Praziquantel, an effective drug used to treat the common parasitic disease schistosomiasis, was believed to be the “silver bullet” to achieve disease elimination upon its introduction in the late 1970s. But decades later, the global schistosomiasis burden has remained largely unchanged.
Today, more than 250 million people worldwide are infected with the potentially deadly disease, most of whom live in poor and rural communities in tropical and subtropical areas where a lack of adequate sanitation and control efforts enables the parasites to thrive in infested waters.
Now, Stanford research on schistosomiasis control efforts over the past century shows that those incorporating ecological interventions – controlling the snail populations that host the parasites – were consistently more effective than drug treatment alone.
“Many countries with endemic schistosomiasis today struggle with an endless cycle of drug distribution and reinfection,” Sokolow recently told me. “Yet, when we look back in history, there has been an impressive variety and creativity of solutions, before praziquantel was available.”
The researchers' analysis looked at control tactics and quantitative outcomes in 83 countries and territories with endemic schistosomiasis in the 20th century. They found that programs that used widespread snail control, either alone or in conjunction with drug administration, reduced the proportion of the population infected with the disease by over 90 percent.
“We have to examine the drivers of infection and address transmission and reinfection cycles from both the human and environmental angles if we want to make a long-term impact. For schistosomiasis control, that means addressing the snails that carry the parasite,” said Sokolow in a Stanford press release.
One of those snail control strategies has been pioneered by Sokolow and Giulio De Leo, PhD, a biology professor at Hopkins Marine Station and senior author of the study. The two are currently working on a demonstration project in the lower basin of the Senegal River aimed at restoring a native prawn that feeds on the disease-carrying snails. Preliminary results showed that reintroduction of prawns in river access points has led to fewer snails, thus helping to curb transmission of the parasites to humans. Tune in to the video above to learn more.
Sokolow and De Leo are both fellows at Stanford's Center for Innovation in Global Health, and De Leo is a senior fellow at the Stanford Woods Institute for the Environment. The researchers recently launched the Program for Disease Ecology, Health and Environment at Stanford focused on finding sustainable ecological solutions to a range of diseases.
“We intend to catalyze the very creative research energies from various schools and departments at Stanford and discover novel ecological solutions to fight a wide group of waterborne, soil borne, vector borne and food borne diseases with an important environmental component in their transmission cycle,” said De Leo.
Previously: Massive campaign against parasitic worm disease is cost-effective, new study shows, A new framework for expanding treatment guidelines for parasitic worm diseases and Tropical disease treatments need more randomized, controlled trials, say Stanford researchers
Video by Ian Fitzgerald and Rob Jordan/Woods Institute