Six Ontario horses test positive for strangles

Six horses in Ontario, including one in the United Counties of Prescott and Russell, recently tested positive for strangles. 

According to EDCC Health Watch, in Prescott-Russell, a yearling Standardbred filly tested positive in June after arriving from another farm in Ontario in November. Two additional horses at the private facility are exposed. 

In Peterborough County, five horses at a private facility are positive. The farm owner is working with their veterinarian to implement movement restrictions and infection control measures. 

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.