Kimura E, Uga S, Migwi D K, Mutua W R, Kiliku F M, Muhoho N D
Institute of Tropical Medicine, Nagasaki University, Japan.
Trop Med Parasitol. 1994 Jun;45(2):112-4.
Hourly change in cercarial densities was studied at different depths in the water and distances from the shore at a dam in Kwale District (Kenya), where Schistosoma haematobium is highly endemic, by using a filtration apparatus for detecting cercariae. The peak of cercarial density at the surface of water (2-3 cm deep) was at 11:00 hours. Those at the middle point (25 cm deep) and the bottom (50 cm deep) were at 12:00 and 13:00 hours respectively. In the morning, the majority of cercariae (79% of the total detected) was obtained at the surface of water, but none at the bottom. After midday, 40% of the cercariae were obtained at the bottom. Cercariae seemed to sink with time resulting in a wider distribution in the water. The numbers of cercariae obtained at a sampling point 20 cm from the shore, which was inside the wire-screened snail-free area, were 3.4-23 times more than those obtained at a sampling point 340 cm from the shore, indicating that cercariae were accumulating immediately near the shore. Winds might cause the accumulation.
在肯尼亚夸莱区的一座大坝，血吸虫病流行程度很高，研究人员使用检测尾蚴的过滤装置，对水中不同深度以及距岸边不同距离处尾蚴密度的每小时变化情况进行了研究。水面（水深2 - 3厘米）尾蚴密度的峰值出现在11:00。中点（水深25厘米）和水底（水深50厘米）的峰值分别出现在12:00和13:00。上午，大部分尾蚴（占检测到的总数的79%）是在水面获得的，水底没有。中午过后，40%的尾蚴是在水底获得的。尾蚴似乎随着时间下沉，导致在水中分布更广。在距岸边20厘米的采样点（该点位于无螺铁丝网区域内）获得的尾蚴数量比距岸边340厘米的采样点多3.4至23倍，这表明尾蚴在岸边附近立即聚集。风可能导致了这种聚集。
