Southeast Asian J Trop Med Public Health

Complete nucleotide sequences of the mitochondrial cytochrome b (Cytb) and cytochrome c oxidase subunit 1 (CO1) genes from various isolates of Taenia solium were examined. Eleven isolates were analyzed; two isolates from China, two isolates from Indonesia, one isolate each from India, Thailand, Mexico, Ecuador, Peru, Mozambique and Tanzania. In both genes, two isolates from Indonesia shared the same sequences. Similarly, the isolate from Mexico shared same sequences with that from Peru, and the isolate from Mozambique shared same sequences with that from Tanzania. Phylogenetic trees inferred from different mitochondrial genes yielded almost the same topology. Both the UPGMA and NJ-trees were also very similar. These trees indicate that T. solium may be diverged to 2 genetic groups; isolates from Asia form one group and isolates from Africa and Latin America belong to the other. It seems that T. solium prevalent in Africa and in Latin America shares the related origin and has recently been introduced to each area, perhaps with domestic pigs or human. from Asia, that is, two from China (TsolCHI1, TsolCHI2), two from Indonesia (TsolIRI1, TsolIRI2), one from India (TsolIND), and one from Thailand (TsolTHA). Three isolates were collected from Central and Latin America, one each from Mexico (TsolMEX), Ecuador (TsolECU), and Peru (TsolPER). Two isolates were collected from Africa, one from Mozambique (TsolMOZ) and one from Tanzania (TsolTAN). Geographical origins, hosts and stages of the isolates analyzed are presented in Table 1. DNA extraction, amplification and sequencing We determined the complete sequences of two mitochondrial genes, Cytb and CO1. The lengths of Cytb and CO1 genes are 1,068 bp and 1,620 bp, respectively. DNA from each sample was extracted with commercial available DNA Isolation Kit. DNA sequencing was performed by Dye Terminator Cycle Sequencing Kit and Model 377 DNA Sequencing System. Phylogenetic analysis DNA sequences were aligned for the phylogenetic analyses using the CLUSTAL W computer program (Thompson et al, 1994). The evolutionary distances were computed by Kimura’s two-parameter method (Kimura, 1980). The phylogenetic tree was constructed by the neighborjoining (NJ) method (Saitou and Nei, 1997) and UPGMA using the PHYLIP 3.5c phylogeny package (Felsenstein, 1993). The tree was evaluated using the bootstrap test (Felsenstein, 1985) based on 100 resamplings. Phylogenetic trees were outgroup-rooted using the nucleotide sequences from T. saginata or Echinococcus multilocularis. INTRODUCTION Cysticercosis is one of the most serious larval cestodiases of medical importance in humans and of economic importance in pigs. Now cysticercosis is spreading worldwide, especially in Asia, Africa and Latin America. In order to control the parasitic disease, it is important to know the extent of intraspecific variations because variants may differ in their infectivity or pathogenicity to man and to domestic animals. However, intraspecific variation of T. solium has been rarely discussed. With the development of molecular biology, the sequences of various genes have been used for molecular phylogenetic study. Mitochondrial DNA (mtDNA) is considered one of the best neutral markers for revealing phylogenetic relationships among related groups. This is because mitochondria are maternally inherited, mtDNA evolves fairly rapidly, most of the nucleotide substitutions occur at neutral sites, and mtDNA is unlikely to be responsible for morphological changes (Osawa et al, 1999). In the present study, we examined complete sequences of the mitochondrial cytochrome b (Cytb) and cytochrome c oxidase subunit 1 (CO1) genes from several isolates of T. solium, and inferred the phylogenetic relationships within T. solium in the world. MATERIALS AND METHODS Parasite materials Eleven isolates of T. solium collected from various countries were examined. Six isolates were collected