Woodruff D S, Merenlender A M, Upatham E S, Viyanant V
Am J Trop Med Hyg. 1987 Mar;36(2):345-54. doi: 10.4269/ajtmh.1987.36.345.
Electrophoretically-detected allozyme variation is described in strains of Schistosoma japonicum (4 Philippine strains), S. mekongi (Laos), and an undescribed anthropophilic S. japonicum-like schistosome from Peninsular Malaysia. Result, together with those reported previously for 8 other strains (S. japonicum, China, Formosa, Japan, Philippines; S. mekongi, 2 substrains; Malaysian schistosome, 2 strains) permit a composite genetic characterization of 15 strains of Asian schistosomes at 9-18 presumptive loci. The proportion of polymorphic loci (P) and the mean heterozygosity per locus (H) were zero in all strains. Although this was expected for strains that had been in laboratory culture for up to 50 years, we expected to detect variation in strains based on 10-50 recently field-collected infected snails. We expected S. japonicum to be as variable as S. mansoni (P = 0.13 (0-0.33), H = 0.04, 18 loci, 22 strains) as it is believed to reproduce sexually, has an evolutionary history of several million years, inhabits a wide geographic range, coevolved with a genetically variable intermediate snail host, and has a diversity of mammalian hosts. No differences were detected between the 5 S. japonicum strains from Leyte and Luzon (Philippines), between the 3 S. mekongi strains, or between the 3 Malaysian schistosome strains; these groups and the remaining S. japonicum strains representing Mindoro (Philippines), China, Formosa, and Japan each have distinctive multilocus electromorphic patterns. Nei's genetic distances (D) were calculated to estimate interstrain and interspecific divergence. Interstrain genetic distances in S. japonicum averaged greater than 0.3; much higher than those reported previously for S. mansoni (D = 0.06, D(max) = 0.24). S. japonicum (Mindoro) was moderately differentiated from the Leyte-Luzon strains (D = 0.29, 12 loci). Estimates of the S. japonicum China-Philippine distance (D greater than 0.4, 11 loci) are high for conspecific populations and further studies of the still poorly characterized Chinese parasite may reveal that these are, in fact, separate species. S. japonicum is shown to be only distantly related to S. mekongi and the Malaysian schistosome (D greater than 1); the latter is closely related to, but genetically quite distinct from, S. mekongi (D = 0.61 +/- 0.275, 11 loci) and warrants recognition as a new species. The medical significance of the isogenic nature of the Asian schistosome strains and their evolutionary divergence are discussed.
本文描述了日本血吸虫（4个菲律宾株系）、湄公血吸虫（老挝）以及来自马来西亚半岛一种未描述的嗜人似日本血吸虫的电泳检测同工酶变异情况。研究结果与之前报道的其他8个株系（日本血吸虫，中国、台湾、日本、菲律宾株系；湄公血吸虫，2个亚株系；马来西亚血吸虫，2个株系）的数据相结合，使得我们能够在9 - 18个假定基因座上对15个亚洲血吸虫株系进行综合遗传特征分析。所有株系的多态性基因座比例（P）和每个基因座的平均杂合度（H）均为零。虽然对于在实验室培养长达50年的株系来说这是预期的结果，但我们期望能在基于10 - 50只近期野外采集的感染性钉螺的株系中检测到变异。我们预计日本血吸虫的变异性与曼氏血吸虫相当（P = 0.13（0 - 0.33），H = 0.04，18个基因座，22个株系），因为据信它进行有性繁殖，有几百万年的进化历史，分布在广泛的地理范围内，与基因可变的中间钉螺宿主共同进化，并且有多种哺乳动物宿主。未检测到来自莱特岛和吕宋岛（菲律宾）的5个日本血吸虫株系之间、3个湄公血吸虫株系之间或3个马来西亚血吸虫株系之间存在差异；这些组以及代表棉兰老岛（菲律宾）、中国、台湾和日本的其余日本血吸虫株系各自具有独特的多位点电形态模式。计算了内氏遗传距离（D）以估计株系间和种间差异。日本血吸虫株系间的遗传距离平均大于0.3；远高于之前报道的曼氏血吸虫的遗传距离（D = 0.06，D(max) = 0.24）。棉兰老岛的日本血吸虫与莱特岛 - 吕宋岛株系有适度分化（D = 0.29，12个基因座）。对于同种群体而言，中国 - 菲律宾日本血吸虫的距离估计值（D大于0.4，11个基因座）较高，对特征仍不清楚的中国血吸虫进行进一步研究可能会发现它们实际上是不同的物种。研究表明日本血吸虫与湄公血吸虫和马来西亚血吸虫的关系较远（D大于1）；后者与湄公血吸虫密切相关，但在遗传上有明显差异（D = 0.61±0.275，11个基因座），值得被认定为一个新物种。文中还讨论了亚洲血吸虫株系的同基因性质及其进化差异的医学意义。
