Outbreak Alert: July 25 & 26, 2021 – Equine Herpesvirus- CA and West Nile Virus, WA

July 25, 2021

Equine Herpesvirus- Neurologic
Sonoma County, CA

Number Confirmed: 5;
Number Suspected: 4;
Number Exposed: 19
Facility Type: Showgrounds;
Horse #1: Age: 6; Gender: Mare; Breed: Warmblood (WB); Onset of Clinical Signs: 7/23/2021;
Clinical Signs: Hind-end Weakness, Limb edema, Nystagmus, Recumbency; Confirmation
Date: 7/24/2021; Horse Status: Euthanized; Vaccination Status: Vaccinated;
Horse #2: Age: 15; Gender: Gelding; Breed: Warmblood (WB); Onset of Clinical
Signs: 7/22/2021;
Clinical Signs: Ataxia, Cranial Nerve Deficit, Fever, Neurologic Signs, Urine Dribbling; Confirmation Date: 7/23/2021; Horse Status: Affected And Alive; Vaccination
Status: Unknown
Notes: A 6-year-old Warmblood mare displaying neurological signs has been confirmed positive for EHM secondary to EHV-1. She attended a show in Sonoma County from 7/19-7/24 but did not compete, and event management has notified all participants to monitor temperatures twice daily and report any fevers or neurologic signs to their veterinarians and CDFA, as well as isolate all horses returning from shows at their home premises for at least 7 days. CDFA was onsite, and 19 exposed horses from the index mare’s barn were removed from the show facility and have been isolated and quarantined at the home premises in Sacramento County with the remaining 18 horses at the home premises with twice daily temperature monitoring and enhanced biosecurity measures. Six (6) horses from the home premises displaying fever and/or limb edema have also tested positive for EHV-1. A 15-year-old Warmblood gelding at the home premises that was febrile and tested positive for EHV-1 began displaying neurological signs, ataxia, urine dribbling, and cranial nerve deficits and was moved to isolation under quarantine at a veterinary hospital for care. CDFA continues to actively monitor the situation.; For more information go to: Equine Herpesvirus Myeloencephalopathy
Source: California Department of Food and Agriculture
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July 26, 2021

West Nile Virus
Yakima County, WA

Number Confirmed: 1;
Facility Type: Private Facility;
Horse Status: Euthanized; Vaccination Status: Status Unknown;
Notes: A horse at a private facility in Yakima County has tested positive for West Nile Virus.
Source: Washington State Veterinary Office
All information is sourced from

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