EVA

Equine Viral Arteritis

EVA – Major Concerns

• Abortions
• Carrier (shedding) stallions
• Rapid transmission of the disease due to clinical and sub-clinical disease

Abortions

70% of unvaccinated or unprotected mares will abort when exposed to Equine Arteritis Virus from respiratory secretions or semen laden with Equine Arteritis Virus.

Carrier Stallion

Any sexually MATURE stallion (greater than 12 months of age) that is unvaccinated has up to a 60% chance of becoming a carrier of the Equine Arteritis Virus (shedding EVA in his semen) if exposed to the disease.

• EVA remains viable in fresh, cooled, and frozen semen

Disease Spread

Unprotected (unvaccinated, no previous exposure) horses when infected with EVA will become sick with EVA.  Symptoms will vary between horses, from no obvious symptoms (sub-clinical disease) to severe outward signs of the disease (clinical disease).

Horses with either clinical or sub-clinical disease will shed the virus (are infectious) by direct or indirect contact.  Stallions will also shed the virus in their semen.  In some stallions this shedding is short term, in others it’s lifelong.

Disease Spread

Due to the sub-clinical nature of the disease in a large number of affected horses, most go undetected and continue to be transported to competitions, veterinary clinics, breeding farms, etc.  These horses very effectively infect any unprotected horses they come in contact with.  The horses they infect will become infective for about 3 weeks and spread the disease in their home area.  Any unprotected stallion in competition, going to the hospital for surgery, being shown in a stallion showcase, teasing mares, etc. is at risk of becoming infected with EVA and becoming a lifetime shedding stallion.

Current EVA Outbreaks

• New Mexico – 2005
• New Mexico – 2006
• Utah – 2006

In our current era of highly mobile horses and shipped semen, all horses are within reach of areas where there are current outbreaks.  Outbreaks of EVA are a concern for all breeds.  Breeds commingle in the confines of commercial haulers, trailers, veterinary hospitals, boarding facilities, breeding farms, etc.

Protection From EVA – Requires Aggressive Vaccination

Modified live vaccine requires vaccinated horses be isolated from non-vaccinated horses for 21 days.  Arvac, manufactured by Fort Dodge, is a very effective vaccine.

All Stallions – Vaccination of a mature stallion that has had no previous exposure to EVA will prevent him from becoming a carrier.  Testing and lifelong documentation is required.  He should not be used for breeding to non-vaccinated mares for 21 days.

Weanling Stallions – Vaccination of weanling stallions between 7 and 12 months of age is the ideal time to vaccinate and will prevent them from becoming carrier stallions.  This is the key to control EVA long-term.  Proper documentation is required by many sale companies.

Mares

• Non-pregnant – Vaccination of a non-pregnant mare will protect her from becoming sick with EVA and spreading the virus to other horses.  The best time to vaccinate a broodmare is when she is open.
• Pregnant – Vaccination of pregnant mares will protect them from becoming sick with EVA and save them from losing their pregnancy due to the effects of EVA.  Arvac (vaccine) is not approved for use in pregnant mares.  It has been used mid gestation for pregnancy protection in the face of an outbreak.

Geldings – Vaccination will protect them from getting the disease, performing poorly due to the affects of EVA, and spreading the virus via their respiratory secretions to other horses.