Morphological and Molecular Identification of Spirometra Tapeworms (Cestoda: Diphyllobothriidae) from Carnivorous Mammals in the Serengeti and Selous Ecosystems of Tanzania

Abstract

Spirometra tapeworms (Cestoda: Diphyllobothriidae) collected from carnivorous mammals in Tanzania were identified by the DNA sequence analysis of the mitochondrial cytochrome c oxidase subunit 1 (cox1) and internal transcribed spacer 1 (ITS1), and by morphological characteristics. A total of 15 adult worms were collected from stool samples and carcasses of Panthera leo, Panthera pardus, and Crocuta crocuta in the Serengeti and Selous ecosystems of Tanzania. Three Spirometra species: S. theileri, S. ranarum and S. erinaceieuropaei were identified based on morphological features. Partial cox1 sequences (400 bp) of 10 specimens were revealed. Eight specimens showed 99.5% similarity with Spirometra theileri (MK955901), 1 specimen showed 99.5% similarity with the Korean S. erinaceieuropaei and 1 specimen had 99.5% similarity with Myanmar S. ranarum. Sequence homology estimates for the ITS1 region of S. theileri were 89.8% with S. erinaceieuropaei, 82.5% with S. decipiens, and 78.3% with S. ranarum; and 94.4% homology was observed between S. decipiens and S. ranarum. Phylogenetic analyses were performed with 4 species of Spirometra and 2 species of Dibothriocephalus (=Diphyllobothrium). By both ML and BI methods, cox1 and ITS1 gave well supported, congruent trees topology of S. erinaceieuropaei and S. theileri with S. decipiens and S. ranarum forming a clade. The Dibothriocephalus species were sisters of each other and collectively forming successive outgroups. Our findings confirmed that 3 Spirometra species (S. theileri, S. ranarum, and S. erinaceieuropaei) are distributed in the Serengeti and Selous ecosystems of Tanzania.

Keywords: ITS1; Spirometra erinaceieuropaei; Spirometra ranarum; Spirometra theileri; cox1.

Fig. 1

Map of the Serengeti ecosystem in Tanzania indicating the locations of 5 areas where 15 adult worms were collected in 2011–2018.

Fig. 2

Mature proglottids of Spirometra species collected from carnivorous mammals in the Serengeti and Selous ecosystems of Tanzania (stained with acetocarmine). (A) S. erinaceieuropaei. (B) S. ranarum. (C) S. theileri. Characteristic genital organs, cirrus sac (CS), genital pore (GP), ovary (OV), vaginal pore (VP), and uterus (U) are designated in (A–C).

Fig. 3

Phylogenetic trees of Spirometra species based on mitochondrial (A) cox1 and (B) ITS1 sequences. Numbers above the branches represent bootstrap values for trees obtained by maximum likelihood and Bayesian inference.