Olaogun O M, Kanci A, Barber S R, Tivendale K A, Markham P F, Marenda M S, Browning G F
Asia-Pacific Centre for Animal Health, Faculty of Veterinary and Agricultural Sciences, The University of Melbourne, Parkville, Victoria 3010, Australia.
Aust Vet J. 2017 Oct;95(10):392-400. doi: 10.1111/avj.12634.
Regarded as one of the most expensive production diseases of dairy sheep and goats, contagious agalactia (CA) is caused by any of four agents: Mycoplasma agalactiae, M. mycoides subspecies capri (Mmc), M. capricolum subspecies capricolum (Mcc) and M. putrefaciens. Although CA is worldwide in distribution, it has not been reported in Australia, even though studies between the 1950s and 1980s isolated each agent from sheep or goats without any clinical signs associated with it. The aim of this study was to examine sheep and goats in Victoria, Australia, for the presence of CA-associated mycoplasmas and to investigate the evolutionary relationships of these isolates by comparing their genetic differences with their counterparts from other parts of the world.
A 3-year epidemiological survey of small ruminant populations in Victoria, Australia, was conducted for the presence of CA-associated mycoplasmas and the isolates obtained were genotyped by multilocus sequence typing (MLST).
Mmc was the only CA-associated agent isolated from the 1358 samples analysed in the study, but was not associated with CA on the property where it was found. MLST analyses of Mmc strains revealed a distinct clustering of Australian isolates into a novel clade, with the closest relatives being strains from Europe. The distinct clustering is consistent with the absence of clinical disease in Australia.
The isolation of Mmc indicates that this subspecies persists in Australian small ruminant populations. However, full genome sequencing and in vitro animal experimentation are needed to unequivocally demonstrate the avirulence of Australian strains.
传染性无乳症（CA）被认为是奶山羊最昂贵的生产性疾病之一，由四种病原体中的任何一种引起：无乳支原体、山羊支原体山羊亚种（Mmc）、山羊支原体山羊变种（Mcc）和腐败支原体。尽管CA在全球范围内都有分布，但在澳大利亚尚未有报道，尽管在20世纪50年代至80年代的研究中，从绵羊或山羊中分离出了每种病原体，且没有任何与之相关的临床症状。本研究的目的是检测澳大利亚维多利亚州的绵羊和山羊是否存在与CA相关的支原体，并通过比较其与世界其他地区对应菌株的基因差异，研究这些分离株的进化关系。
对澳大利亚维多利亚州的小反刍动物群体进行了为期3年的流行病学调查，以检测是否存在与CA相关的支原体，并对获得的分离株进行多位点序列分型（MLST）基因分型。
Mmc是本研究分析的1358个样本中唯一分离出的与CA相关的病原体，但在所发现的养殖场中并未与CA相关联。对Mmc菌株的MLST分析显示，澳大利亚分离株明显聚类成一个新的进化枝，其亲缘关系最近的是来自欧洲的菌株。这种明显的聚类与澳大利亚没有临床疾病的情况一致。
Mmc的分离表明该亚种在澳大利亚小反刍动物群体中持续存在。然而，需要进行全基因组测序和体外动物实验，以明确证明澳大利亚菌株的无毒力。
