White Line Abscesses of the Equine Hoof
By Pat Wagner, Hoof Rehabilitation Practitioner
We've noticed there is little information online about hoof abscesses. Often hoof abscesses are improperly diagnosed, which delays proper treatment and may worsen the horse’s condition. Learn what a hoof abscess is, common causes of hoof abscesses, symptoms, treatments, and how hoof abscesses affect the hoof. Find out what symptoms to look for, how to reduce the pain of hoof abscesses and how to help with recovery.
Both Shod and Unshod Horses are at Risk
Chronic abscessing of the bars or wall is generally caused by incorrect trimming or neglect. Whether a horse is shod or unshod has almost no bearing on whether a horse is having issues with abscesses except for the fact that a shod hoof is often a hoof that has been trimmed incorrectly. A shod hoof must be trimmed to support a shoe and that type of trimming cannot allow the hoof to be trimmed as it would be worn in nature.
What Is a White Line Abscess?
A hoof abscess is a purulent inflammation of the connect tissues, lamina and solar papillae, where the pressure produced by the accumulation of pus between the dense structures of the hoof - hoof wall and bone causes the horse extreme pain and is often, but not always, accompanied with swelling of the affected leg and noticeable lameness.
Hoof abscesses enter in the connective tissues of the hoof, the area termed "white line". Abscesses can enter in one of two parts of the hoof. In the white line of the hoofwall (where the wall connects to the sole) or the white line of the bar.
The outer hoofwall is the more obvious location where abscesses can start. An abscess then takes the path of least resistance toward soft tissue where it ruptures at the coronet band. As the hoofwall grows, we see the rupture site grow down with new wall growth, and eventually is trimmed off.
The bar is the less obvious location where abscesses can start. The abscess that enters in the white line of the bar makes it assent up the area of whiteline in the bar tracking toward soft tissue where it can rupture in the heel bulb. Bar abscesses are often missed, because our attention isn’t usually drawn to the back of the hoof as routinely as the front of the hoof.
Therefore, bar abscess are most often diagnosed as a mystery lameness. The pocket left by the abscess in the bar can be re-infected several times, which can be baffling to professionals who do not understand the anatomy of the hoof and the cause of bar abscessing.
Causes of Hoof Abscesses
Abscessing is a common occurrence in the hoof transitioning from shod (and/or neglected) to barefoot. Abscesses are considered as part of the detoxification process of an unhealthy hoof to a healthy hoof, not because the abscesses develop after the hoof begins the transitioning process, but because the abscesses had been festering in the hoof and deshoeing the hoof, or the implementation of correct trimming allowed the abscesses to finally migrate to soft tissue where it can rupture.
I believe that the highest degree of pain from an abscess is just prior to rupturing.
Diet imbalances may have a bearing on hooves that chronically abscess only in that the hoof wall of horses who lack proper nutrition may not be as dense or strong as a horse on a healthy diet. But the actual connection, I believe, isn’t that the diet is a direct factor in unhealthy hooves, so much as the horses on poor diets are generally also not receiving regular hoof care and flare is more likely the issue causing the abscesses.
Flare caused by neglect or incorrect trimming is the leading cause of abscesses. Flare typically leads to stretching of the white line and if flare is not corrected it leads to separation of the white line allowing an entrance site for dirt, manure, urine (debris) to infect the laminae and that infection begins an assent up the laminae between the hoof wall and the coffin bone (leaving a trail of dead tissue in its wake) and erupting when it arrives at soft tissue - the coronet band or the heel bulb depending on whether the abscess entered at the white line of the outer hoof wall or the white line of the bar.
As stated above, it’s the swelling and eventual eruption at the coronet band (soft tissue) that the horse feels the highest degree of pain and usually becomes lame prior to rupture. Once rupture takes place, the horse will gradually become sound again.
Bar abscesses often become a chronic problem because the trimming strategies are not changed. The bars will become re-infected over and over and in more than one hoof, due to the fact that whatever hoofcare one hoof is receiving, all four hooves suffer with that same lack of correct hoof care. So lameness can be seen, off and on, in all four hooves.
Bar abscess often affect the entire solar papillae. This is an important consideration and that type of abscess is often referred to as a sub-solar abscess further explained below. The bars of the hoof must be trimmed along with the wall because the bars ARE an extension of the wall. If the bars are not tended to in the same manner as the wall, then they will cause pain and or begin the abscess process. My hope is that it becomes common practice to trim bars (not take them completely down to the sole plane) but simply trim bars as we do the walls.
Hoof Abscesses Are Often Misdiagnosed.
Horses suffering from an abscess (or multiple abscesses) may not exhibit pain/lameness. However, typically abscesses are an extremely painful process. Symptoms displayed by the horse are often misdiagnosed as founder, navicular, or other “mystery lameness” such as stone bruising which in my opinion isn't a logical cause for lameness.
Many suffering horses are started down a traditional path of “corrective” shoeing (which more often than not is done to correct the hoof ailments caused by the shoes in the first place) and eventually put down.
Because bar abscesses can go completely undetected or are often misdiagnosed as a mystery lameness, it’s difficult to say how many horses have been euthanized when correct trimming could have resolved the problems.
Relieving the Pain of Hoof Abscesses
Booting the horse to give it relief from the pain of an abscess as it is surfacing is beneficial, but may slow the the process of eruption, so time out of the boots is critical for healing. We use he Soft Ride Comfort Boots or the RX hoof boots by Easycare, Inc.
I absolutely do not recommend the traditionally treatment of cutting away a large part of the sole or frog and applying bandaging and leaving the horse in a stall for extended periods. Digging with sharp tools into an abscessing hoof only adds insult to injury. The abscessed hoof that we dig into will have one more issue to heal from and often the hole left by a veterinarian or farrier with the best of intentions is the injury that takes longer for the hoof to heal from than the initial abscess.
My recommendation is to wait for the abscess to find its own way to the surface where it will rupture. As stated above, the severe pain and lameness we generally see during the abscesses process happens just before the rupture at soft tissue. Digging into the sole with the idea of finding a foreign object that may have (although rarely) invaded the hoof or attempts to cause the hoof to drain generally does nothing more than creates a wound in the hoof. Abscesses likely happen in the wild as well, and hooves heal from them without humans digging around in the hoof with their tools.
In my experience, treating pain with inexpensive powdered aspirin which can be purchased in most feed retailers or online actually seems to have the highest level of affect on hoof pain.
After a Hoof Abscess Erupts
Once the abscess has erupted and drained, bandaging is not necessary. To speed up the healing process, allow movement at liberty (not forced) on soft ground. Spraying the area with a very mild iodine (no more than 2%) can help with healing. I sometimes also apply over the counter antibiotic salves.
How the Location of an Abscess Affects the Hoof
An abscess in the outer hoof wall of erupts at the coronet band, but it’s not commonly understood that the trail of dead connective tissue left in the wake of an abscess that travels up the wall and exits at the coronet band no longer connects wall to bone inside the wall. So as the rupture site grows to the ground with the new growth of wall, we often see the area of wall below the rupture site snap off. That’s normal progression and eventually the site itself will migrate to the ground where it can be trimmed off. There is really no treatment that benefits the hoof at the point where leverage from the ground snaps the area of wall off the hoof below the rupture site. This is just a natural progression of the abscess.