Scientists have identified genetic changes in wild populations of the parasitic worm that causes schistosomiasis which may reduce its response to praziquantel, the only available treatment, according to a July 17 study. The research provides an early warning for disease control and elimination programs.
Researchers from the Wellcome Sanger Institute, the Royal Veterinary College, and Medical College of Wisconsin led a large-scale international collaboration analyzing hundreds of Schistosoma mansoni genomes collected from people in several African and Caribbean countries. The study is described as the largest genomic analysis of the parasite from human infections to date.
Published in Science Advances, the findings highlight a need for ongoing genomic surveillance to help protect the long-term effectiveness of praziquantel. Schistosomiasis affects more than 250 million people across 79 countries and is particularly common among children and vulnerable communities. Infection occurs when larval-stage parasitic worms penetrate human skin during contact with infested water.
Praziquantel has been used as a tablet treatment since mass drug administration programs began in Uganda in 2003, later expanding across sub-Saharan Africa and beyond. Concerns about potential resistance have grown as use has increased over two decades. In this new study, researchers analyzed whole-genome sequencing data from 570 Schistosoma mansoni parasites—alongside samples from related species—and combined it with public datasets to track genetic shifts under long-term treatment pressure.
The team found clear genetic differences between parasite populations by country and evidence that parasites can spread over large geographic distances. Four naturally occurring genetic changes were identified in the gene Sm.TRPMPZQ that were associated with reduced sensitivity to praziquantel during laboratory testing. Analysis also showed some parasites persisted after treatment, suggesting reduced drug effectiveness may already exist at low levels within endemic populations.
Professor Joanne Webster, co-senior author at the Royal Veterinary College and Director of the Global Centre for Neglected Tropical Disease Research, said, "Since mass drug administration programmes began across sub-Saharan Africa in 2003, praziquantel has been used to treat millions of people and has become the foundation of schistosomiasis control efforts. This widespread use places increasing evolutionary pressure on parasite populations. While praziquantel remains largely highly effective, our findings provide a sobering warning about the reliance on a single drug for schistosomiasis control and highlight the need for comprehensive surveillance to monitor the potential emergence of drug resistance."
