Foot abscesses are very common in horses and are caused by bacteria getting into the foot forming a pocket of pus /infection (abscess). It is often very painful to the horse resulting in quite a severely lame animal; which continues until the pressure in the foot is relieved by draining the abscess. Usually performed by a farrier or veterinary surgeon. The condition can be distressing for any owner to see due to the severity of lameness. But why does it keep happening to some horses?

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There are many reasons why bacteria can enter the hoof and form an abscess. But they all relate to there being a deficit in the hoof wall either through poor structure, internal disease of the horse or external factors such as injury or foreign body penetration (such as a nail etc). 

Penetration injuries 

Standing on foreign objects such as nails that poke into the foot sometimes deeply into the structures, glass, stones from uneven surfaces any object small enough to enter the foot and take dirt and bacteria with it is bad for the foot and can lead to an abscess. 

The environment 

Wet weather and boggy underfoot conditions can soften the hoof. And therefore the protective barrier that usually prevents bacteria entering the inner structures of the foot, giving bacteria a way in. Also, weather conditions changing from wet to very dry can lead to hoof cracks and hoof conformational changes that allow bacteria to creep in. 

Farriery

It is very important for foot health that you find yourself an experienced farrier. The foot should be kept balanced with regular trimming to allow the forces of a heavy body to be spread evenly and throughout the hoof. And take the strain without causing the hoof wall to split and splay. Poor hoof care or failure to have the feet correctly trimmed regularly can lead to many other conditions that predispose our horse friends to abscesses such as Sandcrack/ sheered heals/ bruised soles and corns or white line disease, where the sensitive white line of the foot (the connection between outer hoof wall and sole of the foot) separates due to overloading of the foot letting bacteria invade. 

Illnesses  

Laminitis (inflammation of the sensitive tissue or laminae that hold the internal structures and bones to the hoof wall, within the foot) can lead to disruption of the hoof wall and capsules allowing bacteria to invade and form an abscess. Mechanical overload, high intake of soluble carbohydrate (sugars and starch such as long grass), hormonal diseases such as EMS/ PPID are some of the possible causes of laminitis, but the result is a weakened hoof structure leading to further problems within the hoof itself such as chronic (frequent) abscess formation.

Keratoma formation 

A keratoma is an area of hardened hoof wall that forms between the pedal bone inside the hoof and the hoof wall. This leads to internal separation of the hoof structures which can allow bacterial invasion. (Once the keratoma is large enough to disrupt the external hoof wall itself). 

Pedal bone disease e.g. pedal osteitis 

Inflammation and / or subsequent infection of the pedal bone within the foot, due to injury / repetitive concussive injury can also result from a bruised sole, corns or laminitis. Again, disruption to the hoof structure can lead to infection penetration and abscess formation. 

Hormonal disease 

Equine metabolic syndrome (EMS) is a condition where the horse has an inability to regulate their own insulin levels due to insulin resistance. These horses are often overweight leading to mechanical overload of the structures of the hoof; and therefore weakening of the structures making them more prone to abscesses. But also too much insulin within the bloodstream itself has an effect on the growth of the hoof causing it to overgrow and form less strong bonds between the internal structures and the hoof wall. This weakness can lead to cracks / laminitis, infections and abscesses.   

Pituitary Pars Intermedia dysfunction (PPID) also known as Cushing’s

Horses with Cushing’s disease produce too much natural steroid in their body. This imbalance of hormones can lead to a reduced immune function making them prone to infections such as hoof abscesses but also the excess steroid in their bodies has a direct effect on the hoof structure leading to instability and therefore the opportunity for abscesses to form. Cushing’s – like EMS – also leads to insulin resistance and subsequent laminitis, making hoof problems a serious issue for these horses. 

Pregnancy

The hormones involved in pregnancy such as relaxin, a hormone that helps relax the soft tissues of the reproductive tract in mares about to foal, can also act on the structures of the hoof in late pregnancy in turn leading to laminitis / disruption of the hoof structure and possible abscess formation. 

So why does it keep happening to MY horse?!

In summary, if your horse experiences ongoing or multiple abscesses you need to consider the environment. Is it safe, free of potential penetrating foreign objects, clean, not boggy? Does your horse have regular hoof care with a farrier? If all of that is up to scratch, your vet may need to look for underlying conditions for recurrent hoof disease and infection such as hormonal disease or disease of the deeper structure of the hoof. Investigations may include blood tests and / or x-rays. Treatment is usually drainage of the abscess followed by treatment of any underlying condition. See your vet if you have concerns about your horse and recurrent abscesses. 

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