Red Shores racetrack places 45 horses in isolation after strangles tests

The Red Shores racetrack in Charlottetown has placed 45 horses in isolation after receiving a positive PCR test for the bacteria that causes strangles —Streptococcus equi. 

Yet according to a release from Red Shores, out of the 199 horses tested on the grounds, not a single one was identified as having clinical signs of strangles.

Strangles is an upper-respiratory illness that can cause swollen lymph nodes, nasal discharge and fevers in horses, donkeys and mules. While the illness can be fatal, most animals do survive. 

It is highly contagious and spreads easily through nose-to-nose contact between horses, or even contact with people. If handlers get the bacteria from one horse on their hands, feet or clothing, they can pass it on to another horse.

Treat as if contagious

PCR, or polymerase chain reaction, is a highly sensitive form of testing that detects bacterial DNA, such as that of Streptococcus equi. (If it sounds familiar, it's also the technology that is used to test for the presence of the virus that causes COVID-19 in humans.)

"It just basically means that they've come back as PCR positive, which indicates that the horse has been exposed to Strep equi, and therefore that the potential to infect other horses might be there," said Brett Revington, director of racing for the Atlantic Provinces Harness Racing Commission.

Revington said the strangles PCR test does not distinguish between the DNA of live bacteria or dead bacteria, and can't detect if the bacteria is there because the horse had been recently vaccinated.

"So for this reason, a positive test does not necessarily indicate that a horse is clinically ill with strangles," he said. "But it does mean that we have to treat the horse like the horse is contagious, and it may affect other horses, until further sampling and testing confirms that the horse is negative." 

Revington said those 45 horses, and some others, will be tested again. That testing is now underway.

In the meantime, he said the horses with the positive PCR tests have been separated from the rest of the horse population.  

"All 45 horses, they've been separated within zones, within their barns, generally positive horses at one end, and then a stall in between, and then with the negative horses on the other end," Revington said.

"They're being monitored by the attending veterinarian, and the trainers and grooms that work in those barns." 

Get a 'good handle'

Revington said he was not surprised that 45 of 199 tests came back positive, given how the test probes the horse's DNA.

"We were expecting a large number," he said. "Horses do get exposed to strangles throughout their lives and we just weren't quite sure where it would fall. But I think that's a number that we were somewhat expecting."

The Atlantic Commission is helping to pay for the testing, along with Red Shores and the P.E.I. Harness Racing Commission. 

"We want to get a broad sense of how far it might have been exposed, how many horses were exposed, and just kind of get a good handle on it instead of doing isolated barns, and then two or three weeks down the road, another barn might pop up," Revington said.

"We would just rather get what we're dealing with as a whole."

Revington said everyone will be watching closely.

"We definitely want to see that number decrease. Racing isn't scheduled to return for another eight weeks so it's really too early to comment about racing at the present time.

"We're focused on the current situation at hand. The priority remains getting this cleaned up — not only as quickly as possible, but more importantly, as safely as possible." 

Revington also said Red Shores has established a biosecurity officer on the premises, taking on responsibility for enforcing the mandatory measures.

"It's new for a lot of people and it's a stressful time for everyone as well. So I think just to have someone designated to that position, to really answer questions, and just to offer reassurance that everything is being done that they possibly can."

Strangles vaccine 

Meanwhile, a veterinarian at the Atlantic Veterinary College said he and his colleagues are fielding more questions about strangles these days.

J Trenton McClure specializes in large animal internal medicine and infectious disease control. He said there is one vaccine that is readily available in Canada, a modified live vaccine injected in the nose of the animal.

Vaccines for strangles have been shown to prevent the disease, or reduce its severity in horses. But McClure said there is a danger in administering it if the animal has already been exposed to strangles.

"The concern is that, if the horse has been exposed — especially fairly recently — and has a strong immune response already, that there is a rare condition called Purpura hemorrhagica," McClure said.

"The body's own immune system kind of overreacts, and that causes a severe disease, where you get swelling in the legs and fevers.Those are relatively rare but when they do occur, it's because the horse already has a strong immune response. So that's the major concern." 

McClure said a horse that has never been vaccinated before requires two doses of vaccine two to three weeks apart, and the protection will begin seven to 14 days after the second dose.

He recommends vaccinating at least a month ahead of taking a horse to a place with a high risk of exposure, such as a farm with a previous history of strangles, or racetracks, horse shows or broodmare farms.

McClure added that the vaccine is approved only for horses nine months of age and older.

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