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- Title
Determining the viability of Schistosoma mansoni cercariae using fluorescence assays: An application for water treatment.
- Authors
Braun, Laura; Hazell, Lucinda; Webb, Alexander J.; Allan, Fiona; Emery, Aidan M.; Templeton, Michael R.
- Abstract
Background: Schistosome cercariae are the human-infectious stage of the Schistosoma parasite]. They are shed by snail intermediate hosts living in freshwater, and penetrate the skin of the human host to develop into schistosomes, resulting in schistosomiasis infection. Water treatment (e.g. filtration or chlorination) is one way of cutting disease transmission; it kills or removes cercariae to provide safe water for people to use for activities such as bathing or laundry as an alternative to infested lakes or rivers. At present, there is no standard method for assessing the effectiveness of water treatment processes on cercariae. Examining cercarial movement under a microscope is the most common method, yet it is subjective and time-consuming. Hence, there is a need to develop and verify accurate, high-throughput assays for quantifying cercarial viability. Method: We tested two fluorescence assays for their ability to accurately determine cercarial viability in water samples, using S. mansoni cercariae released from infected snails in the Schistosomiasis Collection at the Natural History Museum, London. These assays consist of dual stains, namely a vital and non-vital dye; fluorescein diacetate (FDA) and Hoechst, and FDA and Propidium Iodide. We also compared the results of the fluorescence assays to the viability determined by microscopy. Conclusion: Both fluorescence assays can detect the viability of cercariae to an accuracy of at least 92.2% ± 6.3%. Comparing the assays to microscopy, no statistically significant difference was found between the method's viability results. However, the fluorescence assays are less subjective and less time-consuming than microscopy, and therefore present a promising method for quantifying the viability of schistosome cercariae in water samples. Author summary: The role of water treatment in integrated interventions, alongside preventive chemotherapy and behavior change programs, is growing, as we now look towards elimination of schistosomiasis as a public health concern. So far, no guidelines have been developed for treating schistosome infested water. This is partially due to the lack of appropriate methods for measuring cercarial viability, which has impeded the research into the effectiveness of water treatment processes against schistosome cercariae. This study develops and validates two dual-staining, high-throughput fluorescence assays for quantifying cercarial viability in water samples. These methods will facilitate the testing of water treatment processes against cercariae, thereby bringing the knowledge of water treatment for schistosomiasis up to speed with the level of our knowledge of how to control other waterborne and water-based diseases. This will promote the development of water treatment guidelines and the design of effective water infrastructure for schistosomiasis-endemic regions.
- Subjects
NATURAL History Museum (London, England); UNITED States. Food &; Drug Administration; WATER purification; SCHISTOSOMA mansoni; WATER sampling; FLUORESCENCE; SOLANUM; WATERBORNE infection; WATER use
- Publication
PLoS Neglected Tropical Diseases, 2020, Vol 14, Issue 3, p1
- ISSN
1935-2727
- Publication type
Article
- DOI
10.1371/journal.pntd.0008176