EVA

[Nathan Luszcz]

Just as a FYI...

So many of the people here either breed or own stallions I thought this would be important to post.

The following is excerpted from the Colorado Department of Agriculture, and is viewable complete here.

"The purpose of this rule regarding equine viral arteritis (EVA) is to protect the equine industry of the state of Colorado. Clinical disease due to EAV infections is a reportable disease to the Colorado State Veterinarian. Equine Viral Arteritis (EVA) is a contagious disease of horses caused by the equine arteritis virus (EAV) EVA is of special economic concern because it can result in abortion in pregnant mares, illness and death in young foals, and establishment of the carrier state in stallions. The import control policies of most countries currently deny entry to carrier stallions and EAV-infective semen because of the associated disease risks. It is important to enable the ability to require testing of some horses prior to vaccination to demonstrate that antibody titers are due to vaccination rather than natural infection. The vast majority of Colorado have never been exposed to the vurus; therefore, the risk of spread of infection in Colorado is significant."

My second-to-last paragraph describes the vaccination process for stallions. This middle section describes the disease (feel free to skip to the end )

EVA presents just like flu or rhino with depression, snots, and a minor fever. Just like flu and most strains of rhino, it's not a big deal for most animals. They get sick, get over it, and move on with life. However, it's extremely contagious, spreading rapidly if presented with the chance. The infected animals shed the virus copiously for approximately 21 days. Nose-to-nose contact is the largest method of transmission, but feces and urine in the infected animal are also contagious. Stallions infected with EVA have a 50% chance of becoming a carrier animal, shedding the virus in their semen (and therefore possibly in their urine, since the stallion eliminates extra spermatozoa and fluids in their urine). Mares bred to these stallions have a 98%+ chance of getting infected. If a pregnant mare (not a just bred mare) is infected with EVA, they have a very, very high chance of aborting their foal. This is a huge concern all over the US with the major outbreak this past breeding season in New Mexico. Semen from this single infected stallion was shipped nation-wide, mares were bred, then those mares cause secondary infections causing hundreds of abortions and a huge problem.

This disease is not new; on the contrary, the vaccine has been available commercially for several decades, and the disease identified for even longer than that. There are minor outbreaks every decade or so. This past one was devastating due to the increased travel and use of shipped semen from these carrier stallions.

It is said that the majority of Standardbred horses have been exposed to EVA sometime in their life (with upwards of 70% being sero-positive). Many STB stallions are carriers. However, for some reason that is not understood, STBs do not seem to react to the disease. It is suspected that the STB strain of the virus has mutated and isn't the same as the older disease. This new outbreak IS the older strain and causes major abortions everywhere it goes.

There is a test for EVA. It is a very simple blood test that tests for the presence of antibodies. Horses that test positive are said to be "sero-positive". That means that they have been exposed to the disease sometime in their life and have formed antibodies against it. All EVA vaccinated horses will test sero-positive for the remainder of their lives. This is not a big deal for a horse that is not a stallion. Adult geldings and mares get over the disease quickly and usually easily. Foals can die if they are infected at an early age, but that's not all that unusual for any disease outbreak.

Stallions who have reached sexual maturity are susceptible to be carriers. They harbor the virus in their accessory sex glands (the ampula, prostate, seminal vesicles, and BU gland) and shed it constantly in their semen. The virus requires testosterone to maintain its presence, so castrating the stallion will kill the virus in their bodies. Carrier stallions are 100% healthy and are not affected in any way from the virus being harbored in their bodies. If a stallion tests sero-positive, you must then test the semen to see if they are a shedder. If they are a shedder, you must make the choice to tell all of your potential clients that your horse is EVA positive so they can make (very simple) arrangements to avoid spreading the disease, take the horse off the market as a breeding horse, or geld the stallion. It is not ethical to continue breeding the stallion without telling the mare owners he is a shedder.

There is a vaccine available for this disease. Given to mares or geldings, they can still get EVA but the incubation time drops from 21 days of potential spreading to 3 days, and a lot less virus being shed in their mucus and urine.

ALL STALLIONS SHOULD BE VACCINATED. To do this you need to ask your vet to purchase the vaccine (they must get permission from their state veterinarian before Fort Dodge will sell the vaccine). Then you do a blood test on the stallion to confirm that they are negative. WITHIN 10 DAYS of drawing the blood, and after the lab confirms they are negative, the vet must come out and vaccinate the horses. It's a simple vaccine, just like any other spring shot. The stallion then builds antibodies and is protected. The best time for this vaccine is now; in November or December, before the breeding season. They also require an annual booster. The initial vaccination is reportable to the state vet; they must be informed that a stallion was vaccinated.

As far as I know the disease hasn't spread across the mini population, but they can harbor the disease just as well as a full sized horse, so its important for the welfare of the whole equine species to attempt to limit or even wipe out the disease. There are concerns about exporting both horses and semen, but TB's routinely are exported for the fall breeding season and all countries, including Australia, accept them with proper proof of status and vaccination. Consult your vet, and learn what you can! This disease is important to be aware of and to address in your herds.

Ug, I wrote all this in MS Word, but apparently " and ' don't translate here, lol. Edited to correct.

 

[sedeh]

Thanks for the info Nathan. I'll have to ask my vet about it.

 

[SkipsMom]

If you own a stallion and bred to outside mares it is in your interest to have your stallion tested and vaccinated against EVA. This will protect you down the road when a mare owner comes back and says "my mare aborted the foal and it was because of EVA" you can say "not from my stallion."

The Quarter horse stallion owners that I personally know are having blood drawn for testing so they can vaccinate in mid-January to be ready for breeding March 1.

 

[Nathan Luszcz]

That's not true... a naieve mare bred to an EVA positive stallion will not abort because of that exposure. She will get over the infection before she aborts the newly concieved embryo. She would have to be exposed again to another source of infection.

The risk is of that mare being bred, getting infected, then spreading it to other horses or pregnant horses. The danger isn't to the bred mare, any more than a flu or rhino infection.

 

[Michelle@wescofarms]

ALL STALLIONS SHOULD BE VACCINATED. To do this you need to ask your vet to purchase the vaccine (they must get permission from their state veterinarian before Fort Dodge will sell the vaccine). Then you do a blood test on the stallion to confirm that they are negative. WITHIN 10 DAYS of drawing the blood, and after the lab confirms they are negative, the vet must come out and vaccinate the horses. It's a simple vaccine, just like any other spring shot. The stallion then builds antibodies and is protected. The best time for this vaccine is now; in November or December, before the breeding season. They also require an annual booster. The initial vaccination is reportable to the state vet; they must be informed that a stallion was vaccinated.

Interesting information, and definitely something everyone should know about. I've only dealt with testing on horses being exported. Shipped semen isn't that common yet in minis, and

Nathan perhaps you know the answer to this, but if I horse builds up antibodies, why would it need an annual booster? And why wouldn't the booster shots be reportable if you have to order them from Ft. Dodge and have it cleared through the state etc.

If they are a shedder, you must make the choice to tell all of your potential clients that your horse is EVA positive so they can make (very simple) arrangements to avoid spreading the disease, . . .

By simple arrangements do you mean vaccinating and/or quarantine or ?

 

[SkipsMom]

Nathan, guess I misunderstood what my vet told the stallion owners. I would swear it was based on a non-vaccinated stallion breeding a mare who later slipped a foal.

Nevertheless, folks who own stallions should talk w/ their veterinarian.

 

[Nathan Luszcz]

Nathan perhaps you know the answer to this, but if I horse builds up antibodies, why would it need an annual booster? And why wouldn't the booster shots be reportable if you have to order them from Ft. Dodge and have it cleared through the state etc.

My guess about the booster is even though they TEST positive, you still want to maintain enough antibodies in the blood to prevent infection. Your horse most likely would test positive to having EEE antibodies a few years after being vaccinated, but they wouldn't be enough to protect against exposure to EEE. I bet the same is true for EVA... you have to keep boostering in order to maintain protection enough to prevent an infection.

You would have to still get the vaccine through the vet, and depending on the state that vet might have to get it from the State Vet, but I do not think the act of vaccinating is reportable after the first injection. You'd have to ask the vet about it... This is one of those injections that should stay in the vet's hands unfortinately. Even worse than rabies... rabies at least you can give yourself if you don't mind it not "counting", but EVA is so touchy a vet shouldn't even give you the shot unless they really, really trust you and are willing to put their license on the line. Hopefully it'll settle down and become routine after a while.

By simple arrangements do you mean vaccinating and/or quarantine or ?

yup! Its easy to quarentine a mare for a month if you know you have to. But if you DON'T know..... that's where the problems come up. Even if you vaccinate you still should quarentine for 3-5 days after the last breeding. The dates and figures about mares I'm not so comfortable relating because I'm not as familier with them as I am with the stallion side... I'd have to read up on it a little more. The Colorado recommendations are in that link in the beginning, I think it covers mares too.

 

[Just Us N Texas]

When EVA first showed up in Ky. it could be traced to one horse in particular. A very popular and in demand stallion. We were scared like heck for a long time, but, it turned out to be not nearly as bad as we thought. On the farm where I worked at the time, we were sending a mare to Ireland to be bred. Remember, this was at the very beginning, and when the mare was ready to be sent back, she showed positive titers. This was because the mare had been vaccinated prior to being sent abroad. It took several months to finally clear her for shipment back to the U.S. I think it also took some time for the powers that be to decide that all horses vaccinated would show positive titres. Anyway, as it turned out, we could pasture mares that were positive, vaccinated or not, with other non positive mares, with no ill effects. Used to be at the sales when you told someone that a horse was EVA positive, they would run like heck from them. Now the only comment made is "Oh, this horse couldn't be shipped to Europe then." It is not as big a deal as you think, and nothing to be extremely worried with or about. I personally would not vaccinate my horses or even have them tested. This is almost a thing of the past in Ky. with the thoroughbred industry, except for testing the breeding stallions. These stallions will breed 40 plus outside mares per year, so the incidence of spreading is much greater. This of course is just my opinion. Do what you think best. But since I have had the experience with it that I have, I opt not to worry about it.

 

[Nathan Luszcz]

That's a dangerous way to think. Yes, positive and negative horses can EASILY live with each other. Once the horse is over the 21 day infection and is done shedding, they are done. But during that 21 days it can (will) cause abortions in any exposed pregnant mare. Stallions with positive titers and no history of vaccination are shunned by breeders.

But stallions will harbor the disease and spread it to everyone they are bred to, and even theoretically in their urine. Its very important for people who own stallions to know their stud's status and take appropriate percautions.

I wouldn't vaccinate a non-stallion; I don't think its nessesary (except for mares actively being bred, and even then, if the stallion is proven negative, I wouldn't do it).

But please, all you stallion owners out there, please test and vaccinate your intact male horses.