One cause of filled or swollen legs is infection, while a generalised illness, such as heart failure, may cause all four limbs to fill at once. In such cases, the filled legs will be part of a sick horse, commonly with other signs. It will be obvious there is something wrong and that you need a vet.
Another critical condition affecting all four limbs is equine purpura haemorrhagica (EPH), which can follow strangles and other infections, such as flu. It is believed to be an allergic reaction that usually shows up 2-4 weeks after a strangles infection, just when you think your horse is getting better.
EPH signs vary, but can include:
- Oedema of the head, limbs and other parts of the body
- Tiny haemorrhages on the lips, gums and other mucous membranes, for example around the eye
- Stiffness and reluctance to move
- Fluid may ooze through the skin and areas of skin may die, leaving ugly raw patches
The most obvious sign that something is wrong is the oedema; even spindly legs will appear as thick as tree trunks with this disease. Aggressive treatment should be started as soon as the disease is suspected.
Treatment tends to involve high doses of steroids to suppress the immune response that is the underlying cause of the damage. High-dose antibiotics are also useful to control any associated infection. Practical help should include support bandages and hosing to control limb swelling, plus tempting the horse to eat and move about.
Just one leg
Far more frequently a horse will develop a localised infection involving one leg only, often following a wound. Sometimes there is an obvious area of broken skin where infection has entered; for instance, a patch of mud fever on the heels can cause the whole leg to swell. Often a tiny puncture wound is the cause and can be hard to identify. Occasionally, unidentified pus in the foot will cause swelling up the leg.
Cellulitis is the technical term for infection within the tissues. Cellulitis from a wound can result in swelling up the leg to above the knee or hock. In severe cases where the lymphatic system is also involved, this is termed lymphangitis. This means inflammation of the lymphatics, the body’s drainage channels that carry fluid back towards the heart. When they become inflamed and blocked, fluid will accumulate.
Acute lymphangitis occurs more commonly in hindlimbs than forelimbs, and is soft tissue swelling throughout the affected limb. The superficial lymphatic vessels may appear more prominent than usual and bloodstained fluid (serum) may ooze through the taut stretched skin of the swollen areas.
The horse will be lame, in pain and often has a raised temperature. The degree of swelling inevitably results in stiffness, as the affected limb is simply too fat to bend freely, although this will often improve with gentle walking.
Your vet should be contacted as soon as this is suspected, since prompt treatment with appropriate antibiotics provides the best chance for a full recovery. The milder forms of such limb infections usually respond to treatment, unless there is a particularly unpleasant type of bacteria involved.
Severe lymphangitis can be more difficult to control. Potent intravenous antibiotics may be required in conjunction with strong anti-inflammatory treatments. Steroids are a commonly used treatment, but are a double-edged sword, since they reduce the body’s immune response as well as being anti-inflammatory. But in certain circumstances they are beneficial.
Diuretics to reduce the amount of fluid are sometimes useful and all sorts of pressure wraps have been devised to reduce the swelling. Impressive results have been achieved in some cases with intensive hydrotherapy.
Despite all efforts, it seems that once a horse has had a severe attack of lymphangitis the condition has a tendency to recur or remain as fibrous scarring, possibly because the normal fluid drainage is permanently disrupted.
In the past, many such limb infections were potentially fatal and lymphangitis can still cause major complications. It is best to catch it early and treat it aggressively.
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