Digital Dermatitis in Cattle: Current Bacterial and Immunological Findings

Abstract

Globally; digital dermatitis is a leading form of lameness observed in production dairy cattle. While the precise etiology remains to be determined; the disease is clearly associated with infection by numerous species of treponemes; in addition to other anaerobic bacteria. The goal of this review article is to provide an overview of the current literature; focusing on discussion of the polybacterial nature of the digital dermatitis disease complex and host immune response. Several phylotypes of treponemes have been identified; some of which correlate with location in the lesion and some with stages of lesion development. Local innate immune responses may contribute to the proliferative, inflammatory conditions that perpetuate digital dermatitis lesions. While serum antibody is produced to bacterial antigens in the lesions, little is known about cellular-based immunity. Studies are still required to delineate the pathogenic traits of treponemes associated with digital dermatitis; and other host factors that mediate pathology and protection of digital dermatitis lesions.

Keywords: anaerobes; dairy cattle; digital dermatitis; immune response; treponemes.

Figure 1

Bovine Digital Dermatitis. (A) A characteristic bovine digital dermatitis lesion on the left rear foot of a female adult Holstein cow; (B) M4.1 digital dermatitis lesion on the rear foot of a female adult Holstein cow; (C) Cross-section of the inactive lesion in (B), showing a central area of active hyperemia and congestion under the crust-like scab. This lesion was positive for the presence of spirochetes. Images generated from author’s research, previously unpublished.

Figure 2

Transmission Electron Micrograph of Multiple Treponeme Morphologies Isolated from DD lesion. TEM of broth culture inoculated with DD lesion tissue homogenate showing multiple Treponeme morphologies: black arrows indicate one morphotype, white arrows indicate a second in the same sample as determined by flagella numbers (not visible), full length and width. Image generated from author’s research, previously unpublished.

Figure 3

Gram Stain of DD lesion tissue homogenate. A characteristic Gram Stain with phenol-red counterstain of tissue homogenate from a DD lesion showing multiple bacterial shapes including Gram+ cocci (purple), Gram—rods (red), and Spirochete (arrow). Image generated from author’s research, previously unpublished.