Genetic characterization of Dibothriocephalus latus and Dibothriocephalus dendriticus (Cestoda: Diphyllobothriidae) from Chile based on haplotype analysis using mitochondrial DNA markers.

Dibothriocephalus latus and Dibothriocephalus dendriticus are found throughout the temperate and sub-arctic zones of the northern hemisphere, but they are also found in the southern core countries of South America, Chile and Argentina. Genetic characteristics of D. latus and D. dendriticus from South America have yet to be fully defined. The present study aimed to understand the genetic characteristics of D. latus and D. dendriticus from Chile by haplotype network analysis of mitochondrial cytochrome c oxidase subunit I gene (cox1) and cytochrome b gene (cob), as well as their origins. Dibothriocephalus latus and D. dendriticus plerocercoid larvae were obtained from feral and/or wild salmonids captured in Lake Llanquihue in Región de Los Lagos, and Lake Panguipulli in Región de Los Ríos, located south of central Chile. Haplotype analysis of D. latus revealed that H1 in cox1 and H2 in cob are the key haplotypes common to D. latus across the world, including Chile, and both genes exhibited limited genetic diversity in D. latus. It was assumed that D. latus was brought into South America by European and Russian immigrants in the 19th century as previously reported. In contrast, both the cox1 and cob of D. dendriticus display considerable genetic diversity, with no common haplotypes between D. dendriticus populations from Chile and the northern hemisphere. More intriguingly, two cob haplotypes (H24, H25) detected in Chilean D. dendriticus were closely linked to haplotypes (H30, H31) detected in North American D. dendriticus, strongly implying that D. dendriticus in Chile was brought by piscivorous migrating birds from North America. It has also been estimated that the D. dendriticus from Chile genetically diverged from the D. dendriticus from the northern hemisphere approximately 1.11 million years ago, long before humans migrated to the southern parts of South America.

Genome of the fatal tapeworm Sparganum proliferum uncovers mechanisms for cryptic life cycle and aberrant larval proliferation.

The cryptic parasite Sparganum proliferum proliferates in humans and invades tissues and organs. Only scattered cases have been reported, but S. proliferum infection is always fatal. However, S. proliferum's phylogeny and life cycle remain enigmatic. To investigate the phylogenetic relationships between S. proliferum and other cestode species, and to examine the mechanisms underlying pathogenicity, we sequenced the entire genomes of S. proliferum and a closely related non-life-threatening tapeworm Spirometra erinaceieuropaei. Additionally, we performed larvae transcriptome analyses of S. proliferum plerocercoid to identify genes involved in asexual reproduction in the host. The genome sequences confirmed that the S. proliferum has experienced a clearly distinct evolutionary history from S. erinaceieuropaei. Moreover, we found that nonordinal extracellular matrix coordination allows asexual reproduction in the host, and loss of sexual maturity in S. proliferum are responsible for its fatal pathogenicity to humans. Our high-quality reference genome sequences should be valuable for future studies of pseudophyllidean tapeworm biology and parasitism.

Infection status of commercial fish with cystacanth larvae of the genus Corynosoma (Acanthocephala: Polymorphidae) in Hokkaido, Japan.

Acanthocephalans of the genus Corynosoma are known as intestinal parasites, mainly of pinnipeds. Human corynosomiasis has been reported as an infrequent foodborne disease in Hokkaido, the northernmost island of Japan. Potential sources of the human infection are marine fish, because they are paratenic hosts of these parasites. In this study, the prevalence and intensity of larval Corynosoma in commercial fish from 17 fishing ports of Hokkaido were examined from April 2016 to January 2019. Out of a total of 1217 fish examined, 122 (10.0%) were infected with cystacanth larvae. The infected fish assemblage was composed of 7 families and 13 species from all the coastal seas of Hokkaido (the Pacific Ocean, Okhotsk Sea, and Japan Sea), showing that commercial fish can be source of human infection when eaten raw. Flatfish of the family Pleuronectidae showed the highest intensity of cystacanths, ranging from 1 to 56. A DNA barcoding system was developed in this study, based on the standard mitochondrial cox1 sequences of morphologically identified adults of Corynosoma spp. from pinnipeds in Hokkaido. By using the DNA barcoding, most of the fish-derived cystacanths were identified as either C. strumosum or C. villosum, and furthermore, a clinical isolate from human as C. villosum. Both of the species were commonly detected from various fish of Hokkaido, irrespective of the coastal seas. Flatfish frequently harbored C. villosum. Considering the wide range of commercial fish in Hokkaido and the advanced transportation system of fresh fish, there is a possibility that human corynosomiasis will occur everywhere in Japan.

Re-evaluation of Tellervotrema katadara (Kuramochi, 2001) Kuramochi, 2009 (Opecoelidae: Plagioporinae) and supplementary morphological data for T. beringi (Mamaev, 1965) Gibson & Bray, 1982 with new host and locality.

The trematode genus Tellervotrema Gibson & Bray, 1982 was erected for Podocotyle-like species that parasitize archybenthal macrourid fishes (also known as grenadiers or rattails) and that possess no vitelline follicles dorsal to the ceca but do have a symmetrical pair of isolated groups of vitelline follicles in the posterior forebody. Tellervotrema katadara (Kuramochi, 2001) Kuramochi, 2009 is resurrected as a valid species based on an examination and re-description of holotype and paratype specimens collected from the intestine of the bathygadine macrourid Gadomus colletti Jordan & Gilbert from 518-582 m depth in Tosa Bay, off the Pacific coast of southern Japan. Tellervotrema beringi (Mamaev, 1965) Gibson & Bray, 1982 is re-described from specimens originally identified as T. katadara, collected from the intestine of the longfin grenadier, Coryphaenoides longifilis Günther, and found at 1,196 m depth off the Pacific coast of the Tohoku region, northern Honshu, Japan. New host and locality records for T. beringi are presented along with a brief listing of museums housing type and voucher specimens of the three species now recognized in Tellervotrema. A comprehensive listing is given of all parasites reported from the two macrourid species relevant to this study and a key is presented for members of Tellervotrema. Finally, we hypothesize that the life cycles for T. beringi and T. katadara in the deep waters of the North Pacific Ocean off Japan most likely include a gastropod as a first intermediate host, one or more of a variety of invertebrates (amphipods, decapods, mysids) and/or finfish as second intermediate hosts, and the grenadiers, C. longifilis and G. colletti, as definitive hosts, respectively.

Molecular and histological identification of the acanthocephalan Bolbosoma cf. capitatum from the human small intestine.

Acanthocephalans of the genus Bolbosoma are intestinal parasites of marine mammals with a lifecycle similar to that of anisakid nematodes. Several cases of Bolbosoma infection in humans have been reported, but no species identification has been made. Here, we report a case of Bolbosoma infection, in which the worm was found in histological sections of the partially resected small intestine of a Japanese man. Morphological features of the worm reconstructed from serial sectioning indicated that the worm was most likely to be a sexually immature female of Bolbosoma capitatum. DNA extraction from paraffin-embedded sections and ITS1-5.8S rRNA-ITS2 sequencing showed that this species formed a monophyletic group with Bolbosoma nipponicum, and was clearly distinguishable from Corynosoma spp. or Polymorphus spp. These results may provide a reference for identifying and characterizing unknown acanthocephalans found in histological sections.

Complete mitochondrial genomes of Diplogonoporus balaenopterae and Diplogonoporus grandis (Cestoda: Diphyllobothriidae) and clarification of their taxonomic relationships.

Although the diplogonadic human tapeworm, Diplogonoporus grandis, has long been considered to be a synonym of the whale tapeworm, Diplogonoporus balaenopterae, the identity of the both species at the complete mitochondrial genomes and nuclear DNA levels has been not sufficiently undertaken to date. In the present study, to clarify the taxonomic relationships between D. balaenopterae and D. grandis at the molecular level, the complete mitochondrial genomes of both species were sequenced and compared. In addition, the genetic variation in the mitochondrial cytochrome c oxidase subunit 1 gene (cox1) and the nuclear internal transcribed spacer-1 (ITS-1) region of the ribosomal RNA gene were examined. The complete mitochondrial genomes of D. balaenopterae and D. grandis consisted of 13,724 bp and 13,725 bp, respectively. These mitochondrial genomes contained 12 protein-coding, 22 transfer RNA and 2 ribosomal RNA genes and two longer non-coding regions. Except for Hymenolepis diminuta, the genomic organization in both species was essentially identical to that in other cestode genomes examined to date. However, differences were observed between Diplogonoporus and Diphyllobothrium species in abbreviated stop codons, sequences and the number of repeat units in the 2nd non-coding regions. The genetic differences observed in the mitochondrial genomes, cox1 and ITS-1 regions of both species were considered typical of intraspecific variation. In conclusion, D. balaenopterae is a taxonomically valid species and D. grandis is a junior synonym of D. balaenopterae based on the zoological nomenclature. Further, molecular-phylogenetic analysis confirmed that D. balaenopterae is more closely related to Diphyllobothrium stemmacephalum, the type-species of the genus Diphyllobothrium, and the taxonomical validity of the genera Diplogonoporus and Diphyllobothrium was also discussed.

Molecular identification of a causative parasite species using formalin-fixed paraffin embedded (FFPE) tissues of a complicated human pulmonary sparganosis case without decisive clinical diagnosis.

PCR-based molecular diagnosis was made for the identification of causative agents of the clinically suspected pulmonary proliferative sparganosis case found in Thailand using formalin-fixed paraffin-embedded (FFPE) biopsy specimens. As a reference, FFPE biopsy specimen from a typical cutaneous sparganosis case was examined together. DNA samples were extracted from tissues and two partial fragments of cytochrome c oxidase subunit 1 (cox1) gene were amplified for the detection of Spirometra DNA. Two cox1 fragments were amplified successfully for both specimens. After alignment of nucleotide sequences of the PCR-amplicons, the causative agents of both cases were identified as Spirometra erinaceieuropaei.

A case of Diphyllobothrium nihonkaiense infection possibly linked to salmon consumption in New Zealand.

Global increases in salmon consumption and changes in fish-eating habits have meant that Diphyllobothrium infections now occur in regions where they were previously absent. In the present paper, a case of diphyllobothriasis through the likely ingestion of raw salmon in New Zealand in a Japanese patient is reported. The causative tapeworm species was identified as Diphyllobothrium nihonkaiense based on mitochondrial DNA analysis of proglottid expelled from the patient.

Diplogonoporiasis in Japan: genetic analyses of five clinical isolates.

Infection of the whale tapeworm Diplogonoporus balaenopterae (Diphyllobothriidae) is occasionally found in humans, especially among Japanese. In the present study, we analysed the nucleotide sequences of the 18S rDNA, ITS1 and cox1 genes of the immature and mature proglottids of Diplogonoporus species recovered from five Japanese patients. The nucleotide sequences of 18S rDNA, ITS1 and cox1 showed little, if any, intraspecific divergence. Phylogenetic analyses of several diphyllobothriid species revealed a close relationship of Diplogonoporus isolates with the cetacean tapeworm Diphyllobothrium stemmacephalum. The results suggest that the genus Diphyllobothrium is paraphyletic and raise a question regarding the validity of the genus Diplogonoporus.