EVA Outbreak Sparks Concern in Horse Industry

A recent outbreak of Equine Viral Arteritis (EVA) on an American Quarter Horse Farm in New Mexico has sparked concern among horse owners in the U.S. Although only some mild clinical signs were reported in a number of mares on the index farm, the more worrisome feature of the outbreak has been the significant number of abortions that have occurred on this and other affected premises. Four of the stallions on the farm have been confirmed carriers of equine arteritis virus (EAV).

Recent equine arteritis virus infection has been confirmed in at least three other states: Kansas, Oklahoma and Utah. The virus was introduced through infected semen from a carrier stallion on the index premises in New Mexico and/or through donor/recipient mares returning from that farm. Investigations are being conducted in a number of other states and in Mexico and Canada to determine if additional spread of the virus may have occurred.

Equine viral arteritis is a contagious viral disease of horses caused by EAV. It is primarily spread by direct contact with horses acutely infected with the virus. While it is considered a respiratory infection of the horse, the disease can also be spread venereally by the acutely infected as well as the chronically infected carrier stallion. Horse owners should be aware that management practices can play a key role in spread of the virus. Although not usually fatal in healthy adult horses, EVA can cause abortion and very infrequently, death in young foals. Abortion rates can vary but may be as high as 70 percent. The virus can spread rapidly through a population of horses kept closely congregated with one another. The major significance of the disease is the devastating economic damage that can be sustained from abortion in mares and establishment of the carrier state in stallions.

A modified live virus vaccine against EVA is produced by Ft. Dodge Animal Health. It is safe and stimulates protective immunity to infection. It is recommended for use in stallions and non-pregnant mares. Due to intermittent demand for the vaccine over the years, existing stocks were rapidly depleted following confirmation of EVA in New Mexico in June. What little vaccine may still be available will be released on a priority basis. It will be late September/October before additional supplies will be available.

Under the present circumstances, horses need to be managed effectively to prevent the introduction or limit the dissemination of this virus. Proper management can readily prevent the dissemination of EAV while allowing the continued use of carrier stallions. This is essential to the horse industry because these stallions can represent superior blood lines in their respective breeds.

More complete information can be gathered from the following resources:

Understanding Equine Viral Arteritis (EVA)

http://www.xcodesign.com/aaep/displayArticles.cfm?ID=285

AAEP Guidelines for breeding a mare to an equine arteritis virus-shedding

stallion

http://www.xcodesign.com/aaep/displayArticles.cfm?ID=36

Understanding Equine Viral Arteritis

http://www.netpets.org/horses/healthspa/viral.html

Equine Viral Arteritis (from USDA/APHIS)

http://www.aphis.usda.gov/lpa/pubs/fsheet_faq_notice/fs_ahequineva.html

Q&A on EVA with Dr. Tom Lenz

http://www.aqha.com/aqharacing.com/news/06stories/06evaqandawdrlenz.html

Equine Viral Arteritis - Uniform Methods and Rules, Effective April 19, 2004

(from USDA/APHIS)

http://www.aphis.usda.gov/vs/nahps/equine/eva/eva-umr.pdf

EVA Video -

The USDA Veterinary Services, as part of an EVA educational program, offers

free of charge, a video/booklet information packet titled Equine Viral

Arteritis: A Manageable Problem. It is a collective effort of USDA, the

University of Kentucky, and EQUUS Magazine. This video is available from

USDA at no charge from the USDA. To order a copy for your clients or

practice, please contact: Dr. Timothy R. Cordes, Senior Staff Veterinarian,

Equine Diseases, USDA, APHIS, VS at Timothy.R.Cordes@usda.gov