Monitoring and early-warning research on oncomelania in Hexi reservoir

Abstract

Objective To understand the distribution of oncomelania and the current situation of schistosomiasis of Hexi reservoir, in order to adjust schistosomiasis monitoring programs in this region timely, and provide the basis for establishment of early warning system. Methods The conventional methods were used to monitor human and animal schistosomiasis disease in the upstream area, the reservoirs and the downstream area from 2009 to 2014. Fifteen sites from 6 areas such as the source, the middle, 1 km from the storage port, storage port of the south stream and the north stream and so on were selected to monitor the number of oncomelania. The floating debris was fished from the storage port of the south stream and the north stream as well as the reservoir area from May to July, and September 2014. Results The areas with snails accounted respectively for 81.62%, 15.28%, and 3.10% in the upstream area, the project area (the bottom, the tail, the fluctuating zone and the dam area) and the downstream area before the Hexi reservoir was built (2009) . There was no oncomelania found in the reservoir area (the tail, the fluctuating zone and the dam area) and the downstream area in the reservoir operation period during 2011—2014. The areas of snail were all distributed in the upstream catchment area. The area of oncomelania was 7.69 hm2 in 2014 which decreased 25.63%, compared with 10.34 hm2 in 2009. The density of living snails decreased 87.10% in the upstream area from 2009 to 0.8/0.1 m2 in 2014. There were no patient suffered from schistosomiasis and sick animal found in this monitor. There were no infected oncomelanias found in 15 monitoring sites. Conclusions The effect of schistosomiasis control projects in Hexi reservoir was remarkable for prevention of oncomelania in the tail and the downstream of the reservoir. The establishment of a new snail monitor, control and early warning mechanisms is very urgent because of the large area of oncomelania in the upstream catchment area. Key words: Schistosomiasis; Reservoir project; Oncomelania; Monitoring