ABSTRACT
Objective To evaluate and compare the short-term effects of two kinds of plastic mulch on Oncomelania hupensis snail control in irrigation and drainage ditches with snails in Yunnan Province. Methods The irrigation and drainage ditches with high density of Oncomelania hupensis snails were chosen as the investigation sites,and then 4 groups were set,namely a colorless plastic mulch group,black plastic mulch group,colorless plastic mulch with molluscicide group and black plastic mulch with molluscicide group. The snail situation of the 4 groups was surveyed before the experiment and 7,14,21,30 days after covering plastic mulch,and the snail death rates were compared among the 4 groups. Meanwhile,the hourly temperatures of soil surface,soil surface under plastic mulch and soil layer 5,15 cm under the surface as well as the weather situation during the study period were measured and recorded. Results The average snail mortality rate of the colorless plastic mulch group was only 15.29% that was higher than that of the black plastic mulch group(6.56%)(P 0.05). Both kinds of plastic mulches could raise the temperature of the soil surface under plas-tic mulch and the soil layer below it,and the temperature of soil under the mulches increased over the cover time,and the aver-age temperature of the soil surface under the black mulch in 30 days was higher than that under the colorless mulch. Conclu-sion It is not suitable to use plastic mulch only in irrigation and drainage ditches with snails widely in Yunnan Province be-cause of its low effect,and if necessary,the molluscicide should be added.
ABSTRACT
Objective To understand the Oncomelania hupensis distribution and infection status in the schistosomiasis sur?veillance sites of Yunnan Province,so as to provide the evidence for making the control and prevention measures. Methods Eighteen administrative villages were selected as the surveillance sites where the schistosomiasis endemic was serious in 18 epi?demic counties,one village for one county. The snail status was investigated with the systematic sampling and environmental sampling methods,and the infection status of the snails was detected by a microscope and loop?mediated isothermal amplifica?tion(LAMP). The surveillance database was established and descriptively analyzed. Results In 2015,the total surveillance ar?ea was 1 826.55 hm2,and the area with snails was 55.03 hm2,that was reduced by 57.70% as compared to that in 2013,and by 40.63% as compared to that in 2014. No new snail area was discovered,and also no schistosome infected snails were discovered. Totally 718 532 frames were surveyed,and the occurrence rate of frames with snails was 0.45% and the density of living snails was 0.013 9 snail/0.1 m2. In the endemic controlled areas,the snail area and density of living snails were both the highest. The snails concentrated on the environments of paddy field,ditch,bottomland,small reservoir,and dry land,and the vegetations of rice,dry crop,weed and wood. The snail area,occurrence rate of frames with snails,total number of snails and number of liv?ing snails all showed a downward trend. No infected snails were found for three years. Conclusions The Oncomelania hupensis snails have been effectively controlled in the national schistosomiasis surveillance sites of Yunnan Province. However,the com?prehensive snail control measures still should be continually strengthened in order to consolidate the achivements.
ABSTRACT
Objective To develop a spatio-temporal model of mountainous Oncomelania hupensis snails based on the Bayes-ian model,and to analyze and identify the spatio-temporal pattern at a village scale. Methods The data including the intensity and spatial distribution of live and infected snails from 2000 to 2006 and the village boundary were collected. The independent and interactive spatio-temporal models were established,and then the best fitness model was selected to analyze the spatio-temporal pattern of live and infected snails. Results The interactive model of live snails and the independent model of infected snails were relative fitness models,and the models showed 95%CI(confidence interval)of the spatial and temporal coefficient included ze-ro,and indicated that the spatial and temporal correlation of live and infected snails was not significant at a village scale. Conclu-sion There is no significant spatial and temporal correlation of live and infected mountainous snails at a village scale,and the fur-thermore study should be carried out at a small scale.