UPDATE 9/3/2025: Three additional horses in Maryland have tested positive for strangles, a contagious equine infection.
A 5-year-old warmblood gelding at a boarding facility in Calvert County tested positive. In St. Mary’s County, two horses at a private facility are positive, including a suckling Hanoverian colt. All affected horses are under official quarantine.
17 horses at a boarding facility in Baltimore County are suspected to be positive for strangles. In addition, 28 horses have been exposed. The suspected cases are under official quarantine. Updates can be found by clicking here.
Additionally identified.
- One pony mare at a private facility in Montgomery County age 12
- Two warmblood geldings at a show barn in Anne Arundel County —ages 5 and 6
- Two Thoroughbred geldings used for pleasure riding at a boarding facility in Baltimore County, an 8-year-old and 9-year-old.
- One horse on a 50-horse farm in Cecil County (reported May 6
- One horse on a 20-horse farm in Carroll County (reported May 6)
- Five horses at a 76-horse boarding facility in Montgomery County (reported April 16 and 22).
Strangles Outbreak Alert: The Maryland horse community is currently experiencing a significant outbreak of Strangles, a highly contagious upper respiratory disease of horses. Multiple facilities across the state have confirmed positive cases.
These affected sites are under quarantine to restrict horse movement and prevent further spread of the disease.
Strict biosecurity measures and prompt recognition of clinical signs are essential to control the outbreak. If you suspect a horse may be showing signs of Strangles, contact your veterinarian immediately.
Strangles is a highly contagious bacterial disease of the upper respiratory tract in equids. It is caused by Streptococcus equi equi. Strangles is one of the most common infectious diseases of horses worldwide. Transmission occurs via direct contact with infected horses or with contaminated equipment or clothing.
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
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. For more information about Strangles, biosecurity and disinfecting tips, please click the pictures below
