As clinical toxoplasmosis is not considered a problem in pigs, the main reason to implement a control strategy against Toxoplasma gondii (T. gondii) in this species is to prevent or reduce the establishment of T. gondii tissue cysts in pork, and consequently reduce the risk of the parasite entering the human food chain. Consumption of T. gondii tissue cysts from raw or undercooked meat is one of the main sources of infection for humans, with infected pork being considered a high risk. This study incorporates a mouse bioassay with molecular detection of T. gondii DNA to study the effectiveness of a vaccine (incomplete S48 strain) in its ability to reduce tissue cyst burden in pigs, following oocyst (M4 strain) challenge. The results from the mouse bioassay show that 100% of mice which had received porcine tissues from vaccinated and challenged pigs survived compared with 51.1% of mice which received tissues from non-vaccinated and challenged pigs. The presence (or absence) of T. gondii DNA from individual mouse brains also confirmed these results. Overall this research indicates a reduction in the load of viable T. gondii tissue cysts within tissues from pigs which have been previously vaccinated with the S48 strain. In addition, the study demonstrated that the main predilection sites for the parasite were found to be brain and highly vascular muscles (such as tongue, diaphragm, heart and masseter) of pigs, while meat cuts used as human food such as chop, loin, left tricep and left semitendinosus, had a lower tissue cysts burden. The results from this work begin to answer the question recently raised in a report by the Advisory Committee on the Microbiological Safety of Food (ACMSF), which highlighted that it was unknown whether the live attenuated vaccine (S48), already used against T. gondii induced ovine abortion, was effective at reducing tissue cysts within commercial livestock species. These promising results highlight the potential of S48 for reducing the number of T. gondii tissues cysts in pork and improving food safety.