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REDUCTION OF INFECTIVITY OF SCHISTOSOME CERCARIAE BY APPLICATION OF CERCARICIDAL OIL TO WATER

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  • 1 Department of Molecular Microbiology and Immunology, and Department of Environmental Health Sciences, Center for Water and Health, Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland

Schistosomiasis continues to plague populations living in disease-endemic areas, and exposure to infective cercariae results in more than 200 million cases worldwide. Laboratory experiments were conducted to test whether a cercaricidal film applied directly to the water surface can reduce viability of cercariae. A distillate from inexpensive cedarwood oil enriched for cedrol in a mixed oil fraction was formulated (1:5) with the surfactant Tween 80. When applied to the surface of clean and turbid water in test vessels, the formulation spread across and just below the air-water interface, causing inactivation of Schistosoma mansoni cercariae within minutes. The active ingredient was heat stable and reduced schistosome survival and infectivity by 90% and 99.2%, respectively in a mouse model. The effective dose (13 μg/cm2) was dependent on surface area rather than volume of water treated. We conclude that application of the biodegradable formulation to the surface of schistosome-infested waters may be an effective, economical, and safe means of reducing human infections.

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