Greasy Heel & Thrush with Dr. Luke Wells-Smith

This article is from the August 2020 Horse Deals magazine.

Greasy heel and thrush are two common diseases of the lower limb which we see during the wet months of the year - typically the winter months in the southern states and the summer months in the northern states. This article aims to describe each of the conditions and how they can be managed.

Greasy Heel

What is it?

Greasy heel is the inflammation and subsequent infection of the skin, typically below the fetlock and towards the heel. Greasy heel is a form of dermatitis. It appears to occur most commonly on non-pigmented skin, i.e. white socks. It appears to be more common in hind limbs, however, can occur on the forelimbs as well.

Greasy heel is associated with wet conditions, more common in horses turned out in wet and muddy paddocks for a prolonged period of time. We frequently see greasy heel at the skin junction of the heel bulbs or in the pastern region. This is likely because these areas are frequently in contact with the moist grass.

Greasy heel can also occur in horses that aren’t turned out. These horses are typically washed frequently or have been exercised in water, such as a water walker or treadmill.

How is it diagnosed?

Greasy heel is diagnosed most commonly from the clinical appearance. It typically starts as small, non-painful crusty areas. Over time, these areas become painful, red with some discharge and in many cases, the horses resent us touching the area. The more severe forms of greasy heel can cause lameness. In the chronic cases, we sometimes see increased oedema and swelling in the lower limbs associated with infection.

In severe and chronic cases, a skin biopsy may be required to differentiate between other possible skin lesions.

How can we manage it?

If your horse develops greasy heel, it is important to avoid moisture. This may mean locking your horse up in a stable or a dry yard while in the wetter months of the year. Reducing the moisture content in your horses’ environment is the best way to manage this condition.

Once your horse starts to develop crusty or areas of scabs, the hair from the area needs to be clipped. Long hair will trap moisture close to the skin causing an increase in microbes leading to further infection. Be careful with the clippers to not further irritate the skin. Once the hair is removed, soak the affected area for five to ten minutes - this allows the scabs to soften. Remove the scabs with a soft towel and dry the leg. Topical antiseptics can be used to reduce further infection.

Resolving a case of greasy heel is time-consuming and may require multiple treatments. The best long term management strategy is to reduce your horse’s access to a wet and moist environment.

Thrush

What is it?

Thrush is the infection of the underlying sensitive tissue of the hoof, typically associated with the frog. The hoof is constantly covered in microbes such as bacteria and fungi. Thankfully, the hoof has a protective outer shell comprising of the hoof wall, sole and frog. When this outer shell is penetrated and underlying sensitive tissue is exposed, this can lead to an infection, like thrush.

The most common location for thrush to occur is around the sulcus of the frog. The horse has three sulci (i.e. grooves) - lateral, medial and central. The depth of these grooves predispose the horse to developing thrush - i.e. the deeper the groove, the more likely thrush is to occur because the groove becomes closer to the underlying sensitive tissue.

Horses with a deep central sulcus are at a high risk to develop thrush, particularly if they are kept in wet, unhygienic environments. Horses with a high heel height, tend to be more likely to develop a deep central sulcus when compared to low heel horses. Over time, when the sulcus of the frog becomes packed with debris it deepens further, into the underlying sensitive tissue, causing an infection.

Horses with a very deep central sulcus of the frog, where the groove extends past the hairline at the heel bulbs are very susceptible to chronic thrush. In some severe cases, the central sulcus extends through the corium of the frog and into the digital cushion.

How is it diagnosed?

Thrush can be diagnosed by the clinical appearance, presence of pain when touching the area and a lameness. Horses with an active thrush infection and a deep central sulcus will typically be lame at the trot, worse when lunging on a hard surface.

As mentioned, the underlying sensitive tissue needs to be exposed for thrush to occur. Thrush is commonly over-diagnosed as a black accumulation of fluid, sometimes seen in wet conditions, under sole pack or when maintaining horses in boots. This is not thrush, but merely an accumulation of moisture and microbes. Yes, this could be associated with thrush, if the sensitive tissue is exposed and the horse is maintained in a wet and unhygienic environment.

Biopsies or swabs to culture microbes are rarely helpful due to the high number of bacteria and fungi living naturally on the hoof.

How can we manage it?

If your horse has a deep sulcus to the frog, it is important to maintain your horse in a clean and dry environment. This is not always possible, however, to truly reduce your horse’s chances of developing thrush or managing the chronic case of thrush, it is the most effective strategy. This means maintaining horses on clean and dry stable bedding. Manure and urine-soaked bedding that becomes packed in the bottom of the hoof predisposes your horse to developing thrush, therefore

it is important that you regularly clean your stable and add new bedding where necessary.

When horses are yarded or in a paddock, it is important to pick up manure and hay left on the ground where the horses are commonly fed. When horses are fed a round bale, the loose hay can easily become contaminated with manure and urine. This then becomes packed in the bottom of the hoof. Regularly removing the loose hay or changing the location where the round bale is placed in the paddock is important.

There are many topical sprays for thrush. The biggest issue is keeping the topical spray on the hoof. As soon as you put the foot back into the wet environment, it is likely that the topical spray will be washed away, reducing the effectiveness.

There are two options when dealing with the horse with a deep central sulcus in terms of hoof management. Our aim is to stop the movement at the heel bulbs by improving the landing pattern at the back part of the hoof. The best way to do this is to either have the horse barefoot or shoe in a heartbar. Both encourage frog contact with either the shoe or the ground. I find that horses in work, tend to improve, particularly on the circle, when maintained in a heartbar. I like to fill the in the sole with Vettec EquiPak when applying heartbars to stop debris from becoming trapped between the shoe and the hoof.

luke.wellssmith@gmail.com | www.motionepc.com.au

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