THE lower legs of a horse contain very little soft tissue – the tendons and ligaments are held snugly against the bones by an encircling layer of dense connective tissue, with an outer wrapping of tightly stretched skin. It’s as if the horse is permanently wearing a set of those compression stockings recommended for passengers on long haul flights.
The tissues under the skin contain tiny lymphatic vessels which act as a backup supply to the circulation, ensuring the small volume of fluid that constantly leaks out of the blood vessels is returned to the bloodstream. These lymphatic vessels are not connected to the heart, so they rely on contraction of the surrounding muscles and tissues as the animal moves to help push the fluid through them. This squeezing effect is especially important in the limbs, as the fluid needs to flow back up them, against gravity, on its way back to the circulation.
If bacteria gain entry to the deeper skin layers via a cut or nick, they may start to multiply and the affected area will become hot, swollen and very painful. Infection of the deeper layers of the skin is known as cellulitis. Once established, the infection can start to spread away from its entry point along the tissue seams under the skin. The lymphatic vessels may become inflamed and swollen. As they are squeezed shut, lymphatic drainage stops and the excess tissue fluid starts to accumulate, as its passage back to the circulation is now blocked.
Within a few hours the characteristic signs of lymphangitis will develop. The leg will swell dramatically and the normal contours of the joints are lost. Severe lameness occurs – with only brief toe touching or a three-legged hop when the horse is asked to move. The affected area feels firm and hot and the horse will object to even very gentle handling of the limb. The swollen skin may start to ooze beads of yellowish fluid, along with visible reddening on white areas. Patients also typically have an elevated body temperature.
Lymphangitis is extremely painful, so suspected cases should receive prompt veterinary attention to allow pain relief to be administered rapidly. As well as controlling the pain, medication may also be prescribed to reduce swelling, treat the infection, manage a wound (if present), reduce fever, prevent tetanus and restore limb function. Blood samples and swabs may be taken for testing to establish the most effective choice of antibiotic and to monitor the response to treatment. The goal is to get the infection and swelling under control as rapidly as possible, thereby preventing further tissue damage, abscess formation or the loss of the overlying skin.
While veterinary-prescribed medication is usually crucial for treatment, it is not the only management option and there is a lot of effective husbandry measures that can be used to promote recovery. Cold hosing or bathing can help reduce pain and swelling. Once the horse is more comfortable it should be hand walked, as movement and weight bearing will help to re-establish normal blood flow and fluid drainage in the leg.
I find bandages best avoided, especially in the early stages, as they just tend to add to the patient’s discomfort and may further obstruct tissue drainage. Consult with your vet on this, as bandaging and poulticing may be helpful in individual cases if an abscess starts to develop.
A support bandage on the opposite leg is recommended, as the horse is likely to be transferring as much weight as possible off the painful side. Flies are often attracted to the oozing skin or wound and are an additional torment. A cool and well-ventilated stable or small paddock will allow the horse to rest. Fly repellents and/or fans to create a breeze to dissuade flying insects are helpful in summer months. Avoid the temptation to provide a very deep straw bed, as it tends to get wrapped around the affected leg, thereby reducing mobility. Shavings and rubber matting may be better bedding options.
It may take several weeks before the swelling and lameness resolves completely. Prompt treatment also reduces the risk of reoccurrence, as once the infection gets established it can result in a lot of scar tissue formation under the skin. Scar tissue is inelastic and may result in permanent thickening of the leg. Once there, it’s practically impossible to remove and it increases the risk of repeat bouts of lymphangitis in the future.
Traditional horsemanship emphasises the importance of carefully checking horses’ legs daily for any nicks or cuts. This remains excellent advice as it’s remarkable just how quickly infection can take hold: the sooner it’s detected, the better. Thankfully, we have access to a broader range of treatment options than previous generations of horse keepers, but ‘big legs’ retain their ability to significantly impact on equine health and welfare.
SHARING OPTIONS: