Discussion
Taenia multiceps circulates in a two-host life cycle including various canids, but primarily dogs, as definitive hosts and a wide range of intermediate hosts, particularly sheep and goats, which typically carry the larval stage (coenurus cerebralis) in the CNS. However, the coenuri have been occasionally observed outside the CNS (e.g., subcutaneous tissues), particularly in goats. Based on a limited number of analyzed isolates, genetic variants and/or strains of
T. multiceps have been proposed for extra-CNS coenuri, and in a specific animal species from a certain geographical region (e.g., cattle from Turkey). The present study provides the first comprehensive genetic analysis for all published
T. multiceps nucleotide sequences from various definitive and intermediate hosts. A total of 233 partial cox1 nucleotide sequences that represented 442
T. multiceps isolates (cerebral and non-cerebral) deposited in GenBank were collected after consulting the NCBI website. The retrieved sequences were aligned using the software MEGA6, which was also used to construct the phylogenetic trees. Various genetic indices as well as intra- and inter-population variations were calculated using the software DnaSp6. Haplotype networks were constructed using PopArt1.7. The analyzed sequences displayed 51 haplotypes with 59-point mutations, of which 28 were parsimony informative.
High haplotype (0.859 ± 0.00009 SD) and low nucleotide (0.00915 ± 0.00032 SD) diversities were detected. Significant negative values for the neutrality indices; Tajima`s D and Fu`s Fs tests were also determined, which are suggestive for the recent population expansion. Six geographic populations (China, Iran, Turkey, Greece, Italy and Egypt) were defined suitable for population analyses. Five major haplotypes were noticed; 2 of them as well as their associated minor haplotypes were common in China, Iran and Turkey. The 3 other haplotypes and their adjoining minor haplotypes were prevalent in Italy and Egypt. This pattern of haplotype distribution could be related to some factors that probably include the geographical neighborship; for example, Iran and Turkey. However, haplotypes from Greece do not follow this assumption and circulate worldwide, which was then confirmed after population structure analyses; the calculated pairwise distance and gene flow values for the Greek population in comparison to the other populations were comparable. The haplotype networks revealed no specific patterns for distribution of the detected haplotypes among various infected hosts, and the wild life shared the same haplotypes with sheep and goats. In addition, our analyses underline the genetic analogy between the cerebral and non-cerebral coenuri isolates. Overall, the existence of genetic variants in
T. multiceps is highlighted, but due to the limited number of sequenced isolates of these variants, the relationship of these variants to a specific phenotypic character (e.g., non-cerebral locations of the coenuri) cannot be confirmed.
