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Equine Herpesvirus Myeloencephalopathy (EHM) Outbreak
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Disease Alerts

Updates on current disease outbreaks are listed here as they occur and will include the date listed, disease name, location and current status. Specific premises will not be named but the general location by town, county and state will be listed. When locations, events or horses are at risk they will be listed. Updates will be posted as they are received.



Middlesex County, ON
Outbreak Identifier: 7256
Alert ID: 4789
December 10, 2025
Confirmed Case(s) - Voluntary Quarantine

OMAFA

Number Confirmed: 3; 
Number Suspected: 1; 
Number Exposed: Unknown; 
Facility Type: Training Facility; 

Horse 1: 
Breed: Standardbred; Clinical Signs: Two standardbreds, one who hasn't raced since June 2025 and another who last raced 11 days ago developed a high fever and submandibular lymph node swelling. Both tested positive for S. equi by PCR. A pony in the same shedrow with a draining abscess also tested positive for S. equi.; Confirmation Date: 12/10/2025; 

Comments: The infected horses are isolated and their care is being supervised by attending veterinarians. Trainers in the affected part of the barn have voluntarily withdrawn their horses from racing and are monitoring horses for fevers and the development of clinical signs of Strangles. Trainers at the facility are working with their veterinarians to institute biosecurity protocols.;