Equine herpesvirus-1, also known as EHV-1, has been making headlines for the past few years. In 2011, some horses that had attended the National Cutting Horse Association Western National Championship in Ogden, Utah, began showing neurologic signs after leaving the event. This particular outbreak affected the equine industry in multiple states, and lead to fatalities in some horses that developed the neurologic form of EHV-1, called equine herpesvirus myeloencephalopathy (EHM).

EHV-1 is highly contagious to other horses and can cause respiratory disease primarily in juvenile horses, such as nasal discharge, fever and coughing; infection can also result in abortion and neonatal death. The most concerning manifestations of EHV-1 infection are neurologic signs, such as a wobbly gait caused by lack of coordination of the limbs, with the hind limbs often more severely affected, as well as urinary incontinence. These appear when the virus causes damage to blood vessels in the brain and spinal cord. Though EHM is not new, more outbreaks are being recognized with more horses seeming to be affected in each outbreak, causing concern among many equine owners.

EHV-1 can affect horses of all breeds and ages and is spread via direct contact (nose-to-nose contact), indirect contact (from shared water buckets or tack, as well as from people’s hands), and through the air (aerosolized transmission).

Though there are many vaccines containing EHV-1 (the rhinopneumonitis vaccine your horse typically gets in his regular vaccine series), there is no vaccine currently on the market that has a label claim for prevention of the neurologic form of the disease. The goal of vaccination is to boost immunity in order to control respiratory disease or abortion resulting from of EHV-1 infection