Saline water is a problem for rice farmers in coastal regions such as Bangladesh and West Africa as the salt reduces rice yields. The situation was so bad that the Senegalese government decided to build the Diama Dam near the mouth of the Senegal River. The immediate result was not only the blocking of sea water into the Senegal River Valley which is the country’s rice belt, but it also created much needed electricity for one of the world’s least developed countries.
Clearly this must have been a win-win situation, but unfortunately it was not as it ended up severely deteriorating the health of the very people who were supposed to gain the most from the development project, the rice farmers and their families.
A water-borne disease called schistosomiasis or biharzia affects 200 million people around the world and is second only to malaria as a parasitic disease in terms of its global economic impact. Senegal has one of the highest rates of schisto but interestingly the disease in the Senegal River Valley was uncommon before the construction of the Diama Dam. The dam saw the collapse of the local freshwater shrimp which used to be a regular catch for local fishermen. This is because the shrimp spawn their eggs in the saltier water at the mouth of the river, but the dam now blocked the shrimp’s passage to the sea. What ecologists realized was that the collapse of the shrimp population led to an explosion in the water snail population as the shrimp were the snails’ natural predator. The snails harbor the parasitic worms which then get released into the river, canals and rice fields where local people are then infected.
A team of local and international researchers are now working to reintroduce the freshwater shrimp to the Senegal River Valley and there is a plan for the Diama Dam to be modified to allow the shrimp to pass through the dam so their breeding cycle is no longer interrupted. The researchers of the Project Crevette tested the effectiveness of controlling the infected water snails with shrimp and found the disease disappeared after a year of introducing the shrimp so there is great excitement that local farmers and their families can be protected once more by shrimp.
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