Influence of the low temperature on the viability and infectivity of Trichinella spiralis muscle larvae

Objective: To investigate the influence of the low temperture(-18℃ and -72℃) on the viability and infectivity of Trichinella spiralis muscle larvae.Methods: The viability of the Trichinella spiralis muscle larvae in mice skeletal muscle were observed after -18 and -72℃ of freezing.Fifty-five mice were infected with 300 muscle larvaes treated with low temperature(-18 and -72℃) by oral.The muscle larvae in mice was collected after 35 d of infection,the reproductive capacity index(RCI) of which was determined.Results: The death rate of the muscle larvae stored at the -18℃ for 0 h,6 h,12 h,24 h,36 h and 48 h were 0.00%,6.30%,18.23%,35.81%,74.60% and 100.00%.The death rate of the muscle larvae stored at the -72℃ for 0 min,15 min,45 min and 60 min were 0.00%,21.21%,57.11%,86.24% and 100.00%,respectively.The death rate of the muscle larva stored at -18℃ and -72℃ increased with the prolonging of the storing time(P<0.01).The RCI of the muscle larvae stored at -18℃ for 0 h,6 h,12 h,24 h and 36 h were(163.70±10.70),(126.38±6.90),(68.58±4.83),(12.58±1.77) and(5.77±0.77),respectively,and the difference of which was statistically significant(P<0.01).The RCI of the muscle larva stored at -72℃ for 0 min,15 min,30 min,45 min,were(163.70±10.70),(18.19±2.15),(8.83±1.39) and(3.10±0.26),respectively,and the difference of which was statistically significant(P<0.01).The RCI of the muscle larva stored at the -18℃ or -72℃ decreased with the prolonging of the storing time(P<0.01).Conclusions: Cryopreservation can lead to the decreasing of viability and infectivity of Trichinella spiralis muscle larvae in Henan.The muscle larvae stored at the 18℃ for 48h or -72℃ for 60 min can be completely inactivated.