Michelson E H, DuBois L
Am J Trop Med Hyg. 1978 Jul;27(4):782-6. doi: 10.4269/ajtmh.1978.27.782.
Seventeen populations of snails (Biomphalaria glabrata) from the state of Bahia, Brazil were studied with respect to their susceptibility to infection with an allopatric strain of Schistosoma mansoni. Two of the populations were from the city of Salvador, 3 from other sites in Bahia, and 12 from habitats in the municipio Castro Alves. Our data show that the Bahian snail populations are extremely variable in their susceptibility to an allopatric strain of S. mansoni and that the phenomenon is not associated solely with distantly separated strains, but is present, as well, in adjacent populations situated in a restricted geographic region. Of the 6 populations found to be completely refractory to infection when exposed at a size of 5--7 mm, only 2 were refractory when exposed at 5--12 days of age. It is suggested that the variability to infection displayed by populations in a restricted geographic area may be explained by assuming that the Founder Principle was operative.
对来自巴西巴伊亚州的17个蜗牛种群（光滑双脐螺）进行了研究，以了解它们对曼氏血吸虫异地菌株感染的易感性。其中两个种群来自萨尔瓦多市，3个来自巴伊亚州的其他地点，12个来自卡斯特罗·阿尔维斯市的栖息地。我们的数据表明，巴伊亚州的蜗牛种群对曼氏血吸虫异地菌株的易感性差异极大，而且这种现象并非仅与远距离分离的菌株有关，在地理区域有限的相邻种群中也存在。在6个被发现当大小为5 - 7毫米时完全抵抗感染的种群中，只有2个在5 - 12日龄时暴露时具有抗性。有人提出，在有限地理区域内种群表现出的感染易感性差异可以通过假设奠基者效应起作用来解释。
