A yearling paint colt in Otsego County, Michigan, presented with a fever on June 2, and the Michigan Department of Agriculture and Rural Development (MDARD) reported a positive test on June 14. The horse is currently recovering in voluntary quarantine and has an unknown vaccination status.
Two horses in Genesee County, Michigan, also tested positive. The first, an unvaccinated 6-year-old Thoroughbred gelding, presented with a fever, cough, lethargy, nasal discharge, and enlarged lymph nodes on May 4 and was confirmed positive on June 9, accordg to the MDARD. A 10-year-old Quarter Horse mare on the same premises presented with a fever and nasal discharge on June 3 and tested positive on June 13. She was also unvaccinated. Both horses are recovering in voluntary quarantine, and a third horse on the property was exposed and is suspected positive.
Lastly, an unvaccinated stallion in Van Buren County, Michigan, presented with enlarged lymph nodes on May 16, and the MDARD confirmed a positive diagnosis. He’s in voluntary quarantine and is recovering.
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.