1. A lower pathogenicity of the Kenya strain of T. spiralis was substantiated in mice as compared with our laboratory strain; infection with a dose of 2,000 larvae from the laboratory strain resulted in the death of all the animals, whereas 7 out of 10 and 6 out of 20 mice infected with the Kenya strain survived.
2. The reason for the lower pathogenicity of the Kenya strain is related to its weaker infectivity; after the infection with 200 larvae of the Kenya strain the number of muscle larvae produced was half (on average 17,595 larvae) that of the laboratory strain (average 32,792 larvae).