Arvac

Equine Arteritis

What is the Equine Arteritis Virus?

                Equine viral arteritis (EVA) is a contagious disease of horses caused by equine arteritis virus (EAV), an RNA virus that is found in horse populations in many countries. While typically not life-threatening to otherwise healthy adult horses, EAV can cause abortion in pregnant mares; uncommonly, death in young foals; and establish a long-term carrier state in breeding stallions. While various horse breeds appear equally susceptible to EAV, the prevalence of infection can vary widely, with higher sero-positivity rates occurring in Standardbreds and Warmbloods.

Clinical signs, if they occur, typically develop 3 to 7 days post-infection and are variable but may include any combination or all of the following:

• Fever
• Depression
• Anorexia
• Dependent edema
• Localized or generalized urticaria
• Supra or periorbital edema
• Conjunctivitis
• Lacrimal discharge
• Serous to mucoid nasal discharge

Abortion is a frequent sequel to infection in the unprotected, pregnant mare. When pregnant mares are exposed to the virus very close to term, they may not abort but give birth to a congenitally infected foal, affected with a rapidly progressive interstitial pneumonia. Foals within a few months of age, if exposed to EAV can develop a life-threatening pneumonia or pneumoenteritis.

How it’s spread

Much like a human would contract a respiratory virus infection, like a cold or flu, horses can contract EAV infection from acutely affected horses. In addition, stallions can shed the virus in their semen. The respiratory route is the primary means whereby the virus is spread during outbreaks of EVA at racetracks, horse shows, sales and veterinary clinics. Venereal transmission, in contrast, has frequently been associated with the primary spread of EAV on breeding farms. As a result, every precaution should be taken with EAV positive semen to ensure that outbreaks do not occur.

Protect your Horse from Equine Arteritis Virus

It should be emphasized that EVA is a very manageable disease. Vaccination against the disease is a first line of defense, particularly of colts between the ages of six and nine months in breeds in which EAV is endemic, e.g. the Standardbred. ARVAC is a vaccination for healthy non-stressed adult horses as an aid in the prevention of viral abortion and respiratory infection due to equine arteritis virus. It is a desiccated preparation containing viable modified Equine Arteritis virus.  The vaccine virus has been modified to the extent that it may be irregularly infective when given by natural portraits of entry. A high degree of safety has been demonstrated for horses of any age and pregnant mares. By vaccinating in a number of years, this will significantly reduce the number of carrier stallions. Testing of all breeding stallions and identification of carrier animals among those testing sero-positive is critical. Carrier stallions should be managed properly and used only for breeding with mares which are also positive for antibodies as a result of previous natural infection or from vaccination. It is also important to note that not all positive stallions are shedders and carriers of EVA. Stallions vaccinated against EVA have never been shown to become carriers of the virus as a result of vaccination. There is a very real risk of introducing the virus into a susceptible horse population through the use of infected fresh-cooled or frozen semen. If vaccinated mares are bred with EAV infective semen, they should be isolated from other sero-negative mares and unvaccinated horses for an additional three-week period to minimize the risk of the transmitting the virus.

Why use ARVAC

                ARVAC is one of the only vaccines available to prevent Equine Viral Arteritis. It should be used to help prevent any carrier stallions, this way it is not passed down the bloodline. Also, it is strongly recommended that mares be vaccinated against EVA at least three weeks before insemination. The reasons for this are twofold: first, vaccinated animals need to be provided with adequate opportunity to mount an immune response to the virus; second, first-time vaccinated animals may shed small amounts of vaccine virus for a short interval after vaccination, during which time they should be isolated from other horses negative for antibodies to the virus. This vaccine has been tested and shown to be satisfactory for marketing in accordance with procedures required by the U.S. Department of Agriculture.