Equine viral arteritis (EVA) isn't something you hear about every day. In fact, most of you have probably never even known someone who has seen a case of EVA. But there are some Quarter Horse owners in New Mexico who now know more than they wanted to about this easily passed virus that causes respiratory disease, stocking up, abortion, and a persistent carrier state in stallions. That's a pretty versatile virus.

One of the major problems with this disease is how easily it can be transferred from one horse to another. Of course there is the respiratory route, where nasal secretions spread the virus from horse to horse through a barn or training stable. Then there are the contaminated fluids from an aborted fetus, which are loaded with the virus.

As mentioned before, stallions can become persistent shedders of the virus. But the most incredible way this virus is spread is through overnight mail. That's right, you can FedEx a container of semen anywhere in the world and take the unwanted virus right along with the desired sperm. Think about that next time you order semen. Has that stallion been tested for EVA? If it were my farm and my mare, you bet those tests would be negative, or my mares would be vaccinated and protected.

Currently, the United States has no semen import restrictions for EVA, which means infected semen can be imported for breeding purposes and thus expose resident horses.

In 2002, a study was conducted in California to compare the seroprevalence of equine arteritis virus (EAV) in California horses and horses imported from other countries. Serum samples from 364 horses from 44 farms in California were compared to 226 samples from imported horses. The results indicated only 1.9% of resident horses were seropositive for EAV, compared to 18.6% of foreign horses (16% of which were stallions). Certain breeds appear to be more susceptible to EAV infection, most notably warmbloods.

It is clear that importation restrictions on EAV-positive horses and semen should be considered as a means of preventing this virus from spreading in the United States.