Epidemiology and Diversity of Echinococcus spp. in the Republic of Sakha, Russia

棘球蚴病是一种世界性的人畜共患病，被世界卫生组织列为最重要的“被忽视的疾病”之一。病原体棘球绦虫属的物种和基因型，对动物和人类的传染性和致病性有很大的不同。对于两种最重要的人类致病菌，E. multilocularis和E. canadensis，遗传多样性的地理中心似乎在俄罗斯的亚洲部分。这一假设是基于小样本量的个体研究，其中显示了E. multilocularis分布于该地区及其邻近的蒙古，表明E.多室的。这同样适用于E。canadensis，其中三个世界上已知的基因型发生在萨哈共和国的家养和野生动物。俄罗斯关于包虫病的知识主要基于较早的研究，这些研究通常不会在国际期刊上发表。然而，已知泡状和囊状棘球蚴病在动物和人类中广泛且频繁，但关于各自病原体的信息很少。本项目首次系统研究了我国棘球蚴病的流行状况。应在萨哈共和国进行，将收集相关样本量的分离株并进行分子分析。E.应在萨哈北方和南部的不同生态区采集多室蜱样本，以分析宿主物种和生境中基因型的分布，并得出传播周期的结论。最重要的宿主是北极狐（在北方）、赤狐（在南方）和狼（在整个地区）作为最终宿主，以及各种啮齿动物作为中间宿主。大肠对于加拿大驯鹿，将采用类似的抽样模式，检验两个不同生命周期的假设：北部为家养循环（家养狗-驯鹿），南部为森林传播（狼-鹿物种）。线粒体和选定的核基因的序列分析将允许在地理上或生态上不同的寄生虫种群之间进行单倍型模式的比较。此外，还将研究种内变异性，并与其他地区进行比较，以收集有关寄生虫地理来源的信息。部分核基因组的调查将提供信息的频率之间的杂交事件同域基因型，从而有助于澄清棘球绦虫属的分类。此外，所获得的数据将有助于估计对人类的感染压力，因为两种棘球绦虫的不同基因型似乎在其感染性和致病性方面存在很大差异。

Echinococcosis is a worldwide zoonosis and considered by the WHO to be one of the most important “neglected diseases”. Species and genotypes of the causative agents, Echinococcus spp., differ greatly in infectivity and pathogenicity for animals and humans. For two of the most important human pathogenic species, E. multilocularis and E. canadensis, the geographical centre of genetic diversity seems to be in the Asian part of Russia. This hypothesis is based on individual studies with small sample sizes in which it was shown that several divergent genotypes of E. multilocularis occur in this area and neighbouring Mongolia, which indicates a geographic origin of E. multilocularis in this region. The same applies to E. canadensis, where three of the four worldwide known genotypes occur in domestic and wild animals in the Republic of Sakha. The knowledge about echinococcosis in Russia is mainly based on older studies, which are usually not published in international journals. However, it is known that both alveolar and cystic echinococcosis are widespread and frequent in animals and humans, but little information is available on the respective pathogens. In this project, the first systematic study on prevalence of Echinococcus spp. in the Republic of Sakha should be conducted, isolates in relevant sample sizes will be collected and molecularly analysed. E. multilocularis samples shall be collected in various ecological zones in northern and southern Sakha in order to analyse the distribution of genotypes among host species and habitats and to draw conclusions about transmission cycles. The most important hosts are arctic foxes (in the north), red foxes (in the south) and wolves (in the whole area) as final hosts, and various rodent species as intermediate hosts. For E. canadensis, a similar sampling pattern will be carried out, testing the hypothesis of two separate life cycles: a domestic cycle (domestic dog - reindeer) in the north, and sylvatic transmission (wolf - deer species) in the south. Sequence analyses of mitochondrial and selected nuclear genes will allow a comparison of haplotype patterns between geographically or ecologically distinct populations of parasites. In addition, intraspecific variability will be studied and compared with other regions in order to gather information on the geographical origin of the parasites. The investigation of parts of the nuclear genome will provide information on the frequency of hybridization events between sympatric genotypes and thus contribute to clarify the taxonomy of Echinococcus spp.. In addition, the data obtained will help to estimate the infection pressure on humans, since the different genotypes of both Echinococcus species seem to differ strongly in their infectivity and pathogenicity.