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.



Equine Herpesvirus- Neurologic
San Mateo County, CA
Outbreak Identifier: 5236
Alert ID: 2611
June 07, 2022
Confirmed Case(s) - Official Quarantine

California Department of Food and Agriculture

Number Confirmed: 1;
Age: 7; Gender: Mare; Breed: Holsteiner; Clinical Signs: fever, mild neurological signs; Confirmation Date: 6/6/2022; Horse Status: Affected And Alive; Vaccination Status: Vaccinated;
Notes: A 7-year-old Holsteiner mare in San Mateo County displaying fever followed by mild neurological signs was confirmed positive for Equine Herpesvirus Myeloencephalopathy (EHM) secondary to EHV-1 (non-neuropathogenic strain) on June 6th. She was referred to a veterinary hospital at onset of neurological signs, and isolated and quarantined. She attended an equine event in Sacramento County the weekend prior, asymptomatic throughout the show, and departing on Saturday May 28th with 5 other horses from her home barn. Event management has notified all show attendees to observe best biosecurity practices and isolate any horses returning from the event for 14 days following departure from the show grounds. CDFA was onsite at the index mare’s home premises, and 9 potentially exposed horses were also quarantined and enhanced biosecurity measures implemented. There is no known epidemiological link between this case and the previously confirmed active EHM incident in San Mateo County. CDFA will actively monitor the situation. For more information go to EHM factsheet.