Veterinary Sciences Division, Agri-food and Biosciences Institute (AFBI), Stoney Road, Stormont, Belfast BT4 3SD, UK; School of Biological Sciences, Queen's University Belfast, Belfast BT7 1NN, UK.
Veterinary Sciences Division, Agri-food and Biosciences Institute (AFBI), Stoney Road, Stormont, Belfast BT4 3SD, UK.
Infect Genet Evol. 2020 Apr;79:104131. doi: 10.1016/j.meegid.2019.104131. Epub 2019 Nov 29.
Investigating genetically-structured diversity in pathogen populations over time is important to better understand disease maintenance and spread. Herd-level surveillance of Mycobacterium bovis genotypes (multi-locus VNTR analysis types, MLVA types) from all culture-confirmed bovine tuberculosis (TB) herd cases was undertaken in Northern Ireland (NI), generating an unparalleled, longitudinal, population-level 14-year survey for this pathogen. Across this population, 295 genetically-distinct M. bovis MLVA types were identified in the 19,717 M. bovis isolates surveyed. Of these, the most frequent was MLVA type 002 (23.0%); 151 MLVA types were represented more than once, in groups ranging from 2 to 4438 isolates. Only 23 MLVA types were isolated in all 14 years. Investigating inter-annual frequency of M. bovis MLVA types, examples of statistically-significant expansions (MLVA types 002, 004, 006, 009 and 027), contractions (MLVA types 001, 007 and 011) and maintenance (MLVA types 003 and 005) were disclosed, during a period of fluctuating bovine TB herd-level incidence at the NI scale. The fixed period frequency distribution of MLVA types remained highly right-skewed. Novel VNTR copy number variant MLVA types (N = 242; an average of 17 per annum) were identified throughout the survey. The MLVA type distribution in the landscape was not random; MLVA types showed statistically-significant geographical localization and strong spatial associations with Divisional Veterinary Office (DVO) regions. There was also evidence of differential risk of particular MLVA types across breeds (Holstein/Friesian vs. other), age-class, and sex and some evidence of an association between the number of animals testing positive for bovine TB during the disclosing test and particular MLVA types, although there was substantial variation.
研究病原体种群随时间变化的遗传结构多样性对于更好地了解疾病的维持和传播非常重要。在北爱尔兰（NI）对所有经培养确认的牛结核病（TB）牛群病例的分枝杆菌基因型（多位点 VNTR 分析类型，MLVA 类型）进行了畜群水平监测，为该病原体提供了前所未有的、纵向的、人群水平的 14 年调查。在该人群中，在所调查的 19717 株牛分枝杆菌分离株中发现了 295 种具有遗传差异的牛分枝杆菌 MLVA 类型。其中，最常见的是 MLVA 类型 002（23.0%）；151 种 MLVA 类型不止一次出现，范围从 2 到 4438 株不等。只有 23 种 MLVA 类型在所有 14 年中都被分离出来。通过调查牛分枝杆菌 MLVA 类型的年度频率，发现了一些具有统计学意义的扩张（MLVA 类型 002、004、006、009 和 027）、收缩（MLVA 类型 001、007 和 011）和维持（MLVA 类型 003 和 005）的例子，这是在 NI 规模上牛结核病畜群发病率波动期间发生的。MLVA 类型的固定周期频率分布仍然高度右偏。在整个调查过程中发现了 242 种新的 VNTR 拷贝数变异 MLVA 类型（平均每年 17 种）。景观中的 MLVA 类型分布并非随机；MLVA 类型在地理上具有统计学意义的本地化和与分区兽医办公室（DVO）区域的强烈空间关联。还存在特定 MLVA 类型在不同品种（荷斯坦/弗里生牛与其他品种）、年龄组和性别之间的风险差异的证据，以及在披露测试期间检测出的牛结核病阳性动物数量与特定 MLVA 类型之间存在关联的一些证据，尽管存在很大的差异。
