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2014-2016 Parasites in Fresh Leafy Vegetables


Produce such as berries, herbs and vegetables have been identified in the past as sources of contamination for parasites. Produce can become contaminated with parasites during production, harvest, post-harvest handling, processing, packaging and distribution. Parasites can infect humans primarily through contaminated food and water. In general, symptoms of infection can include mild to severe flu-like (Toxoplasma) and gastrointestinal symptoms (Cyclospora, Cryptosporidium, Giardia). Previous targeted surveys have reported on the occurrence and distribution of Cyclospora cayetanensis (C. cayetanensis) and Cryptosporidium spp. in berries, fresh leafy herbs, mushrooms and green onions. This report focuses the occurrence and distribution of C. cayetanensis, Cryptosporidium spp., Toxoplasma gondii (T. gondii), and Giardia spp. in minimally processed (pre-washed and pre-packaged) fresh leafy vegetables.

Considering the factors mentioned above and their relevance to Canadians, fresh leafy vegetables were selected for targeted surveys. Over the course of this study (April 1, 2014 to March 31, 2016), a total of 2233 samples of leafy vegetables were collected from retail locations in 11 cities across Canada and tested for parasites of concern (C. cayetanensis, Cryptosporidium spp., T. gondii, and Giardia spp.). Parasite DNA of Cryptosporidium spp., and T. gondii were detected in 0.1% (2/2233) and 0.1% (3/2233) of the leafy vegetable samples, respectively. C. cayetanensis and Giardia spp. DNA were detected in 0.3% (6/2233) and 0.7% (15/2233) of the leafy vegetable samples respectively.

Due to the perishable nature of the products and the time elapsed between sample pick up and the completion of analysis, the implicated products were no longer available on the market when the parasite DNA was detected and as such, no direct product action was possible. In addition, the analytical methods used to analyse the samples are unable to discriminate between infectious and non-infectious parasites, rendering it difficult to determine if these products represented an immediate health risk. There were no reported illnesses linked to the parasite positive samples.

Overall, our survey results suggest that most fresh leafy vegetables were free of parasitic contamination. Regardless, fresh leafy vegetables are a known potential source of foodborne illness causing parasites and as such, safe handling practices are recommended for producers, retailers and consumers.

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