Dazo B C, Hairston N G, Dawood I K
Bull World Health Organ. 1966;35(3):339-56.
The respective vectors of the two forms of bilharziasis in Egypt do not have the same ecological distribution. Bulinus truncatus is most abundant in large canals, and decreases in density as the water approaches and flows into drains. Biomphalaria alexandrina is most abundant in drains, and decreases in density upstream from these habitats. Both species are most abundant in the presence of aquatic vegetation, but they differ in their respective associations with the water hyacinth, Eichhornia crassipes. Biomph. alexandrina reaches maximum abundance in the presence of this plant, but Bul. truncatus is as uncommon in the absence of plants as in the presence of E. crassipes.Calculation of life-table parameters from field data shows that, under optimum field conditions, both species can double their populations in 14-16 days. The reproductive rates of both species are greatest in March and the death rates in midsummer. The observed peak densities in May and June give a false impression of optima because of undercollection of young snails, which are most abundant in March and April.Control operations should take advantage of the findings on population parameters. A single area-wide treatment with molluscicide in April is recommended. During the remainder of the year, search for isolated foci of snail breeding and individual treatment of these will effect large savings of chemical and will be effective in controlling the transmission of the parasites.
埃及两种血吸虫病的各自病媒没有相同的生态分布。截形小泡螺在大型运河中最为常见，随着水流接近并流入排水渠，其密度会降低。亚历山大双脐螺在排水渠中最为常见，在这些栖息地的上游密度会降低。这两个物种在有水生植物的情况下最为常见，但它们与凤眼莲（Eichhornia crassipes）的各自关联有所不同。亚历山大双脐螺在有这种植物的情况下数量最多，但截形小泡螺在没有植物的情况下与有凤眼莲时一样不常见。根据实地数据计算生命表参数表明，在最佳实地条件下，这两个物种的种群数量都能在14 - 16天内翻倍。这两个物种的繁殖率在3月最高，死亡率在仲夏最高。5月和6月观察到的峰值密度给人一种最佳状态的错误印象，因为幼螺收集不足，幼螺在3月和4月最为常见。防治行动应利用关于种群参数的研究结果。建议在4月进行一次全区域的杀螺剂处理。在一年的剩余时间里，寻找蜗牛繁殖的孤立疫点并对其进行单独处理，将大幅节省化学药剂，并有效控制寄生虫的传播。
