Abstract
Background: Most Toxoplasma gondii infections in
humans are considered foodborne, but the relative
importance of the various routes of infection is largely
unknown. Consumption of green produce contaminated
with T. gondii oocysts has been identified as a
possible source. Aim: We aimed to estimate the
occurrence and prevalence of T. gondii oocysts in
commercially available ready-to-eat (RTE) salad mixes
in 10 European countries. Methods: A real-time PCRbased method for oocyst detection was developed
and optimised by two laboratories and validated in
an interlaboratory test. This detection method and a
harmonised sampling strategy were applied in a multicountry study. Multivariable logistic regression was
used to investigate risk factors for oocyst contamination of RTE salad. Results: The real-time PCR method
had a detection limit of 10 oocysts per 30 g of salad.
We collected 3,329 RTE salad samples (baby leaf and
cut leaf mixes) from October 2021 to September 2022.
The prevalence of T. gondii oocyst contamination
was 4.1% (95% confidence interval (CI): 3.4–4.8%;
n=3,293). In multivariable regression analysis,
winter season, sampling and packaging of salad in
Northern Europe and production of salad in Western
Europe were associated with detection of T. gondii,
with no statistically significant differences between
salad types. Conclusion: We estimated the prevalence
of T. gondii oocysts in RTE leafy green salads using a
validated and standardised procedure to assess the
potential risk for human infection; highlighting the
need to address this risk at each critical point of the
salad production chain.