March, 2015 - A discussion that centers on a hoof condition currently labeled White Line Disease (WLD) can be difficult to follow, since it will often include several other labels such as “seedy toe,” pododermatitis, “hollow hoof” or onycomycosis. Only by looking into the rest of the story will you have a better understanding of this condition.
WLD (at times, more accurately referred to as equine onycomycosis) is a “horn-digesting” infection that thrives when hooves are over-exposed to extreme moisture conditions, particularly those accompanied by filthy stabling conditions. This “disease” occurs exclusively within the inner third of the hoof wall itself and not actually entering into the white line tissue. Other hoof disorders, such as thrush, recurring-suppurating abscesses, or chronic pododermatitis can also occur in those extreme situations.
Intimidating as it may be, the reference or label of equine onycomycosis /ungulamycosis leaves less room for misinterpretation. To summarize this in a less complex manner, I’ve developed an easier way to communicate and relate such terminology on a working level. Borrowed from the traditional sailor’s distress signal (SOS), meaning to “save our ship”… I’ve found that this revised acronym works well:
S – Reminds us to identify any Structures/anatomy that are or may be involved.
O – Stands for Opportunity for occurrence/when the situation is most likely to occur.
S – Represents the Solution/possible recommended treatments.
The [S]tructures involved are the intermediate layer/stratum of the hoof wall and the outer border of the white line (nearest to the epidermal layer and not the dermis) that is adjacent to the white line region of the hoof. What you’ll notice in the earliest stage of WLD, when viewing the bottom (solar surface) of the foot, is a distortion, “seedy” or “cheesy” granulated separation nearest the toe region. In most cases, it may be mistaken for a widespread case of thrush, however this would be inaccurate since thrush is a “frog/sensitive tissue-digesting” infection.
The [O]pportunities for occurrence are overly moist environments, where the hoof stays saturated for extended periods, causing the formation of necrotic tissue adjacent to the white line region. This will cause a distortion of the wall to white line union, but does not directly target the tissue that makes up the white line. Often, there is no apparent lameness unless excessive hoof is lost due to deeper separation. In the most advanced cases, the inner wall would deteriorate and lose its ability to support the weight of the horse. Finally, [S]olutions include debridement of all infected hoof wall, along with a daily application of an antifungal/antiseptic solution. In some extreme cases, involving structural hoof wall damage, a modified bar shoe (heart bar) may be applied by a qualified farrier to temporarily transfer the weight/stress off of the wall and onto the frog. Providing a living environment that will allow the hoof to recover and restore its natural moisture equilibrium should be your highest priority, as to avoid any reoccurrence.
In retrospect, it becomes more evident that WLD is not the best label, since it is not so much your typical disease and would appear to be more a condition. Furthermore, it has no contagious transfer from one horse to another and its rate of progression among individual horses can vary greatly. Interestingly enough, you can find horses of like-situations, being influenced in completely different ways; where some can suffer chronically, others may experience only minor symptoms.
Now you can be a bit more confident the next time you find yourself in the midst of a conversation about a condition that has — for better or worse, and for no clear reason — inherited such a misleading title as White Line Disease. On that note, I’ll close with a phrase borrowed from one of my favorite radio personalities, popular from the 1950s and lasting until the late 2000s, Mr. Paul Harvey: “and now you know the rest of the story.”
References & Recommended Reading:
The Merck Veterinary Manual, 7th edition, C. M. Fraser
The Principles of Horseshoeing (P3), D. Butler, J. Butler
Understanding the Equine Hoof, F. Jurga
Maximum Hoof Power, C. Hill and R. Klimesh
Bio: Bryan S. Farcus MA, CJF, is the creator of a select line of “Farrier-Friendly™” products and author of the “Farrier-Friendly™” series of articles that appear in horse magazines throughout the US. Bryan currently works with horses and their owners in Ohio and West Virginia. www.farrierfriendly.com