Bovine Digital Dermatitis Study Guide

Overview and Clinical Importance

Digital dermatitis (DD), also known as Mortellaro disease, papillomatous digital dermatitis, or hairy heel warts, is a polymicrobial infectious disease first described in Italy in 1974 by Cheli and Mortellaro. It is characterized by painful, ulcerative, and proliferative skin lesions typically located on the plantar surface of the hind foot between the heel bulbs and adjacent to the coronary band. DD is now the leading cause of infectious lameness in dairy cattle worldwide and is emerging as a significant concern in beef feedlot operations.

DD causes substantial economic losses through decreased milk production (estimated 5-25% reduction in affected cows), reduced reproductive performance, increased culling rates, treatment costs, and significant welfare concerns due to the painful nature of lesions. The disease affects an estimated 47% of U.S. dairy herds, with within-herd prevalence ranging from 5% to over 50% in severely affected operations.

Etiology and Pathogenesis

Polymicrobial Nature

DD is a polymicrobial disease involving multiple bacterial species that act synergistically. Treponema species (spirochetes) are consistently identified as the primary pathogens and are found in abundance in mature lesions, comprising up to 94% of bacterial sequences in chronic lesions. These organisms are phylogenetically related to treponemes causing human periodontal disease.