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United States Department of Agriculture

Agricultural Research Service


item Borchardt, Mark
item Spencer, Susan
item Bertz, Phillip
item Ware, Michael
item Dubey, Jitender
item Lindquist, H.d Alan

Submitted to: Journal of Microbiology
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/1/2009
Publication Date: 9/1/2009
Citation: Borchardt, M.A., Spencer, S.K., Bertz, P.D., Ware, M.W., Dubey, J.P., Lindquist, H. 2009. Concentrating Toxoplasma gondii and Cyclospora cayetanensis from surface water and drinking water by continuous separation channel centrifugation. Journal of Microbiology. 107:1089-1097.

Interpretive Summary: Toxoplasma gondii is a single-celled parasite of all warm-blooded hosts worldwide. It causes mental retardation and loss of vision in children, and abortion in livestock. Cats are the main reservoir of T. gondii because they are the only hosts that can excrete the resistant stage (oocyst) of the parasite in the feces. Humans become infected by eating undercooked meat from infected animals and food and water contaminated with oocysts. Scientists at the Beltsville Agricultural Research Center and US Environmental Protection Agency report separation of Toxoplasma oocysts from water. These findings will be of interest to biologists, public health workers and parasitologists

Technical Abstract: Aims: To evaluate the effectiveness of continuous separation channel centrifugation for concentrating Toxoplasma gondii and Cyclospora cayetanensis from drinking water and environmental waters.Methods and Results: Ready-to-seed vials with known quantities of Toxoplasma gondii and Cyclospora cayetanensis oocysts were prepared by flow cytometry. Oocysts were seeded at densities ranging from 1 to 1000 oocysts l-1 into 10 to 100 l test volumes of finished drinking water, water with manipulated turbidity, and the source waters from nine drinking water utilities. Oocysts were recovered using continuous separation channel centrifugation and counted on membrane filters using epifluorescent microscopy. Recovery efficiencies of both parasites were =84% in 10 l volumes of drinking water. In source waters, recoveries ranged from 64-100%, with the lowest recoveries in the most turbid waters. Method precision was usually between 10% and 20% coefficient of variation.Conclusion: Toxoplasma gondii and Cyclospora cayetanensis are effectively concentrated from various water matrices by continuous separation channel centrifugation.Significance and Impact of the Study: Waterborne transmission of Toxoplasma gondii and Cyclospora cayetanensis has been documented, presenting another challenge in producing clean drinking water and protecting public health. Detection of these parasites relies on effectively concentrating oocysts from an ambient water sample, otherwise false negatives may result. While several concentration methods are available, validation data specific to Toxoplasma gondii and Cyclospora cayetanensis recoveries are limited. Using continuous separation channel centrifugation, oocysts are recovered with high efficiency and precision, the method attributes required for accurately assessing the risk of waterborne transmission.

Last Modified: 10/19/2017
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