In the first-ever large-scale study of its kind, Canadian researchers have tested how clean pre-washed packages of leafy greens really are, and found parasites in dozens of samples purchased in Ontario.
Looking at 544 samples of store-bought, pre-washed salads, researchers from Health Canada and the Public Health Agency of Canada found nearly one-tenth of the samples were contaminated with either cyclospora, cryptosporidium or giardia — parasites that can cause intestinal illness, such as diarrhea.
“In the present study, a relatively high prevalence of all three parasites was found in packaged, ready-to-eat leafy greens,” said the study, published recently in the Journal of Food Protection.
To conduct the study, the research team purchased a total of 544 prewashed salad samples between April 2009 and March 2010 — all in the Waterloo, Ont. area. After testing the samples, the team found:
- Nine (1.7%) of the samples tested positive for cyclospora;
- 32 (5.7%) of the samples tested positive for cryptosporidium;
- 10 (1.8%) of the samples tested positive for giardia.
