Talk:Lethal white syndrome

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IMHO, Lethal White affects enough horses and more than one breed, especially with its controversial, possible, (probabe??) link to the Frame Overo gene that it should be ranked medium importance. There is a DNA test as well. Seems to have the numbers, publicity and concern amongst laypeople to justify a higher ranking. (As should, when you get to them, HYPP and HERDA)

This is exactly why I asked for more input on the equine medicine articles - I knew I would mess up the importance ratings. Thanks for clarifying this. By the way, I already rated the HERDA article as low importance, but please change it if you think it warrants a higher rating. --Joelmills 02:34, 10 July 2007 (UTC)
Sigh. There is no link of LWS to the frame overo gene, as this article goes to great lengths to explain, and this common misunderstanding is the cause of dangerous and wasteful breeding practices. I agree with the medium importance. Dcoetzee 06:38, 10 July 2007 (UTC)
Well, the frame overo thing is a dispute between UC Davis and the University of Minnesota, but we won't argue that here. Montanabw(talk) 21:36, 10 July 2007 (UTC)
There is no dispute, and I think it's worth arguing here if it affects the factual presentation of the topic. I'm not aware that UC Davis has ever made a statement after Minnesota published their results contesting them in any way - Laurie Fio's work clearly predates the blood test and Minnesota's findings by several years, and had no basis in experimentation. Dcoetzee 23:03, 10 July 2007 (UTC)
If anybody is interested in reading a slightly more recent article about this, there is one from the Canadian Veterinary Journal here, entitled "Foal with Overo lethal white syndrome born to a registered quarter horse mare", which would seem to bear out what Dcoetzee is saying. The gene that OLWS has been linked to is the endothelin receptor B gene, which interestingly is the same one that causes a similar disease in humans, Hirschsprung's disease. --Joelmills 23:25, 10 July 2007 (UTC)

This wikipedia article itself sidesteps this issue and I am not going to join the controversy in the article at all, just discuss it here. But please note I said LINK, not CAUSE. And a UCD researcher is the one who found the Hirschsrpung-like gene, see http://www.vetmed.ucdavis.edu/CCAH/Genetics/Person_Metallinos-Bannasch.htm Joel, bless ya, but the article you cite says "The mare's sire, a registered American paint horse, was sorrel with an Overo pattern." (grin) You have landed yourself in the middle of horse politics, m'laddie, so hang on and get out yer popcorn, it's going to be a heckuva ride!

I am just throwing in my oar because I have been studying various genetic diseases in various horse breeds for a while now and I am beyond fed up with the attitude of breeders (of any breed, take your pick) and their routine state of claiming total shock that their horse/program/breed could possibly have genetic problems. (hey Joelmills, are the dog people this way too?) Besides being flat out dishonest, or at least a major case of psychological denial, this attitude has slowed research-- we'd have tests for all this stuff -- and sooner -- and better understood -- if not for the denial and covering up. (far easier to shoot, shovel and shut up) And yes, I've read the MN study, bought and paid for by the APHA, which had a financial interest in its outcome. The UC Davis stuff would be removed in a lawsuit if it were made up of whole cloth and unsupported or discredited. And they have the DNA test. So, obviously, there is still a controversy and the issue isn't fully settled. I've read the stuff on the APHA site and indeed, Overo doesn't "cause" LWS, but there IS some kind of link. see http://www.vgl.ucdavis.edu/service/horse/coatcolor.html#lwo

What people don't seem to "get" is that frame overo is not a simple dominant gene, it is more complex, (I can't find anything explaining if we even know if it is a gene complex like sabino, or if its an incomplete dominant, or even a recessive, but it obviously is not a simple dominant like tobiano. One site said that as many as 10 genes could make up overo, but it has no cites to genetics literature, just mentions Sponenberg.) but whatever it is, it can "lurk" in solids (as anyone who ever had a cropout QH under the old white rule knew only too well) and in tobianos (and a link to how a tobiano can throw an LWS foal-- see here http://www.horsequest.com/journal/educate/lethaltt.html (. Even Fio said, " In overo to overo breedings, there is no firm evidence that a lethal white foal is a definite possibility in every cross." http://www.vgl.ucdavis.edu/~lvmillon/overo.htm Though some articles suggest it's a dominant, seems LWS acts like a recessive as it must be from both parents to produce an affected foal. Clearly it isn't just the color-producing part of the overo gene alone, as there would never be an overo-colored horse if the color gene itself "caused" LWS. And one web site I ran across suggests the test seems to have now demonstrated that there are overo-patterned horses without being carriers of LWS.

However, LWS never appears in breeds of horses that do not produce overo coloring, for example, Clydesdales carry sabino, but not overo, and they do not have LWS. Neither do Arabians or Andalusians or Welsh ponies, or any other non-overo-producing breed. It's mostly a Paint/Quarter Horse thing. So is some kind of link to overo, we just don't know what it is, and the defensiveness of Paint breeders does not change reality. Saddlebreds, who produce tobianos, don't have LWS. Neither do shetland ponies, who also have tobiano (though it apparently has appeared in minis).

Sorry that I am ranting, I'm just tired of people who don't like reality. Overo and LWS are somehow connected. Correlation is not causation, but you cannot deny that the correlation exists. Joel, forgive us for dragging you into this. If I may pun a bit, I'd love a more black and white answer to this question! Montanabw(talk) 05:03, 11 July 2007 (UTC)

I see what you are saying, Montana, and I missed that part of the article saying that the mare's sire had an overo pattern. I didn't think that the frame overo trait might have a polygenic base, and that accounts in part for my misunderstanding of the question. If it was a single gene, and that gene is different from the endothelin receptor B gene, than the two are not linked (unless they are linked). If multiple genes are involved in the frame overo trait, than they could be linked. It seems to me that the recent completion of the first draft of the equine genome gives some hope that these questions will be answered. In the meantime, we depend on seven measly journal articles, the most recent five years old, and only two of which we can access fully. This is one of the frustrations of trying to seriously write a vet med article - sometimes there is a real dearth of research. Regardless, don't worry about dragging me into all this. I find this kind of thing fascinating, all the more so because I don't know anything about it. --Joelmills 03:59, 12 July 2007 (UTC)
Agreed that more research is needed. Genetic linkage is an interesting thing, and what does make LWS puzzling is that the condition only shows up in horse breeds who also sometimes exhibit the overo pattern; the reason for the correlation is hard to figure out, but it's there. Bottom line on ALL the genetic diseases in various purebred animals is that it doesn't help when breeders just stick their heads in the sand and pretend it doesn't exist. Montanabw(talk) 19:06, 12 July 2007 (UTC)
I agree that a correlation exists, and it is certainly the case statistically that a random horse carrying LWS is currently much more likely to be overo paint than any other breed. But now that a blood test is available, and that test has demonstrated that it's unpredictable which horses carry it, sound breeding practices should be based on the test results, and not any phenotype. You might use breed to determine which horses to test. To accuse MN of fabricating results for the APHA's financial interests is silly - I think they would value their reputation as a research institute more. Dcoetzee 19:52, 12 July 2007 (UTC)

[edit] Facing the facts

I have sympathy for people who have overos and have to constantly deal with uninformed people who think the color causes the disease. Obviously that isn't true; I believe we did point out in the article that many overo horses test negative for LWS. However, facts don't stop the doggedly uninformed. I also know people who dismiss every horse in a breed I know particularly well, in part because some representatives have carrier genes for four genetic diseases that can't yet be tested, and only one that can, so my sympathies only go so far. My axe to grind on the entire topic of genetic lethal diseases (and this includes any breed of horse or dog) is that people need to be honest and to put the good of the breed ahead of personal greed. That starts with accurate statements and not hiding from some of the uncomfortable truths. That is why I like to work on wikipedia, it is the search for truth that counts. To say there is NO connection to overo is to distort the truth. The truth is that now there is a test, people need to use it, and yes, even people with solids and tobianos.

A university does not falsify results, please do not put words into my mouth. What I am saying is that it is a reality that who pays for research cannot help but have an interest in its outcome and exert subtle and not so subtle pressure on which results may be focused upon and which are filed in the back drawer. The tobacco industry banked on that factor for years. The APHA was happy to get a test, I am sure U Minn found the proper markers, but then the money seems to have dried up -- We still haven't figured out why there is a connection to overo ancestry, even if not visible in the phenotype of every carrier. We still don't even have a good study to determine if overo is a gene complex, and incomplete dominant, or what.

That said, it also matters that what goes here is stated as carefully and fully and accurately as it can be. I just spent a good two hours last night checking the statements in the article against what the research and sources actually said and had to correct a great deal of text in the article that didn't have it quite right (probably including a few of my own earlier edits) The disease, to the best of my knowledge, has not ever appeared in a breed of horse that doesn't have overo members of that breed, and every known LWS foal has at least one overo ancestor. For example, there has never been a LWS Saddlebred or Clydesdale. Curious to know if any other breeds besides Paints and Quarter Horses (or crossbreds with those breeds in them) have had LWS other than apparently one mini.(?) Montanabw(talk) 04:32, 13 July 2007 (UTC)