Link Between Appaloosa Coloring and Night Blindness

[R3]

I thought this was interesting. I hadn't heard about it before. Apparently, nightblindness is associated with homozygous appaloosa genes. If I'm reading this article correctly, homozygous Appies will have nightblindness? Here is an excerpt and a link to the full article.

"Appaloosas with coat patterns indicating they are homozygous for LP, the main gene responsible for Appaloosa spotting, are affected by congenital stationary night blindness (CSNB), according to new research by Lynne Sandmeyer, DVM, DVSc, Dipl. ACVO, associate professor at the Western College of Veterinary Medicine..."

Full article available at: http://www.thehorse.com/ViewArticle.aspx?ID=10852&nID=17

(This article is only viewable by registered members, but registration is free and well worth it for being able to read some excellent articles.)

 

[rabbitsfizz]

Nightblindness (Moon blindness) has been a problem in Appy patterned horses since forever- it is not just H/Z horses that are affected, but h/Z as well.

IME all Appy patterned |(not characteristic) animals are affected to some degree.

H/Z animals are, though, always affected and can also have poor eyesight in good light as well, but do not necessarily have such a problem.

I am sure at least ten people will now appear out of the woodwork to tell me that they know of at least 10 "Fewspots" with perfect eyesight but the App.Project is sure enough to be considering using the "moon blindness" to "prove" homozygosity.

The only tow true (proven by breeding) Fewspots I have known both had moonblindness and I also know of one I did not see (but whose breeder I trust) who was completely blind from dusk onwards.

I also know of at least one h/Z app patterned horse who is totally sightless at night.

 

[Bunnylady]

Does this occur in blanket Apps also?

 

[R3]

I'm no expert on the subject, I'm just learning about this stuff too, but I did a little more research and discovered that Night Blindness, also known as Congenital Stationary Night Blindness (CSNB), is different from Moon Blindness which is also known as Equine Recurrant Uveitis (ERU). The study that showed homozygous Appies have CSNB only dealt with that disorder, not ERU.

From what I just looked up, ERU is the result of an infection and the aftermath of the infection, and CSNB is a genetically caused condition, so are totally different in their causes. One is genetic, the other not. According to what I saw, ERU is most often associated with a Leptospirosis (Lepto) infection. For some reason it seems that Appies are more prone to ERU than other breeds, so some people think there may be some kind of a genetic suseptibililty to that infection in Appies, or possibily in some Appies lines, but so far no research has been done to prove or disprove that idea. But, I think it is safe to say, since Non-Appies get ERU, that whether a horse is homozygous or heterozygous Appie doesn't really matter when talking about ERU.

However, according to the original article I referenced, homozygous Appies are the ones with CSNB, and according to that article, horses with 'spots' are not normally homozygous (generally homozygous Appies are few-spots or snowcap type patterns, without spots), so a 'spotted' horse is most likely not homozygous.

Did that help any?

 

[Bunnylady]

I asked about blanket types because of a "big" App gelding I knew a couple of years ago. He was fine in the ring, but was jumping out of his skin every time his owner tried to take him on trails. She thought he was just an abject coward, but now I'm wondering if he may have had vision problems. As I remember, he may have been a snowcap, but was not any kind of leopard. Of course, this was in full daylight, but perhaps this might be a more extreme case?

 

[Knighthawke]

My Big pinto warmblood has uveitis. He is very controled with ointment put in his eye daily for the REST of his LIFE. I do it once a day. He contracted his because of Lepto. Which someone listed earlier. But they can also get it if the get Lyme disease an my vet that has helped me with mine said the worst she saw it was with a horse that tested positive for both Lepto and Lyme. They finally had to put the horse down because he had it in both eyes. And the treatment for one disease would flar up the other disease. They could never control it.

There medication my horse is on is Optimune (cyclosporin) which is used for dog dry eye and people dry eye.

The University of NC is accually doing a surgery where they will incert a little pump into lower eye lid and it will continually administer the cyclosporin so you dont have to medicate it. It is in an area that you cannot even see it. It is a couple thousand dollars so I have just done the daily treatment.

If you horse starts squinting or showing pain with an eye. Even if it is not a appaloosa contact your vet. It might just be a simple eye ulcer but. Mine was not. His started with a swollen eye that looked like someone had kicked him. I let it go the first time but then 2 weeks later it came back and ran him to the vet. We caught it early enough to save my horses vision because they can go blind. My friends horse that was at the same boarding stable. Contacted it I told her got to the vet and get care immeditely. It is not to fool with well her horse has a cataract in one eye and is blind in that eye now too. And she was a beautiful palomino paint mare that was a top show pony.

Barb