Katie Hennessy

Strangles: In horses, it can be as bad as it sounds

STRANGLES is a highly contagious bacterial infection of the upper respiratory tract of horses. The infection is caused by the bacterium Streptococcus equi subspecies equi. The term “strangles” arose from the occasional suffocation of horses with the disease due to lymph nodes of the head and obstruction of the airway.

The bacteria that causes the disease can survive on buckets and water troughs for more than a month.

Asymptomatic carriers can shed the bacterium for months or even years. These horses are often the cause of recurrent outbreaks on a farm, even though they show no clinical signs of disease.

Clinical signs include fever, nasal discharge, difficulty swallowing, anorexia, and increased size of lymph nodes around the head and neck. The disease is diagnosed by culturing the bacteria in the nasal discharge or from PCR, which detects the bacterial DNA.

Antibiotic treatment of strangles is not necessary in many cases unless complications occur. Early antibiotic therapy may actually prevent a horse from developing immunity to the bacteria, rendering them susceptible to re-infection. The majority of horses with a strangles infection recover normally, while some may develop secondary complications. These complications can include infection of lymph nodes throughout the body (“bastard” strangles), muscular disorders, pain, and severe immune mediated diseases, which can be fatal. Any horse with complications should receive antibiotic therapy.

Vaccination is something that you should discuss with your veterinarian to assess your horse’s risk factors. It’s important to remember that the vaccination does not prevent the disease but reduces the clinical signs in infected horses. Once given, the vaccine needs a booster vaccine in three to four weeks and then requires one month for the body to develop immunity.



BIO: Dr. Katie Hennessy graduated from the University of Illinois College of Veterinary Medicine in 2008 with a degree in large animal health and equine medicine. She completed an advanced internship at The Equine Medical Center of Ocala and now is the owner and practicing veterinarian at Polk Equine. Her expertise ranges from small and exotic creatures to large animals, specializing in equine medicine.

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