Nine months after a potentially fatal equine virus swept western states, the disease is back. Five new cases of Equine Herpes Myoencephalitis (EHM), also referred to as neurological Rhino, a mutated form of the Equine Herpes Virus 1 (EHV-1) were reported at a facility in California by the California Department of Food and Agriculture (CDFA) during the past week.
On January 11, 2012, a gelding displaying neurologic signs from an Orange County premises was confirmed positive for the neuropathogenic strain of Equine Herpes Virus-1. The gelding was isolated, quarantined and placed under veterinary care.
The large multi-discipline facility has been quarantined with no movement of horses on or off the property. The potentially exposed horses on the premises are being monitored. A full epidemiologic investigation at the affected premises was initiated by the CDFA Animal Health Branch.
On January 12, 2012, two additional horses displaying fever and respiratory signs were confirmed positive for the neuropathogenic strain of Equine Herpes Virus- 1, on the Orange County premises. All horses on the premises remained under quarantine and were being monitored for disease.
Then on January 13, 2012, two additional horses displaying a fever were confirmed for the neuropathogenic strain of Equine Herpes Virus-1. There are now a total of five confirmed positive cases on the Orange County premises. All horses on the property continue to be monitored.
Last May, equestrian events throughout the western United States were cancelled due to an outbreak of the potentially lethal virus that began at an equestrian event at the Golden Spike Equestrian Center in Ogden, Utah, and spread rapidly to horses in California, Washington, Nebraska, Colorado, Texas, Arizona, Nevada, and Utah.
EHM attacks the horse's neurological system and in some cases, the horse must be euthanized. The virus is easily spread and has a high morbidity and mortality rate. Signs of EHM in horses may include nasal discharge, incoordination, hindquarter weakness, recumbency, lethargy, urine dribbling and diminished tail tone.
According to the CDFA all of the cases have been confined to one unidentified facility in Orange County and are under quarantine. The property where the horses are located was described as a large multi-discipline facility by the CDFA, with no movement of any horses on or off the premises.
Last May, more than 400 horses were exposed in Utah and 54 of those horses returned to California. Nearly half of the exposed horses contracted the virus. There were 22 confirmed cases in California by the CDFA and several of those horses had to be euthanized.
Since the outbreak last May, 11 cases have been reported in California but none were linked to the May 2011 incident.
Although there is no vaccination currently on the market that can make a "label claim" against EHM, vaccinating against EHV-1 is still advised to reduce a horse's chances of catching EHM.