Nia Cooke DEP MEPA(UK)
Alistair Taylor DEP MEPA(UK)

LAMINITIS

LAMINITIS - A SPECTRUM DISEASE? 

Laminitis is still a word that strikes fear into any owner, and rightly so, it is the second biggest killer of horses in the UK (after colic). It is now widely understood within the equine podiatry community, and more recently in the wider equine community, to be more of a spectrum of severity of inflammation and damage to the laminae.

 

In the severest of laminitis cases, the catastrophic failure of the laminae leads to the rotation/founder of the pedal bone. And right at the other end of the spectrum, is the horse that's mostly sound in winter but maybe a little footy spring and has 'poor feet'.

It has been linked to too much or too rich grass and feed room break-ins for as long as it's been in existence, but we're only just starting to realise just how much even very small changes in starch intake, can affect the health of the hoof. The feed room incidents are the easy ones to identify and fix, the more tricky cases are the chronic cases which flare up on occasion with seemingly no major change in environment or diet. Sometimes these chronic cases are severe and really impede the usability and quality of life of the horse. But I think in most of these cases, there are probably early warning signs that show the hoof is suffering inflammation on a lower level, prior to the more recognisable laminitis attacks.

 

Some of the signs that there is inflammation happening include:


Flare - the hoof wall being curved or bell shaped towards the ground, rather than a straight line of growth. This is thought to occur as the laminae become inflamed they lose the integrity of connection between the pedal bone and wall, and the mechanical forces of the horses movement, over time allow the wall to flare out.


Growth rings - instead of a smooth wall surface, there are ridges present. This indicates that the coronary band was inflamed when the hoof wall was created, creating bumps in the structure.

 

Bruising / Abscessing - much easier to spot in a paler hoof, orange, pink or red discolouration occurring mainly in rings or lines. This is evidence that there was damage at the coronary corium at the time of the wall growth creation. It is not really understood if this is because there is also inflammation in the other coria of the hoof, such as the coronary corium and solar corium, or whether it is a by-product of the laminae inflammation. I personally think the former is most likely. And bruising causes an opportunity for an abscess to brew.

 

Raised digital Pulses and/or Raised Hoof Temperature - Inflammation causes heat, and an increased blood flow. If the laminae or other corium were damaged, as we assume they would be on even a low end of the spectrum laminitis event, they inevitably become inflamed and show as raised pulses or hoof temperature.

 

Stretched White Line - This again is evidence that the laminae has suffered a loss in integrity of connection of the pedal bone to the wall, being as the insensitive laminae forms half of the white line, so it makes sense that a stretched white line must have been created by stretch laminae.

There are more subtle signs too, flat footedness and things like being a good-doer could mean they have insulin resistance problems, which in turn could lead to hoof inflammation.

 

The above is pretty scary, and it affects a lot of horses in the UK, it affects a lot of horses that I see. Think of all the times you've seen a flared hoof or visibly obvious growth rings. My current practice has the following percentages of cases; 10% diagnosed with Cushings/PPID, 24% having had laminitis at some point, and 62% showing signs of some level of hoof inflammation.

 

But, it is exciting times in laminitis research (some references to interesting articles and research is listed below if you want to read further), it's recently been found that up to 90% of chronic laminitis cases are caused by an underlying hormonal disease. Equine Cushing’s disease (PPID) and Equine Metabolic Syndrome (EMS) are the two most common hormone or “endocrine” disorders of horses and ponies. That's a scarily high number. And is it something we've created as a result of the environment we've created? Does the disorder come before laminitis or the laminitis cause the disorders? There is still a lot more research that needs to happen before we'll have anywhere near the entire picture, but I think we're maybe, finally on the right track to understanding enough about this disease to prevent it in hopefully the majority of cases.

 

Sources/Further Reading:

http://www.talkaboutlaminitis.co.uk/

Talk About Laminitis is a national disease awareness initiative provided by Boehringer Ingelheim Vetmedica, to improve awareness and understanding of the underlying endocrine causes of laminitis and is funding Cushings test lab fees until 31st October 2014.).

 

Richard Vialls - EP, Tutor at EPT with a research interest in laminitis. Some very interesting articles on his website.

http://www.unshod.co.uk/articles/lowgradelaminitis.php

 

Donaldson MT et al. JAVMA 2004; 224(7): 1123-1127.

Karikoski NJ et al. Domestic Animal Endocrinology 2011;41;111-117.



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