Yousif F, Kamel G, el Emam M, Mohamed S
Department of Medical Malacology, Theodor Bilharz Research Institute, Embaba.
J Egypt Soc Parasitol. 1993 Apr;23(1):29-42.
The patterns of spreading and seasonal variation of population density of Biomphalaria alexandrina, the snail vector of Schistosoma mansoni in Egypt, in correlation with some environmental parameters were studied for 1988-1990 in four irrigation canals in Giza and Qalyoubiya Governorates. Results shown that the spreading patterns of snails along canals are changeable because of water current and irrigation activities. The snail population density showed two peaks, different in height, in April-May and November-December separated by two bottoms following the Winter Closure and during the hot summer season. The height of the peaks appears to be dependent on the extent of the "Winter Closure" and the prevailing water temperature. Two snail sampling tools, the dip-net and drag scoop, were used concurrently in this study. No considerable difference in sampling efficacy was recognized between these tools in the case of Biomphalaria. However, the dip-net appears to be more efficient in sampling other pulmonates while the drag scoop is more efficient in sampling prosobranchs. It is also realized that double sampling of 50% of sampling sites the next day should be satisfactory as a quality control system in snail population studies.
1988 - 1990年期间，在吉萨省和盖勒尤比省的四条灌溉渠道中，研究了埃及曼氏血吸虫的中间宿主——亚历山大双脐螺的种群密度扩散模式和季节变化及其与一些环境参数的关系。结果表明，由于水流和灌溉活动，蜗牛沿渠道的扩散模式是可变的。蜗牛种群密度出现两个高度不同的峰值，分别在4 - 5月和11 - 12月，中间隔着冬季停水期和炎热夏季的两个低谷期。峰值高度似乎取决于“冬季停水”的程度和当时的水温。本研究同时使用了两种蜗牛采样工具，即抄网和拖网。对于双脐螺而言，这两种工具在采样效率上没有显著差异。然而，抄网在采集其他肺螺亚纲动物时似乎更有效，而拖网在采集前鳃亚纲动物时更有效。同时还认识到，作为蜗牛种群研究中的质量控制体系，次日对50%的采样点进行二次采样应该是令人满意的。
