1- I'd like to breed my mare to a EVA shedding stallion;from the EVA article, I see that a mare infected through semen is not likely to loose her pregnancy, so wouldn't it be the same to just breed her and then quarantine for 21 days, thus either she becomes infected and she is then "vaccinated", or she doesn't and then no harm done ?
I mean is it really necessary to vaccinate ? the old dillemna, if I want to vaccinate her prior to breeding, I have to wait until she foals, then I won't be able to use the foal heat and probably not the second one either...
2- if the suckling foal is a male, likely to become a stallion, is it a risk for him if his dam is vaccinated or infected ?
is it possible/necessary to vaccinate a young foal, and if yes, at what age ?
If the mare had not recently foaled, then one could breed the mare and quarantine her for about 28 days, allowing time for her to become infected and get through being infectious.
If you read the EVA article carefully, you will find that item number four on the list observes:
"EVA is rarely fatal, although it can be fatal to young foals or debilitated animals."
Breeding an unvaccinated mare to an EVA shedding stallion on her foal heat presents a great potential risk for the foal!!!
WRT a nursing colt foal - bearing in mind the risk outlined above - there is no risk as far as the possibility of his becoming infected and a "shedder" which is I presume what you are alluding to. In order for the virus to be harboured within the system, there must be testosterone present. With a colt <270 days of age, there is little likelihood of testosterone presence (the colt not yet having passed through puberty). Consequently one does not have to be concerned about exposure prior to puberty leading to a "shedding" status. One does however need to be concerned about the fact that a colt so exposed - either to acute infection or the vaccine virus following vaccination of his dam - may seroconvert - in other words show antibody presence to EAV in his blood. This could cause confusion at a later date when tested and found to have the antibodies, as after puberty (if not tested prior) one would then have to have a virus isolation test performed on the semen to confirm absence of the virus in the semen (i.e. to confirm he is not a "shedder").
If dealing with a young colt, a good management protocol is to vaccinate (in conjunction with obtaining a negative antibody test of the blood) between 180-270 days. In that time frame, the colt will not have become a shedder if previously exposed (not yet having passed through puberty), and once vaccinated (and boostered annually) will remain protected. The usual caveats apply about confirming market status and regulations relative to the targeted market, as there are still a few minor countries in the world that will not allow importation of semen from a seropositive horse, or of the horse itself (these are not major horse-producing countries, but check your market prior to vaccination!).
Okay to make sure I am clear on this. My vet told me that the virus is airborn. My understanding from your post JOS is that it is mucus transported. Which is correct? I have a stallion coming to my property who is being tested and vaccinated if all goes well. Would it be prudent of me to test and vaccinate my stud foal before this a stallion arrives? Could this stallion then be a carrier if noses were touched through the fence?
I'm just a bit confused still.. So forgive me if this is frustrating.
The equine arteritis virus (EAV) has two modes of transmission, and the mode will vary upon the condition and sex of the transmitting animal.
An acutely infected animal of either gender - one that is in the active stages of infection which lasts about 21 days - can infect by aerosol droplets through the respiratory route.
A non-vaccinated mare that is bred to a "shedder" stallion is likely to become infected, and therefore capable of infecting other animals through the aerosol droplet route. This may last for up to 28 days after breeding.
A vaccinated mare that is bred to a "shedder" stallion will not become infected herself, but may shed the virus in post-breeding clearance of the infected semen (the same may occur with a non-vaccinated mare bred to a "shedder" stallion). This is only likely to last for a short period after breeding - 7 days is likely.
A "shedder" stallion that is not in the acute stages of the disease will only be capable of shedding the virus in secondary sex gland secretions, not aerosol droplets.
An animal of either sex that has just been vaccinated may shed the vaccine virus - not the "active" virus - for a short period of time following vaccination. Unvaccinated animals that come into contact with a vaccinated animal for up to 21 days following vaccination (usually less) may seroconvert. Note that this is not the same as becoming "infected", and a colt becoming a shedder as a result of exposure to the vaccine virus has not been seen to happen.
Thank you Jos, if I ever breed to this stallion, it will be with a mare with no foal at her side then ! and with appropriate quarantine. the funny thing is here in Europe no mention is made of his EVA status, and mares are inseminated with his semen with no particular precaution, no blood test, no vaccination, no quarantine, nothing ! the centers selling the semen don't mention it, and are not even informed if asked; and this stallion is widely used (he's the famous dressage world champion 2004 and 2005)
In Europe there is a different attitude toward EVA, with many adopting the point of view that "it's out there, so why worry about it" - and it is more prevalent than in the USA, so animals tend to be exposed to it with more frequency, and will therefore develop natural immunity. The unfortunate thing is that the virus can mutate, and there is therefore a greater possibility of the development of a new strain (and not therefore covered by existing vaccines), which is of concern.
I am a little unclear if the "center" to which you refer is a licensed AI center. If it is, then my understanding is that one of the requirements for a stallion to be standing at such a center and shipping semen is that he has tested negative for EVA or at least semen negative (i.e. not shedder), and that shipping "shedding" semen is not permitted under EU law (at least internationally) - correct me if I am wrong. If that is the case, one has to wonder about the ethicallity of the center... I suspect that the "loophole" that they are using is that he is not being shipped outside the country (so no need for a negative EVA test). The attitude in the US is that it is unethical to not notify mare owners that the stallion is an EVA shedder, and I feel that should be considered the same world-wide. I must add that most people in the industry very quickly learn which stallions are "shedders", so it does no good to anybody's credibility to hide the issue...
Check out the regulations for importation of semen to Germany (follow that link - it's a .pdf file). Those regulations will be pretty much the same for any EU country. You make the call as to whether the semen is being shipped legitimately if he is genuinely EVA-positive!
Stallions that are shedders may naturally spontaneously cease to shed. They will not restart shedding if they do cease.
There has been work performed with the use of a GnRH immunization which suppresses testosterone secretion in an attempt to "clear" EAV from the system. Daels et. al. showed limited success in 2002, but I am sure there has been more work done since then. That is probably what they are referring to by "chemical means". It is not however to be regarded as a solid "cure" as up to now research has not shown it to be (a) universal in success, and (b) always long-term in it's effects. It is different from the spontaneously shedding stallion in that some of the research animals in Daels' research that ceased to shed during treatment restarted a little while after treatment ended.
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