Schock A, Innes E A, Yamane I, Latham S M, Wastling J M
Moredun Research Institute, Pentland Science Park, Penicuik, Edinburgh, UK.
Parasitology. 2001 Jul;123(Pt 1):13-23. doi: 10.1017/s003118200100796x.
Neospora caninum is a protozoan parasite that causes bovine abortion. The epidemiology of N. caninum is poorly understood and little is known about the genetic diversity of the parasite, or whether individual isolates differ in virulence. Such diversity may, among other factors, underlie the range of pathologies seen in cattle. In this study we analysed biological and genetic variation in 6 isolates of N. caninum originating from canine and bovine hosts by measurement of growth rate in vitro, Western blotting and random amplification of polymorphic DNA (RAPD). This comparative analysis of intra-species diversity demonstrated that heterogeneity exists within the species. The relative growth rate in vitro, as assessed by 3[H]uracil uptake, showed significant variation between isolates. However, no significant differences were detected between the antigenic profiles of each isolate by Western blotting. RAPD-PCR was performed on DNA from the 6 Neospora isolates; 3 strains of Toxoplasma gondii, Sarcocystis sp. and Cryptosporidium parvum were also analysed. Twenty-six RAPD primers gave rise to 434 markers of which 222 were conserved between all the Neospora isolates and distinguished them from the other Apicomplexa. An additional 54 markers were unique for Neospora but were polymorphic within the species and able to differentiate between the individual isolates. The RAPD data were subjected to pair-wise similarity and cluster analysis and showed that the Neospora isolates clustered together as a group, with T. gondii as their nearest neighbour. N. caninum isolates showed no clustering with respect either to host or geographical origin. The genetic similarity between Neospora isolates from cattle and dogs suggests that these hosts may be epidemiologically related, although further analysis of bovine and canine field samples are required. The genetic and biological diversity observed in this study may have important implications for our understanding of the pathology and epidemiology of neosporosis.
犬新孢子虫是一种导致牛流产的原生动物寄生虫。人们对犬新孢子虫的流行病学了解甚少，对该寄生虫的遗传多样性，以及各个分离株在毒力上是否存在差异也知之甚少。除其他因素外，这种多样性可能是牛群中出现一系列病理状况的原因。在本研究中，我们通过体外生长速率测定、蛋白质免疫印迹法以及随机扩增多态性DNA（RAPD）分析了6株源自犬类和牛类宿主的犬新孢子虫的生物学和遗传变异。这种种内多样性的比较分析表明该物种内部存在异质性。通过[³H]尿嘧啶摄取评估的体外相对生长速率在各分离株之间显示出显著差异。然而，通过蛋白质免疫印迹法未检测到各分离株抗原谱之间存在显著差异。对6株犬新孢子虫的DNA进行了RAPD-PCR分析；还分析了3株刚地弓形虫、肉孢子虫属和微小隐孢子虫。26条RAPD引物产生了434个标记，其中222个在所有犬新孢子虫分离株之间保守，并将它们与其他顶复门原虫区分开来。另外54个标记是犬新孢子虫特有的，但在该物种内具有多态性，能够区分各个分离株。对RAPD数据进行了成对相似性和聚类分析，结果表明犬新孢子虫分离株聚为一组，刚地弓形虫是它们最近的亲缘种。犬新孢子虫分离株在宿主或地理来源方面均未显示出聚类现象。来自牛和犬的犬新孢子虫分离株之间的遗传相似性表明，尽管需要对牛和犬的野外样本进行进一步分析，但这些宿主在流行病学上可能相关。本研究中观察到的遗传和生物学多样性可能对我们理解新孢子虫病的病理学和流行病学具有重要意义。
