The Latest EHV-1 and EHM cases from the Equine Disease Communication Center

Several counties in California have reported EHV1 and EHM cases occurring at various barns.

Orange County California

On March 3, the Equine Disease Communication Center (EDCC) posted an update that two additional horses at a facility in Orange County California have been confirmed positive for EHV-1. To date, there are 86 exposures reported at the premises. The two newest positive horses displayed fever only and no neurological signs per the report. California Department of Food and Agriculture (CDFA) continues to monitor the situation. As of March 3, there had been one confirmed EHM case (EHV-1 infection with neurological signs) and sixteen (16) positive EHV-1 fever-only cases associated with this incident.

Riverside & Sonoma Counties in California

On March 1, one additional horse that had attended the event in Riverside County and had subsequently returned to his home premises in Sonoma County displaying fever only with no neurologic signs was confirmed positive for EHV-1. The horse is currently isolated and under veterinary treatment at an offsite facility for an unrelated condition. Three additional horses on the index event premise, one inside and two outside of the index quarantine barn, displaying fever only with no neurologic signs confirmed positive for EHV-1. To date, there have been three confirmed EHM cases (EHV-1 infection with neurological signs) and 23 confirmed EHV-1 fever-only cases associated with this incident. CDFA continues to be on site at the event premises and is actively monitoring the situation.

Los Angeles County

A 20-year-old Warmblood gelding in Los Angeles County displaying neurological signs on February 22 was confirmed positive for Equine Herpesvirus Myeloencephalopathy (EHM) secondary to equine herpesvirus-1 (EHV-1 non-neuropathogenic strain) on February 24. The horse was euthanized due to severity of clinical signs. This gelding attended a show in LA County the week prior.

For additional updates from other counties affected visit Equine Disease Communication Center.

Clinical Signs & Diagnosis

Clinical signs of the life-threatening disease EHM include but are not limited to depression, loss of coordination, hind limb weakness, loss of tail tone and nasal discharge. According to EDCC, the virus typically causes a two-phase fever and neurological signs may not present until the second fever. To diagnosis the disease, a veterinarian collects nasal swabs and blood for lab analysis.

There is no USDA licensed EHV-1 vaccine which is proven to protect against the neurological disease associated with EHV-1. Biosecurity and vaccinations are considered the best forms of disease prevention.

It is always a good idea to visit with your veterinarian with questions and concerns relating to equine infectious diseases, especially if you have plans to be on the road traveling to events.  


Read Containing Contagions

The American Association of Equine Practitioners (AAEP) has updated the resources they have available on EHV and EHM HERE.

EDCC EHM Fact Sheet

EHV1 & EHV4 Fact Sheet