This 13 year old Half-Arabian gelding presented for a non-healing wound on his left hind leg. The wound has a foul smell and is draining grey discharge with yellow chunks. The horse's temperature, heart rate, and respiration rate were all normal. The gelding lives in a pasture that gets swampy when it rains. What things might you be worried about?
Two things to worry about with non-healing wounds of the leg and foot (especially in Florida horses) are Habronemiasis (summer sores) and Pythium insidiosum infection. A biopsy will help differentiate the two. In this case, the horse had Pythium. Pythium is an oomycete (kind of like a fungus) that lives in fresh water habitats and invades traumatized skin. Pythium causes ulcerated nodules on the legs, belly, and sides. They are known to drain foul smelling fluid with "kunkers," or chunks of tissue being expelled as the body tries to fight off the infection. Pythium can invade blood vessels, bones, and lungs if not treated promptly.
Once diagnosis is confirmed by biopsy, treatment for Pythium includes removal of the mass (not possible in this case due to the location), topical and systemic therapy. A topical treatment is available from some pharmacies that is made of DMSO, an anti-fungal, and hydrochloric acid. The topical treatment is applied daily and the wound kept covered. Meanwhile, the horse may be started on an anti-fungal drug orally. Recently, a vaccine has become available to be administered during a Pythium infection. The vaccine helps the horse's immune system better fight the infection. With aggressive treatment, the prognosis is better - although once a horse has Pythium, he should be monitored closely to make certain it does not recur.