P.E.I. vet says isolation and testing key to stopping spread of strangles

·5 min read
Brielle Doyle, a medical laboratory technician in the AVC Diagnostic Services's bacteriology lab, examines bacterial growth on culture plates.
Brielle Doyle, a medical laboratory technician in the AVC Diagnostic Services's bacteriology lab, examines bacterial growth on culture plates.

(Anna MacDonald/AVC - image credit)

A P.E.I. vet is recommending isolation and testing as keys to stopping the spread of strangles.

Two P.E.I. horses tested positive last week, one at the Red Shores Racetrack in Charlottetown and another at the Shamrock Training Centre in Ontario. It had just been transported from Red Shores on Sunday, Feb. 14.

Dr. Ben Stoughton, large animal medicine clinician at the Atlantic Veterinary College, said strangles is highly contagious.

"I typically explain strangles as being strep throat of horses, just like people get strep throat and a sore throat and can have a fever and feeling badly," Stoughton said.

"Similar to people, they may get a fever, they may have a sore throat, have difficulty swallowing. They could get swollen lymph nodes that you can palpate and can also have stuff coming out of their nose."

Taking temperature and testing

Since the first outbreak at Red Shores in Charlottetown in November 2020, the Atlantic Provinces Harness Racing Commission recommended horse owners at Red Shores locations in Charlottetown and Summerside monitor their animals' temperatures twice daily.

"We're looking for a fever," Stoughton said.

"As the body tries to fight infection, like in this case, it's a bacterial infection, the body responds by increasing the temperature, which can be measured with a thermometer."

Dr. Stoughton said a sample is collected from a horse exhibiting symptoms by sticking a tube up its nose and washing out the area with a saline solution, collecting it in a cup and culturing it.
Dr. Stoughton said a sample is collected from a horse exhibiting symptoms by sticking a tube up its nose and washing out the area with a saline solution, collecting it in a cup and culturing it.

Dr. Stoughton said a sample is collected from a horse exhibiting symptoms by sticking a tube up its nose and washing out the area with a saline solution, collecting it in a cup and culturing it.

Stoughton said a sample is collected from a horse exhibiting symptoms by sticking a tube up its nose and washing out the area with a saline solution, collecting it in a cup and culturing it.

He said they also use a PCR, or polymerase chain reaction, test to detect DNA of bacteria, a kind of test also being used for COVID-19.

Identification of bacteria can be performed in minutes using the MALDI-TOF Mass Spectrometer in the AVC Diagnostic Services's bacteriology lab.
Identification of bacteria can be performed in minutes using the MALDI-TOF Mass Spectrometer in the AVC Diagnostic Services's bacteriology lab.

Identification of bacteria can be performed in minutes using the MALDI-TOF Mass Spectrometer in the AVC Diagnostic Services's bacteriology lab.

Stoughton said it's crucial to isolate horses as quickly as possible once they have shown symptoms.

"Because the bacteria that causes this is very contagious among horses, so it's easily spread from nose to nose, or even contact with people," Stoughton said.

"If they have a nasal discharge that has the bacteria in it, it gets on the environment, gets on a person, and then a horse goes and actually licks that, or smells that, and they get it back up into their nose. That's how it would spread."

Dr. Ben Stoughton, large animal medicine clinician at the AVC, said strangles is highly contagious.
Dr. Ben Stoughton, large animal medicine clinician at the AVC, said strangles is highly contagious.

Dr. Ben Stoughton, large animal medicine clinician at the AVC, said strangles is highly contagious.

Stoughton said that's why the biosecurity measures now in place at Red Shores are important, including wearing gloves, disinfecting horse gear, disinfecting the feed and water tubs and limiting the people in and out of barns in quarantine.

He said the majority of sick horses only need supportive care, but will occasionally need antibiotics if the horses have a severe obstruction.

"They call it strangles because the lymph nodes that get infected with this bacteria can get so large that they actually obstruct the ability for the horse to breathe," Stoughton said.

"So that's how it got the name strangles because they can get so swollen that the horse can't race."

Signage at Red Shores Racetrack aimed at restricting acccess to the barn area.
Signage at Red Shores Racetrack aimed at restricting acccess to the barn area.

Signage at Red Shores Racetrack aimed at restricting acccess to the barn area.

Most horses recover

Stoughton said strangles is not widespread, but also not uncommon.

"If you have horses, mules, ponies, donkeys, anywhere in the world, you're going to eventually have this bacteria pop up," Stoughton said.

"But thankfully, it's not bad outbreaks all the time, but it wouldn't be surprising to have it occur once a year, once every other year, depending on where you are in the world."

Dr. Stoughton said the infection spreads through close contact. These horses do not have strangles but demonstrate the kind of nose to nose contact that can lead to transmission.
Dr. Stoughton said the infection spreads through close contact. These horses do not have strangles but demonstrate the kind of nose to nose contact that can lead to transmission.

Dr. Stoughton said the infection spreads through close contact. These horses do not have strangles but demonstrate the kind of nose to nose contact that can lead to transmission.

Stoughton said a very low percentage of horses die from strangles, and most will recover in two to three weeks.

He said they only start testing to confirm that the horse is no longer a carrier three weeks after the last clinical signs.

In the Atlantic provinces, the harness racing commission requires three negative tests for strangles before a horse is cleared for racing.

The harness racing season is finished for now at Red Shores Racetrack, resuming in May.
The harness racing season is finished for now at Red Shores Racetrack, resuming in May.

The harness racing season is finished for now at Red Shores Racetrack, resuming in May.

Stoughton said if they only did one test, they could miss some of the bacterial organisms.

"We're less likely if you do it three consecutive times to miss a carrier horse," Stoughton said.

"It's important that we not miss the carrier horse, because if we call that horse negative and it's technically positive, then that horse gets put out with other horses, and then could restart the problem all over again. So it's just to be extra cautious."

Red Shores Racetrack has taken measures to prevent the spread of strangles, including adding security and restricting who can enter the barns.
Red Shores Racetrack has taken measures to prevent the spread of strangles, including adding security and restricting who can enter the barns.

Red Shores Racetrack has taken measures to prevent the spread of strangles, including adding security and restricting who can enter the barns.

Stoughton said there have been occasional reports of this bacteria spreading to humans, in people that have immune suppression.

He said the main concern with humans is that they would get the bacteria on their body or hands, and spread it from horse to horse.

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