The effect of temperature and time on the viability of Taenia solium metacestodes in pork

Objective: Taenia solium taeniosis is a growing health problem in large parts of the world including Sub-Saharan Africa. Humans are infected by eating undercooked pork with T. solium metacestodes, which cause taeniosis. The aim of the present study was to assess the effect of increasing temperatures on T. solium metacestode viability in pork. Methods: Heavily T. solium infected pieces of pork were cooked in a water-bath at five different temperatures (40 degrees C, 50 degrees C, 60 degrees C, 70 degrees C and 80 degrees C) for 10-60 min. At each temperature/time point, five 5x5x5 cm pieces of pork fitted with thermometers at the core were placed in the water-bath. Controls were kept at 5 degrees C throughout exposure. After exposure, approximately 100 intact metacestodes were harvested and after a maximum of 6 h incubation at 37 degrees C in a culture media consisting of 50% porcine bile and 50% saline, the metacestodes were evaluated for viability. Results: The metacestodes were fully viable after cooking at a core temperature of 40 degrees C for up to an hour. The metacestodes were non-viable after cooking for > 40 min at a core temperature over 50 degrees C. All metacestodes were dead after cooking for 30 min at a core temperature of 60 degrees C; at 70 degrees C, non-viability was found after 20 min and all metacestodes were dead after 10 min cooking at 80 degrees C. Conclusion: Findings showed that pork pieces cooked at > 80 degrees C for > 10 min proved safe for human consumption. This means that dishes consisting of pork pieces in sizes not greater than a 5 cm cube which are immersed in continuously boiling water for at least 10 min would be safe to eat. However, pork deep-fried in oil may entail a risk due to generally shorter cooking time. More research on the cooking practises is needed in order to produce safe guidelines for risk-free pork consumption.