An experimental infection model for rapid reproduction of treponeme-associated hoof disease in captive elk ( Cervus canadensis )

Treponeme-associated hoof disease (TAHD) is an emerging, polybacterial infection that causes painful foot lesions and lameness in free-ranging elk (Cervus canadensis) across the northwestern USA. Although TAHD is associated with multiple Treponema species and other anaerobic bacteria, current understanding of disease etiology is limited and based primarily on cross-sectional analyses of naturally infected elk, in which lesions were examined at single time points using histopathology and 16S rRNA gene sequencing. Our objective was to develop a rapid and reliable experimental infection model to study TAHD pathogenesis in captive elk under controlled conditions. Inoculum consisting of macerated lesion tissue and mixed cultures of Treponema spp. and other anaerobic bacteria derived from TAHD lesions was applied onto abraded interdigital skin on the hind feet of five treatment elk. Inoculated feet were wrapped to expedite lesion development. Over the 7 week study period, all inoculated feet (10/10) developed interdigital erosions consistent with mild to moderate TAHD lesions observed in free-ranging elk. Lesions were observed on the majority of inoculated feet (9/10) after 28 days, coinciding with concurrent 16S rRNA gene amplicon sequencing detection of three putative pathogens of TAHD: Treponema, Fusobacterium, and Mycoplasma. In contrast, mock-inoculated control elk feet did not exhibit pathological or microbiological changes indicative of TAHD. This experimental infection model provides a valuable platform to investigate the complex interactions between the host, pathogens, and environmental factors that influence TAHD susceptibility, lesion progression, and disease transmission.IMPORTANCEOur study details a new approach for consistent and rapid induction of treponeme-associated hoof disease (TAHD) lesions in captive elk. TAHD is an emerging polybacterial disease of conservation concern that causes chronic lameness and debilitation in free-ranging elk across the northwestern USA. We rapidly and reliably reproduced TAHD lesions following challenge with inoculum consisting of macerated lesion tissue and mixed cultures of Treponema spp. and other anaerobic bacteria. This experimental infection model provides a valuable platform for investigation of the complex interactions between the host, pathogens, and environmental factors influencing TAHD susceptibility, lesion progression, and disease transmission in elk.