A Google Earth-based surveillance system for schistosomiasis japonica implemented in the lower reaches of the Yangtze River, China

A total of 45 sites were selected and the risk was assessed monthly by water exposure of sentinel mice at these sites from May to September in 2009 and 2010. The results were assembled and broadcast via the Google Earth platform.The intensity of schistosomiasis transmission showed peaks of risk in June and September of 2009, while there was only one small peak in June in 2010 as the number of detected positive transmission sites dropped dramatically that year thanks to improved mollusciciding. River ports were found to be areas of particular risk, but ferry terminals and other centres of river-related activities were also problematic.The results confirm that the surveillance system can be rapidly updated and easily maintained, which proves the Google Earth approach to be a user-friendly, inexpensive warning system for schistosomiasis risk.The transmission of schistosomiasis depends on the presence of aquatic or amphibious intermediate snail hosts and the disease is therefore closely related to water-bodies and water courses [1,2]. The maturation process in the snail is governed by the ambient temperature, while the shedding of cercariae (the infective stage) from the snail not only requires water of proper temperature but also sufficient day light [3,4]. Once emerged from their snail host, the cercariae move towards the surface, contaminating the water and thus turning the area into one of risk for schistosome infection. When humans and/or other definitive animal hosts are exposed to water under such circumstances, the cercariae home in, penetrate the skin and move through the systemic circulation via the lungs and liver to finally settle in the mesenteric microcirculation [3].Schistosomiasis japonica, distributed in China and the Philippines, is one of the three major forms of human schistosomiasis which all belong to the neglected tropical diseases (NTDs) [1,5]. The morbidity due to infection by Schistosoma japonicum is more severe than that caused by the two othe