HYDROLOGICAL IMPACT ON PARASITIC DISEASE TRANSMISSION: SCHISTOSOMIASIS IN THE POYANG LAKE REGION, CHINA

Schistosomiasis is a water-dependent parasitic tropical disease involving an intermediate snail host in the transmission cycle. Second only to malaria in prevalence and over 200 million infections occur annually worldwide including areas in Africa, Southeastern Asia, and China. This chronic disease shortens average lifespans by ten years and leads to increased cancer risks. Hydrology plays a critical role in the snail ecology and thus affects the human disease burden. Our research focuses on the influence of hydrology on the schistosomiasis transmission cycle in the Poyang Lake region in southeastern China where health education and behavioral changes are insufficient to control the disease. Poyang Lake is the largest freshwater body in China, and the stage of the Yangtze River acts a baseline control for the draining of the lake. Conversely, the lake acts as flood storage during extremely high river flows. Our hypothesis is that the historical large-scale spring floods on the Yangtze River act to control the snail populations. TOPEX/POSEIDON and ENVISAT satellite radar altimetry have been used to monitor water levels in large lakes and rivers. Here we used both TOPEX (1992-2004) and ENVISAT (2002-2006) observed water level change over Poyang Lake and part of the Yangtze River for this study. These measurements are analyzed against epidemiological disease burden data to identify the influential hydrological factors. Preliminary results show that the hydrological factors affecting the snail populations, which influences disease transmission, include the: (1) amount of time to reach peak flood levels, (2) average depth of water during peak flood, (3) duration of the flood, and (4) area of land covered by water during peak flood. This study is a first step to investigate hydrological factors in disease transmission, which are an emerging area of interest in public health.