The cause of the infection in cattle is two species of anaerobic bacteria, Fusobacterium necrophorum and Bacteroides melaninogenicus.[1] Both bacteria are common to the environment in which cattle live, and Fusobacterium is present in the rumen and fecal matter of the cattle. In sheep, F. necrophorum first invades the interdigital skin following damage to the skin, and causes interdigital lesions and slight inflammation. The second stage of the disease is marked by the invasion of the foot by the foot rot bacterium Dichelobacter nodosus, a Gram-negative anaerobe.