Ovine and caprine brucellosis, caused by Brucella melitensis , is one of the world’s most widespread zoonoses and is a major cause of economic losses in domestic ruminant production. In Italy, the disease remains endemic in several southern provinces, despite an ongoing brucellosis eradication programme. In this study, we used whole-genome sequencing to detail the genetic diversity of circulating strains, and to examine the origins of the predominant sub-lineages of B. melitensis in Italy. We reconstructed a global phylogeny of B. melitensis , strengthened by 339 new whole-genome sequences, from Italian isolates collected from 2011 to 2018 as part of a national livestock surveillance programme. All Italian strains belonged to the West Mediterranean lineage, which further divided into two major clades that diverged roughly between the 5th and 7th centuries. We observed that Sicily serves as a brucellosis burden hotspot, giving rise to several distinct sub-lineages. More than 20 putative outbreak clusters of ovine and caprine brucellosis were identified, several of which persisted over the 8 year survey period despite an aggressive brucellosis eradication campaign. While the outbreaks in Central and Northern Italy were generally associated with introductions of single clones of B. melitensis and their subsequent dissemination within neighbouring territories, we observed weak geographical segregation of genotypes in the southern regions. Biovar determination, recommended in routine analysis of all Brucella strains by the World Organisation for Animal Health (OIE), could not discriminate among the four main global clades. This demonstrates a need for updating the guidelines used for monitoring B. melitensis transmission and spread, both at the national and international level, and to include whole-genome-based typing as the principal method for identification and tracing of brucellosis outbreaks.

中文翻译：

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意大利布鲁氏菌西地中海谱系的进化历史和现状分布

由羊布鲁氏菌引起的绵羊和山羊布鲁氏菌病是世界上分布最广的人畜共患病之一，是国内反刍动物生产经济损失的主要原因。在意大利，尽管正在进行布鲁氏菌病根除计划，但该病在南部几个省份仍然流行。在这项研究中，我们使用全基因组测序来详细说明循环菌株的遗传多样性，并检查意大利B. melitensis主要亚系的起源。我们重建了B. melitensis的全球系统发育 ，通过 339 个新的全基因组序列得到加强，这些序列来自 2011 年至 2018 年收集的意大利分离株，作为国家牲畜监测计划的一部分。所有意大利品系都属于西地中海血统，在 5 世纪和 7 世纪之间进一步分为两个主要分支。我们观察到西西里岛是布鲁氏菌病负担热点，产生了几个不同的亚谱系。确定了 20 多个假定的绵羊和山羊布鲁氏菌病爆发群，尽管开展了积极的布鲁氏菌病根除运动，但在 8 年的调查期间，其中一些仍持续存在。虽然意大利中部和北部的暴发通常与引入羊双歧杆菌单株有关 以及它们随后在邻近地区的传播，我们观察到南部地区基因型的地理隔离很弱。世界动物卫生组织 (OIE)在对所有布鲁氏菌菌株进行常规分析时推荐的 Biovar 测定不能区分四个主要的全球进化枝。这表明需要在国家和国际层面更新用于监测B. melitensis传播和传播的指南，并将基于全基因组的分型作为识别和追踪布鲁氏菌病暴发的主要方法。