Rollinson D, Stothard J R, Southgate V R
Department of Zoology, The Natural History Museum, London.
Parasitology. 2001;123 Suppl:S245-60. doi: 10.1017/s0031182001008046.
Within each of the four species groups of Bulinus there are species that act as intermediate hosts for one or more of the seven species of schistosomes in the Schistosoma haematobium group, which includes the important human pathogens S. haematobium and S. intercalatum. Bulinus species have an extensive distribution throughout much of Africa and some surrounding islands including Madagascar, parts of the Middle East and the Mediterranean region. Considerable variation in intermediate host specificity can be found and differences in compatibility between snail and parasite can be observed over small geographical areas. Molecular studies for detection of genetic variation and the discrimination of Bulinus species are reviewed and two novel assays, allele-specific amplification (ASA) and SNaPshot, are introduced and shown to be of value for detecting nucleotide changes in characterized genes such as cytochrome oxidase 1. The value and complexity of compatibility studies is illustrated by case studies of S. haematobium transmission. In Senegal, where B. globosus, B. umbilicatus, B. truncatus and B. senegalensis may act as intermediate hosts, distinct differences have been observed in the infectivity of different isolates of S. haematobium. In Zanzibar, molecular characterization studies to discriminate between B. globosus and B. nasutus have been essential to elucidate the roles of snails in transmission. B. globosus is an intermediate host on Unguja and Pemba. Further studies are required to establish the intermediate hosts in the coastal areas of East Africa. Biological factors central to the transmission of schistosomes, including cercarial emergence rhythms and interactions with other parasites and abiotic factors including temperature, rainfall, water velocity, desiccation and salinity are shown to impact on the intermediate host-parasite relationship.
在小泡螺属的四个物种组中，每个物种组内都有一些物种可作为埃及血吸虫组中七种血吸虫中的一种或多种的中间宿主，该组包括重要的人类病原体埃及血吸虫和间插血吸虫。小泡螺物种广泛分布于非洲大部分地区以及包括马达加斯加在内的一些周边岛屿、中东部分地区和地中海地区。可以发现中间宿主特异性存在相当大的差异，并且在小地理区域内可以观察到蜗牛与寄生虫之间的相容性差异。本文综述了用于检测遗传变异和鉴别小泡螺物种的分子研究，并介绍了两种新方法，即等位基因特异性扩增（ASA）和SNaPshot，结果表明它们对于检测细胞色素氧化酶1等特征基因中的核苷酸变化具有重要价值。通过埃及血吸虫传播的案例研究说明了相容性研究的价值和复杂性。在塞内加尔，球形小泡螺、脐形小泡螺、截形小泡螺和塞内加尔小泡螺都可能作为中间宿主，已观察到不同分离株的埃及血吸虫在感染性方面存在明显差异。在桑给巴尔，为区分球形小泡螺和鼻形小泡螺而进行的分子特征研究对于阐明蜗牛在传播中的作用至关重要。球形小泡螺是奔巴岛和温古贾岛的中间宿主。还需要进一步研究以确定东非沿海地区的中间宿主。事实表明，血吸虫传播的核心生物学因素，包括尾蚴逸出节律以及与其他寄生虫的相互作用，以及包括温度、降雨、水流速度、干燥和盐度在内的非生物因素，都会影响中间宿主与寄生虫的关系。
