Mitchell Rebecca M, Beaver Annabelle, Knupfer Elena, Pradhan Abani K, Fyock Terry, Whitlock Robert H, Schukken Ynte H
Emory University Department of Mathematics and Computer Science, 400 Dowman Drive, Atlanta, GA 30322, USA.
Department of Population Medicine and Diagnostic Sciences, Cornell University, 618 Tower Road, Ithaca, NY 14853, USA.
Vet Sci. 2019 Mar 20;6(1):32. doi: 10.3390/vetsci6010032.
Mycobacterial diseases are persistent and characterized by lengthy latent periods. Thus, epidemiological models require careful delineation of transmission routes. Understanding transmission routes will improve the quality and success of control programs. We aimed to study the infection dynamics of subsp. (MAP), the causal agent of ruminant Johne's disease, and to distinguish within-host mutation from individual transmission events in a longitudinally MAP-defined dairy herd in upstate New York. To this end, semi-annual fecal samples were obtained from a single dairy herd over the course of seven years, in addition to tissue samples from a selection of culled animals. All samples were cultured for MAP, and multi-locus short-sequence repeat (MLSSR) typing was used to determine MAP SSR types. We concluded from these precise MAP infection data that, when the tissue burden remains low, the majority of MAP infections are not detectable by routine fecal culture but will be identified when tissue culture is performed after slaughter. Additionally, we determined that in this herd vertical infection played only a minor role in MAP transmission. By means of extensive and precise longitudinal data from a single dairy herd, we have come to new insights regarding MAP co-infections and within-host evolution.
分枝杆菌病具有持续性，且潜伏期较长。因此，流行病学模型需要仔细界定传播途径。了解传播途径将提高防控计划的质量和成功率。我们旨在研究副结核分枝杆菌亚种（MAP）——反刍动物约翰氏病的病原体——的感染动态，并在纽约州北部一个纵向界定的MAP奶牛群中区分宿主内突变与个体传播事件。为此，在七年时间里，我们从一个奶牛群中每半年采集一次粪便样本，此外还从一些被扑杀动物身上采集了组织样本。所有样本都进行了MAP培养，并使用多位点短序列重复（MLSSR）分型来确定MAP的SSR类型。从这些精确的MAP感染数据中我们得出结论，当组织负荷较低时，大多数MAP感染通过常规粪便培养无法检测到，但在屠宰后进行组织培养时会被识别出来。此外，我们确定在这个牛群中，垂直感染在MAP传播中只起了很小的作用。通过来自单个奶牛群的广泛而精确的纵向数据，我们对MAP合并感染和宿主内进化有了新的认识。
