Survival of Toxoplasma gondii tachyzoites in simulated gastric fluid and cow's milk

- Tachyzoites survive and retain infectivity in near neutral SGF for min. 90 min.
- Addition of milk to SGF extends survival of tachyzoites.
- T. gondii infection by milk is supported to be likely by the results.

The protozoan parasite Toxoplasma gondii is one of the most important food-related pathogens worldwide. Besides contact to oocysts or ingestion of tissue cysts mainly by consumption of raw or undercooked meat from infected animals, raw milk is considered to be a risk factor and possible route of transmission for tachyzoites. This stage of the parasite is usually very sensitive to acidic pH and, therefore, considered unlikely to survive stomach passage. However, tachyzoites were shown to survive for several days in milk and there are also reports on transmission of toxoplasmosis via milk. Thus, the aim of the study was to examine retention of infectivity of tachyzoites in simulated gastric fluid (SGF) of different acidity and to elucidate whether addition of different shares of milk would affect survival of the parasites. Tachyzoites were exposed to SGF of pH 2.0 through 6.0 and their remaining infectivity was examined by cell culture. Furthermore, the impact on survival was investigated in different admixtures of milk to the SGF (25, 50, 75%) as well as in pure milk. Tachyzoites were shown to retain infectivity in SGF of pH 5.0 and 6.0 for at least 90 min while they were more sensitive to lower pH values. Admixture of milk resulted in extension of survival. The results support the hypothesis of tachyzoites to survive stomach passage and their retention of infectivity.