Environmental transmission of Treponeme-associated hoof disease in captive elk

Objectives

Treponeme-associated hoof disease (TAHD) is an emerging disease identified in free-ranging elk (Cervus elaphus) in the northwestern U.S. Although Treponema spp. are associated with lesions, the definitive etiology has not been determined and transmission has not been confirmed. Our objective was to determine whether TAHD was transmissible to healthy captive elk through soil contaminated with hooves from affected elk.

Materials and methods

Six captive elk were housed in individual concrete-lined stalls at a research facility at Washington State University (WSU), Pullman, with oversight and approval from the WSU Institutional Animal Care and Use Committee. Between October 2020 and March 2021, four treatment elk were exposed to an inoculum prepared with hoof homogenate from TAHD positive elk and mixed with soil. An aliquot of the inoculum was applied to an abraded interdigital space (IDS) and held in place temporarily with a light foot wrap. Additionally, inoculum was mixed with pen soil. Two control elk were challenged identically except with inoculum prepared using TAHD-negative hooves. Over the study period, eight challenges were conducted at 2- to 4-week intervals. Daily lameness scoring was conducted and marked lameness was mitigated with an oral non-steroidal anti-inflammatory drug. At each challenge, hooves were examined for the development of gross lesions, and IDS scrapings were collected for 16S amplicon sequencing of DNA. IDS biopsies were collected at the end of the experiment for histologic examination and 16S amplicon sequencing of DNA. [...]