Freshwater shrimp farming would help control deadly parasitic disease

Freshwater shrimp (river prawns) consumes snails that transmit parasites that cause schistosomiasis, so increased farming would reduce the spread of deadly parasitic disease, according to a study from the University of California, Berkeley.

The study provides a roadmap for how entrepreneurs can harness freshwater shrimp voracious appetite for snails to reduce the transmission of these parasites, also known as "blood flukes".

"These are some of the most common predicaments of schistosomiasis," said Christopher Hoover, a doctoral student who led the study. "What has we been able to do is to have the benefits of prawn aquaculture with the disease-control activity of the prawns."

As the shrimp grow, they feed on the snails that carry the parasitic schistosome. The parasite is unable to infect the shrimp themselves, and schistosomiasis is not transmitted via ingestion, so raising, harvesting and shrinking can not pbad along the disease.

The researchers used economic and epidemiologic modeling to pinpoint the optimal points for which to stock and harvest the prawns, with the joint goals of reducing schistosomiasis transmission and generating revenue from selling harvested prawns.

"Our results show that it is highly beneficial to reduce the risk of slash and burn transmission," Hoover said. "We can design systems to maximize profit while having a substantial impact on disease reduction, helping people to lift populations out of poverty in emerging and developing economies."

Schistosomiasis, also known as "snail fever", affects around 250 million people and is estimated to be 200,000. Not enough in some settings, because of the parasite's transmission cycle, which is very vulnerable to reinfection, even soon after treatment.

By acting on the environmental component of the transmission cycle – the intermediate host snail population – shrimp-based interventions can complement drug treatment, yielding greater population benefits, according to the study.

The model was shown to reduce parasite loads, introducing shrimp to infected waterways and comparing it to the standard approach of widescale administration of schistosomiasis-fighting drugs, and that it could decrease the parasite burden to nearly zero after 10 years.

Shrimp may have environmental benefits, including substituting for chemical pesticides to control snail populations and restoring native biodiversity in areas where native prawn species have been decimated by dams.

"This research contributes to our overall efforts to fight schistosomiasis," said University's Justin Remais, co-senior author of the study. "Poverty and schistosomiasis are intrinsically linked, and transmission of the parasite is known to stunt growth and cognitive development in children and to prevent adults from working, reinforcing poverty. By targeting the parasite itself, while also supporting a locally-sourced production system where increased economic benefits to the community, this approach has great potential to supplement ongoing disease control campaigns.