Karunaweera Nadira D, Ferreira Marcelo U, Munasinghe Anusha, Barnwell John W, Collins William E, King Christopher L, Kawamoto Fumihiko, Hartl Daniel L, Wirth Dyann F
Department of Immunology and Infectious Diseases, Harvard School of Public Health, Boston, MA 02115, USA.
Gene. 2008 Feb 29;410(1):105-12. doi: 10.1016/j.gene.2007.11.022. Epub 2008 Jan 15.
The population structure of Plasmodium vivax remains elusive. The markers of choice for large-scale population genetic studies of eukaryotes, short tandem repeats known as microsatellites, have been recently reported to be less polymorphic in P. vivax. Here we investigate the microsatellite diversity and geographic structure in P. vivax, at both local and global levels, using 14 new markers consisting of tri- or tetranucleotide repeats. The local-level analysis, which involved 50 field isolates from Sri Lanka, revealed unexpectedly high diversity (average virtual heterozygosity [H(E)], 0.807) and significant multilocus linkage disequilibrium in this region of low malaria endemicity. Multiple-clone infections occurred in 60% of isolates sampled in 2005. The global-level analysis of field isolates or monkey-adapted strains identified 150 unique haplotypes among 164 parasites from four continents. Individual P. vivax isolates could not be unambiguously assigned to geographic populations. For example, we found relatively low divergence among parasites from Central America, Africa, Southeast Asia and Oceania, but substantial differentiation between parasites from the same continent (South Asia and Southeast Asia) or even from the same country (Brazil). Parasite relapses, which may extend the duration of P. vivax carriage in humans, are suggested to facilitate the spread of strains across continents, breaking down any pre-existing geographic structure.
间日疟原虫的种群结构仍然难以捉摸。真核生物大规模种群遗传学研究的首选标记，即短串联重复序列（又称微卫星），最近据报道在间日疟原虫中多态性较低。在此，我们使用由三核苷酸或四核苷酸重复序列组成的14个新标记，在本地和全球层面研究间日疟原虫的微卫星多样性和地理结构。本地层面的分析涉及来自斯里兰卡的50个野外分离株，结果显示在这个疟疾低流行地区意外地具有高多样性（平均虚拟杂合度[H(E)]，0.807）和显著的多位点连锁不平衡。2005年采集的分离株中有60%发生了多克隆感染。对野外分离株或猴适应株的全球层面分析在来自四大洲的164个寄生虫中鉴定出150个独特单倍型。无法明确地将单个间日疟原虫分离株归属于地理种群。例如，我们发现中美洲、非洲、东南亚和大洋洲的寄生虫之间差异相对较小，但来自同一大陆（南亚和东南亚）甚至同一国家（巴西）的寄生虫之间存在显著分化。寄生虫复发可能会延长间日疟原虫在人体内的携带时间，这被认为有助于菌株在各大洲传播，打破任何预先存在的地理结构。
