New article. eDNA detects schistostomiasis (snail fever), the second largest cause of death in the world after malaria. The article presents a paradigm shift in moving from disease control to elimination.
An international team, including a researcher from AquaBiota, has published a research article in PNAS showing that eDNA detects schistosomiasis at an early stage of development prior to human and mammalian infection. Schistosomiasis is a water-based, infectious disease with high morbidity and significant economic burdens infecting >250 million people and affecting more than 700 million people, mostly women and children, globally.
The parasites require aquatic snail hosts for the first part of their lifecycle. The trematode larvae are shed into the surrounding where they penetrate human (and other mammalian) skin to complete their lifecycle. Traditional/current snail-host/parasite inventory methods are slow, expensive and imprecise. Disease control has, with notable success, for decades focused on drug treatment of infected human populations. For successful elimination it is crucial to identify transmission hotspots at an early stage.
The research article presents a paradigm shift in moving from disease control to elimination. The article reports on eDNA as a revolutionary tool to efficiently detect DNA traces of the parasite Schistosoma mansoni directly in the aquatic environment, where the nonhuman part of the parasite life cycle occurs. True eDNA was detected in as few as 10 cercariae per liter of water in laboratory experiments. The field applicability of the method was tested at known transmission sites in Kenya, where comparison of schistosome detection by conventional snail surveys (snail collection and cercariae shedding) with eDNA (water samples) showed 71% agreement between the methods. The eDNA method furthermore detected schistosome presence at two additional sites where snail shedding failed, demonstrating a higher sensitivity of eDNA sampling. The study concludes that eDNA provides an efficient tool to substantially improve the environmental surveillance of S. mansoni. eDNA could become an essential future component of the schistosomiasis control tool box needed to achieve the goal of elimination.
Sengupta ME, Hellström M, Kariuki HC, Olsen A, Thomsen PF, Mejer H, Willerslev E, Mwanje MT, Madsen H, Kristensen TK, Stensgaard AS. Environmental DNA for improved detection and environmental surveillance of schistosomiasis. Proceedings of the National Academy of Sciences. 2019 Apr 11:201815046.
Read more about using eDNA for inventory studies: www.aquabiota.se/edna/