Four horses in Ontario have tested positive for strangles:In Elgin County, one mare tested positive on Dec. 31 after developing an abscessed, draining lymph node. A 12-year-old gelding in Elgin County tested positive on Jan. 3; this horse was purchased from a horse dealer in Lambton County and arrived at his owners facility on Dec. 21 with nasal discharge.In the Regional Municipality of Durham, a 19-year-old Paint gelding at a boarding facility tested positive on Dec. 31 after developing unilateral nasal discharge.In Grey County, a 14-year-old Quarter Horse mare tested positive on Jan. 6 after developing abscessed submandibular lymph nodes. Two horses from her paddock have developed draining lymph nodes, and a third horse from the paddock has mild clinical signs; these horses are suspected to be positive.All of the positive horses are quarantined.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. TheEDCCis an independent nonprofit organization that is supported by industry donations in order to provide open access to infectious disease information.About StranglesStranglesin horses is an infection caused byStreptococcus equisubspeciesequiand spread through direct contact with other equids or contaminated surfaces. Horses that arent 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:FeverSwollen and/or abscessed lymph nodesNasal dischargeCoughing or wheezingMuscle swellingDifficulty swallowingVeterinarians 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 helplower the risk of outbreakorcontain one when it occurs.