Seedy toe is an infection of the horse's hoof caused by the yeast genus candida.
To gain a better understanding of seedy toe a knowledge of the anatomy of the hoof is helpful.
LAYERS OF THE HOOF
The first layer is the part we see every day - the hoof wall. This is hard insensitive tissue similar to the tips of your fingernails.
Inside the hoof wall is the second layer - known as the white line. Anyone who has watched closely a horse being trimmed or shod and looking at the sole after trimming would have noticed a quite visible white line just inside the perimeter of the hoof and basically mirroring the shape of the hoof wall. The white line is softer and more flexible than the wall. It is also insensitive tissue and basically exists to provide a juncture between the hoof wall and the third layer of the hoof, the sensitive laminae.
The third layer which is known as the the sensitive laminae is highly sensitive, vascular (blood carrying) tissue which provides nutrients and blood to the internal structures of the foot.
The hoof wall and the sensitive laminae interlock, with the white line in between, bonding them together.
In a normal healthy hoof micro-organisms cannot gain entry to hoof tissue. However when the structure of the hoof wall is compromised, for any number of reasons, varying degrees of infection can occur.
1. Growing overlong.
In my experience the most common cause of breakdown in hoof wall integrity is allowing a horse's feet to grow overlong. Apart from the obvious fact that long feet are pre-disposed to chipping, splitting or cracking, long toes significantly delay hoof break-over (the action of the foot when walking) creating a lever arm effect on the foot. This in turn creates a shearing force between the hoof wall and the sensitive laminae weakening and stretching the bond between the two. In my opinion, this stretching creates microscopic gaps in the laminae allowing undesirable organisms access to the foot. Imagine the feeling when you bend back a fingernail.
2. Horses feet absorb moisture.
This causes the hoof to expand when wet, contract when dry. Typical South Eastern Australian Springtime weather commonly sees continual periods of wet, followed rapidly by periods of dry. This climate sees the hoof exposed to repeated periods of expansion and contraction. This also can contribute to weakening the bond between the hoof wall and the laminae. Exacerbating this problem, is that it appears that candida genus is most active in warm moist conditions.
3. Other less common causes can include:
- Acute trauma.
- Abscess formation that introduces infection
- A case of laminitis that causes tears in the laminae
- Sole or toe bruising near the white line where dried blood provides growth nutrients for the candida organism
LONG TERM EFFECTS OF SEEDY TOE
If left untreated seedy toe can have serious long term effects. I have seen cases where the hoof has become infected to the point that over half of the hoof wall has literally rotted and peeled off exposing the sensitive laminae. This has caused acute lameness for several weeks. These worst case scenarios seem to leave scar tissue on the sensitive laminae resulting in a permanent weakness in the hoof.
In extreme cases the organism can penetrate to the pedal bone possibly causing bone erosion or infection.
I have found the best results for prevention of seedy toe are a regular (5 to 6 weeks) trimming program in order to keep the hoof wall short and prevent cracks appearing through shearing forces.
Where possible try to provide your horse relief from extended periods in wet environments. I am frequently asked about the use of hoof oils and conditioners and whether they help. In my opinion (i stress this is only an opinion) the short answer is no.
In most cases seedy toe shows significant improvement with aggressive trimming and shortening of the toe. Generally two to three (regular!!!) trimming cycles is enough to cut the majority of the infection away.
In more severe cases the hoof wall will need to be resected (cut away) in order to get to the origin of the infection. Generally after resection the area is treated daily with a topical agent in order to kill any remaining pathogens. My personal favorite is iodine as I have some reservations about the use of harsher agents such as peroxides so close to live tissue. Again I stress that is just an opinion.
Resection is a tricky job and I recommend you find an experienced and qualified master farrier to undertake the task.
In nearly all cases, with proper treatment and regular trimming, horses recover fully from seedy toe without any lasting side effects.