Studies on the freezing resistance of different Trichinella isolates

Objective To observe the freezing resistance of different Trichinella isolates.Methods Seventy-five male Kunming mice were randomly divided into 3 groups(25 mice per group).Each group was infected with Henan and Yunnan isolates of Trichinella spiralis(T1)as well as T.nativa(T2)stored at-18℃ for different time,respectively.Each mouse was orally inoculated with 300 muscle larvae.All infected mice were slaughtered at 42 days post-infection.The muscle larvae were collected after all the skeletal muscles were digested,and reproductive capacity index(RCI) were determined.Results The RCI of Henan isolate of T.spiralis stored at-18℃ for 0,6,12 h was 91.4,0.03 and 0,respectively(χ2= 26.453,P0.05).The RCI of Yunnan isolate placed at-18℃ for 0,6,12,24 h was 235.6,0.04,0.01 and 0,respectively(χ2= 21.115,P0.05).The RCI of T.nativa freezed at-18℃ for 0,6,12,24,48 h was 34.6,26.8,21.9,10.8 and 7.4,respectively(F=8.505,P0.05).Conclusions The resistance to freezing of Henan and Yunnan isolates of T.spiralis was lower,their infectivity has completely lost following storage at-18℃ for 12 and 24 h;resistance to freezing of T.nativa was higher,it remains infective after storing at-18℃ for 48 h.