Prawn solution prevents spread of deadly disease

According to research, the prawns can serve as an effective natural solution in the battle against schistosomiasis, a potentially deadly parasitic disease that infects about 230 million people. The prawns prey on parasite-infected snails, while providing a source of marketable protein-rich food. Because prawns cannot support schistosomiasis' complex life cycle, they do not transmit the disease themselves.

"The results of our study open the pathway to a novel approach for the control of schistosomiasis," said co-author Giulio De Leo, a biology professor at Stanford's Hopkins Marine Station and a senior fellow at the Stanford Woods Institute for the Environment.

The study, published in the Proceedings of the National Academy of Science, tracked parasite-infected snails and people in two villages. In one village, the international research team and Senegalese partner Biomedical Research Center Espoir pour la Santé stocked a river access point with prawns. Over the course of 18 months, they found 80% fewer infected snails and a 50% lower disease burden (the mean number of parasite eggs in a person's urine) in people living in the prawn-stocked village.

In a mathematical model of the system, stocking prawns, coupled with infrequent mass drug treatment, eliminated schistosomiasis in high-transmission sites. "Where drugs, alone, fail to control schistosomiasis due to rapid reinfection, prawns may offer a complementary strategy" for controlling the disease, the study's authors write.

Local communities could be incentivised to maintain prawn populations in order to market them as a food product, the researchers said.

"They are delicious,” added lead author Susanne Sokolow. "They can synergise with local efforts in the developing world to fight parasitic disease and to foster new aquaculture-based industries."

And the solution could go worldwide, where almost 800 million people are at risk of getting schistosomiasis. Currently, the only treatment for the disease is the drug praziquantel. Insufficient global supplies, cost and other factors limit that drug's effectiveness.

In addition to stocking river access points, the researchers suggest prawns could be restored to rivers through the use of dam-bypassing passages similar to salmon ladders used in the Western United States.

Co-authors on the paper, Reduced transmission of human schistosomiasis after restoration of a native prawn that preys on the snail intermediate host, include researchers from the 20/20 Initiative; the University of California, Santa Barbara; the Institut Pasteur de Lille, France; and the Biomedical Research Center Espoir pour la Santé, Saint-Louis, Senegal.