Investigation of persistence of infectious Toxoplasma gondii in raw sausages using in-house developed and validated real time-PCR

The question, if and to what extent raw-sausage-products represent a possible source of infection for the globally distributed and potentially health-threatening toxoplasmosis gave reason for this study. For this, the survival capability of Toxoplasma gondii in relation to the raw-sausage-manufacturing-process including different ripening-processes was investigated. To enable a fast and reliable parasite-detection, a real time-PCR-system based on a specific 529-bp-fragment of T. gondii and an internal amplification control (IAC) was developed and established. The applicability was tested in various experiments where T. gondii-tachyzoites were mixed into different types of raw-sausages and then investigated by using the real time-PCR-system. The latter was also used to investigate the possible infection-risk of raw-sausages. For this, two pigs were intravenously infected with T. gondii-tachyzoites and after having reached the typical slaughtering age, their meat was manufactured to different raw-sausage-products ("Mett"- and "Teewurst" as well as "Salami"). In order to prove the potential infectivity of these products under conditions close to reality, sausages in different ripening stages were fed to laboratory mice. The animals' organs (brain, heart and spleen) were examined employing the real time-PCR. T. gondii-DNA was detected in four out of 288 (1.4%) mice indicating that marketable raw-sausage-products generally bear a risk for consumers. However, the probability of an infection seems to be quite marginal.