Abstract:

Objective To longitudinally evaluate the inhibition of the afforestation project for schistosomiasis control on Oncomelania snails. Methods Four sites along the Yangtze River in Anhui province were selected as the pilots, including Nangeng of Anqing City along the upper reaches (forests were built in 1989),Liudu Park and Liudu Babuque of Wuwei County along the middle reaches (forests were built in 2001), and Dongjiangliulin, Chenqingzhou of Hexian County along the lower reaches (forests were built in 1997). The changes of snail status were compared in the aforementioned 4 pilots before and after the forest building through the collection of historical snail survey data and field snail survey conducted in autumn of 2010, so as to evaluate the effect of the afforestation project for schistosomiasis control on the inhibition of snails. Results In 2010, a total of 992 frames of snails were surveyed in the four pilots, and higher occurrence of frames with living snails, density of living snails and snail mortality were observed in forest land than that in the control area of marshland (all P values < 0.01). In Nangeng of Anqing City, the occurrence of frames with living snails and the density of living snails appeared a decline tendency grossly following forest building, and the occurrence of frames with living snails and the density of living snails reduced by 23.6% (χ2=14.8, P<0.01) and 72.4% one year after the forest building, respectively; low occurrence of frames with living snails and density of living snails were found within 6 years of forest building, whereas appearing a rise tendency after 6 years; however, a gross decline tendency was observed. In Liudu Park of Wuwei County, the occurrence of frames with living snails reduced from 50.4% to 1.16% (χ2=180, P<0.01) and the density of living snails reduced from 3.6 to 0.017 snails/0.11m2 one year after the forest building, respectively, and the occurrence of frames with living snails and density of living snails were lower within 5 years of forest building than before forest building, whereas appearing a rise tendency after 6 years. In Liudu Babuque, the occurrence of frames with living snails reduced from 83.7% to 48.4% (χ2=32.9, P<0.01) and the density of living snails reduced from 8.7 to 2.5 snails/0.11m2 one year after the forest building, respectively, and the occurrence of frames with living snails and density of living snails were lower in most years after the forest building than before forest building, whereas appearing a rise tendency from 4 to 7 years after the forest building. In Dongjiangliulin, Chenqingzhou of Hexian County, a gross decline tendency was observed in the occurrence of frames with living snails and the density of living snails after the forest building. Conclusions The afforestation project for schistosomiasis control showed unfavorable effect on the survival of snails, and forest building on marshland exhibits a remarkable long-term inhibition on snails.

Key words: Schistosoimasis, Oncomelania snail, Afforestation project for schistosomiasis control, Snail control effect, Longitudinal observation