Mubila L, Rollinson D
Department of Biological Sciences, University of Zambia, Lusaka.
Ann Trop Med Parasitol. 2002 Mar;96(2):165-73. doi: 10.1179/000349802125000592.
Reduced snail-parasite compatibility might be at least partially responsible for the decrease observed, over the last three decades, in the prevalence of urinary schistosomiasis on the shores of Lake Kariba, Zambia. To explore this possibility, the prevalences of urinary schistosomiasis in schoolchildren were investigated in three disparate areas of Zambia (Lake Kariba, Lake Bangweulu and Lusaka), and attempts were made to infect the snails that developed from the eggs of snails collected from each of these sites with Schistosoma haematobium from each of the sites. The prevalence of S. haematobium infection in schoolchildren ranged from 0% around Lake Bangweulu to 76% around Lake Kariba. The F1 progeny of Siavonga (Lake Kariba) snails showed good compatibility with the local parasite but were also susceptible to all of the geographical strains of S. haematobium tested. The interaction between the S. haematobium and S. mansoni found along the shores of Lake Kariba may favour S. mansoni, since prevalences of urinary schistosomiasis tend to be relatively high where S. mansoni is absent. Although Lake Bangweulu was confirmed to be an area of very low endemicity for urinary schistosomiasis, the snails bred from snails collected in this area were compatible with isolates of S. haematobium from the same region and also those from the other regions. In general, sympatric snail-parasite combinations were the most successful. All the snails were identified as Bulinus globosus, on the basis of common enzyme profiles, although polymorphism was evident for malate dehydrogenase (MDH): two samples had type-1 MDH and the rest were of type 3. Isoenzyme patterns for both acid phosphatase (AcP) and MDH could be used to distinguish between infected and uninfected snails.
蜗牛与寄生虫兼容性的降低可能至少部分导致了赞比亚卡里巴湖沿岸过去三十年中观察到的埃及血吸虫病患病率下降。为了探究这种可能性，对赞比亚三个不同地区（卡里巴湖、班韦乌卢湖和卢萨卡）学童中的埃及血吸虫病患病率进行了调查，并尝试用来自每个地点的埃及血吸虫感染从这些地点采集的蜗牛所产的卵发育而成的蜗牛。学童中埃及血吸虫感染率从班韦乌卢湖周边的0%到卡里巴湖周边的76%不等。锡亚翁加（卡里巴湖）蜗牛的F1后代与当地寄生虫表现出良好的兼容性，但也易感染所有测试的埃及血吸虫地理株系。在卡里巴湖沿岸发现的埃及血吸虫和曼氏血吸虫之间的相互作用可能有利于曼氏血吸虫，因为在没有曼氏血吸虫的地方，埃及血吸虫病的患病率往往相对较高。尽管班韦乌卢湖被证实是埃及血吸虫病低流行区，但从该地区采集的蜗牛培育出的蜗牛与来自同一地区以及其他地区的埃及血吸虫分离株兼容。一般来说，同域蜗牛 - 寄生虫组合最为成功。根据常见的酶谱，所有蜗牛都被鉴定为球茎巴蜗牛，尽管苹果酸脱氢酶（MDH）存在明显的多态性：两个样本具有1型MDH，其余为3型。酸性磷酸酶（AcP）和MDH的同工酶模式均可用于区分感染和未感染的蜗牛。
