Equine lymphangitis is a serious emergency condition in horses. The condition is characterized by acute progressive swelling of one or more of the horse's hindlimbs, with serum oozing from the skin. Equine lymphangitis is frequently caused by Corynebacterium pseudotuberculosis, the causative agent of Pigeon fever in horses residing in the western United States. The disease has also been associated with infection by a number of other bacteria and fungal organisms.