High frequency of DNA detection of Toxoplasma gondii and zoonotic Sarcocystis spp. in ready-to-eat meat products purchased in Switzerland

Toxoplasma gondii and Sarcocystis spp. are globally distributed, intracellular, cyst-forming coccidian parasites that infect a wide range of animal species, and humans. These protozoan parasites have indirect life cycles and can be transmitted to hosts through food sources, such as infected meat. Resulting infections may pose serious health risks, especially for immunocompromised individuals and developing foetuses. While their prevalence in Switzerland has been studied serologically and molecularly in live animals or after necropsy or slaughter, there are no studies on ready-to-eat (RTE) meat products. This study aimed to assess the presence of these parasites in RTE meat products sourced from Swiss supermarkets, retail stores and local butcher shops. A total of 201 RTE meat products consisting of pork, beef, poultry, game, and equine meat, as well as mixes thereof, were tested. Hundred-gram samples were homogenized, followed by a sequencespecific magnetic capture and real-time PCR for T. gondii DNA, and a crude DNA extraction and PCR-Sanger sequencing for Sarcocystis spp. For two zoonotic species (S. suihominis and S. hominis), additional PCRs were performed. Furthermore, the homogenates were analyzed for Sarcocystis spp. cysts by stereomicroscopy. Variables associated with the presence of these parasites were identified by multivariable LASSO regression. Toxoplasma gondii DNA was detected in 14.9 % (30/201) of the samples, while Sarcocystis spp. DNA was present in 58.2 % (117/201). Zoonotic S. suihominis DNA was found in 3.2 % (4/125) of the samples containing pork, and S. hominis DNA in 29.6 % (24/81) of the samples containing beef. No viable cysts were observed in any sample. The presence of T. gondii DNA was associated with the variables pork, salami-like products, and wild boar. Sarcocystis spp. DNA was positively associated with beef and salami-like products, and negatively with chicken and Swiss pork. Sarcocystis hominis was positively associated with Swiss beef. These findings reveal a notable rate of RTE meat products positive for zoonotic parasites, suggesting a potential public health risk. Further research is needed to evaluate their role in transmission to humans.