Eight new cases of strangles have been reported in three states this week. Three of the horses reside in Florida, four in Michigan, and one in Ohio.
A 5-year-old Warmblood at a boarding facility in Manatee County, Florida, presented with a fever, nasal discharge, enlarged submandibular lymph nodes, and possible ocular neurologic signs on May 14. The horse was reported as positive for strangles by the Florida Department of Agriculture and Consumer Services (FDACS) on May 19, and 39 horses were exposed. Also on May 19, FDACS officials reported a horse in St. Lucie County and a horse in Indian River County had tested positive. Strangles vaccination status for these horses was not available, and all have been quarantined.
On May 18 the Michigan Department of Agriculture and Rural Development reported two Kent County, Michigan, Thoroughbreds—a 14-year-old gelding and a 4-year-old mare, with clinical signs starting March 28 and April 29, respectively—tested positive for strangles on May 11. Both horses, which live on the same premises, presented with nasal discharge, the gelding developed a fever, and the mare had enlarged lymph nodes. Another four horses are suspected to be infected. These horses’ vaccination status is unknown, and they are recovering in voluntary quarantine.
Two unvaccinated Tennessee Walking Horse geldings in Oakland County, Michigan, tested positive (ages 29 and 22) for strangles on May 10. Both horses presented with nasal discharge, and the Michigan Department of Agriculture and Rural Development reported in the May 18 Equine Disease Communication Center alert that the horses are recovering in voluntary quarantine.
Finally, a 10-year-old Thoroughbred in Hamilton County, Ohio, tested positive after presenting with a 103.5-degree fever, nasal discharge, and swollen lymph nodes. The horse has been isolated, and two other horses were possibly exposed at the boarding facility.
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.