Four horses in Ontario recently tested positive for strangles. The horses live in Simcoe and Essex counties. 

In Simcoe County, a 10-year-old gelding at a boarding facility tested positive after he and another horse were purchased from a different facility. The two horses were appropriately isolated upon arrival at the new boarding facility. This horse developed purulent nasal discharge, which was positive on PCR for S. equi. 

In Essex County, three senior horses at a private facility were noted to be mildly off feed the week of January 6. One horse developed an abscess under the jaw on January 12, and all three horses tested positive for S. equi on PCR. The positive horses have been isolated, and eight additional horses are exposed. 

EDCC Health Watch is an Equine Network marketing program that utilizes information from the Equine Disease Communication Center (EDCC) to create and disseminate verified equine disease reports. The EDCC is an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.

About Strangles

Strangles in horses is an infection caused by Streptococcus equi subspecies equi and spread through direct contact with other equids or contaminated surfaces. Horses that aren’t showing clinical signs can harbor and spread the bacteria, and recovered horses remain contagious for at least six weeks, with the potential to cause outbreaks long-term.

Infected horses can exhibit a variety of clinical signs:

• Fever
• Swollen and/or abscessed lymph nodes
• Nasal discharge
• Coughing or wheezing
• Muscle swelling
• Difficulty swallowing

Veterinarians diagnose horses using polymerase chain reaction (PCR) testing with either a nasal swab, wash, or an abscess sample, and they treat most cases based on clinical signs, implementing antibiotics for severe cases. Overuse of antibiotics can prevent an infected horse from developing immunity. Most horses make a full recovery in three to four weeks.

A vaccine is available but not always effective. Biosecurity measures of quarantining new horses at a facility and maintaining high standards of hygiene and disinfecting surfaces can help lower the risk of outbreak or contain one when it occurs.