High morphological plasticity and global geographical distribution of the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum): molecular and morphological survey

Human diphyllobothriasis in Argentina: assessing the epidemiological significance from historical records and reports of new cases

Between 1898 and 1940, eight human cases of diphyllobothriasis were reported in Argentina, always in recently arrived European immigrants. In 1982, the first autochthonous case was detected, and since then, 33 other autochthonous cases have been reported, totaling 42 cases of human diphyllobothriasis in Argentina before the present study. Our aim is to update the information on diphyllobothriasis in Argentina by identifying specimens from new cases using morphometrical and/or molecular methods. We also aim to assess the epidemiological relevance of this food-borne disease in the country. Anamnestic data were obtained from patients or professionals, along with 26 worms identified using morphometrical (21 samples) and molecular techniques (5 samples). All the patients acquired the infection by consuming freshwater salmonids caught in Andean lakes in Northern Patagonia. Morphometrics and DNA markers of worms were compatible with Dibothriocephalus latus. In total, 68 human cases have been detected in Argentina, 60 of which were autochthonous. The human population living North-western Patagonia, whose lakes are inhabited by salmonids, is increasing. Similarly, the number of other definitive hosts for Dibothriocephalus dendriticus (gulls) and for D. latus (dogs) is also increasing. In addition, salmonid fishing and the habit of consuming home-prepared raw fish dishes are becoming widespread. Therefore, it is to be expected that diphyllobothriasis in Argentina will increase further.

PALEOEPIDEMIOLOGY OF DIPHYLLOBOTHRIOSIS: CULTURAL AND ENVIRONMENTAL FACTORS AFFECTING ADENOCEPHALUS INTENSITY AND PREVALENCE

Peruvian and Chilean mummies and coprolites provide a source of population-based parasitological information. This is especially true of the fish tapeworm, Adenocephalus pacificus. Our analysis of Chinchorro and Chiribaya mummies and diversified coprolite samples from Chile and Peru show variation in infection. There is a statistically significant difference in prevalence between Chinchorro hunter-gatherer and Chiribaya mixed-subsistence contexts. Furthermore, the most pronounced differences occur between populations within these groups. Chinchorro differences in cemeteries at the same location can be related to El Niño-Southern Oscillation variations. Pronounced prevalence variations between 3 Chiribaya villages within 7 km of each other relate to fish distribution and preparation variation. As with other recent archaeoparasitology studies, eggs-per-gram data exhibit overdispersion.

Plerocercoids of Adenocephalus pacificus in Argentine hakes: Broad distribution, low zoonotic risk

Adenocephalus pacificus is a tapeworm parasitic of marine mammals and the main agent of human diphylobothriosis caused by consumption of raw or undercooked marine fishes, being considered as a reemerging disease. Despite having a broad distribution in marine mammals in both hemispheres, plerocercoid larvae in fish have only been reported in the Pacific Ocean, in Peruvian waters, from where most human cases are known. In Argentine waters larval stages of Diphyllobothriidae have been recorded in Merluccius hubbsi, a main fish resource mostly exported frozen, headed and gutted (H&G) or as fillets; therefore, the possible presence of A. pacificus in edible products, and the extent of the risk of parasitism for humans becomes of health and commercial relevance. With the aim of detecting and identifying potentially zoonotic diphyllobothriids and quantifying infection levels in viscera and fillets of hakes, 43 entire fish, 471 H&G, and 942 fillets obtained from research cruises in 2019 and 2021 from the southern Argentine Sea (44-53°S; 63-68°W) were examined by transillumination and under stereoscopic microscopy. Plerocercoids were recovered at low prevalence and mean abundance in entire fish (13.95 % and 0.35) and H&G fish (2.76 % and 0.03) but no larval worms were found adhered to musculature or peritoneum, furthermore, no larvae were found in the fillets. Larvae were genetically identified, based on sequences of the large subunit ribosomal RNA nuclear gene (lsrDNA) and the cytochrome c oxidase subunit 1 (cox1) mitochondrial gene, as members of A. pacificus, representing the first report of this species in a fish host outside South American Pacific coasts. No spatial nor bathymetric patterns in parasite burdens were observed across sampling sites, but prevalence increased with fish size. The recorded low parasite burdens, the absence of infective stages in fillets and the fact that most products are commercialized deeply frozen, diminish the risk of parasitism for consumers to a minimum. However, the identification of this zoonotic agent and the assessment of its distribution in fish products are a first indispensable step for the design of efficient and suitable measures, such as freezing or cooking meet, to ensure the prevention of human infections.

Spirometra mansoni sparganosis identified by metagenomic next-generation sequencing: a case report

A 30-year-old male patient had a cyst on the left hip and progressive enlargement for more than 2 months. Combined blood tests, magnetic resonance imaging, and pathology findings, cysticercosis infection was suspected. However, the treatment for cysticercosis was ineffective. We conducted a metagenomic next-generation sequencing (mNGS) analysis on the formalin-fixed, paraffin-embedded specimen of the patient's surgically excised tissue, and the results suggested Spirometra mansoni, mNGS was further confirmed by polymerase chain reaction and phylogenetic analysis of cytochrome c oxidase subunit 1 (cox1) gene. Based on these results, we found that mNGS provided a better method of diagnosing parasitic infections.

Helminths of South American fur seals (Arctocephalus australis) from the Subtropical Convergence Zone of the Southwestern Atlantic

Parasites are important components of ecosystems and may contribute to the ecological aspects of their hosts and indicate the integrity of their environment. To identify the gastrointestinal helminths of the South American fur seal, Arctocephalus australis, 52 animals found dead on the Rio Grande do Sul coast, Southern Brazil, were necropsied. All studied animals were parasitized, and 104,670 specimens of helminths from three phyla and 14 taxa were collected. Adult specimens represented five of the identified species: Contracaecum ogmorhini, Adenocephalus pacificus, Stephanoprora uruguayense, Ascocotyle (Phagicola) longa, and Corynosoma australe; and one of the identified genera: Strongyloides sp. Immature forms represented the other eight taxa: Anisakidae gen. sp., Anisakis sp., Pseudoterranova sp., Contracaecum sp., Tetrabothriidae gen. sp., Cestoda gen. sp., Corynosoma cetaceum, and Bolbosoma turbinella. The acanthocephalan C. australe was the most prevalent and abundant parasite, whereas Strongyloides sp. had the highest intensity. This is the first record of the nematode Anisakis sp., digenean S. uruguayense, and acanthocephalan B. turbinella in this host. Trophic generalist species such as A. australis can be good indicators of the composition of the helminth fauna of their ecosystems, indicating the presence of zoonotic parasites transmitted by the consumption of fish.

Molecular Characterization and Phylogenetic Analysis of Spirometra Tapeworms from Snakes in Hunan Province

Sparganosis is a neglected zoonotic parasitic disease that poses huge threats to humans worldwide. Snakes play an important role in sparganosis transmission because they are the most common second intermediate hosts for Spirometra parasites. However, the population genetics of Spirometra isolates from snakes is currently not well studied in China. The present study was performed to explore the molecular characteristics and phylogenetic analysis of Spirometra tapeworms from different species of snakes in Hunan Province. This study obtained 49 Spirometra isolates from 15 geographical areas in Hunan Province, Central China. Subsequently, the 18S and 28S ribosomal DNA (rDNA) fragments were amplified from the isolated parasites, and their sequences were analyzed to assess their genetic diversity. Phylogenetic analyses were performed using the maximum likelihood algorithm. The results showed that sequence variations among these isolates were 0–2.3% and 0–0.1% for 18S and 28S rDNA, respectively. The phylogenetic analysis showed that all Spirometra isolates from Hunan Province were clustered into the same branch with Spirometra erinaceieuropaei isolated from other areas (China, Vietnam, Australia). Moreover, the phylogenetic trees revealed that Spirometra is closely related to Adenocephalus, Pyramicocephalus, Ligula, Dibothriocephalus, Schistocephalus, and Diphyllobothrium. The Spirometra isolates of different hosts/regions in Hunan Province are not host segregated or geographically isolated, and support for the taxonomic status of Spirometra tapeworms in China has been added. These results provide reference values for future accurate identification and taxonomic status of Spirometra tapeworms in China.

Molecular Diet Analysis of Adélie Penguins (Pygoscelis adeliae) in the Ross Sea Using Fecal DNA

Simple Summary

The diet of Adélie penguins, Pygoscelis adeliae, in the Ross Sea was studied applying quantitative polymerase chain reaction (qPCR) protocols to their feces. Two krill species (Euphausia superba and Euphausia crystallorophias) and notothenioid fish (mainly Pleuragramma antarctica and Pagothenia borchgrevinki) were among the most abundant components of the diet. The composition of the two krill species and notothenioid fish was found to be strongly related to the geographic characteristics of the Ross Sea.

Abstract

The diet of Adélie penguins, Pygoscelis adeliae, is a useful indicator in understanding the ecological conditions of their habitats. The diets of Adélie penguins were studied using metabarcoding and quantitative PCR (qPCR) analyses of fecal DNA from seven habitats along the Ross Sea region. Using metabarcoding analysis with dual universal primers (18Sv9 and miniFish), the overall diet composition and detailed information about piscine prey were clearly elucidated. It was found that two krill species (Euphausia superba and Euphausia crystallorophias) and notothenioid fish were the most abundant in the diets of Adélie penguins. Among the notothenioid prey, Pleuragramma antarctica (56.50%) and Pagothenia borchgrevinki (18.21%) were the two most abundant species. qPCR analysis showed a significant geographic difference in the composition of main prey. Penguins inhabiting outbound parts of the Ross Sea (Capes Adare (CA) and Duke of York Island (DY)) mainly preyed on E. superba, without any significant changes in prey composition. By contrast, those inhabiting the inbound parts of the Ross Sea (Edmonson Point (EP) and Inexpressible Island (II)) preyed on E. crystallorophias and notothenioid fish rather than E. superba. Compared with the outbound habitats, prey compositions for penguins inhabiting the inbound regions were significantly different year to year, which was presumably due to the food availability based on the annual environmental and meteorological conditions of the coastal region along with the inbound parts of the Ross Sea.

An annotated checklist of the eukaryotic parasites of humans, exclusive of fungi and algae

The classification of "parasites" in the medical field is a challenging notion, a group which historically has included all eukaryotes exclusive of fungi that invade and derive resources from the human host. Since antiquity, humans have been identifying and documenting parasitic infections, and this collective catalog of parasitic agents has expanded considerably with technology. As our understanding of species boundaries and the use of molecular tools has evolved, so has our concept of the taxonomy of human parasites. Consequently, new species have been recognized while others have been relegated to synonyms. On the other hand, the decline of expertise in classical parasitology and limited curricula have led to a loss of awareness of many rarely encountered species. Here, we provide a comprehensive checklist of all reported eukaryotic organisms (excluding fungi and allied taxa) parasitizing humans resulting in 274 genus-group taxa and 848 species-group taxa. For each species, or genus where indicated, a concise summary of geographic distribution, natural hosts, route of transmission and site within human host, and vectored pathogens are presented. Ubiquitous, human-adapted species as well as very rare, incidental zoonotic organisms are discussed in this annotated checklist. We also provide a list of 79 excluded genera and species that have been previously reported as human parasites but are not believed to be true human parasites or represent misidentifications or taxonomic changes.

IMPORTANCE OF MUSEUM SPECIMENS: RESOLVING THE TAXONOMIC PUZZLE OF HUMAN-INFECTING BROAD TAPEWORMS DESCRIBED BY O. NYBELIN IN 1931, AND REDESCRIPTION OF THE TYPES OF ADENOCEPHALUS PACIFICUS

To avoid confusions related to the resurrection of AdenocephalusNybelin, 1931 (Cestoda: Diphyllobothriidea), the type material of the Pacific broad tapeworm, Adenocephalus pacificusNybelin, 1931, which also infects humans, is morphologically characterized. Transverse protuberances on the ventral side of proglottids anterior to gonopores, which are a diagnostic feature of the genus, are illustrated for the first time. The present study supports the importance of a study of type material even in the 'molecular era' of taxonomy, where the value of morphology is often underestimated. It also points out the need for specimen deposition in publicly accessible collections.

Evolutionary transitions in broad tapeworms (Cestoda: Diphyllobothriidea) revealed by mitogenome and nuclear ribosomal operon phylogenetics

Broad tapeworms (Diphyllobothriidea) are parasites whose adults are capable of infecting a wide range of freshwater, marine and terrestrial tetrapods including humans. Previous works examining the evolution of habitat and host use in this group have been hampered by the lack of a well-resolved phylogeny. In order to produce a robust phylogenetic framework for diphyllobothriideans, we sequenced the complete mitochondrial genome of 13 representatives, carefully chosen to cover the major clades, and two outgroup species representing the Spathebothriidea and Haplobothriidea. In addition, complementary data from the nuclear ribosomal operon was sequenced for 10 representative taxa. Mitogenomes and ssrDNA and lsrDNA were used towards elucidating the phylogenetic framework for the Diphyllobothriidea. The Cephalochlamydidae is confirmed as the earliest diverging diphyllobothriidean lineage, and Solenophoridae and Diphyllobothriidae are sister groups. We infer a probable freshwater origin of the diphyllobothriideans. The ancestral condition for life cycle complexity could not be unambiguously resolved. However, we infer exclusive use of a three-host life cycle following the origin of the Solenophoridae + Diphyllobothriidae. Regarding definitive host use, although we infer reptiles as the most likely ancestral condition, this result should be revisited with a more densely sampled phylogeny in future studies. Freshwater habitat is used by the early diverging lineages within the Solenophoridae + Diphyllobothriidae clade. For the latter, habitat use shifts between freshwater and marine environments, and definitive host use includes marine and terrestrial mammals and birds. We use mitochondrial genomes to distinguish Schistocephalus species occurring in different species of sticklebacks and demonstrate conspecificity of Ligula cf. intestinalis specimens collected from two Fennoscandian ringed seal subspecies.

DNA barcoding reveals different cestode helminth species in northern European marine and freshwater ringed seals

Three subspecies of the ringed seal (Pusa hispida) are found in northeastern Europe: P. h. botnica in the Baltic Sea, P. h saimensis in Lake Saimaa in Finland, and P. h. ladogensis in Lake Ladoga in Russia. We investigated the poorly-known cestode helminth communities of these closely related but ecologically divergent subspecies using COI barcode data. Our results show that, while cestodes from the Baltic Sea represent Schistocephalus solidus, all worms from the two lakes are identified as Ligula intestinalis, a species that has previously not been reported from seals. The observed shift in cestode communities appears to be driven by differential availability of intermediate fish host species in marine vs. freshwater environments. Both observed cestode species normally infect fish-eating birds, so further work is required to elucidate the health and conservation implications of cestode infections in European ringed seals, whether L. intestinalis occurs also in marine ringed seals, and whether the species is able to reproduce in seal hosts. In addition, a deep barcode divergence found within S. solidus suggests the presence of cryptic diversity under this species name.

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COI barcoding reveals different cestodes in marine and freshwater ringed seals.

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Ligula intestinalis is reported for the first time from seals.

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A deep barcode divergence is found within Schistocephalus solidus in the Baltic Sea.

Marine fish imported from Argentina as source of human diphyllobothriosis in Europe? Ecological evidence from dolphins

Diphyllobothriosis caused by the Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum) is an emerging parasitic disease reported also from non-endemic areas, including Europe (Spain). The origin of these human cases is unknown but should be related to fresh marine fish imported from endemic areas. In this study, we molecularly confirmed common dolphins Delphinus delphis off Argentina as euparatenic transit hosts of A. pacificus. Preliminary analysis of their stomach content, together with data from previous studies from the Southwest Atlantic, showed that common dolphins feed almost exclusively on schooling Argentine hake Merluccius hubbsi and Argentine anchovy Engraulis anchoita. Therefore, we suggest that Argentine hake and Argentine anchovy may represent the intermediate hosts of A. pacificus in the Southwest Atlantic, but also in Europe to where M. hubbsi is imported on ice (unfrozen).

Diphyllobothrium sprakeri n. sp. (Cestoda: Diphyllobothriidae): a hidden broad tapeworm from sea lions off North and South America

BACKGROUND

The systematic of several marine diphyllobothriid tapeworms of pinnipeds has been revised in recent years. However, 20 species of Diphyllobothrium from phocids and otariids are still recognized as incertae sedis. We describe a new species of Diphyllobothrium from the intestine of California sea lions Zalophus californianus (Lesson) (type-host) and South American sea lions Otaria flavescens (Shaw).

METHODS

Zalophus californianus from the Pacific coast of the USA and O. flavescens from Peru and Argentina were screened for parasites. Partial fragments of the large ribosomal subunit gene (lsrDNA) and the cytochrome c oxidase subunit 1 (cox1) mitochondrial gene were amplified for 22 isolates. Properly fixed material from California sea lions was examined using light and scanning electron microscopy.

RESULTS

A total of four lsrDNA and 21 cox1 sequences were generated and aligned with published sequences of other diphyllobothriid taxa. Based on cox1 sequences, four diphyllobothriid tapeworms from O. flavescens in Peru were found to be conspecific with Adenocephalus pacificus Nybelin, 1931. The other newly generated sequences fall into a well-supported clade with sequences of a putative new species previously identified as Diphyllobothrium sp. 1. from Z. californianus and O. flavescens. A new species, Diphyllobothrium sprakeri n. sp., is proposed for tapeworms of this clade.

CONCLUSIONS

Diphyllobothrium sprakeri n. sp. is the first diphyllobothriid species described from Z. californianus from the Pacific coast of North America, but O. flavescens from Argentina, Chile and Peru was confirmed as an additional host. The present study molecularly confirmed the first coinfection of two diphyllobothriid species in sea lions from the Southern Hemisphere.

Ex Uno Plures? Morphotype and Lineage Diversity of Bothriocephalus (Cestoda: Bothriocephalidea) in North American Freshwater Fishes

Morphological and molecular evaluation of tapeworms of the genus Bothriocephalus Rudolphi, 1808 (Cestoda: Bothriocephalidea), based on newly collected and uniformly fixed worms from freshwater fishes in Canada and the United States has revealed unexpected diversity. With a combination of selected morphological features and 4 molecular markers (18S rDNA V8 region, ITS1, ITS2, and COI gene sequences), the following morphotypes and lineages of the Bothriocephalus cuspidatus Cooper, 1917 complex were identified, several of which are specific to their respective fish definitive hosts and may represent separate species: B. cuspidatus sensu stricto from walleye, Sander vitreus (type host), which likely includes a miniature morphotype from Johnny darter, Etheostoma nigrum (both Percidae); Bothriocephalus morphotype from pumpkinseed, Lepomis gibbosus (Centrarchidae); and Bothriocephalus morphotype from rock bass, Ambloplites rupestris (Centrarchidae). The Bothriocephalus morphotype from goldeye, Hiodon alosoides (Hiodontidae), may also represent a separate lineage (possibly Bothriocephalus texomensisSelf, 1954) but requires additional studies. A morphotype from smallmouth bass, Micropterus dolomieu, based on a single specimen, is morphologically and genetically very similar to the morphotype from rock bass. Morphological study of the scolex and strobila of heat-killed and fixed specimens has revealed consistent differences, often subtle, that allowed us to differentiate between these morphotypes.

Review of metazoan parasites of the northern fur seal (Callorhinus ursinus) and the analysis of the gastrointestinal helminth community of the population on St. Paul Island, Alaska

The northern fur seal (NFS), Callorhinus ursinus (Mammalia: Otariidae), is a marine mammal species included into the IUCN Red List as the vulnerable species which population is dramatically declining. A significant amount of parasitological data collected previously and our recent data allowed us to clarify the list of NFS metazoan parasites and to perform a comprehensive analysis of the gastrointestinal helminth community. Gastrointestinal tracts from 756 NFSs (3- to 4-year-old males) were collected during the annual Aleut subsistence harvests in July-August of 2011-2014 from five separate rookeries on St. Paul Island, Alaska. Totally, 27,625 specimens of helminths and approximately 1000 nasal mites were collected and identified. Detailed analysis of the previously published and newly obtained data revealed 32 species of metazoan parasites, including trematodes (6 species), cestodes (4), nematodes (9), acanthocephalans (9) and arthropods (4). The gastrointestinal helminth community of newly studied NFSs comprised 19 species including trematodes (4), cestodes (3), nematodes (5) and acanthocephalans (7). Temporal changes in the helminth community structure were small but statistically significant. Gastrointestinal helminth infracommunities comprised from 1 to 10 species (average of 4). Small but significant correlation was found between the abundances of acanthocephalans (Corynosoma similis and C. strumosum), nematodes (Contracaecum osculatum, Pseudoterranova spp.) and cestode Diphyllobothrium tetrapterum.

First identification and molecular phylogeny of Sparganum proliferum from endangered felid (Panthera onca) and other wild definitive hosts in one of the regions with highest worldwide biodiversity

After decades of being neglected, broad tapeworms now attract growing attention thanks to the increasing number of reports from humans but also thanks to many advancements achieved by application of molecular methods in diagnosis and epidemiological studies. Regarding sparganosis, unfortunately general uniformity of most species, their high intraspecific variability and lack of agreement among researchers has led to confusion about the classification of Spirometra/Sparganum species. For the first time we determined adult, eggs and plerocercoid life cycle stages and the molecular phylogeny of Sparganum proliferum obtained from endangered wild felids (Panthera onca, Leopardus pardalis, Leopardus guttulus and Herpailurus yagoauroundi) in one of the largest continuous remnants of worldwide biodiversity, the Atlantic Forest from South America. Our results showed that at least 57% of total species of wild felids in this natural area could act as definitive hosts of Sparganum proliferum. We conclude that the availability of more morphological characteristics are needed in order to secure reliable characterization and diagnosis of sparganosis. The integration of these data with molecular analysis of mitochondrial DNA sequences will be useful for species discrimination.

Molecular Identification of Adenocephalus pacificus (Cestoda) from Three Human Cases in Lima Province, Peru

The Pacific tapeworm Adenocephalus pacifcus (syn. Diphyllobothrium pacificum) is a causative agent of diphyllobothriosis occurred in Pacific coast of South America, mainly in Peru. Source of infections are traditional meal from raw or undercooked marine fish such as “cebiche”. We confirmed 3 new cases, one including scolex and the other two headless. A strobila 46 cm long without scolex was discharged from an 8-year-old boy before treatment. Specimens were confirmed morphologically by presence of tegumental protuberances on proglottids and small sized eggs. Partial sequence of cytochrome c oxidase subunit 1 gene was congruent with A. pacificus sequences.

Intestinal Parasites in an Ottoman Period Latrine from Acre (Israel) Dating to the Early 1800s CE

The aim of this study is to determine the species of parasites that affected the inhabitants of the city of Acre on the coast of the eastern Mediterranean during the Ottoman Period. This is the first archaeological study of parasites in the Ottoman Empire. We analysed sediment from a latrine dating to the early 1800s for the presence of helminth eggs and protozoan parasites which caused dysentery. The samples were examined using light microscopy and enzyme-linked immunosorbent assay (ELISA) kits. We found evidence for roundworm (Ascaris lumbricoides), whipworm (Trichuris trichiura), fish tapeworm (Dibothriocephalus sp.), Taenia tapeworm (Taenia sp.), lancet liver fluke (Dicrocoelium dendriticum), and the protozoa Giardia duodenalis and Entamoeba histolytica. The parasite taxa recovered demonstrate the breadth of species present in this coastal city. We consider the effect of Ottoman Period diet, culture, trade and sanitation upon risk of parasitism in this community living 200 years ago.

Morphology is not a reliable taxonomic tool for the genus Lernaea: molecular data and experimental infection reveal that L. cyprinacea and L. cruciata are conspecific

Background

Species belonging to the genus Lernaea are cosmopolitan parasites that can infect many different freshwater fish hosts. Due to a high degree of morphological intraspecific variability and high levels of interspecific similarities, their classification is extremely difficult and controversial. Although the suitability of the shape of cephalic horns has been questioned decades ago by some experimental infection studies, this character still plays the central role in the identification of Lernaea spp.

Methods

We used the nominal species Lernaea cyprinacea and Lernaea cruciata to test the hypothesis that the shape of the anchor can exhibit host-induced morphological variability, and that the two taxa may be synonymous.

Results

We examined 517 wild or farmed specimens of five host fish species (four cyprinids and a mosquitofish), and found that all 16 parasite specimens collected from mosquitofish could be morphologically identified as L. cruciata, whereas the remaining 25 parasite specimens were all identified as L. cyprinacea. We experimentally infected goldfish and mosquitofish specimens with offspring (copepodids) of a single L. cyprinacea specimen: the adult parasites from goldfish were morphologically identified as L. cyprinacea, and those from mosquitofish as L. cruciata. We then used molecular data to corroborate that all these specimens are conspecific.

Conclusions

Our results suggest that L. cyprinacea and L. cruciata may be synonyms, misidentified as different species as a result of host-induced morphological variation. Given the current shortage of molecular data for the genus Lernaea, in order to resolve the taxonomy of this genus (determine the exact number of species), future studies should aim to sequence as much molecular data as possible, and conduct further experimental infections.

Checklist of marine mammal parasites in New Zealand and Australian waters

Marine mammals are long-lived top predators with vagile lifestyles, which often inhabit remote environments. This is especially relevant in the oceanic waters around New Zealand and Australia where cetaceans and pinnipeds are considered as vulnerable and often endangered due to anthropogenic impacts on their habitat. Parasitism is ubiquitous in wildlife, and prevalence of parasitic infections as well as emerging diseases can be valuable bioindicators of the ecology and health of marine mammals. Collecting information about parasite diversity in marine mammals will provide a crucial baseline for assessing their impact on host and ecosystem ecology. New studies on marine mammals in New Zealand and Australian waters have recently added to our knowledge of parasite prevalence, life cycles and taxonomic relationships in the Australasian region, and justify a first host-parasite checklist encompassing all available data. The present checklist comprises 36 species of marine mammals, and 114 species of parasites (helminths, arthropods and protozoans). Mammal species occurring in New Zealand and Australian waters but not included in the checklist represent gaps in our knowledge. The checklist thus serves both as a guide for what information is lacking, as well as a practical resource for scientists working on the ecology and conservation of marine mammals.

Complex insight on microanatomy of larval "human broad tapeworm" Dibothriocephalus latus (Cestoda: Diphyllobothriidea)

BACKGROUND

In Europe, the tapeworm Dibothriocephalus latus (syn. Diphyllobothrium latum) is a well-known etiological agent of human diphyllobothriosis, which spreads by the consumption of raw fish flesh infected by plerocercoids (tapeworm's larval stage). However, the process of parasite establishment in both intermediate and definitive hosts is poorly understood. This study was targeted mainly on the scolex (anterior part) of the plerocercoid of this species, which facilitates penetration of the parasite in intermediate paratenic fish hosts, and subsequently its attachment to the intestine of the definitive host.

METHODS

Plerocercoids were isolated from the musculature of European perch (Perca fluviatilis) caught in Italian alpine lakes. Parasites were examined using confocal microscopy, scanning electron microscopy (SEM) and transmission electron microscopy (TEM). Immunofluorescence tagging was held on whole mount larvae.

RESULTS

The organisation of the central and peripheral nervous system was captured in D. latus plerocercoids, including the ultrastructure of the nerve cells possessing large dense neurosecretory granules. Two types of nerve fibres run from the body surface toward the nerve plexus located in the parenchyma on each side of bothria. One type of these fibres was found to be serotoninergic and possessed large subtegumental nerve cell bodies. A well-developed gland apparatus, found throughout the plerocercoid parenchyma, produced heterogeneous granules with lucent core packed in a dense layer. Three different types of microtriches occurred on the scolex and body surface of plerocercoids of D. latus: (i) uncinate spinitriches; (ii) coniform spinitriches; and (iii) capilliform filitriches. Non-ciliated sensory receptors were observed between the distal cytoplasm of the tegument and the underlying musculature.

CONCLUSIONS

Confocal laser scanning microscopy and electron microscopy (SEM and TEM) showed the detailed microanatomy of the nervous system in the scolex of plerocercoids, and also several differences in the larval stages compared with adult D. latus. These features, i.e. well-developed glandular system and massive hook-shaped uncinate spinitriches, are thus probably required for plerocercoids inhabiting fish hosts and also for their post-infection attachment in the human intestine.

Broad tapeworms (Diphyllobothriidae), parasites of wildlife and humans: Recent progress and future challenges

Tapeworms of the family Diphyllobothriidae, commonly known as broad tapeworms, are predominantly large-bodied parasites of wildlife capable of infecting humans as their natural or accidental host. Diphyllobothriosis caused by adults of the genera Dibothriocephalus, Adenocephalus and Diphyllobothrium is usually not a life-threatening disease. Sparganosis, in contrast, is caused by larvae (plerocercoids) of species of Spirometra and can have serious health consequences, exceptionally leading to host's death in the case of generalised sparganosis caused by 'Sparganum proliferum'. While most of the definitive wildlife hosts of broad tapeworms are recruited from marine and terrestrial mammal taxa (mainly carnivores and cetaceans), only a few diphyllobothriideans mature in fish-eating birds. In this review, we provide an overview the recent progress in our understanding of the diversity, phylogenetic relationships and distribution of broad tapeworms achieved over the last decade and outline the prospects of future research. The multigene family-wide phylogeny of the order published in 2017 allowed to propose an updated classification of the group, including new generic assignment of the most important causative agents of human diphyllobothriosis, i.e., Dibothriocephalus latus and D. nihonkaiensis. Genomic data of selected representatives have also begun to accumulate, promising future developments in understanding the biology of this particular group of parasites. The list of nominal species of taxonomically most complicated genus Spirometra as well as host-parasite list of 37 species of broad tapeworms parasitising marine mammals (pinnipeds and cetaceans) are also provided.

Medical Parasitology Taxonomy Update, 2016-2017

Parasite taxonomy continues to change as molecular and morphologic studies enhance our understanding of parasite relatedness. This minireview builds on the information provided in the last taxonomy update in this journal to summarize new and revised clinically relevant human parasite taxonomic changes that have occurred in 2016 and 2017.

Diphyllobothriidea in the north area of the Andean Patagonia: Epidemiology in urban dogs, morphometrical and molecular identification, with comments on wild carnivores

Diphyllobothriidea are the principal agents of Diphyllobothriosis, a widespread food-borne cestodosis. Accurate identification of the species in samples is therefore crucial for diagnosis and epidemiology in wild and domestic animals, and also humans. We aim to identify at specific level the causative agent, and provide an observational, descriptive, and transversal study of the epidemiology of this zoonosis in urban dogs. Also data on wild carnivores from Northwestern Patagonia are presented. Dog feces were collected in thirteen neighborhoods of varying socioeconomic status, and stools were analyzed by two concentration methods. Adult worms were collected and identified by molecular methods. The population of free-roaming dogs in each neighborhood was estimated, and surveys were conducted at all veterinary clinics registered in the Veterinary Medical College of Bariloche city. A total of 36 wild carnivores road killed or found dead in three National Parks were analyzed. Molecular and morphometric analyses of proglottids and eggs from dogs indicate they are infected with D. latum. Twenty out of 118 dog feces were positive for Diphyllobothrium, from 9 out of 13 neighborhoods, with infection values between 10% and 66%. Percentage of infection was correlated positively with the number of free roaming dogs per block, and with Unsatisfied Basic Needs (UBN %), but not with distance to nearest water body. Infection by D. latum in dogs is widely distributed throughout the city. Not all local veterinarians know the occurrence of Diphyllobothriosis in the dogs of the city, and it is evident that this zoonosis is underdiagnosed in relation to the percentage of infection found in this study. None of the analyzed wild carnivores were positive for Diphyllobothrium.

Metazoan parasites of California sea lions (Zalophus californianus): A new data and review

The population of California sea lion Zalophus californianus (CSL) has steadily increased during the last several decades. Despite extensive research addressing CSL biology and ecology performed during the last decades, there has been a minimal number of published papers documenting their parasite fauna. Our objective was to analyze the actual list of the metazoan parasites reported from CSLs and add new data on the age-related differences in the prevalence and biodiversity of the parasite community. There have been 33 species recorded but this study considers only 24 of them valid. Among them, 11 species are specific parasites of CSLs and 13 species are not specific. Additional species represent accidental infections or misidentifications. In total, 6653 helminths and 847 mites were collected and identified from 34 CSLs for this study. Six species of nematodes, Anisakis simplex sensu lato s. l. (prevalence 41%; intensity 7.6), Contracaecum ogmorhini s. l. (38%; 269.6), Pseudoterranova decipiens s. l. (29%; 33), P. azarazi (9%; 2.7), Acanthocheilonema odendhali (15%; 3.5) and Parafilaroides decorus were found. Two species of cestodes, Diphyllobothrium sp. (38%; 8.5) and Anophryocephalus sp. (15%; 14.6) represent novel undescribed species. Two species of trematodes, Apophallus zalophi (18%; 19.7) and Zalophotrema hepaticum (12%; 39.2), and five species of acanthocephalans, Corynosoma obtuscens (68%; 100.8), C. strumosum (53%; 4.6), Andracantha phalacrocoracis (3%; 1), Andracantha sp. (9%; 4.3) and Profilicollis altmani (6%; 8.5) were found. Mites Orthohalarchne attenuata (prevalence 85%) were found in the nasal cavity, while O. diminuata (21%) parasitized in the trachea and bronchi. The highest levels of infection with nematodes and trematodes were found in adult CSLs (3-16 years old), whereas the highest level of infection with acanthocephalans was found in young CSLs (pups and yearlings).

Intestinal parasites in Galapagos sea lions (Zalophus wollebaeki) Sivertsen, 1953 on San Cristóbal Island, Galápagos, Ecuador

Knowledge regarding endoparasites of Galapagos sea lions, Zalophus wollebaeki Sivertsen, 1953, is limited to 1 report. Herein, we examined feces extracted from the lower gastro-intestinal tract of 15 Galapagos sea lions (GSL) plus 14 fecal mounds nearby GSL at 4 locations on San Cristobal Island, Galapagos beginning in May continuing through June 2016. Using standard fecal flotation and sedimentation techniques, lungworm larvae, suggestive of Parafilaroides and Otostrongylus sp., eggs of pseudophyllidea cestodes and anisakid nematodes, and coccidian oocysts were collected from study samples. This is the first report of potential lungworm larvae, anisakids, pseudophyllidea cestodes and coccidian parasites in GSL.

Does the number of genital organs matter? Case of the seal tapeworm Diphyllobothrium (syn. Diplogonoporus) tetrapterum (Cestoda: Diphyllobothriidea)

The seal tapeworm Diphyllobothrium tetrapterum (von Siebold, 1848) Baer, 1932 (syn. Diplogonoporus tetrapterus) is exceptional among cestodes because it possesses two types of the strobila, one with a multiple set of genitalia per proglottid and another with a single set of reproductive organs per proglottid. In this study, Diph. tetrapterum is redescribed on the basis of extensive, well-fixed material from the northern fur seal (Callorhinus ursinus (Linnaeus, 1758)) from Alaska, USA. A critical morphological and molecular study of comprehensive material from several hosts throughout the Northern Hemisphere is provided. As a result, Diplogonoporus mutabilis Belopolskaia, 1960 and Diplogonoporus violettae Yurakhno, 1986 become junior synonyms of Diph. tetrapterum. Our study provides evidence of intraspecific and even individual variability of Diph. tetrapterum in the number of genital complexes, thus making this generic feature questionable for circumscription of the diphyllobothriid genera. The seal tapeworm has been found exclusively in the Northern Hemisphere and exhibits a wide (euryxenous) specificity at the level of the definitive host, having been found in a number of seals, the sea otter (Enhydra lutris (Linnaeus, 1758)), and exceptionally, in other terrestrial mammals. Plerocercoids of Diph. tetrapterum are reported from the second (fish) intermediate host for the first time, in this case the pink salmon (Oncorhynchus gorbuscha (Walbaum, 1792)) from Alaska.

Complete sequence and characterization of the mitochondrial genome of Diphyllobothrium stemmacephalum, the type species of genus Diphyllobothrium (Cestoda: Diphyllobothriidae), using next generation sequencing

We first constructed and characterized the complete mitochondrial genome (mitogenome) sequence of Diphyllobothrium stemmacephalum, the type species of genus Diphyllobothrium, using next generation sequencing (NGS). The mitogenome of D. stemmacephalum was 13,716bp, including 12 protein-coding genes, 22 tRNA genes, 2 rRNA genes and 2 longer intergenic non-coding regions, and has features common to mitogenomes of other cestodes. Although it has been accepted that tRNA for serine (trnS2_(UCN)) in Platyhelminthes lacks a D arm, the trnS2_(UCN) of D. stemmacephalum was predicted to have a paired D arm as in Diplogonoporus balaenopterae. The non-coding region 2 contained eight tandem repeat units (34nucleotides/unit). This study also corroborated that D. stemmacephalum is phylogenetically more closely related to Dip. balaenopterae than to Diphyllobothrium latum and Diphyllobothrium nihonkaiense. As demonstrated here, mitogenome sequence data obtained using NGS is useful for gaining a better understanding of the systematics, phylogeny and taxonomic revisions involving valuable specimens preserved in museums, universities or research institutes for which sequence data are not yet available, and also for making diagnoses based on clinical samples.

First Report of an Adult Tapeworm (Cestoda: Diphyllobothriidea) in a Southern Sea Otter (Enhydra lutris nereis)

We present a novel case of an intestinal cestode infection in a southern sea otter (Enhydra lutris nereis). The cestode species Diphyllobothrium tetrapterum (syn. Diplogonoporus tetrapterus) was confirmed genetically. Stable isotope analysis of whiskers collected from the sea otter did not confirm the consumption of fish as the route of exposure.

Annotated checklist of fish cestodes from South America

An exhaustive literature search supplemented by a critical examination of records made it possible to present an annotated checklist of tapeworms (Cestoda) that, as adults or larvae (metacestodes), parasitize freshwater, brackish water and marine fishes, i.e. cartilaginous and bony fishes, in South America. The current knowledge of their species diversity, host associations and geographical distribution is reviewed. Taxonomic problems are discussed based on a critical evaluation of the literature and information on DNA sequences of individual taxa is provided to facilitate future taxonomic and phylogenetic studies. As expected, the current knowledge is quite uneven regarding the number of taxa and host-associations reported from the principal river basins and marine ecoregions. These differences may not only reflect the actual cestode richness but may also be due to the research effort that has been devoted to unravelling the diversity of these endoparasitic helminths in individual countries. A total of 297 valid species, 61 taxa identified to the generic level, in addition to unidentified cestodes, were recorded from 401 species of fish hosts. Among the recognized cestode orders, 13 have been recorded in South America, with the Onchoproteocephalidea displaying the highest species richness, representing c. 50% of all species diversity. The majority of records include teleost fish hosts (79%) that harbour larval and adult stages of cestodes, whereas stingrays (Myliobatiformes) exhibit the highest proportion of records (39%) among the elasmobranch hosts. Fish cestodes are ubiquitous in South America, being mostly recorded from the Warm Temperate Southeastern Pacific (WTSP; 31%) for marine hosts and the Amazon River basin (45%) for freshwater ones. The following problems were detected during the compilation of literary data: (i) unreliability of many records; (ii) poor taxonomic resolution, i.e. identification made only to the genus or even family level; (iii) doubtful host identification; and (iv) the absence of voucher specimens that would enable us to verify identification. It is thus strongly recommended to always deposit representative specimens in any type of studies, including faunal surveys and ecological studies. An analysis of the proportion of three basic types of studies, i.e. surveys, taxonomic and ecological papers, has shown a considerable increase of ecological studies over the last decade.

Eggs as a Suitable Tool for Species Diagnosis of Causative Agents of Human Diphyllobothriosis (Cestoda)

Background

Tapeworms of the order Diphyllobothriidea are parasites of tetrapods and several species may infect man and cause neglected human disease called diphyllobothriosis. Identification of human-infecting diphyllobothriid cestodes is difficult because of their morphological uniformity, which concerns also their eggs in stool samples.

Methods

In the present study, we analysed by far the largest dataset of more than 2,000 eggs of 8 species of diphyllobothriid cestodes that may infect humans, including the most frequent human parasites Diphyllobothrium latum, D. nihonkaiense and Adenocephalus pacificus (syn. Diphyllobothrium pacificum). Size (length, width and length/width ratio) and the surface of the egg shell from naturally and experimentally infected hosts were studied using light and scanning electron microscopy.

Results

A high degree of intraspecific and host-related size variability has been detected, but combination of morphometrical and ultrastructural data made it possible to distinguish all of the studied species, including otherwise quite similar eggs of the 3 most common species infecting man, i.e. D. latum, D. nihonkaiense and D. dendriticum. The surface of all marine species is covered by numerous deep pits with species-specific density, whereas the surface of freshwater species is smooth or with isolated shallow hollows or wrinkles.

More than 2,000 eggs of 8 species of diphyllobothriid cestodes infecting humans were compared. Combination of morphometrical and ultrastructural (surface morphology) data made it possible to distinguish all species.

Pacific Broad Tapeworm Adenocephalus pacificus as a Causative Agent of Globally Reemerging Diphyllobothriosis

Certain types of marine fish, eaten raw or undercooked, may serve as a source of human infection with these parasites.

The Pacific broad tapeworm Adenocephalus pacificus (syn. Diphyllobothrium pacificum) is the causative agent of the third most common fish-borne cestodosis among humans. Although most of the nearly 1,000 cases among humans have been reported in South America (Peru, Chile, and Ecuador), cases recently imported to Europe demonstrate the potential for spread of this tapeworm throughout the world as a result of global trade of fresh or chilled marine fish and travel or migration of humans. We provide a comprehensive survey of human cases of infection with this zoonotic parasite, summarize the history of this re-emerging disease, and identify marine fish species that may serve as a source of human infection when eaten raw or undercooked.

The cestode community in northern fur seals (Callorhinus ursinus) on St. Paul Island, Alaska

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Three species of cestodes were found in northern fur seals (Callorhinus ursinus).

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Prevalence and intensity of cestodes collected from five haul-outs were studied.

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Ecology and maturity of cestodes were analyzed.

The diversity and ecology of cestodes from the northern fur seals, Callorhinus ursinus (NFS), were examined using newly collected material from 756 humanely harvested subadult males between 2011 and 2014. NFSs were collected from five different haul-outs on St. Paul Island, Alaska. A total of 14,660 tapeworms were collected with a prevalence of 98.5% and intensity up to 107 cestodes per host (mean intensity 19.7 ± 16.5 SD). Three species of tapeworms were found: Adenocephalus pacificus (Diphyllobothriidea) was the most prevalent (prevalence 97.4%), followed by Diplogonoporus tetrapterus (49.7%), and 5 immature specimens of Anophryocephalus cf. ochotensis (Tetrabothriidea) (0.5%). Most of the cestodes found in the NFS were immature (69.7%). However, only 0.9% of cestodes were in larval (plerocercoid) stages. The species composition, prevalence and intensity of cestodes from these NFSs were not statistically different between the five separate haul-outs. Significant increases in the intensity of NFS infections were observed during the study period.