Ulcerative lymphangitis is a bacterial infection of the cutaneous lymphatic vessels. It is most frequently caused by Corynebacterium pseudotuberculosis associated with Pigeon fever. Other, less common causes include Streptococcus equi, Pasteurella hemolytica, Staphylococcus aureus, Dermatophilus spp., and Streptococcus equi.

Ulcerative lymphangitis is characterized by painful inflammation, edematous swelling, and skin nodules on the lower limbs, usually the hindlimbs of the horse. The nodules will ulcerate and drain thick, tan-colored, blood-tinged fluid onto the skin surface.