Department of Medical Sciences, University of Wisconsin, School of Veterinary Medicine, 2015 Linden Dr., Madison, WI 53706, USA.
Vet J. 2012 Sep;193(3):685-93. doi: 10.1016/j.tvjl.2012.06.054. Epub 2012 Aug 15.
Digital dermatitis (DD) is an infectious claw disease of cattle that causes painful lesions, principally along the coronary band of the claws. In the US alone, the estimated economic impact of DD is estimated to be $190 million. The etiology of DD remains unclear and there is no reliable laboratory test, so DD is most often diagnosed clinically. Spirochetal bacteria of the genera Treponema have been implicated in DD infections following their isolation using culture techniques, serological detection of bovine antibodies against treponemes, and amplification of treponemal 16s DNA sequences by PCR. During in vitro growth of spirochetes and treponemes isolated from DD, morphological changes have been observed indicating the presence of a spiral form and an encysted form. It is not known why encysted forms appear or what role they have in the progression of DD. The current study established growth curves for three subtypes of treponemes, Treponema denticola-like, Treponema phagedenis-like, and Treponema medium-like, while photographically monitoring changes in morphology. In addition to observing spiral and encysted forms, two intermediate forms were also observed. These appeared as either spiral forms with spherical bodies or as enveloped clusters of granules. The observation of encysted forms adds further support to the theory that treponemes causing recurrent infections deep in bovine skin have mechanisms to facilitate persistence and the chronic character of DD.
数字性皮炎（DD）是一种感染性牛蹄病，会导致疼痛性病变，主要沿蹄冠带发生。仅在美国，DD 的估计经济影响就达 1.9 亿美元。DD 的病因仍不清楚，也没有可靠的实验室检测方法，因此 DD 通常是临床诊断。在使用培养技术、针对螺旋体的牛抗体的血清学检测以及通过 PCR 扩增螺旋体 16s DNA 序列分离出螺旋体属和密螺旋体属的螺旋体细菌后，它们与 DD 感染有关。在从 DD 中分离出的螺旋体和密螺旋体的体外生长过程中，观察到形态变化，表明存在螺旋形式和囊包形式。目前尚不清楚囊包形式为何出现，以及它们在 DD 进展中起什么作用。本研究建立了三种密螺旋体亚型（类似于齿密螺旋体、类似于吞噬密螺旋体和类似于中型密螺旋体）的生长曲线，同时通过摄影监测形态变化。除了观察螺旋和囊包形式外，还观察到两种中间形式。这些形式要么是带有球体的螺旋体，要么是包膜状的颗粒簇。囊包形式的观察进一步支持了这样一种理论，即导致牛深层皮肤反复感染的密螺旋体具有促进持久性和 DD 慢性特征的机制。
