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Identification and evaluation of putative pathogens of treponeme-associated hoof disease in free-ranging elk (Cervus canadensis)
Dissertation

Identification and evaluation of putative pathogens of treponeme-associated hoof disease in free-ranging elk (Cervus canadensis)

Elizabeth Willis Goldsmith
Doctor of Philosophy (PhD), Washington State University
12/2025
DOI:
https://doi.org/10.7273/000008385
pdf
GoldsmithDissertationFINAL25.00 MB
Embargoed Access, Embargo ends: 02/26/2028

Abstract

16S rRNA gene amplicon sequencing in situ hybridization Mycoplasma pododermatitis polybacterial etiology Treponema Animal diseases
Treponeme-associated hoof disease (TAHD), an emerging disease causing lameness and apparent increased mortality in free-ranging elk (Cervus canadensis), is characterized by ulceration, hoof overgrowth, and undermining of the heel bulb. TAHD diagnosis and surveillance relies on identification of grossly abnormal hooves and histologic detection of argyrophilic spirochetes colocalized with erosive to ulcerative and necrosuppurative pododermatitis. The central goal of my research was to identify and characterize putative TAHD pathogens. On assessment of 16S rRNA gene amplicon sequencing data and interdigital histologic sections from 129 free-ranging elk, I identified Treponema, unidentified Spirochaetaceae, Mycoplasma, and Fusobacterium along with associated bacterial families and taxa as strongly associated with TAHD and with more severe lesions of pododermatitis characterized by a histologic lesion categorization system. I also observed a strong positive correlation between Treponema and Mycoplasma, suggesting that Mycoplasma has a more significant role in TAHD’s etiology than previously recognized. On assessment of interdigital tissues from 46 free-ranging elk with in situ hybridization assays, I detected Treponema pedis signal in the majority of TAHD-positive elk with more frequent detection of high T. pedis signal within TAHD lesions relative to tissues adjacent to TAHD lesions. I also identified high Mycoplasma signal detections more frequently in TAHD-positive elk relative to TAHD-negative elk and in TAHD lesions relative to adjacent tissues. My research confirms the importance of Treponema to TAHD’s etiology and highlights the importance of Mycoplasma as a putative TAHD pathogen. Overall, this work enhances our understanding of TAHD’s etiology, supporting a polybacterial etiology and providing a foundation for future research and development of improved diagnostic testing.

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