Latest Information Regarding Equine Herpes

Equine Herpes Virus

Alert

California EHV-1 Causing EHM Disease Update as of 12 pm 5/21/2011

California has one new confirmed case of Equine Herpes Myeloencephalopathy (EHM) caused by EHV-1.  There are 16 confirmed EHM cases in the state.

• The positive confirmed cases are located in the following 11 counties: Amador(1), Glenn(2), Kern(2), Los Angeles(1), Marin(1), Napa(1), Placer (2), Plumas(1),  Shasta(1), Stanislaus(3), Ventura(1). 
• Fifteen(15) of the confirmed positive EHM CA cases participated in the National Cutting Horse Association’s Western National Championships in Ogden, Utah.
• One(1) of the confirmed positive EHM CA cases participated only in the Kern County Cutting Horse Event on May 13th in Bakersfield, CA.  
• One confirmed positive EHM horse was euthanized after showing severe neurological signs associated with EHM.
• Two confirmed positive EHM horses are being treated at the University of California Veterinary Medical Teaching Hospital in Davis.
• Six positive horses have displayed neurological signs.  The other cases have only been febrile.
• All positive confirmed EHM cases are under a State Quarantine.

A suspect case of Equine Herpes Myeloencephalopathy (EHM) was investigated by Animal Health Branch veterinarians.  This mare did not participate in the National Cutting Horse Association’s Western National championships in Ogden, Utah from April 30 – May 8, 2011, nor did she participate in the Kern County Cutting Horse Event on May 13th.  This mare did participate in the Rancheros Vistadores ride in Santa Ynez, CA from May 5 – 12, 2011.  This mare is exhibiting neurological signs compatible with a number of equine diseases or conditions.  Three sets of nasal swabs and blood testing on this mare indicate she is negative for the mutant strain of EHV-1 that causes EHM and she is positive for the common strain of EHV-1 that most commonly causes respiratory signs but may also cause neurological signs in a low percentage of these cases. These findings indicate this mare is not associated with the ongoing EHM outbreak.   This mare is quarantined, isolated and continues to receive intensive supportive treatment at the Veterinary Medical Teaching Hospital in Davis as the veterinarians continue consideration of other differential diagnoses. 

California EHV-1 Disease Update as of 3pm 5/20/2011 California has two new confirmed cases of Equine Herpes Myeloencephalopathy (EHM) caused by EHV-1. There are 15 confirmed EHM cases in the state. The positive confirmed cases are located in the following 10 counties: Amador(1), Glenn(2), Kern(2), Los Angeles(1), Marin(1), Napa(1), Placer (2), Plumas(1), Shasta(1), and Stanislaus(3). All confirmed positive EHM CA cases participated in the National Cutting Horse Association’s Western National Championships in Ogden, Utah. One confirmed positive EHM horse was euthanized after showing severe neurological signs associated with EHM while at the Kern County Cutting Horse Event on May 13th in Bakersfield, CA. Two confirmed positive EHM horses are being treated at the University of California Veterinary Medical Teaching Hospital in Davis. Six positive horses display neurological signs. The other cases have only been febrile. All positive confirmed EHM cases are under a State Quarantine. A suspect case of Equine Herpes Myeloencephalopathy (EHM) is under investigation by Animal Health Branch veterinarians. This mare did not participate in the National Cutting Horse Association’s Western National championships in Ogden, Utah from April 30 – May 8, 2011. This mare did participate in the Rancheros Vistadores ride in Santa Ynez, CA from May 5 – 12, 2011. This mare is exhibiting neurological signs compatible with a number of equine diseases or conditions, including EHM. Initial testing did not provide a confirmatory diagnosis. Confirmatory tests are ongoing at the veterinary hospital where this mare is quarantined, isolated and receiving intensive supportive treatment. CDFA will continue to monitor the situation and provide daily updates. Currently, in California, all confirmed cases of EHM are horses that participated in the Ogden, Utah cutting event.