Four more horses have been confirmed with EHV-1 at Desert International Horse Park in Thermal, California, the California Department of Food and Agriculture reported late Monday, Feb. 21, bringing the total number of cases to 12.

One of the new cases was within the index barn where the disease first was reported on Feb. 11, and the other three were stabled elsewhere. The positive horses are displaying fever only with no neurologic signs and have been placed in isolation, and all horses in the exposure cohorts have been isolated and placed under quarantine.

To date, there have been three confirmed equine herpesvirus myeloencephalopathy cases (EHV-1 infection with neurological signs), including one horse who was euthanized Friday, and nine confirmed EHV-1 fever-only cases at the horse park. Showing has been canceled for the week and new, site-specific biosecurity protocols put in place to help prevent further spread.

CDFA continues to be on site at the DIHP premises and is actively monitoring the situation.

Test results are pending for a febrile horse who was at Los Angeles Equestrian Center last week for the LA February show, however the horse is improving, show officials reported Monday. Several horses at that show had come from Thermal after only five days in isolation rather than the recommended seven.