 You may have heard some frightening stories about an equine disease called EVA. Fortunately, much of the information in circulation is not fact, it's myth. Yes, EVA is a problem, but with some relatively simple corrective measures, it's a manageable one. Let's start by debunking the biggest myths about EVA. First, EVA or equine viral arteritis is not a new disease. More than a century ago, a disease fitting the clinical description of what we now call EVA was reported in the European Veterinary Literature. Second, EVA in its naturally occurring form seldom kills mature horses, no matter what the older textbooks may state. Back in the 50s, researchers developed an experimental strain of the virus that causes EVA that can kill between 50 and 80% of infected horses. Unfortunately, this experimentally derived disease became the basis for descriptions of EVA in the 60s and 70s. But that highly virulent strain of this virus has never been found in nature. In 1984, equine viral arteritis broke out for the first time on a significant number of thoroughbred breeding farms in Kentucky. A total of 41 breeding farms were involved in that epidemic of the disease. That epidemic was not associated with any mortality whatsoever. Another myth is that outbreaks of EVA are widespread. Although the virus is widely distributed in certain horse populations, the presence of the virus does not necessarily lead to an outbreak. In fact, confirmed outbreaks of EVA are relatively sporadic. EVA can pose very real problems though for owners, breeders and the performance horse industry. By far the most economically damaging, EVA can cause abortion and pregnant mares. Also, stallions that become infected are very likely to become virus carriers, perhaps for life. Once that carrier state is established, the virus is transmitted very efficiently to a mare during breeding. When the virus that causes EVA is introduced into a herd, it can spread quickly, primarily through infective aerosols, among susceptible mares and foals. Horses are herd animals. They tend to commingle when they can. But this close contact is what facilitates the spread of the virus. The industry can protect itself from EVA if it has the facts about the disease. The disease can be controlled and prevented if breeders and owners take the appropriate measures. If EVA broke, the quickest and most effective way that the spread of the virus is going to be minimized and ceased is working cooperatively with state officials, federal officials, researchers, your practicing veterinarians, and most importantly, your industry. Industry support is critical in the control of EVA. EVA is principally a disease of the respiratory tract. Clinical signs include fever, depression, loss of appetite, nasal discharge, conjunctivitis, dependent edema, and skin rash. Other clinical signs that may develop in infected animals include swelling around the eyes and ocular discharge, swollen limbs, swollen genitals in the stallion, and swollen mammary glands in the mare are also signs of the disease. Keep in mind that many infected horses exhibit no signs of illness at all. They appear perfectly normal. An infected horse can look like this or this. EVA is more complex than other equine respiratory infections in one major respect. It can be transmitted venerally during breeding, either by natural service or by artificial insemination. When a mare, gelding or sexually immature colt gets the disease, EVA will run its course. The animal eliminates the virus from its system and develops a strong immunity to reinfection. But once a stallion is infected, the virus frequently makes a long-term home in his reproductive system. Such animals are very efficient in infecting susceptible mares they are bred to because the virus is shed continuously in the semen. If a mare is infected, she can spread the virus to close-in contacts through infective aerosols. If she's pregnant, the foal in her uterus may become infected, die, and be aborted. If a mare becomes infected late in pregnancy, however, she may foal normally, but the foal is infected. It will probably die within a few days of birth. During its brief life, the foal can also spread the virus to its close-in contacts via infective aerosols. In summary, any horse that becomes infected with the virus that causes EVA can spread the infection, whether that horse appears sick or not. That transmission can be via the respiratory route, during breeding, or from mare to fetus. Abortion may be the first sign of EVA that an owner or breeder encounters. It can take place late in the acute phase or early in the recovery phase of the disease. Abortion rates in infected pregnant mares can be as low as 10% or as high as 70%. Because an infected mare can spread the disease through infective aerosols, by the time she aborts, she may easily have exposed many of the horses she's been in close contact with. Rapid spread of the virus among pregnant mares could wipe out a breeding season and potentially drive small operations out of business. Another outbreak in our stallion barn would certainly shut down our breeding shed and an outbreak in somebody else's breeding shed would shut down our brood mares going to those breeding sheds and represent a loss of millions of dollars. EVA can also strike at the heart of the performance horse industry. Fever, depression, loss of appetite, and dependent edema can take a performance horse out of competition. Because the virus can spread quickly when horses come into close contact, for example, when stabled at a racetrack, an EVA outbreak may strike at the worst possible time. Sick horses don't feel good, they don't look good, and they don't perform well. An outbreak of EVA could have a dramatic economic impact on a racing or equestrian event. The good news is that EVA is a very controllable disease. We know a great deal about the virus that causes EVA, how it can be spread, and how it is maintained between outbreaks. And above all, we've got a good and safe vaccine against EVA. Vaccination is an integral part of any control program against this disease. And the control protocol is really quite simple. It's all spelled out in the brochure that accompanies this videotape. Colts should be routinely vaccinated when they are sexually immature in areas where infection with the virus is widespread. In a generation or two, this practice could all but eliminate the population of carrier stallions. These horses represent the primary reservoir of the virus. Until that is accepted and widely implemented by the horse industry, every breeding stallion, regardless of breed, should be blood tested to determine whether he has antibodies to the virus that causes EVA. If the blood test comes back positive, the stallion should then be tested to find out if he is a carrier and transmitting the virus in his semen. An owner of a stallion which has tested positive in the blood test for antibodies to equine arthritis virus should have semen collected from that stallion and the semen examined for the presence of equine arthritis virus in an appropriately qualified laboratory for that purpose. Any mares booked to be bred to the stallion should be vaccinated and then isolated for a brief period if they are not already immune to the virus. The approved protocol for breeding a mare to a virus shedding stallion is included in the brochure. Vaccinated mares develop antibodies or become seropositive to the virus which means that they have developed an immunity. This protects them from getting EVA from a carrier stallion. They won't become sick or abort as a result of infection. The equine industry has become truly international. Horses travel frequently from country to country for competition, racing, breeding and other purposes. And even if a breeding stallion never leaves the farm, his semen may be shipped anywhere in the world. Some nations, however, still borrow a seropositive stallion from entry. Even if his records confirm that the positive blood test is the result of previous vaccinations against EVA. These restrictions may also apply to seropositive mares, geldings or foals. As an effective EVA control and prevention protocol gains greater acceptance worldwide, these travel and import restrictions may be relaxed. In the meantime, though, virtually all the countries that take part in the international trade in horses bar carrier stallions from entry. The same is true of semen that is contaminated with the virus. It could be argued that some of the precautionary measures applied in the past may have been more politically than scientifically based. This underscores the continuing pressing need to harmonize national control programs for EVA. Experience has shown that we can protect horses against this disease and control its spread. We've seen that EVA can be a problem, but with some relatively simple corrective measures, it's a manageable problem.