The technique of isoenzyme electrophoresis was applied to Japanese wild populations of Taenia taeniaeformis (isolated from Norway rats) and three laboratory reared isolates (KRN isolated from a Malaysian Norway rat, BMM from a Belgian house mouse and ACR from a Japanese gray red-backed vole). The average heterozygosities of Japanese wild populations were fairly small and total genetic variability was 0.0499. The genetic make-up of T. taeniaeformis in Norway rats was rather uniform in the whole of Japan. In KRN isolate, each of all 10 loci examined possessed the allele which was predominant in Japanese wild populations. Similarly, each of 9 loci in BMM isolate possessed the same alleles, but one of 2 alleles at HK locus was different from that in the others. T. taeniaeformis parasitizing house mice and rats were considered to be genetically closely related to each other. In ACR isolate, 7 out of 10 loci possessed different alleles from those in the other populations. It was considered that ACR isolate was genetically distant and its phylogenetic origin in Japan should be different from worms parasitizing Norway rats.
The intraspecific variation of four laboratory-reared isolates of Taenia taeniaformis the SRN and KRN isolates from Norway rats, Rattus norvegicus, captured in Japan and Malaysia, respectively; the BMM isolated from a house mouse, Mus musculus, captured in Belgium; and the ACR isolate from a gray red-backed vole, Clethrionomys rufocanus bedfordiae, captured in Japan was examined by various criteria. Eggs of each of the four isolates were orally inoculated into several species of intermediate host. They were most infective to the rodent species from which the original metacestode of each isolate had been isolated in the field, and only the ACR isolate was infective to the gray red-backed vole. Although little difference was found between the SRN, KRN, and BMM isolates by the other criteria, including the morphology of rostellar hooks, the protein composition of the metacestode, and restriction endonuclease analysis of DNA, the ACR isolate was clearly different from the others. It was considered that the ACR isolate was independent as a strain distinct from the other three isolates.