The plerocercoid larva of the tapeworm Spirometra mansoni can parasitize humans and animals, causing serious parasitic zoonosis. The molecular characteristics and adaptive parasitism mechanism of Spirometra tapeworms are still unknown. In this study, 11 new members of the fatty-acid-binding protein (FABP) family were characterized in S. mansoni. A clustering analysis showed 11 SmFABPs arranged into two groups, and motif patterns within each group had similar organizations. RT-qPCR showed that SmFABPs were highly expressed in the adult stage, especially in gravid proglottid. A high genetic diversity of SmFABPs and relative conservation of FABPs in medical platyhelminthes were observed in the phylogenetic analysis. Immunolocalization revealed that natural SmFABP is mainly located in the tegument and parenchymal tissue of the plerocercoid and the uterus, genital pores, and cortex of adult worms. rSmFABP can build a more stable holo form when binding with palmitic acid to protect the hydrolytic sites of the protein. A fatty acid starvation induction test suggested that SmFABP might be involved in fatty acid absorption, transport, and metabolism in S. mansoni. The findings in this study will lay the foundation to better explore the underlying mechanisms of FABPs involved in Spirometra tapeworms as well as related taxa.

In this study, we report the first complete mitochondrial genome of the tapeworm Nippotaenia mogurndae in the order Nippotaeniidea Yamaguti, 1939. This mitogenome, which is 14,307 base pairs (bp) long with an A + T content of 72.2%, consists of 12 protein-coding genes, 22 transfer RNA (tRNA) genes, two rRNA genes, and two non-coding regions. Most tRNAs have a conventional cloverleaf structure, but trnS1 and trnR lack dihydrouridine arms of tRNA. The two largest non-coding regions, NCR1 (220 bp) and NCR2 (817 bp), are located between trnY and trnS2 and between nad5 and trnG, respectively. Phylogenetic analyses of mitogenomic data indicate that N. mogurndae is closely related to tapeworms in the order Cyclophyllidea.

BACKGROUND: Raillietina species belong to the family Davaineidae, which parasitizes in a wide variety of mammals and birds, causing stunted growth, lethargy, emaciation, and digestive tract obstruction. However, only a limited number of Raillietina species have been identified in wild animals.
METHODS: We analyzed and annotated the complete mitochondrial (mt) genome of a worm from the intestine of a wild pangolin using Illumina sequencing of whole genomic DNA.
RESULTS: These findings showed the presence of two mtDNA sequences in Raillietina sp., designated as mt1 and mt2, with the lengths of 14,331 bp and 14,341 bp, respectively. Both the mts genomes of Raillietina sp. comprised 36 genes, containing 12 protein-coding genes (PCGs), 2 ribosomal RNAs, and 22 transfer RNAs. Gene arrangements of both mt genomes of Raillietina sp. were similar to those of most flatworms, except for taeniids, which shift positions between tRNAL1 and tRNAS2 genes. Twenty of 22 tRNA secondary structures of Raillietina sp. had a typical cloverleaf structure similar to Raillietina tetragona. Sequence differences between the mt1 and mt2 genomes were 4.4%, and this difference arises from the mtDNA heteroplasmic mutations. Moreover, heteroplasmic mtDNA mutations were detected in PCGs, tRNAs, rRNAs, NCRs, and intergenes, but the highest proportion of heteroplasmy of 79.0% was detected in PCGs, indicating the occurrence of mtDNA heteroplasmy in Raillietina sp. To our knowledge, this is the first report of mtDNA heteroplasmy in tapeworm parasites. Phylogenetic analyses of 18S rRNA, ITS2, and 12 PCG sequences demonstrated that the worm was clustered with other Raillietina species in the Davaneidae family.
CONCLUSIONS: We found a novel Raillietina species in wild pangolin with the existence of mitochondrial DNA heteroplasmy. Thus, these findings provide insights into the heterogeneity of the mt genome in parasitic cestodes, and mt genome data contributes to the understanding of pangolin-parasitic cestodes in terms of their molecular biology, epidemiology, diagnosis, and taxonomy.

Taenia pisiformis is one of the most widespread gastrointestinal parasites and its larvae (cysticercosis) causes significant economic loss to rabbit industry. No efficient drug is available for this disease to date. To better understand its genomics, we assembled a 211-Mb high quality genome of T. pisiformis at chromosome level with a scaffold N50 size of 20 Mbp. Totally, 12,097 protein-coding genes was predicted from the genome. Genome-level phylogenetic analysis confirmed the taxonomic affiliations with other tapeworms and revealed that T. pisiformis diverged from its closely related relative T. hydatigena ∼ 14.6 Mya. Comparative genomic analyses revealed that the T. pisiformis genome was characterized by adaptive features of strong positive selection signals from carbohydrate/lipid metabolism and body surface integrity, and of expanded gene families related to metabolism of amino acids and lipids. The high-quality genome of T. pisiformis constitutes a resource for the comparative genomics and for further applications in general parasitology.

Here, we present a draft genome of the tapeworm Dipylidium caninum (family Dipylidiidae) and compare it with other cestode genomes. This draft genome of D. caninum is 110 Mb in size, has a repeat content of ~13.4% and is predicted to encode ~10,000 protein-coding genes. We inferred excretory/secretory molecules (representing the secretome), other key groups of proteins (including peptidases, kinases, phosphatases, GTPases, receptors, transporters and ion-channels) and predicted potential intervention targets for future evaluation. Using 144 shared single-copy orthologous sequences, we investigated the genetic relationships of cestodes for which nuclear genomes are available. This study provides first insights into the molecular biology of D. caninum and a new resource for comparative genomic and genetic explorations of this and other flatworms.

Bile acids in host intestine activate larvae of tapeworms and facilitate its invasion. However, the mechanism underlying this process is poorly understood. In order to better understand responses of tapeworms to host biles, we used RNA-Seq profiling method to study the transcriptomes of Cysticercus Pisiformis (larvae of Taenia Pisiformis) after host bile acid treatment. A total of 338.32 million high-quality clean reads were obtained by Illumina Hiseq platform. Totally, 62,009 unigenes were assembled, 38,382 of which were successfully annotated to known databases. A total of 9324 unigenes were identified as differentially expressed genes (DEGs), of which 5380 and 3944 genes were up- and down-regulated in the group treated with bile acids, respectively. Gene Ontology analysis revealed that biosynthesis and energy metabolism potential were significantly strengthened after host bile treatment in C. pisiformis. Similarly, KEGG pathway analysis revealed an enrichment of pathways related to lipid metabolism and carbohydrate metabolism. Among them, \'AMPK signaling pathway\' which is critical in balancing cellular energy, was significantly enriched after bile acids activation. In addition, pathways of \'Fatty acid biosynthesis\', \'Fatty acid elongation\', \'Starch and sucrose metabolism\', and \'glycolysis gluconeogenesis\' were also significantly changed after bile acid treatment. qRT-PCR analysis confirmed the differential abundances of some key genes in these pathways. Our data suggest that host bile acids remarkably promote the pathways of energy metabolism of this parasite and regulate the genes involved in balancing lipid metabolism and carbohydrate metabolism. These findings provide new insights on the lifecycle of Taenia parasites.

This paper integrates our knowledge from traditional Chinese medical texts and archeological findings to discuss parasitic loads in early China. Many studies have documented that several different species of eukaryotic endoparasites were present in early human populations throughout China. Nevertheless, comprehensive paleoparasitological records from China are patchy, largely due to taphonomic and environmental factors. An examination of early Chinese medical texts allows us to fill in some of the gaps and counteract apparent biases in the current archeoparasitological records. By integrating the findings of paleoparasitology with historic textual sources, we show that parasites have been affecting the lives of humans in China since ancient times. We discuss the presence and prevalence of three groups of parasites in ancient China: roundworm (Ascaris lumbricoides), Asian schistosoma (Schistosoma japonicum), and tapeworm (Taenia sp.). We also examine possible factors that favored the spread of these endoparasites among early humans. Therefore, this paper not only aims to reveal how humans have been affected by endoparasites, but also addresses how early medical knowledge developed to cope with the parasitic diseases.

BACKGROUND: Due to the relative short life span and the limited spatial movement, porcine cysticercosis is an excellent indicator of current local active transmission. The aim of this study was to map at province-level, the occurrence of T. solium and T. asiatica in pigs and areas at risk of transmission to pigs in East and Southeast Asia, based on the density of extensive pig production systems and confirmed reports of porcine cysticercosis.
METHODS: This study covered East and Southeast Asia, which consist of the following countries: Brunei, Cambodia, China, East Timor, Indonesia, Japan, Laos, Malaysia, Mongolia, Myanmar, North Korea, Philippines, Singapore, South Korea, Thailand and Vietnam. Literature searches were carried out to identify current epidemiological data on the occurrence of porcine cysticercosis caused by T. solium and T. asiatica infections. Modelled densities of pigs in extensive production systems were mapped and compared to available data on porcine cysticercosis.
RESULTS: Porcine cysticercosis was confirmed to be present during the period 2000 to 2018 in eight out of the 16 countries included in this study. Taenia solium porcine cysticercosis was confirmed from all eight countries, whereas only one country (Laos) could confirm the presence of T. asiatica porcine cysticercosis. Province-level occurrence was identified in five countries (Cambodia, Indonesia, Laos, Myanmar, and Vietnam) across 19 provinces. Smallholder pig keeping is believed to be widely distributed throughout the region, with greater densities predicted to occur in areas of China, Myanmar, Philippines and Vietnam.
CONCLUSIONS: The discrepancies between countries reporting taeniosis and the occurrence of porcine cysticercosis, both for T. solium and T. asiatica, suggests that both parasites are underreported. More epidemiological surveys are needed to determine the societal burden of both parasites. This study highlights a straightforward approach to determine areas at risk of porcine cysticercosis in the absence of prevalence data.

Parabreviscolexniepini is a recently described caryophyllidean monozoic tapeworm from schizothoracine fish on the Tibetan Plateau. In the present study, the complete mitochondrial genome of P.niepini is determined for the first time. The mitogenome is 15,034 bp in length with an A+T content of 59.6%, and consists of 12 protein-encoding genes, 22 tRNA genes, two rRNA genes, and two non-coding regions. The secondary structure of tRNAs exhibit the conventional cloverleaf structure, except for trnS1 (AGN) and trnR, which lack DHU arms. The anti-codon of trnS1 (AGN) in the mitogenome of P.niepini is TCT. The two major non-coding regions, 567 bp and 1428 bp in size, are located between trnL2 and cox2, trnG and cox3, respectively. The gene order of P.niepini shows a consistent pattern with other caryophyllideans. Phylogenetic analysis based on mitogenomic data indicates that P.niepini has a close evolutionary relationship with tapeworms Breviscolexorientalis and Atractolytocestushuronensis.

The cloacal tapeworm Cloacotaenia megalops (Hymenolepididae) is one of the most common cestode parasites of domestic and wild ducks worldwide. However, limited information is available regarding its epidemiology, biology, genetics and systematics. This study provides characterisation of the complete mitochondrial (mt) genome of C. megalops.
The complete mt genome of C. megalops was obtained by long PCR, sequenced and annotated.
The length of the entire mt genome of C. megalops is 13,887 bp; it contains 12 protein-coding, 2 ribosomal RNA and 22 transfer RNA genes, but lacks an atp8 gene. The mt gene arrangement of C. megalops is identical to that observed in Anoplocephala magna and A. perfoliata (Anoplocephalidae), Dipylidium caninum (Dipylidiidae) and Hymenolepis diminuta (Hymenolepididae), but differs from that reported in taeniids owing to the position shift between the tRNA (L1) and tRNA (S2) genes. The phylogenetic position of C. megalops was inferred using Maximum likelihood and Bayesian inference methods based on the concatenated amino acid data for 12 protein-coding genes. Phylogenetic trees showed that C. megalops is sister to Anoplocephala spp. (Anoplocephalidae) + Pseudanoplocephala crawfordi + Hymenolepis spp. (Hymenolepididae) indicating that the family Hymenolepididae is paraphyletic.
The complete mt genome of C. megalops is sequenced. Phylogenetic analyses provided an insight into the phylogenetic relationships among the families Anoplocephalidae, Hymenolepididae, Dipylidiidae and Taeniidae. This novel genomic information also provides the opportunity to develop useful genetic markers for studying the molecular epidemiology, biology, genetics and systematics of C. megalops.