Snails breed parasites called schistosomiasis. Snails are usually eaten in great amounts by river prawn, excepts in rivers where dams or other environmental disruptions have occurred killing off the prawns and leaving all the snails resulting in wide spread, rampant, deadly schistosomiasis.
This is a very promising and inspired project that if it works, and I see no reason why it won't, would provide a solution/cure to the 4th largest cause of mortality in the world the parasite schistosomiasis abby simply restoring the ecosystem back to what it was before it was altered.
Watch the video below, they explain it much better then I can. If you want to help out or more information check out their site here.
What is so exciting to me about this solution to such a horrible public health issue is how in keeping with nature it is and that when these bodies of water are safe to go into again not only will they not be fill with schistosomiasis they will provide a source of food.