Freezing times and temperatures required to kill cysticerci of Taenia saginata in beef

Calves were given viable Taenia saginata eggs by stomach tube and slaughtered 12, 16 or 24 weeks later. The cysticerci-infected carcasses were frozen at six different temperatures for variable lenghts of time. Meat samples were then allowed to thaw at room temperature and the cysticerci were manually isolated. Criteria of viablity of the metacestodes were scolex evagination and peristaltic movements of the bladder wall. Sixteen and especially 12-week-old cysticerci were much more susceptible to the lethal effects of freezing than were 24-week-old cysticerci. The time and temperature combinations required to ensure death of all cysticerci were 360 h at ?5°C, 216 h at ?10°C, and 144 h at ?15°C or lower.