The gelding was isolated, quarantined and was under veterinary care, the department said.
The large multi-discipline facility where the horse was living was placed under quarantine, with no movement of horses on or off the property.
Potentially exposed horses on the premises were being monitored, it said.
A full epidemiologic investigation at the premises was being undertaken by the department's Animal Health Branch.
On Thursday, the department reported that two additional horses displaying fever and respiratory signs had been confirmed positive for the neurological strain.