Recommendations for Transported Semen as it Relates to Equine Viral Arteritis (EVA)

Equine Viral Arteritis (EVA) with respect to stallions from which semen is collected and transported from the premises in the fresh cooled or frozen state:

1. Breeding stallions unvaccinated for EVA should be tested for evidence of equine arteritis virus exposure/infection using the serum neutralization test. No stallion should be vaccinated for the first time without its pre-vaccination titer first being established. The stallion should be quarantined during the interval between obtaining serum, obtaining the results of the SN assay, and subsequent vaccination to ensure that an animal is not exposed to a natural infection in the interval between testing and vaccination. If quarantine is not possible, blood can be drawn for an initial SN assay then, once a negative titer is documented, a second blood sample can be drawn and submitted for a SN assay immediately prior to vaccination. Should an animal convert from seronegative to seropositive in the time period between the two SN assays, it must be assumed that this titer was due to natural exposure prior to vaccination and immediate and subsequently annual virus isolation testing of semen should be performed (see point 3, below).
2. Seronegative stallions (titers of less than 1:4) should be vaccinated at least 28 days prior to breeding or semen collection and receive an annual booster thereafter. Vaccinated stallions should be isolated for 28 days post initial vaccination and after each annual booster.
3. The viral shedding status of unvaccinated, seropositive stallions should be determined every 12 months either by: Attempted virus isolation on semen or, test breeding to at least two seronegative mares and monitoring for seroconversion of each mare at 14 and 28 days post breeding.
   1. In the case of a positive VI test, or seroconversion of a formerly seronegative mare after breeding, the stallion is considered to be a ‘shedder’ of EAV. This shedding status should be made known to mare owners receiving semen. This information should also be reported to state authorities and breed associations where so required.
4. Vaccinated, seropositive stallions need not be tested for virus shedding if seronegative prior to initial vaccination and as long as vaccination boosters have been administered annually.
5. Stallions seropositive for EVA from natural exposure need not be vaccinated, regardless of shedding status.

Guidelines pertaining to mares which will be inseminated with transported fresh cooled or frozen semen.

1. Seronegative mares to be inseminated with semen from an equine arteritis virus shedding stallion should be vaccinated against EVA at least 21 days prior to insemination. These vaccinated animals should be isolated for 21 days post vaccination.
2. Mares seropositive for EVA from natural exposure need not be vaccinated.

Revised by AAEP board of directors in 2024.