Despite these assay limitations the results of this survey p

Despite these assay limitations, the results of this survey provide a snapshot of the prevalence of protozoan oocyst species of human health concern in domestic and imported leafy greens in Canada, which may assist in developing food safety guidelines, pre- and post-harvest control measures, and risk analysis. In addition, these findings should be considered in the design and direction of future monitoring surveys of imported leafy greens and other fresh produce, and when providing advice to consumers. Guidelines on foodborne parasites are currently being developed by Codex Alimentarius. Although no protozoan oocysts were detected in domestic leafy greens, we tested fewer of these samples overall. The high number of temporary foreign workers employed in the produce industry from countries where C. cayetanensis is endemic, and the widespread incidence of Cryptosporidium spp. and T. gondii in Canada suggest that domestic leafy greens are not of negligible risk for parasites.
Conflict of interest
Acknowledgments
Introduction Toxoplasma gondii is an important coccidian parasite that has a complex reproductive cycle involving two hosts. Members of the family Felidae are the only known definitive hosts, whereas humans and a wide range of domestic and wild animals are intermediate hosts for this parasite (Dubey, 2010). Infection with T. gondii can cause abortion or neurological symptoms in their intermediate hosts (Gilbert et al., 2000; Sushrut and Davis, 2012). Transmission occurs via consumption of meat or other animal tissues containing tissue cysts of this parasite, or of water or other materials contaminated with sporulated Toxoplasma oocysts. Several serological tests have been developed to detect order Tacrolimus to T. gondii in humans and animals for the detection of infection (Dubey et al., 1995). The modified agglutination test (MAT) is a sensitive and specific method for the detection of T. gondii in a wide range of host species, and is simple, rapid and of relatively low cost compared to other serological tests (Dubey, 1997; Hill et al., 2006; Dubey, 2010). However, the routine use of MAT for the diagnosis of T. gondii infection can be challenging because of the lack of readily available commercial kits and the tachyzoite-derived antigen. Typically, tachyzoites used for MAT antigen are generated by intraperitoneal propagation in mice (Desmonts and Remington, 1980). To reduce the use of live animals, antigen required for the assay in this study was prepared from tachyzoites grown in cell culture. Performance of the test was assessed using samples of serum, whole blood or meat juice from experimentally infected pigs and cats, and naturally infected cats, sheep and 20 species of wild animals.
Materials and methods
Results The serum samples from pigs experimentally infected with T. gondii were negative at 0 and 7 DPI by the in-house MAT and the commercial MAT kit which was used as the gold standard. By 11–14 DPI, all inoculated pigs were positive by both tests at a 1:25 serum dilution and remained positive for the duration of the respective experiments until euthanasia (35–66 DPI). All samples of meat juice collected from each of the three muscle sites of experimentally-infected pigs also tested positive at 1:10 and 1:25 dilutions by both tests. Samples of all negative controls used for this study by both methods yielded negative results. Similar results were obtained with serum samples collected from the experimentally infected cats. For these animals, all samples collected at 0 DPI tested negative, whereas those collected post-inoculation at euthanasia tested positive. No significant difference was detected between positive and negative results when comparing MAT results for all tested serum and meat juice samples collected from experimentally infected pigs and cats obtained by either test, using Pearson Chi-square test (P<0.05). The relative specificity and sensitivity of the in-house test were both 100%, compared to the commercial MAT kit. Thus, excellent agreement (k=1.0) was observed between results from samples of serum and/or meat juice from experimentally infected pigs and cats tested by in-house MAT or commercial MAT kit. The results of this study are summarized in Table 1. ROC curve analysis, using the MAT kit result as the gold standard, showed that the in-house MAT performed similarly with area under the curve of 1.0 (Fig. 2).