Prawns could be a vital weapon in the fight against a neglected tropical disease, as well as providing an important source of income and food for farmers on low incomes, a study suggests.
A paper in the journal Nature Sustainability highlights how the African river prawn is a “voracious” predator of the freshwater snail, which is a carrier of schistosomiasis – a debilitating disease of poverty that affects around 200 million people every year.
People pick up the disease when they come into contact with water infected with parasitic worms released by the snails. Children playing in rivers and pools often catch the disease as do farmers.
The disease is rarely fatal but it leads to abdominal and bladder problems and sometimes cancers as well as stunting in children. The female genital form of the disease can also lead to infertility.
The authors of the paper say that if a World Health Organization target of eliminating the disease by 2025 is to be reached more control strategies are needed, beyond the current policy of giving people living in areas where the disease is a risk preventive medicine.
The researchers say that farming the African river prawn could prove a triple whammy in fighting the disease and improving the lives of local people.
Not only would the prawns help wipe out the snails that carry the disease by eating them in vast quantities, they would also provide an important source of income for subsistence farmers in sub-Saharan Africa, where around 90 per cent of cases of the disease occur.
And the prawns would also be an important source of nutrition in countries where food insecurity and malnutrition are prevalent.
Giulio De Leo, professor of biology at Stanford University and lead author of the paper, said that aquaculture – like any form of farming – had its challenges. But he said that a farmer growing rice would find cultivating prawns fairly straightforward.
He added: “Freshwater aquaculture is supported by governments as a way of improving food production and providing revenue for small scale farmers. But there is also potential to integrate this with the goal of fighting schistosomiasis transmission. This is a win-win.”
The authors believe that a small-scale farmer could make a profit of up to around $5,500 over a 10-year period.
Rice is becoming an increasingly important crop in Africa, and the authors say that prawns could be cultivated in rice paddies without damaging crops or the delicate ecosystem.
Using prawns to battle schistosomiasis has already been trialled by Prof De Leo and his team in Senegal. After a much-needed dam was built on the Senegal river the prawn population fell because they were unable to migrate up and down to complete their life cycle. Schistosomiasis rates then went up.
However, when researchers restocked the river there was a dramatic fall in schistosomiasis re-infection rates among the local population.
Prof De Leo said there was no danger of people picking up the disease by eating prawns which had ingested infected snails as schistosomiasis is picked up through the skin.
He said that market analysis in Senegal had shown there was significant interest among restaurant owners and farmers in introducing prawns to the diet.
As well as releasing prawns into rice paddies Prof De Leo’s team said they were also thinking about introducing the shellfish to other areas where people picked up the disease, such as popular swimming and bathing spots.
“At other transmission sites we have been looking at the possibility of building enclosures for the prawns,” he said.
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