Experimental observation of the infectivity of three different Trichinella isolates in mice.

Objective To observe the infectivity of three different geographical isolates of Trichinella spiralis from Heilongjiang,Henan,and Yunnan Provinces in mice. Methods Thirty male Kunming mice were randomly divided into 3 groups (10 mice per group). Each group was orally inoculated with the muscle larvae of trichinella spiralis from one of the three different isolates. Each mouse received 200 motile larvae. The diaphragmatic muscle of the mouse was collected and observed to see if cysts had formed in order to determine when they had formed. The number of larvae in 50 mg of diaphragmatic muscle was counted. Thirty cysts of each isolate were randomly chosen to measure length and width,and then the cyst index of morphology was calculated (length/width). All motile larvae from each mouse were collected and counted. Then,the value of RCI was calculated. The results were compared among the three isolates. Results Cyst formation for the Heilongjiang isolate was 53 days post-infection,which was longer than that for the Henan and Yunnan isolates (40 days post-infection for both). The number of larvae in 50 mg of muscle from mice given the three isolates was 91.8±5.119,301.8±14.839,and 176.4±7.127. There was a significant difference between the cyst index of morphology for the Henan isolate (2.385±0.335) and that of the other two isolates (1.883±0.401,2.360±0.624) (P0.05). The difference between the latter 2 isolates was also significant. The RCI for the Henan isolate was highest (297.500±12.179),followed by the Heilongjiang isolate 66.204±1.569 and Yunnan isolate (154.800±3.894). There was a significant difference among the groups (P0.05). Conclusion The Henan isolate of T. spiralis had a higher level of infectivity than 2 other isolates.