Use of landsat TM satellite surveillance data to measure the impact of the 1998 flood on snail intermediate host dispersal in the lower Yangtze River Basin

To assess the impact of the 1998 flood on snail distribution in the lower Yangtze River Basin, two study areas were selected, one in the Poyang Lake region, and the other along the Yangtze River in Jiangsu province. Using image analysis software, geocoded Landsat TM data were used to create TNDVI maps based on the formula TNDVI=Sqrt[(band4-band3/band4+band3)+0.5]. The images taken in the flood season were classified to produce a map depicting water and land. The images taken during springtime were processed and classified based on TNDVI. Composite images were created based on the time difference analysis, combining the flood season maps and spring vegetation maps to produce a map in which potential snail habitats were identified. When compared with ground survey data collected in the spring of 2000, the correspondence rate between potential snail habitats identified by image analysis of 1998-1999 Landsat TM data and ground survey data was over 90% in both regions. Results indicate that ecology based Landsat TM image analysis provides a new way to predict snail distribution under specific environmental conditions associated with the extent of the annual flood season.

The potential risk and control strategy in low endemic area of schistosomiasis in China

OBJECTIVE

to describe and analyze the potential risk and suggest the corresponding control strategy in low endemic of schistosomiasis in China.

METHODS

referring the 'national criteria of control and elimination of schistosomiasis' and the 'national criteria of classification of endemic area for chemotherapy'; collecting the data of the re-infection of schistosomiasis in lake region and residual snails in mountain areas and evolution of endemic situation in 'snail ridden areas without schistosomiasis'; analyzing the potential risk in different types of low endemic area and suggesting the control strategies according to the analysis results and historical experiment.

RESULTS

the re-infection rate of schistosomiasis in residents is usually higher in high, medium and low endemic areas in the lake region, once chemotherapy is stopped, the infection rate may rise again to the initial level 2 years later and bovine chemotherapy and snail control in susceptible zone will be selected as the optimal strategies for controlling the endemic situation; the potential risk in mountain areas is the enlargement of snail habitats due to residual snail's reproduction and the control strategy will be to strengthen the surveillance and elimination of residual snails; inputting the infective sources of schistosomiasis is the potential risk in 'snail ridden area without schistosomiasis' and the main control strategy should be put the regular monitoring on the infection sources from hyper-endemic areas and treat the infected domestic animals in time.

The role of health education for schistosomiasis control in heavy endemic area of Poyang Lake region, People's Republic of China

For exploring the impact of health education for schistosomiasis control in a heavy endemic area of Poyang Lake region, China, the residents residing in the heavy endemic area were divide into three kinds of target population: pupils, adult women and adult men, and then targeted health education was implemented respectively among the three kinds of population after a baseline survey. The result were compared with that in the control group. The anti-schistosomiasis knowledge level among the three kinds of population improved significantly, the correct rate of attitude to examination and chemotherapy among pupils and adult men and the correct rate of anti-schistosomiasis value concept among women were raised greatly, obedience to examination and chemotherapy among adult men increased, the rate of infested water exposure and infection rate among pupils and adult women declined remarkably. Therefore, infection with Schistosoma japonicum (Sj) can be controlled effectively among women, especially pupils and obedience to examination and chemotherapy among adults men can be improved by implementing health education.