A 4-year-old Thoroughbred mare at a boarding barn in Wellington County, Ontario, is positive for strangles. The mare was recently purchased and arrived on the property on March 4. On March 12, she developed a fever, followed by nasal discharge and swollen submandibular lymph nodes. She tested positive for S. equi by PCR on March 17.
On March 13, a horse on her previous property was confirmed positive for strangles. Now, the positive mare is being isolated in a vacant barn on a nearby property. The remaining horses are being monitored for clinical signs. The facility owner is working with the attending veterinarian on biosecurity and movement restrictions. It is unknown how many 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.
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:
- 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.