Table 1.
Locomotion scores.
Table 2.
Inoculum quality.
Fig 1.
Wraps were applied to the feet of captive study elk at 6/8 experimental challenges to extend contact duration of inoculum with the skin of the interdigital space.
Table 3.
Progression of lesions in treatment elk.
Table 4.
Behavior change in study elk.
Table 5.
Mineral levels in study elk.
Fig 2.
Free-ranging vs. study elk TAHD lesions.
Hoof lesions indistinguishable from those in free-ranging elk with treponeme-associated hoof disease (TAHD) developed in study elk following experimental challenge with inoculum prepared from TAHD-affected hoof material mixed with soil. (A) Characteristic TAHD lesions from free-ranging elk graded as I to IV based on a previously described grading system [3] provide a reference for comparison to lesions observed in (B) representative lesions on experimentally infected elk. Lesions progressed through the study period from grade 0 to III.
Fig 3.
Proportion of treponemes in bacterial composition of foot samples through study period.
Mean proportion of Treponema species and family Spirochaetaceae in the bacterial composition was determined from 16S rRNA gene amplicon sequencing of samples from treatment group elk following experimental challenge with inoculum prepared from TAHD-affected hoof material mixed with soil. Treponemes detected at some point during the study period from every treatment elk are shown. Samples (skin scraping or biopsy) were collected from the interdigital space, and lesion if present, from the foot with the most severe lesion of each elk. Scrapings were collected on sampling days through day post-initial inoculation (dpi) 133, while biopsies were collected on dpi 138 and at individual elk’s endpoints. a Identified by NCBI BLAST as T. medium. b Identified by NCBI BLAST as T. lecithinolyticum.
Fig 4.
Locomotion score vs. lesion grade.
Lameness in treatment elk was correlated with hoof lesion grade (R = 0.702, p≤0.001) following experimental challenge with inoculum prepared from TAHD-affected hoof material mixed with soil. Locomotion scores represent increasing lameness from 0 to 3 with 0 being “sound” locomotion and 3 being severely lame (adapted from [15]). Hoof lesion grades were based on a previously reported grading system [3].
Fig 5.
Body condition of control (blue) and treatment (yellow) groups of elk experimentally exposed to treponeme-associated hoof disease. Body condition of study elk was evaluated on a qualitative scale of 1–5, where 1 represents emaciation and 5 is obese [17]. Experimental groups differed (shown by *) on days post-initial inoculation (dpi) 168, the last timepoint when all study elk were present, and at individual elk’s endpoints.