Signs of respiratory disease include mild fever, occasional coughing and discharge from the nose.
Foals born alive but infected in utero are usually abnormal from birth, showing weakness, jaundice, difficulty in breathing and occasionally neurological signs. They usually die, or require euthanasia, within three days. The most common sign in older foals, usually following weaning, is a nasal discharge. less commonly, secondary bacterial infection may cause pneumonia.
There are usually no warning signs of abortion caused by EHV. A sudden and unexpected abortion with a sometimes-jaundiced foal enclosed within the placenta ("red bag" placenta), should always be treated with suspicion, the mare isolated and veterinary help sought to confirm or rule out EHV infection without delay.
Horses affected by paralytic EHV often display incoordination of the hind, and occasionally front limbs, urine and/or faecal retention and, in severe cases, recumbency (lying down and unable to stand). These signs may or may not be preceded by initial respiratory signs and there may have been a history of EHV abortion on the premises. A sudden and unexpected incoordinated or collapsed horse should always be treated with suspicion, the horse isolated and veterinary help sought to confirm or rule out EHV infection without delay.