their approved stallions. EVA is not a reportable disease in the United States (although some states like Kentucky have their own stricter EVA regulations) so stallions may be imported to the U.S. and semen may be shipped to most states with no EVA- related limitations. Ultimately it is the stallion owner’s responsibility to disclose if their stallion is EVA-positive, and it is also the mare owner‘s responsibility to ask. “Because EVA isn’t that common among Warmblood stallions, it isn’t even on most people’s radars,” says Karen Berk of Florida-based Equine Reproduction Services, who estimates less than half of the mare owners she works with inquire about a stallion’s EVA status prior to breeding.
Breeding to a Carrier Stallion It is definitely possible to breed safely to an EVA-positive carrier stallion, but certain precautions must be taken. EVA-positive carrier stallions should only be bred to EVA-positive mares, which usually means mares must be vaccinated prior to breed- ing to a carrier stallion (or with infected semen). The first step is to have the mare’s serologic status tested.
Mares who have been previously exposed to the virus or who have been vaccinated in the past will test seropositive (or posi- tive) and can be bred to a carrier stallion without concern. Mares who have never been exposed to it or who have never been vaccinated in the past will test seronegative and should be vaccinated against EVA at least 21 days prior to breeding to a carrier stallion. Once vaccinated, as a precaution these mares should be isolated for 21 days from other horses who are sero- negative or whose status is unknown. After 21 days the mare is now seropositive herself and can be bred to a carrier stal- lion, but should then remain isolated from other seronegative horses for an additional 21 days. This 42 day isolation can prove challenging, depending on a farm’s set-up and routines. For some breeders the vaccination and isolation process, and the potential risk to other pregnant mares, is not worth it. Other breeders find the process to be no big deal. For every breeder who casually says “just vaccinate,” there is another breeder who is overwhelmed at the idea of a 42-day isola- tion period or the potential risk to their other pregnant mares. “Vaccinating isn’t as simple as it may sound,” cautions Karen Berk. “Between the cost, the risk and the isolation protocols, I’ve found it’s not something the average mare owner does, or wants to deal with.” Ultimately the decision is up to the indi- vidual breeder, but it is best to be educated about EVA before deciding whether or not to breed to an EVA-positive stallion.
A Firsthand Experience When Canadian Warmblood breeder Veronique Dumas of Formosus Sporthorses wanted to breed to the Hanoverian stal- lion Redwine, she had no choice but to vaccinate her mare for EVA, because Redwine is EVA-positive. “I’d heard plenty of anec- dotal information about EVA,” she recalls. “At first I was quite concerned about the disease, but the more I learned about it the less I became concerned, and I had a particular mare who I really wanted to breed to Redwine.” Her mare was successfully vaccinated and bred. “She carried to term and delivered a lovely filly—the nicest I think she had
92 March/April 2016
Veronique Dumas and her filly Red Ink by Redwine who is EVA-positive.
produced to date—and there were no issues,” according to Veronique. She named the filly Red Ink. She went on to later vaccinate most of her mares, although she adds that vacci-
nation and isolation was easy for her because of the set-up of her farm, and she did it at a time when none of her mares were pregnant. She says she wouldn’t hesitate to breed to an EVA- positive stallion again.
Vaccinating a Stallion Vaccinating a stallion for EVA is more complicated than it may sound. Some countries (and some states in the U.S.) forbid or discourage EVA vaccination. (On the flip side, Kentucky requires the vaccination of all Thoroughbred stallions, illustrat- ing that opinions on EVA vaccination are mixed.) If a stallion is going to be vaccinated for EVA, it is critical
that he is first blood tested to see if he already has the disease. If he is already EVA-positive and is a carrier, there is no point in vaccinating (and all mare owners considering breeding to him should be informed). If he is EVA-negative, this should be documented because once the stallion is vaccinated future testing may show him as EVA-positive, and the documentation will help the stallion owner demonstrate that the seropositive results are from the vaccine and not an indication that the stal- lion is an EVA carrier. Some countries will still forbid import of EVA-positive stallions, even with proof of EVA vaccination and a prior negative status. Once a stallion is vaccinated, he must be isolated (and not
used for breeding) for 28 days. It is further recommended that the vaccine be boostered annually at least one month before the start of the breeding season.
Preventing the Spread of EVA It is theoretically possible to prevent the spread of EVA, and potentially eliminate carrier stallions altogether, by follow- ing a couple of simple steps. One step is the vaccination of mares, stallions and young colts who may become breed- ing stallions. Another step is to identify carrier stallions and follow responsible breeding protocols accordingly. APHIS estimates we could eliminate the population of carrier stal- lions in one to two generations by following these two steps. After the 1984 outbreak threatened Kentucky’s Thoroughbred industry, Kentucky adopted strict protocols and today there are “no known Thoroughbred shedding stallions standing at stud in Kentucky” according to the Kentucky Department of Agriculture. The best defense is education. The more breeders know
about EVA, the better they are able to manage the risks and reduce its spread.
Page 1 |
Page 2 |
Page 3 |
Page 4 |
Page 5 |
Page 6 |
Page 7 |
Page 8 |
Page 9 |
Page 10 |
Page 11 |
Page 12 |
Page 13 |
Page 14 |
Page 15 |
Page 16 |
Page 17 |
Page 18 |
Page 19 |
Page 20 |
Page 21 |
Page 22 |
Page 23 |
Page 24 |
Page 25 |
Page 26 |
Page 27 |
Page 28 |
Page 29 |
Page 30 |
Page 31 |
Page 32 |
Page 33 |
Page 34 |
Page 35 |
Page 36 |
Page 37 |
Page 38 |
Page 39 |
Page 40 |
Page 41 |
Page 42 |
Page 43 |
Page 44 |
Page 45 |
Page 46 |
Page 47 |
Page 48 |
Page 49 |
Page 50 |
Page 51 |
Page 52 |
Page 53 |
Page 54 |
Page 55 |
Page 56 |
Page 57 |
Page 58 |
Page 59 |
Page 60 |
Page 61 |
Page 62 |
Page 63 |
Page 64 |
Page 65 |
Page 66 |
Page 67 |
Page 68 |
Page 69 |
Page 70 |
Page 71 |
Page 72 |
Page 73 |
Page 74 |
Page 75 |
Page 76 |
Page 77 |
Page 78 |
Page 79 |
Page 80 |
Page 81 |
Page 82 |
Page 83 |
Page 84 |
Page 85 |
Page 86 |
Page 87 |
Page 88 |
Page 89 |
Page 90 |
Page 91 |
Page 92 |
Page 93 |
Page 94 |
Page 95 |
Page 96 |
Page 97 |
Page 98 |
Page 99 |
Page 100