Department of Veterinary Microbiology and Pathology, College of Veterinary Medicine, Washington State University, Pullman, Washington, United States of America.
School of Veterinary Medicine, Texas Tech University, Amarillo, Texas, United States of America.
PLoS One. 2023 Aug 10;18(8):e0289764. doi: 10.1371/journal.pone.0289764. eCollection 2023.
Treponeme-associated hoof disease (TAHD) is a debilitating disease of free-ranging elk (Cervus canadensis) in the northwestern U.S. While treponemes are associated with lesions, the etiology and transmissibility between elk are unknown. Our objective was to determine whether the disease can be environmentally transmitted to captive elk. Four individually housed treatment elk and 2 control elk were challenged with soil mixed with inoculum prepared from free-ranging elk hooves from TAHD-positive elk or autoclaved hooves from normal elk, respectively. The inoculum for each group was applied to the interdigital space and added to pre-existing soil in each pen. Eight challenges were conducted at 1-4-week intervals and lesion development was assessed during a 138-day challenge period that was followed by a 170-day monitoring period to document lesion progression. All treatment elk, but no control elk, developed gross and histologic lesions consistent with TAHD. Treponema phylotypes similar to those in bovine digital dermatitis in cattle were detected using 16S rRNA gene amplicon sequencing from lesions in all treatment elk, but no control elk, during the challenge period. Lesions progressed from ulcerations in the interdigital space to extensive ulceration and underrunning of the hoof capsule by 35 and 173 days following the initial inoculation, respectively. Lameness in treatment elk was correlated with lesion development (R = 0.702, p≤0.001), and activity of infected elk was reduced during the challenge (p≤0.001) and monitoring periods (p = 0.004). Body condition was significantly lower in treatment than control elk 168 days following the initial inoculation (p = 0.05) and at each individual elk's study endpoint (p = 0.006). Three of 4 treatment elk were euthanized when they reached humane endpoints, and one elk recovered. These results provide direct evidence that TAHD is a transmissible infectious disease in elk. As such, actions that reduce transmission risk can support disease management and prevention.
螺旋体相关蹄病（TAHD）是美国西北部自由放养麋鹿（Cervus canadensis）的一种衰弱性疾病。虽然螺旋体与病变有关，但病因和麋鹿之间的传染性尚不清楚。我们的目的是确定该疾病是否可以通过环境传播给圈养麋鹿。4 只单独饲养的治疗麋鹿和 2 只对照麋鹿分别用来自 TAHD 阳性麋鹿的蹄部混合接种物或来自正常麋鹿的高压灭菌蹄部制备的土壤接种物进行了挑战。每个组的接种物都应用于趾间空间，并添加到每个围栏中预先存在的土壤中。在 1-4 周的间隔内进行了 8 次挑战，并在 138 天的挑战期内评估了病变发展情况，随后进行了 170 天的监测期以记录病变进展。所有治疗麋鹿均出现了与 TAHD 一致的肉眼和组织学病变，但对照麋鹿没有。在挑战期间，所有治疗麋鹿的病变中均使用 16S rRNA 基因扩增子测序检测到与牛的牛数字皮炎中相似的螺旋体基因型，但对照麋鹿中没有。病变从趾间空间的溃疡发展为广泛的溃疡和蹄壳下的侵蚀，分别在初次接种后的 35 天和 173 天。治疗麋鹿的跛行与病变发展相关（R = 0.702，p≤0.001），并且感染麋鹿的活动在挑战（p≤0.001）和监测（p = 0.004）期间减少。初次接种后 168 天，治疗麋鹿的体况明显低于对照麋鹿（p = 0.05），并且在每个个体麋鹿的研究终点（p = 0.006）。当 3 只治疗麋鹿达到人道终点时被安乐死，1 只麋鹿康复。这些结果提供了 TAHD 是麋鹿中可传播传染病的直接证据。因此，减少传播风险的措施可以支持疾病管理和预防。
