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Imaging Cytometry for Detection and Viability Determination of Protozoan Parasites on Fresh Retail Produce and Environmental Samples in Ontario


The main objectives of this project are to develop and validate a high-throughput method for the rapid detection of Cryptosporidium, Cyclospora, Toxoplasma and Giardia in a variety of food and environmental matrices using imaging cytometry, and to compare the sensitivity, specificity, and speed of this method to microscopy and PCR (Polymerase Chain Reaction) methods which are often used in surveillance studies and outbreak investigations. The effectiveness and accuracy of the method in providing quantitative results for parasites in foods and environmental samples will be evaluated. The accuracy of the method in determining the viability of these parasites will also be evaluated against existing viability assays including microscopy using vital dyes and excystation. Finally, the optimized method will be used in a surveillance study of fresh produce purchased at retail in Ontario, as well as in testing of farm-level environmental samples, including surface waters and livestock manure, as possible sources of contamination of foods.

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Expected Benefits <br/>
Imaging cytometry may be a very effective technology for the detection and quantification of enteric protozoan parasites in fresh produce, as well as in environmental samples as possible sources of contamination. This improvement in detection will be of benefit to food testing laboratories, and could result in an improvement in parasite surveillance and outbreak investigations leading to fewer foodborne illnesses in Ontario. Imaging cytometry also provides a vast improvement over traditional microscopical means in the determination of parasite viability (infectivity), which has not previously been considered in surveillance studies, and is of considerable importance in risk assessments and risk management.

Dixon, Brent
Health Canada, Food Directorate, Bureau of Microbial Hazards
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