Bokt.nl

jeddah schreef:

Dus eerder hadden ze "maar" 10 gevallen, nu binnen 2 jaar 42 binnen hetzelfde ras en uit dezelfde lijnen.

Citaat:

Following is from a post by a vet.....about an article in the Quarter Horse News. (QHN)

HERDA is the acronym for Hereditary Equine Regional Dermal Asthenia, or as it's otherwise known, Hyperelastosis Cutis.

This thing is going to have some far-reaching implications to say the least.

"All the affected horses are related to each other"
For those of you who don't get QHN, in a nutshell --
It's considered to be an autosomal recessive condition. In other words, unless you get both copies of the gene, you don't have a problem (unlike HYPP, where the gene is dominant and one copy of the gene --
heterzygous -- will allow for expression of clinical signs). In the case of HERDA, heterozygotes - horses with only one copy of the gene - are carriers... they look completely normal and never have a problem.

Normal is designated (NN),
Carrier is designated (Nn),
Affected is designated (nn).
This boils down to:
A carrier (Nn) crossed with a negative (NN) will produce 50% carriers, 50% normal
A carrier (Nn) crossed with another carrier (Nn) will produce 50% carriers, 25% normal and 25% affected (nn)

An affected horse doesn't normally live past the age of 4. Since its clinical signs usually show up by the time they're 2, the horse would PROBABLY not have entered the breeding pool. Then again, with AI, it's entirely possible that affected animals have been used; these lines are very inbred.

So what is this disease? Best way to descibe it is a defect in the elastic fibers of collagen (primary component of skin), which causes the skin to be weak and/or baggy. The skin on these horses is hyper-extensible: it's easy to pull it out, then it doesn't immediately snap back into place. According to the article:

"HERDA is a genetic disease characterized by abnormal skin along the back the tears easily and heals into disfiguring scars. Symptoms typically don't appear until the horse is subjected to pressure or injury on its back, neck or hips. These horses cannot be ridden because the saddle literally tears off the skin, a horrible discovery usually postponed until the horse's
initial experience under saddle...."

Where this has real implications for the industry is that unlike HYPP, HERDA can not be managed if a horse is affected. There's no prevention and there's no cure. As one researcher commented, "..You're literally
playing Russian Roulette because if your horse is affected, that's it, you're done."
One thing the article says near its end is that HERDA is often referred to as the "Doc O'Lena disease," but that statement is totally misleading. "THERE HAVE BEEN SEVERAL HERDA-AFFECTED HORSES THAT DIDN'T HAVE A DROP OF DOC O'LENA'S BLOOD IN THEIR PEDIGREES." (that is important, so I had to shout). That made me feel better. You have to look past Doc O'Lena... Dr. Rashmir is cited as believing that she and her researchers have pinpointed the one horse that is listed twice on nearly every HERDA-affected pedigree... and that there is one other horse that appears as a common ancestor of a few affected horses.
In that case, she said that those cases are rare and usually less severe.

There is NO blood test for this disease (yet). The best advice I can give is to ask stud owners if their horse has thrown any of these, to the best of their knowledge... assuming, of course, that they'll be up front. Dr Rashmir is willing to review papers for stallion or mare owners and ascertain the probably HERDA risk level for a particular cross. There's a
nominal fee for this and all proceeds benefit the HERDA research program at MSU.