and most horses develop long-term, but not permanent, immunity to the disease in recovery. But strangles outbreaks are still serious. Because the disease is so contagious, it can quickly affect large populations of horses, a situation that can have significant financial ramifications when authorities must quarantine horses or restrict shipping to combat an outbreak.

Strangles can be spread remarkably easily by horses, people, and even inanimate objects. The bacteria are contained in affected horses' nasal discharge, droplets of which can be carried to uninfected horses by equine-to-equine contact or by handlers who carry equipment from one area to another. Some horses that show no signs of illness can shed the bacteria, making it difficult sometimes to pinpoint the source of an outbreak. Horses generally shed the bacteria starting two or three days after the fever, and they can shed it for two to three weeks, or longer in some cases.

"It's sneaky stuff," said Dr. Mary Scollay, Gulfstream Park's track veterinarian. "The disease can be transmitted from horse to horse, from horse to person to horse, or from horse to inanimate object to horse on buckets, veterinary equipment, sponges, the clothes of a worker, a pitchfork. There are plenty of places that a horse can smear nasal discharge where another horse will come in contact with it."

In addition to quarantining affected horses, racetracks and farms can take other precautions to prevent the bacteria's spread. At Gulfstream, Scollay said, officials are disinfecting the starting gate between races, having the gate crew and jockeys' valets use hand sanitizers throughout the work day, and disinfecting barns. Such measures, combined with quarantine, can be effective at halting an outbreak.

"It's a scary little disease because it is so sneaky, but it can be contained through hygiene, vigilance, and responsible horsemanship," Scollay said.

There are intranasal and intramuscular vaccines for the disease, but veterinary authorities warn that vaccinating horses during an outbreak can sometimes be risky. A small percentage of horses that are incubating the bacteria can have an extreme allergic reaction after vaccination, resulting in hives and swelling in the legs, abdomen, and other areas. The vaccines are most often given in a series of two doses and cost $15 to $20.

"I think it's a highly personal decision that should be reached between the individual veterinarian and trainer based on their risk assessment in that particular barn," Scollay said of vaccination.

Trainer Bill Mott, who stables a South Florida string at Payson Park, said he opted not to vaccinate after consulting with two veterinarians. Mott said he was slightly concerned about potential negative effects such as the allergic reaction, or abscesses at the injection site.

"Also, my understanding is that with a vaccinated horse you're reducing your risk only about 50 percent, not 100 percent," Mott said. "We're using our own van and that sort of thing to try to isolate ourselves as much as possible."

For horses who come down with the disease, there are two main modes of treatment, said central Kentucky veterinarian Dr. Stuart Brown: treatment with antibiotics for up to 21 days, or application of a penicillin-based gel directly into the horse's guttural pouches, air-filled sacs on each side of the throat. The latter procedure requires an endoscope. Treatment costs vary according to the disease's severity, but Brown estimates that it could range from $150 to $200 for mild cases, up to "the upper hundreds" for more severe manifestations.

Fortunately, the disease rarely causes death, especially among adult horses.

"In terms of individual horse health, the risk of fatality is quite low," Scollay said. "But just because a disease doesn't kill, that doesn't mean it can't have a significant financial impact."