Saw this documentary in Discover Channel the other day on a parasite called Schistosoma .

Basically, the parasite alternate infects the two hosts - snail and mammals (read human), in a complex life cycle. The infected snails release the parasite which finds its way to the human body by boring through the human skin . The parasite then finds its way back to the water via human stool or urine, which then infects the snail and starts the whole new cycle.

More info:
http://www.weichtiere.at/Mollusks/Sc...histosoma.html
http://wapedia.mobi/en/Schistosomiasis#2.
http://www.cdfound.to.it/html/si.htm


Country most affected are: Africa, Middle East, Caribbean, Japan, China and Philippines.

The infected snails look like ramhorn and trumpet snail but the scientific name seems to be different. After the documentary, Mrs Rwalker basically bars the kids from touching the snails in the tank!

Not sure whether there is any reported cases in Singapore before but the parasite sure looks scary.