Genetic similarity between cysticerci of Taenia solium isolated from human brain and from pigs.

Mitochondrial (mt) cox1 and ribosomal ITS1 DNA sequences from Taenia solium cysticercus isolates from pigs and cysticerci (racemose and cellulose types) from patients with neurocysticercosis were amplified by the polymerase chain reaction (PCR). The amplicons were sequenced in order to determine the genetic relationship between these types of cysticerci. Phylogenetic trees were constructed and evolutionary distances were calculated. ITS1 and mt cox1 cysticerci sequence data were compared with previously published Taenia spp. sequences. The variation in the ITS1 and cox1 sequences of samples collected from Mexico was minimal, regardless of geographical origin, size or colour of cysticerci from either pigs or human brain. These results suggest that the racemose and cellulose types represent genetically identical metacestodes of T. solium. Alignment of the mt cox1 sequences of the Mexican samples with sequences of other Taenia taxa showed that most were very similar to T. solium from Mexico and T. solium from Colombia; one T. solium Mexican isolate and Taenia hydatigena were placed in the same group close to Taenia crassiceps. The ITS1 sequences for the Mexican T. solium samples indicated the majority were in the same group as the Latin American T. solium. Two Mexican T. solium samples and T. solium from Philippines were placed together in a different group.