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7 Facts About Strangles You Need to Know
Recognized most for its signature symptom, strangles is a bacterial infection in horses similar to strep throat in humans. Are you familiar with how to spot less-obvious symptoms, treat, and prevent its spread?
June 16, 2020
Unlike with strep throat in people, strangles typically doesn’t require treatment so much as quarantine and vigilant cleaning of the surrounding environment to prevent the bacterial infection from spreading to other horses.

If you’ve owned or been around horses, you have most likely heard of strangles. Recognized most for its signature symptom—swollen lymph nodes in the throat—it is a bacterial infection similar to strep throat in humans.

But are you familiar with how to spot less-obvious symptoms, treat, and prevent the spread of strangles? The following are seven facts you may not know about Streptococcus equi equi.

  1. Strangles affects horses throughout the world, and the first time it was described was in 1251.
  2. Unlike with strep throat in people, strangles typically doesn’t require treatment so much as quarantine and vigilant cleaning of the surrounding environment to prevent its spread to other horses. It usually subsides on its own. “The symptoms in horses are certainly more dramatic, even than what you might get with strep throat because they can have large abscessed lymph nodes and a high fever, but they are actually better at clearing it without secondary complications than people are with strep throat,” says Alisha Gruntman of Tufts Equine Center’s internal medicine service.
  3. Strangles can stay active in water buckets and moist areas for four to six weeks, and the bacteria can survive for about one to three days in drier areas such as on fencing or in soil. The bacteria are primarily transmitted through nose-to-nose contact with an infected horse, but horses can catch the illness by encountering something contaminated with the bacteria, such as a water bucket. Though it’s thought to be very uncommon, another possible avenue of transmission is by other animals going through the barn. A barn cat or dog that’s wandering around can pick up the bacteria and spread it to other horses. To prevent that, keep other animals from the barn during an outbreak.
  4. Beyond water and feed buckets, you shouldn’t share any equipment, including pitchforks and grooming tools, during an outbreak. This will help prevent the spread of infection. “If you have a single infected carrier, we recommend all horses on the farm be monitored. Keep the infected horse physically separated from any other horse so that there’s no chance of nose-to-nose contact, and there will be less of a chance of bacteria being spread from one horse to another,” says Dr. Gruntman. Once finished with cleaning the infected horse, Dr. Gruntman recommends changing all clothes, including shoes, so that bacteria aren’t spread around.
  5. One of the best ways to prevent bringing strangles into the barn is to quarantine new arrivals for at least three weeks. “You could also test any new arrivals for strangles before they’re released from that quarantine period to make sure that they’re not shedding the bacteria,” says Dr. Gruntman. And, when around other horses, good hygiene should be practiced, especially at places like shows—don’t share anything like water buckets that are more likely to harbor the bacteria longer.
  6. Unless a horse is having complications, it is best not to treat with antibiotics. A recent study showed that horses that were treated with antibiotics had a lower titer against the bacteria, which may reduce their chance of developing a strong immune response that can then prevent re-infection, according to Dr. Gruntman.
  7. About 75% of horses that get infected have protective immunity from strangles for at least a year afterward. “However, a small percentage of horses do not develop a protective immune response, so it is always best to assume a horse is not immune to it,” says Dr. Gruntman.

Though strangles is endemic and highly contagious, practicing good hygiene and having a biosecurity plan in place ahead of time can help the spread of the infection. If you think your horse may be exhibiting symptoms of strangles, contact your veterinarian immediately to develop a plan for isolation, testing, and treatment.

Dr. Alisha Gruntman is a veterinary internist at Tufts Equine Center. Dr. Gruntman commonly treats colic, colitis, enteritis, gastric ulcers, pneumonia, equine asthma, neurologic diseases, and many other common and vague illnesses.