Recently, two horses in Los Angeles County, California, tested positive for equine herpesvirus-1 (EHV-1). The first case involved a 20-year-old Thoroughbred mare that developed equine myeloencephalopathy (EHM) and was subsequently euthanized. The second case was a 28-year-old warmblood mare who tested positive after showing signs of fever but remains alive. Additionally, 95 other horses on the premises are under quarantine due to potential exposure, with monitoring by the California Department of Food and Agriculture.

EHV-1 is a highly contagious virus that can lead to various health issues in horses, including respiratory diseases, abortions in pregnant mares, and neurological conditions like EHM. Initial symptoms often include fever, which can go unnoticed, along with other signs such as cough and decreased appetite. Infected pregnant mares may not show symptoms before experiencing late-term abortions, which can occur weeks to months after infection.

Preventative measures are crucial, as EHV-1 spreads easily through close contact and contaminated equipment. While current vaccines may reduce viral shedding, they do not prevent the neurological form of the disease. Therefore, maintaining rigorous biosecurity practices is essential for minimizing the risk of infection and controlling the spread of EHV-1 among equine populations.