I have a Thoroughbred mare with Uveitis. Both of my vets have assured me there is no genetic component for her, and she is safe to breed. I have read many articles on it, and none I have read have stated Uveitis is genetic, although Appaloosas are predisposed to it.
I feel confident it will be no issue, I am in contact with owners of her relatives who have not had any Uveitis.
I have taken care of several horses with uveitis, one of them owned by a vet, and I have never understood there was a genetic component. One horse was an appy, and I know that breed has a predisposition to it. The others were an imported Hanoverian mare, a registered QH, and an Arab.
I have been treating a young Hanoverarian (3yrs old) for 7 weeks now. Uveitis is more prevalent in Europe. I needed to call in an Euquine ophthalmologists after 10 days of treatment with steroids, smz, banamine, doxy, atropine, prednisolone, azium. Suspected causes strangles, lepto, lyme and standing water, oppossum poop and various other possibilities. This youngster was bred with imported semen. I would run away from any stallion with this condition. There is no app blood in this horse but again this is more prevalent in Europe, and nobody is going to tell you if this is prevalent as they do not reveal that a stallion is a cribber or has anyother unsoundnesses.
Thanks for the info. I had forgotten that Appaloosas are predisposed to it. I will check out the link Rbow posted. Does the article explain WHY Appaloosas have a genetic link, but not other breeds?
The presentation suggests that German Warmbloods also may have a genetic link.
It states appaloosas have a weak ocular immune system. Not sure what is meant by "weak". A lot of interesting information about appaloosas and some of it I'd have to do a lot more reading to fully understand.
Bottom line, I don't think it's well understood and they compare it to laminitis in that there seems to be a variety of triggers.
I don't really know a lot about the Appy uveitis (though we have one). We have had a lot of Apps over the years....hubby's polo ponies. This mare is a foundation bred App.....the others (none of which had eye issues) were all Appy/TB crosses. Our mare with issues is mostly white/few spot..so likely a homozygous App. I have known a few other Apps with the eye issues...and FWIW they were also the "very white" few spot Appys.
It's the appaloosa characteristics that are associated with uveitis - not the appy breed. Meaning, for example, Knapstruppers could have it as a genetic component as well.
As for the onchocerca (neck threadworm) link - when the juveniles get into the eye area and die (ie after ivermectin or moxidectin), they can indeed cause a case of uveitis. The difference here is that it usually clears up after they are all gone. Not always.
______________________________ The CoTH CYA - please consult w/your veterinarian under any and all circumstances. - ET
It is my understanding that recurrent uveitis is considered immune-mediated (or auto-immune) disorder with many potential initiating causes. From human medicine we know certain individuals may be genetically susceptible to developing autoimmune diseases. We also know that this susceptibility is associated with multiple genes plus other risk factors. Genetically-predisposed individuals do not always develop autoimmune diseases.
I heard about a situation recently where an MO backed out of a breeding because the stallion had developed uveitis.
I know that Arabians with SCID are more at risk of developing uveitis, but what about other breeds such as WBs, TBs, European pony breeds, etc.?
The pathophysiology, i.e., the "how" of what goes on in Equine Recurrent Uveitis, ERU, is the same in ALL horses, however, the causative or associated factors may differ quite a bit...
Fundamentally, ERU is an auto-immune type of condition, and therefore, some "lines/families" of horses will be more susceptible, due to a "genetic" propensity to be "auto-immune"... The same thing can be said of conditions like ARTHRITIS... Clearly, there is a genetic propensity to develop arthritis (and, some types of arthritis more than others!), but ENVIRONMENT (nutrition, comorbid conditions, physical activity, etc...) also plays a huge role!
As many know, I am a huge appaloosa fan, and, unfortunately, I now have my first full blown case of ERU in my beloved, favorite Appaloosa broodmare... She has had a very severe and progressive course over the past year, and due to ongoing vision loss, along with the developement of secondary cataracts and glaucoma in BOTH eyes, she recently underwent a palliative procedure to "kill" her eyes, basically, a lytic injection of gentamycin at the optic nerve of both eyes... This was done to take away the source of the "inflamation" and to keep her comfortable!
As an aside, please take a look this great website:
Now, as a "hobby" breeder, I am struggling with this issue now... The Veterinary Opthalmologists at NC State, as well as a local practitioner in VA, advised me not to breed her, or at least, not to breed her to another appaloosa...
My plans, all along, were to breed her to a TB DRESSAGE stallion, which I already have the frozen semen for...
If I do this, I WILL be responsible for the outcome (I think that's what breeders should do), though often, ERU doesn't really "show up" until later in life... My mare turned 15 this year!
ERU is 8x more common in the Appaloosa breed, and probably also in other LP containing breeds like Knabstruppers, British Spotted Ponies, etc... Also, there is NO data that it is more common in horses that are HOMOZYGOUS for LP, i.e., the fewspot or snowcap patterns... It appears that having one copy of the LP gene, along with ALL the other "factors" may be enough to produce the condition... (The one visual condition that DOES occur in 100% of fewspots and snowcaps is Congenital Stationary Night Blindness, CSNB, or "night blindness")
So, I just wanted to chime in...
From my perspective, as both a mare owner and stallion owner, I think the responsible thing is HONESTY and disclosure for all parties involved... For some people, having a blind horse would not be easy... and, though I am sad my mare is now blind, she has been relatively easy to take care of...