BackgroundMost 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.AimWe aimed to estimate the occurrence and prevalence of T. gondii oocysts in commercially available ready-to-eat (RTE) salad mixes in 10 European countries.MethodsA 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.ResultsThe 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.ConclusionWe 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.

Animal Health and Zoonoses Research Group Animal Health Department Faculty of Veterinary Sciences Complutense University of Madrid Madrid Spain

Anses INRAE Ecole Nationale Vétérinaire d'Alfort Laboratoire de Santé Animale BIPAR Maisons Alfort France

Department of Biological Safety Unit Diagnostics Pathogen Characterization Parasites in Food German Federal Institute for Risk Assessment Berlin Germany

Department of Comparative Biomedical Sciences School of Veterinary Medicine University of Surrey Guildford the United Kingdom†

Department of Infectious Diseases Istituto Superiore di Sanità Rome Italy

Department of Microbiology and Antimicrobial Resistance Veterinary Research Institute Brno Czechia

Department of Parasitology and Invasive Diseases Bee Diseases and Aquatic Animal Diseases National Veterinary Research Institute Pulawy Poland

Laboratory of Parasitology Department of Bacteria Parasites and Fungi Statens Serum Institut Copenhagen Denmark†

Laboratory of Parasitology The National Institute for Agricultural and Veterinary Research Oeiras Portugal

Lewyt College of Veterinary Medicine Long Island University New York New York the United States†

Microtech S R L Moca Espaillat Dominican Republic

Secretariat for Infectious Disease Preparedness and One Health Statens Serum Institut Copenhagen Denmark

Section for Food Safety and Animal Health Research Norwegian Veterinary Institute Ås Norway

Section for Food Safety and Animal Health Research Norwegian Veterinary Institute Tromsø Norway

University of Agricultural Sciences and Veterinary Medicine Cluj Napoca Romania

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