What is White Line Disease?
Updated: Feb 26, 2021
If you have a horse, you've probably heard about white line disease. Maybe your farrier or veterinarian mentioned it at an appointment, or perhaps you've read about it online, but what does it really mean? It goes deeper than a topical treatment can cure or fix, despite what some people might have you believe. White line disease is an infection of the white line area of the hoof. What exactly is the white line? It is made up of half epidermal lamina and half sole, and should be no more than about 1/4" wide. However, all of the white line infections that I have seen are actually located in the lamellar wedge, or stretched lamina, most often caused by laminitis and flaring of the walls, the horse no longer has a well connected white line. Stretched lamina often has voids filled with blood and serum, and is weaker than the lamina of a healthy hoof, with tight connection. The same infection we call thrush is what is invading this weak material often times all the way up the hoof towards the hairline, and we end up calling the resulting infection white line disease.
So, what is thrush? Thrush is best described as a symbiotic relationship between fungus and bacteria. It thrives in damp, dark, tight areas, such as the central sulcus, collateral grooves, and the weakened and stretched lamina of a lamellar wedge and flared walls. So, to combat this white line disease, we need to look at the whole horse instead of just the topical treatment or soaks.
How to Treat White Line Disease at the Core
So how can we treat white line disease? To answer that we have to figure out why the horse has stretched lamina. If it's a thick lamellar wedge, we need to look at the diet and any metabolic diagnosis. The epidermal and dermal lamina will begin to "let go" of each other during a bout of laminitis, the material that fills in the void between is called the lamellar wedge. This separation occurs all the way down at the basement membrane (the membrane that is responsible for keeping the dermal and epidermal lamina connected) as soon as the degenerative enzymes, matrix metalloproteinases (MMP), are activated by circulating bacterial toxins. This separation is the start of what could become white line disease, and can be very painful. Laminitis can be caused by an imbalanced diet, high in sugars and iron. For a deeper dive on what to feed, go check out my post on #supplements and #nutrition
If the stretched lamina is from improper trimming (flared walls), you will need to address that with your hoof care provider. since the coffin bone is shaped like a cup, with an arch from front to back, the hoof should never be trimmed flat to the ground. When it is, the usual areas for flare are the quarters. Sometimes, toe flaring (or hoof capsule rotation) is not caused solely by diet, but can be a result of trimming the toe from below, thinning the sole, and leaving the heels to grow high. The result is a hoof that appears to have rotation, on radiographs, but is not the typical laminitic case as the issue is mechanical instead of the body physically letting go. Both of the above scenarios can be solved by proper trimming and rehabilitation of the hooves.
Topical Treatments for White Line Disease
Once the core issue for the white line disease has been addressed, we can apply topical treatments to help get rid of the thrush and prevent further damage. Daily soaking with a 50:50 water and vinegar solution, for 30min-1hr, will do wonders to rid the hoof of harmful fungus and bacteria. Soaking with a vinegar solution will actually change the pH of the horn material. Fungi do not like to live in acidic environments, so this is a great strategy. Depending on the severity of the infection, soaking may only need to be done daily for a week or two, and then down to 2-3 times a week until all the unhealthy hoof has grown out. My favorite soaking boots are the boots from EasyCare, or the Davis soaking boots. You can also use a feed pan or a bucket, a soaked diaper, or even a soaked towel can be wrapped around the hoof and secured with either vet wrap or duct tape and placed inside a plastic bag for the duration of the soak. Easy way to do this is get the hoof soaking before you need
to do your barn chores, leave the foot soaking until you're done with everything, and take it out of the soak before you leave. You can either leave it open, or pack the area with hoof clay until the next soak. There are other, stronger, chemical soaking options out there. There's White Lightening, Oxine AH, and Cleantrax, all of which can be bought at your local feed store, and probably online. Follow the directions exactly, and be careful not to make the treatment stronger than the directions indicate. These treatments are only required 1-2 times a week at maximum, so it may be easier than the 50:50 water vinegar in that regard. All of these treatments have the potential to make the sensitive horse get irritated skin, so be cautious and switch treatment if you have any issues.
The other thing you can do is fill a squirt bottle with the vinegar solution, and spray down the infected area until you get the debris out, get your favorite hoof clay and pack the voids. You should only have to continue topical treatments until the new, strong, healthy hoof grows down to the ground.
It should also be noted that I've worked on horses with white line infections that never got soaked or treated, and the issue resolved itself with proper trimming and diet alone.