Six Horses in California Test Positive for EHV-1

Recently, six horses in Los Angeles County, California, were confirmed to have tested positive for equine herpesvirus-1 (EHV-1). The initial report on May 16 involved two horses: a 20-year-old Thoroughbred mare, which was subsequently euthanized, and a 28-year-old warmblood mare. Following these cases, authorities placed 95 horses that were potentially exposed under quarantine.

Four additional horses were later reported positive, including a 3-year-old gelding, a 20-year-old mare, a 21-year-old warmblood mare, and a 24-year-old Quarter Horse mare. EHV-1 is known to be highly contagious among horses and can lead to several health issues, such as respiratory problems (rhinopneumonitis), spontaneous abortions in broodmares, and equine herpes myeloencephalopathy (EHM). Symptoms may initially include fever, which can be missed, as well as cough, reduced appetite, lethargy, and nasal discharge, particularly in younger horses. Pregnant mares may not show symptoms before experiencing late-term abortions. In cases of EHM, horses typically exhibit fever alongside respiratory signs, followed by neurological manifestations like ataxia, weakness, and inability to rise.

The virus spreads easily through direct contact or shared equipment and personal items from those who have been around infected horses. To prevent outbreaks, it is crucial to maintain strict biosecurity measures, including routine hygiene and disinfection. While current vaccines may help mitigate viral shedding, they do not guarantee protection against the neurological symptoms of EHV-1. Implementing biosecurity protocols remains the most effective strategy for controlling the spread of this virus.