Cellulitis in Horses

Cellulitis—extreme swelling in a horse’s leg—is caused by a bacterial infection of the soft connective tissues. Unlike the “stocking up” or “filling” of both hind legs (sometimes all four legs) that may be seen in horses that are kept in stalls, cellulitis produces swelling in only one leg, almost always in a hind limb. Horses that stock up from inactivity are not lame, and the swelling usually subsides with exercise. Cellulitis, on the other hand, is characterized by warm, painful tissue that can swell within a few hours to a point where the skin may crack and ooze serum.

A small scratch or wound can cause cellulitis to develop, though in some cases no wound can be found. It’s not known why some wounds, even fairly severe ones, don’t produce cellulitis, while other seemingly insignificant injuries cause a leg to “blow up.”

Besides inflammation in the leg, horses with cellulitis may show fever, inappetence, depression, and nonweight-bearing lameness. Extreme cases may involve laminitis and sloughing of skin tissue.

Treatment is most effective if it is begun early in the course of the infection. Antibiotics and anti-inflammatories are often helpful, and cold hosing can ease the horse’s discomfort. Unfortunately, cellulitis recurs in about a quarter of affected horses, especially if there is a large wound that is slow to heal. Recurrent cellulitis may be seen if serious lacerations have caused disruption of the circulatory and lymphatic systems in an injured leg as well as providing an entry point for bacteria. After a severe case of cellulitis, some horses retain chronic enlargement in the affected leg regardless of treatment methods.