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Abstract

Background

Most 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 oocysts has been identified as a possible source.

Aim

We aimed to estimate the occurrence and prevalence of oocysts in commercially available ready-to-eat (RTE) salad mixes in 10 European countries.

Methods

A real-time PCR-based 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 multi-country 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 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 , with no statistically significant differences between salad types.

Conclusion

We estimated the prevalence of 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.

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A corrected article has been published for this content:
Author’s correction for Euro Surveill. 2025;30(22)
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2025-06-05
2025-06-28
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Molecular detection of Toxoplasma gondii in ready-to-eat salad mixes: multi-country survey using a validated and harmonised standard operating procedure, Europe, 2021 to 2022
<p class="citation"> <span>Citation style for this article:</span> <span class="meta-value authors"> <a href="/search?value1=Rafael+Calero-Bernal&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Calero-Bernal Rafael</a>, <a href="/search?value1=Martha+Betson&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Betson Martha</a>, <a href="/search?value1=Iva+Slana&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Slana Iva</a>, <a href="/search?value1=Barbora+Bartosova&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bartosova Barbora</a>, <a href="/search?value1=Gianluca+Marucci&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Marucci Gianluca</a>, <a href="/search?value1=Alessia+Possenti&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Possenti Alessia</a>, <a href="/search?value1=Gema+%C3%81lvarez-Garc%C3%ADa&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Álvarez-García Gema</a>, <a href="/search?value1=Nadja+Bier&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Bier Nadja</a>, <a href="/search?value1=Anne+Mayer-Scholl&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Mayer-Scholl Anne</a>, <a href="/search?value1=Rebecca+P+Berg&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Berg Rebecca P</a>, <a href="/search?value1=Umer+Chaudhry&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Chaudhry Umer</a>, <a href="/search?value1=Nadia+M+L%C3%B3pez-Ure%C3%B1a&option1=author&noRedirect=true" class="nonDisambigAuthorLink">López-Ureña Nadia M</a>, <a href="/search?value1=Weronika+Piotrowska&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Piotrowska Weronika</a>, <a href="/search?value1=Jacek+Sroka&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Sroka Jacek</a>, <a href="/search?value1=Gro+S+Johannessen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Johannessen Gro S</a>, <a href="/search?value1=Rebecca+Davidson&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Davidson Rebecca</a>, <a href="/search?value1=Filip+D%C3%A1mek&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Dámek Filip</a>, <a href="/search?value1=Radu+Blaga&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Blaga Radu</a>, <a href="/search?value1=Sandra+Thoumire&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Thoumire Sandra</a>, <a href="/search?value1=Barbora+Zalewsk%C3%A1&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Zalewská Barbora</a>, <a href="/search?value1=Helga+C+Waap&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Waap Helga C</a>, <a href="/search?value1=Pikka+Jokelainen&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Jokelainen Pikka</a>, <a href="/search?value1=Marco+Lalle&option1=author&noRedirect=true" class="nonDisambigAuthorLink">Lalle Marco</a></span>. Molecular detection of Toxoplasma gondii in ready-to-eat salad mixes: multi-country survey using a validated and harmonised standard operating procedure, Europe, 2021 to 2022. <a href="/content/ecdc">Euro Surveill.</a> 2025;30(22):pii=2400594. <a href="https://doi.org/10.2807/1560-7917.ES.2025.30.22.2400594" title="doi link" target="_blank">https://doi.org/10.2807/1560-7917.ES.2025.30.22.2400594</a> <span class="ES_Article_citation"> <span class="generated">Received</span>: 06 Sept 2024;&nbsp;&nbsp; <span class="generated">Accepted</span>: 27 Jan 2025 </span> </p>
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