Sunday, November 27, 2011

Laminitis: Three different paths

One cause of laminitis is physical strain on the laminae due to trauma/injury leading to the horse's weight physically tearing the laminae. This is what happened to Barbaro, his laminae gave out due to excessive weight strain. Personally I think that horseshoes can lead to chronic low-level laminitis since they force all the horse's weight on the laminae (Remember when I said the laminae aren't designed to hold up the entire horse?). I think Dr. Bowker says it best, "any weight-bearing responsibilities the laminae have should be considered their secondary role."

There are two more mechanisms that are found in laminitis that I would call chemical based, one affects the anchoring filaments and the other affects the MMPs. Both have the same result but the causation behind them and how they work is completely different. (Refer to my last post if you don't know what these are.)

Glucose overload- most people know about this cause of laminitis, a lot of them think it is the only cause for laminitis. It isn't. Glucose induced laminitis only happens to horses that are insulin resistant (IR). The horse consumes too much sugar so the body freaks out and shuts down all its sugar uptake mechanisms (similar to diabetes in humans).  Remember how I said anchoring filaments  that attach the hemidesmosomes back onto the basement membrane are made of a glycoprotein molecule? Well the body can't make any if the uptake of sugar (glucose) has been inhibited. That means that the MMPs are still doing their job of popping off the hemidesmosomes but there aren't any anchoring filaments to glue them back on, resulting in the separation of the epidermal laminae from the dermal laminae.

There is another, much more sinister, mechanism for laminitis. This one can be caused by anything that results in an inflammatory response: colic, carbohydrate overload, endotoxemia, septicemia, prolapsed uterus, retained placentas, heat cycles in mares, potomac horse fever- basically anything that ends with -itis and messes with the balance of the hindgut can cause this other kind of laminitis. This can also be referred to as SODS- single organ dysfunction syndrome. When there are bacterial toxins in the bloodstream (which often begin in the hindgut) they activate white blood cells, these toxins and white blood cells eventually migrate down to the hooves and into the lamaella, where they cause the MMPs to go haywire and start popping off the hemidesmosomes at a rate too fast and furious for the anchoring filaments to keep up with, resulting in a separation of the laminae. This action can also result in the death of the secondary epidermal laminae cells. (It's a bit more complicated than this, but I'm trying to make it easier to understand.) Unfortunately, in this case, there is usually some pretty nasty damage done to the basement membrane. 

In the case of IR, it's the failure of the anchoring filaments that lead to laminitis, in the case of SODS it's the MMPs that lead to laminitis. The important thing to remember is that even though they both have the same result they are not caused by the same thing so they cannot be treated the same way. If your horse has laminitis the first thing you need to find out is what caused it.

The hoof wall gives evidence of damage to the basement membrane. It might be the characteristic "rings" that most people think of, but it also looks like these two pictures below. In the case of founder (chronic laminitis) horses will often create a "founder ridge," a place where the hoof wall appears to bunch up. I think the cause of this is damage to the basement membrane, basically the hoof wall cannot be moved down because the foundation that it would attach to is non-functional.




References for this post include Chris Pollitt, Jim Belknap, Rustin Moore, Robert Bowker and Debra Taylor.

20 comments:

  1. Thanks for the info. It's a scary diagnosis, so the more understood the better.

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  2. Wow, I'm learning a ton! Thanks for doing this, you are very good at simplifying and condensing everything :)

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  3. I think people tend to think of hooves like we think of our own fingernails and toenails--but as you say, it's important for us to remember that hooves aren't made up of dead tissue. Anyone who doubts that should compare human fingernail clippings with hoof trimmings!

    That said, as a person with a kind of "SODS" myself (bladder issues) I've been irritated by my nail problems for years. Seems like my nails are always detached (or detaching). And I don't have to depend on these structures for locomotion!

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  4. Carol- yes, it is scary. Fortunately there is hope, I think with proper care it doesn't have to be that scary.

    TBA- thanks! I'll post the links to my source material at the end. You can read them and get a bit of a jump on vet school :P

    Fetlock- in humans it is MODS- multiple organ dysfunction syndrome. For some reason the only tissue that gets inflamed in horses is in the hooves, humans get inflamed all over the place.

    Very interesting about your nails- while simultaneously being a bummer :(

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  5. Thanks for the info. There's so much to learn about the different causes of laminitis but you've put it all into a wonderful condensed easy to understand version. It's apparent you've done a lot of research for these posts.

    We've had Dusty tested and she's not insulin resistant. She didn't wear shoes at the time she foundered but she does now to try and correct and support her front hooves. Personally, I think she contracted this for the second time from the Lyme vaccination she received. It's happened twice now right after her shot. Once was a head scratcher, twice is more than coincidence in my mind. She won't be getting those vaccinations any more from that company and we'll see how she does.

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  6. Have you reached out to that company about it? Dusty can't be the only one that happened to...

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  7. I haven't even bothered to inform the company. Obviously, they know about the symptoms and what their drug is causing to equines and they don't care. I've looked on message boards and there are loads of people who have the same problem with this company with horses colicing and dieing(my horse Erik did after his spring shots a few years back) foundering etc. It's a major company and most vets use them, some horses have problems and some don't. I think it's a case of prove it definitively or shut up. We refuse to use them anymore and our vets have ordered from a different company for us. So it comes down to buyer beware and investigate for your own herd.

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  8. Well I was hoping to give them the benefit of doubt but it appears that they've lost their souls like so many corporations do. Care to share the name so I don't make the same mistake?

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  9. I too am SO nervous about some vaccines too.
    As you know, Laz's laminitis was caused by Potomac which lead to endotoxemia...he's sheath was SWOLLEN too during his high fever which is a clue to look for fyi. I still have SUCH a hard time wrapping my brain around if I can get his 'basement' growth to thicken/harden by 'feeding' his hooves via vit/minerals etc at the coronet. It all seems to go to his medial wall and sole remaining thin, although we've made some new nutritional changes just this past Sept/Oct so time surely will tell. LOVE these posts..you've learned so much so fast!

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  10. I'll remember that about the sheath- my next post is going to be about recognizing the signs of laminitis.

    I don't know if anybody has researched fixing the basement membrane, I can only assume that with time and the proper building materials from his diet that he can recover that growth. If he doesn't you'll just have to give that foot a little more protection.

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  11. I'd be happy to share with you but I don't want to open a can of worms on the internet and perhaps get sued. If you would send me your email, I'll mail you back with the name. greyhorsemanor@gmail.com

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  12. I am impressed by this very technical and informative post. It is scary that so many things can lead to laminitis.

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  13. I was a little worried that it was going to be too technical for most people even though I tried to make it as simple as I could. Unfortunately laminitis is not simple. And I agree, the fact that so many things can lead to laminitis is scary as hell. Horses are very sensitive critters.

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  14. Laminitis scares the crap out of me. Thanks for these posts.

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  15. Thanks, smaz, although it's definitely going to take a while for me to totally wrap my head around these posts!
    The more we horse owners know about hooves and understand how they function, the better. Lucky that we have people like you to teach us. :-)

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  16. a founder ridge... interesting. One of my horses just got a small abscess in his hoof. We are watching it closely and it looks like it is growing out and will be fine. Is that the right terminology? With horses, if it isn't one thing, it is another. It seems so much is learned during and after a brush with "bad luck". Thanks for this education!

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  17. You're welcome, Wolfie :)

    Frizzle, thanks for having so much faith in me. You'll get it, I'll post the source material at the end so you can dig through that if you're inclined.

    Margaret- yes, your horse will probably be just fine. Abscesses are really painful but they normally don't do any long-term damage.

    And you make a good point- the worst time to learn about something like laminitis is when your horse suddenly develops it. Better to know what to do before it happens!

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  18. Really informative posts - thank you.

    Laminitis scares the tar out of me. And especially vaccination related. You want to do the right thing for your horse and then bingo...

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  19. Yeah, that's part of why I got Arlene to tell me what company made the vaccine that affected Dusty so badly, I don't want to experience that or anyone else if I can help it.

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  20. This is amazing information! Laminitis is a concern of mine, because my breed of horse (Haflinger) seems to be more prone to it. As far as I know, Shyloh has never had it, but it is something I worry about. I look forward to reading more of your posts!

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