Evolution of codon usage in genomes and its impact on the host.

The beef tapeworm, also known as , is a zoonotic tapeworm from the genus in the order Cyclophyllidea. is a food-borne zoonotic parasite with a worldwide distribution. It poses serious health risks to the host and has a considerable negative socioeconomic impact. Previous studies have explained the population structure of within the evolutionary time scale and adaptive evolution. However, it is still unknown how synonymous codons are used by . In this study, we used 90 strains, applying the codon usage bias (CUB). Both base content and relative synonymous codon usage (RSCU) analysis revealed that AT-ended codons were more frequently used in the genome of . Further low CUB was observed from the effective number of codons (ENC) value. The neutrality plot analysis suggested that the dominant factor of natural selection was involved in the structuring of CUB in . Further analysis showed that has adapted host-specific codon usage patterns to sustain successful replication and transmission chains within hosts ( and ). Generally, both natural selection and mutational pressure have an impact on the codon usage patterns of the protein-coding genes in . This study is important because it characterized the codon usage pattern in the genomes and provided the necessary data for a basic evolutionary study on them.