Equine viral arteritis is another viral infection that causes significant respiratory disease and blood vessel inflammation. It is caused by the equine arteritis virus. The most important consequences of this virus are the carrier state in the stallion and abortion in the mare.

Infected horses show fever, loss of appetite, and depression. The signs of respiratory infection with the equine arteritis virus are clear nasal discharge, cough, eye reddening (conjunctivitis), tears, and swelling of the eyelids and tissue around the eyes. Signs of disease persist for 2 to 9 days. As with equine influenza and equine herpesvirus infection, a diagnosis is determined by identifying the virus in appropriate samples.

Treatment consists of supportive care and nonsteroidal anti-inflammatory drugs to reduce fever and inflammation. Anti-biotics are usually unnecessary. A carrier state occurs in most stallions after natural infection and is primarily responsible for the persistence of the virus in the horse population. Semen from carrier stallions has a tremendous viral content that is unaffected by freezing or semen extenders. Stallions and mares can be protected from equine arteritis virus infection by vaccination prior to the breeding season. The carrier state does not affect semen quality. Persistently infected stallions can be used for breeding by using specific vaccination strategies for the mares.

Last full review/revision July 2011 by Bonnie R. Rush, DVM, MS, DACVIM; Neil W. Dyer, DVM, MS, DACVP; Joe Hauptman, DVM, MS, DACVS; Ned F. Kuehn, DVM, MS, DACVIM; Stuart M. Taylor, PhD, BVMS, MRCVS, DECVP; Wendy E. Vaala, VMD, DACVIM; Maureen H. Milne, BVMS, MVM, DCHP, MRCVS