To Reduce the Global Burden of Human Schistosomiasis, Use 'Old Fashioned' Snail Control

Abstract

Control strategies to reduce human schistosomiasis have evolved from 'snail picking' campaigns, a century ago, to modern wide-scale human treatment campaigns, or preventive chemotherapy. Unfortunately, despite the rise in preventive chemotherapy campaigns, just as many people suffer from schistosomiasis today as they did 50 years ago. Snail control can complement preventive chemotherapy by reducing the risk of transmission from snails to humans. Here, we present ideas for modernizing and scaling up snail control, including spatiotemporal targeting, environmental diagnostics, better molluscicides, new technologies (e.g., gene drive), and 'outside the box' strategies such as natural enemies, traps, and repellants. We conclude that, to achieve the World Health Assembly's stated goal to eliminate schistosomiasis, it is time to give snail control another look.

Figure 1. The Schistosoma sp. lifecycle and snail control strategies

human to snail transmission occurs via free-living miracidia released from eggs in urine and feces; and snail to human transmission occurs through free-living cercariae that exit infected snails into the water, seeking new vertebrate hosts. Control strategies should combine (A) human drug treatment or preventive chemotherapy with praziquantel (PZQ) with (B-F) creative methods to control infected snails such as: (B) chemical molluscicides; (C) natural enemies; (D) habitat modification; (E) creative technologies such as gene drive; (F) traps or repellants and other out of the box strategies.

Figure I

Two different snail scoops designed and deployed to sample snails in schistosomiasis transmission sites in Senegal. Image courtesy of The Upstream Alliance (http://wwwtheupstreamalliance.org), under the terms of the Creative Commons Attribution License CC BY 2.0.