Detection of Cyclospora cayetanensis, Cryptosporidium spp., and Toxoplasma gondii on imported leafy green vegetables in Canadian survey

Abstract

A national survey was performed to determine the prevalence of Cyclospora cayetanensis, Cryptosporidium spp., and Toxoplasma gondii in leafy green vegetables (leafy greens) purchased at retail in Canada. A total of 1171 samples of pre-packaged or bulk leafy greens from domestic (24.25%) and imported (75.75%) sources were collected at retail outlets from 11 Canadian cities between April 2014 and March 2015. The samples were processed by shaking or stomaching in an elution buffer followed by oocyst isolation and concentration. DNA extracted from the wash concentrates was tested for C. cayetanensis, Cryptosporidium spp., and T. gondii using our previously developed and validated 18S rDNA qPCR assay with a universal coccidia primer cocktail and melting curve analysis. Test samples that amplified and had a melting temperature and melt curve shape matching the C. cayetanensis, C. parvum, C. hominis, or T. gondii controls were sequenced to verify the presence of target DNA. Cyclospora cayetanensis was identified in 3 samples of arugula (USA origin), 1 sample of baby arugula (USA and Mexico), 1 sample of baby spinach (USA), and 1 sample of spring mix (USA). Toxoplasma gondii was identified in 3 samples of baby spinach (origin USA or USA and Mexico), and C. parvum was identified in 1 sample of arugula (USA) and 1 sample of baby spinach (USA and Mexico). To our knowledge, this is the first finding of T. gondii in leafy greens in North America. The results of this survey will be useful for assessing the risk of foodborne parasites on ready-to-eat leafy greens that are available at retail. Keywords: Leafy green vegetables, Food safety, Cyclospora, Cryptosporidium, Toxoplasma, qPCR melt curve analysis