Vaccination can help protect horses against strangles. | Erica Larson/The Horse

Strangles, caused by the bacteria Streptococcus equi, is a highly contagious upper respiratory disease most common in young horses. It also has several potentially fatal complications and the capability to cause persistent infections in populations of asymptomatic carrier horses.

Clinical signs of strangles can include fever, nasal discharge, difficulty swallowing, abnormal breathing, and swelling and/or abscesses of the lymph nodes.

“Commonly, a horse with strangles will have profuse nasal discharge and swollen submandibular lymph nodes,” said Kevin Hankins, DVM, MBA, senior equine technical services veterinarian for Zoetis. “With strangles, about 10% of horses don’t fully recover from the disease and can then become persistent carriers. Unfortunately, persistent carrier horses don’t show the outward clinical signs that sick horses