When the breeding cycle of prawns was broken in the Senegal basin, there was an explosion of schistosomiasis (bilharzia/snail fever) upstream from the new dam wall. 

Unable to reach their salty breeding ground, the prawn population was almost wiped out. Prawns are natural predators to snails and with their numbers greatly diminsehd the snail population boomed. 

Snails are the vector for the schisotsomiasis parasite. Can the Projete-Crevette team convince the local authorities to build a "prawn ladder" which allows the prawns to move past the dam wall and back to their breeding grounds?

Lifelines: The Quest for Global Health aired on Al Jazeera in 2014. 'River of Hope' the fourth film in the series focusing on schistosomiasis in Senegal. You can watch it online here

Source: Al Jazeera