Correlation of lesion severity with bacterial changes in Treponeme-Associated Hoof Disease from free-roaming wild elk (Cervus canadensis)

Authors: Wilson-Welder, Jennifer; HAN, SUSHAN - Colorado State University; BAYLES, DARRELL - US Department Of Agriculture (USDA); Alt, David; Kanipe, Carly; GARRISON, KYLE - Washington Department Of Fish & Wildlife; MANSFIELD, KRISTIN - Washington Department Of Fish & Wildlife; Olsen, Steven

Submitted to: Animal Microbiome
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/25/2024
Publication Date: 4/22/2024
Citation: Wilson-Welder, J.H., Han, S., Bayles, D., Alt, D.P., Kanipe, C.R., Garrison, K., Mansfield, K., Olsen, S.C. 2024. Correlation of lesion severity with bacterial changes in Treponeme-Associated Hoof Disease from free-roaming wild elk (Cervus canadensis). Animal Microbiome. https://doi.org/10.1186/s42523-024-00304-9.
DOI: https://doi.org/10.1186/s42523-024-00304-9

Interpretive Summary: Treponeme-Associated Hoof Disease (TAHD) is a polybacterial, multifactorial disease affecting free-roaming wild elk (Cervus canadensis) in the Pacific Northwest. Previous studies have indicated bacterial etiology similar to digital dermatitis, including isolation of Treponema species from lesions. The lesions appear to progress rapidly from ulcerative areas in the interdigital space or along the coronary band to severe, ulcerative, necrotic, proliferative lesions under-running the hoof wall, perforating the sole, contributing to hoof elongation, deformity, and overgrowth. Eventually the lesions undermine the entire laminal structure leading to sloughing of the hoof horn capsule. The objective of this study was to determine the bacterial community associated with hoof lesion categorized into 5 stages or disease grade severities with 0 being unaffected tissue and 4 being sloughed hoof capsule. The goal was to determine if TAHD continued to be bacterial driven disease through the morphological changes observed and was dominated by Treponema, like the livestock diseases. Bacterial 16S rRNA gene was sequenced from 66 hoof skin biopsy samples representing the 5 lesion grades from feet collected by Washington Department of Fish and Wildlife as part of a voluntary hunter program. Analysis of the relative abundance of bacterial sequences showed that lesions were dominated by members of the bacterial phyla Proteobacteria, Firmicutes, Bacteroidetes and Actinobacteria. In lesioned samples, members of the genus Treponema, Porphyromonas, and Mycoplasma increased with lesion severity. Confirming lesion status with Treponeme species specific PCR and histopathology, the bacterial 16S rRNA sequencing confirms the presence of Treponema species in lesion development and persistence, as well as the presence and persistence of other pathogenic anaerobic bacteria associated with other hoof infections. Understanding the bacteria involved, and their persistence in the lesions, will provide evidence for science-based management decisions in TAHD infected elk populations.

Technical Abstract: Wild elk (Cervus canadensis) in the pacific northwest have developed a severe hoof disease with many similarities to digital dermatitis in livestock, including abundance of Treponema at the leading edge of lesions. Researchers have divided the stages of disease in these elk into five categories or lesion grades from 0, a healthy hoof with no signs of disease to grade 4, complete loss of hoof horn. Accompanied by each of these anatomical changes, there is an increase in the relative abundance of treponemal DNA. Patterns of association between and within lesion grades indicate that the lesion grades represent a continual progression of disease with a similar bacterial community. It is likely that multiple bacterial genus and multiple Treponema species are involved in lesion development and progression. Insights into bacterial community patterns and how the correlate with disease severity will help inform science-based management practices for these wild elk.