White line disease is a biodegradative disease that starts adjacent to the white line and works its way toward the outer portion of the stratum medium.

The name WLD is somewhat confusing as the area of the hoof capsule under threat is not the white line, but mainly the non-pigmented inner layer of the stratum medium in the early stages. It later moves to the pigmented layers of the stratum medium as the disease progresses. This area can be seen clearly as the area adjacent to where the sole joins the hoof wall when viewing the ground surfacethe hoof capsule (Figure 1, structures 1, 2 and 3).

In WLD, the hoof wall ultimately becomes compromised due to microbial activity. In the early stages of the disease, the infection takes the form of a darkened area within the hoof wall strata (particularly around the nail holes 2 FIGURE 3. In this lateral view of of shod feet as shown in Figure 2).

As the disease develops it takes on the appearance of a triangle with its apex at the coronary band. Its base spreads laterally while embracing other infected regions (Figure 3). The rate of disease onset and invasion is dependent on the site of infection. If the initial lesion is located in the toe and quarters, it spreads faster than if first noticed in the heels.

When viewing the soles of an infected horse, the effects of the disease can be seen as a powdery area consisting of grey or…