Killing up to 200,000 people annually, schistosomiasis is one of the most deadly parasitic diseases in the world, second only to malaria. Soon, however, prawn aquaculture could be used to control the snails that spread it – and to provide revenue for people in developing nations.
Freshwater river prawns are already widely grown as food, starting out in hatcheries and then being transferred to pens in waterways as they mature. Additionally, scientists already know that the crustaceans feed ravenously on the snails which temporarily host the "blood fluke" parasites which cause schistosomiasis.
Recently, an international research project led by scientists at the University of California, Berkeley, looked at the relationship between these two factors. More specifically, the scientists wanted to know if local-scale prawn aquaculture could have an appreciable effect on snail populations. What they found was indeed promising.
Based on a model of raising native Macrobrachium vollenhovenii prawns at "profit-maximizing densities" in sub-Saharan waterways, it was determined that such aquaculture would substantially reduce parasite loads – in fact, it could do so by approximately as much as the current large-scale administration of schistosomiasis-fighting drugs already does. Looking farther down the road, a combination of aquaculture and drug treatment could conceivably reduce parasite loads to almost zero within 10 years.
As an added bonus, the prawns could serve as an eco-friendly alternative to the chemical pesticides currently used to control the snails, plus they may restore a natural balance to rivers where native prawns are no longer present due to dam construction. And no, prawns that feed on the snails do not end up carrying the parasites themselves.
"Our results show that there are highly beneficial configurations of prawn aquaculture systems that minimize tradeoffs between generating revenue from harvesting prawns and reducing schistosomiasis transmission," says doctoral student and study leader Christopher Hoover. "We can design systems to maximize profit while having a substantial impact on disease reduction, potentially helping to lift populations out of poverty in emerging and developing economies."
A paper on the research was recently published in the journal Nature Sustainability.