How tapeworms interact with cancers: a mini-review

Cancer is one of the leading causes of death, with an estimated 19.3 million new cases and 10 million deaths worldwide in 2020 alone. Approximately 2.2 million cancer cases are attributed to infectious diseases, according to the World Health Organization (WHO). Despite the apparent involvement of some parasitic helminths (especially trematodes) in cancer induction, there are also records of the potential suppressive effects of helminth infections on cancer. Tapeworms such as Echinococcus granulosus, Taenia crassiceps, and more seem to have the potential to suppress malignant cell development, although in a few cases the evidence might be contradictory. Our review aims to summarize known epidemiological data on the cancer-helminth co-occurrence in the human population and the interactions of tapeworms with cancers, i.e., proven or hypothetical effects of tapeworms and their products on cancer cells in vivo (i.e., in experimental animals) or in vitro. The prospect of bioactive tapeworm molecules helping reduce the growth and metastasis of cancer is within the realm of future possibility, although extensive research is yet required due to certain concerns.

Host-gut microbiota interactions shape parasite infections in farmed Atlantic salmon

Animals and their associated microbiota share long evolutionary histories. However, it is not always clear how host genotype and microbiota interact to affect phenotype. We applied a hologenomic approach to explore how host-microbiota interactions shape lifetime growth and parasite infection in farmed Atlantic salmon (Salmo salar). Multi-omics data sets were generated from the guts of 460 salmon, 82% of which were naturally infected with an intestinal cestode. A single Mycoplasma bacterial strain, MAG01, dominated the gut metagenome of large, non-parasitized fish, consistent with previous studies showing high levels of Mycoplasma in the gut microbiota of healthy salmon. While small and/or parasitized salmon also had high abundance of MAG01, we observed increased alpha diversity in these individuals, driven by increased frequency of low-abundance Vibrionaceae and other Mycoplasma species that carried known virulence genes. Colonization by one of these cestode-associated Mycoplasma strains was associated with host individual genomic variation in long non-coding RNAs. Integrating the multi-omic data sets revealed coordinated changes in the salmon gut mRNA transcriptome and metabolome that correlated with shifts in the microbiota of smaller, parasitized fish. Our results suggest that the gut microbiota of small and/or parasitized fish is in a state of dysbiosis that partly depends on the host genotype, highlighting the value of using a hologenomic approach to incorporate the microbiota into the study of host-parasite dynamics.IMPORTANCEStudying host-microbiota interactions through the perspective of the hologenome is gaining interest across all life sciences. Intestinal parasite infections are a huge burden on human and animal health; however, there are few studies investigating the role of the hologenome during parasite infections. We address this gap in the largest multi-omics fish microbiota study to date using natural cestode infection of farmed Atlantic salmon. We find a clear association between cestode infection, salmon lifetime growth, and perturbation of the salmon gut microbiota. Furthermore, we provide the first evidence that the genetic background of the host may partly determine how the gut microbiota changes during parasite-associated dysbiosis. Our study therefore highlights the value of a hologenomic approach for gaining a more in-depth understanding of parasitism.

Two new species of Scyphophyllidium (Cestoda: Phyllobothriidea) from Chaenogaleus macrostoma (Bleeker) (Elasmobranchii: Carcharhiniformes) from the Persian Gulf, Iran

Two new species of Scyphophyllidium Woodland, 1927 are described from the Hooktooth shark, Chaenogaleus macrostoma (Bleeker), from the Persian Gulf, Iran. Scyphophyllidium hormuziense n. sp. is assigned to morphological category 2 of its genus because it possesses bothridial marginal loculi and an apical sucker on each flat bothridium, and lacks bothridial facial loculi. Within category 2, it is distinguished from its congeners, except for S. janineae (Ruhnke, Healy and Shapero, 2006), by possessing, rather than lacking, a prominent cephalic peduncle. It differs from S. janineae in the distribution of the vitelline follicles. Scyphophyllidium iraniense n. sp. is assigned to morphological category 5 because its bothridia are essentially flat and lack proximal apertures, marginal loculi, facial loci and semi-circular muscle bands, and bears weakly serrate gladiate spinitriches on its distal bothridial surfaces. Within its morphological category, the presence of a long cephalic peduncle distinguishes S. iraniense n. sp. from its congeners lacking this structure or possessing a short cephalic peduncle. It further differs from S. arnoldi (Ruhnke and Thompson, 2006) and S. typicum (Subhapradha, 1955) in total length, from S. paulum (Linton, 1897) in lacking a conspicuous band of muscles along the locular periphery of the bothridia, and from S. kirstenae (Ruhnke, Healy and Shapero, 2006) in the distribution of the vitelline follicles. This study brings the number of the valid Scyphophyllidium species of the Persian Gulf to five.

A new species of Versteria (Cestoda: Taeniidae) parasitizing Neogale vison and Lontra canadensis (Carnivora: Mustelidae) from Western Canada

Via molecular and morphological analyses, we describe adult specimens of a new species of Versteria (Cestoda: Taeniidae) infecting mink and river otter (Carnivora: Mustelidae) in Western Canada, as well as larval forms from muskrat and mink. These sequences closely matched those reported from adult specimens from Colorado and Oregon, as well as larval infections in humans and a captive orangutan. We describe here a new species from British Columbia and Alberta (Canada), Versteria rafei n. sp., based upon morphological diagnostic characteristics and genetic distance and phylogeny. Versteria rafei n. sp. differs from the three other described species of the genus in the smaller scolex and cirrus sac. It also differs from V. mustelae (Eurasia) and V. cuja (South America) by having an armed cirrus, which is covered in hair-like bristles, and in the shape of its hooks, with a long thorn-like blade, and short or long handle (vs. a short sharply curved blade and no difference in handle size in previously described species). The poorly known V. brachyacantha (Central Africa) also has an armed cirrus and similarly shaped hooks. However, it differs from the new species in the number and size of hooks. Phylogenetic analysis of the cox1 and nad1 mitochondrial regions showed that our specimens clustered with isolates from undescribed adults and larval infections in North America, and separate from V. cuja, confirming them to be a distinct species from the American Clade.

Monoecocestus (Cestoda: Anoplocephalidae) diversity in Sigmodontinae rodents characterized by morphology and molecular methods

This paper provides new morphological and molecular data for identifying Monoecocestus species from rodents: a) morphological update of Monoecocestus spp., b) morphological data on Anoplocephalidae taxa from Sigmodontinae rodents, c) analyses of the genetic distances between the specimens studied and other Anoplocephalidae from rodents available in GenBank, and phylogenetic inferences. A total of 25 specimens of Holochilus spp. were examined from four provinces of Argentina. Cestodes specimens were removed from the rodents small intestines. Conventional studies were used for the morphological and molecular analysis. Four taxa of Monoecocestus were identified. Monoecocestus threlkeldi was identified as first record in Holochilus chacarius and from Argentina. Molecular and morphological aspects of Monoecocestus sp.1, Monoecocestus sp.2 and Monoecocestus sp.3 were described. Specimens belonging to the genus Monoecocestus may represent closely related species, demonstrating the importance of using integrative taxonomic approaches to understand biological diversity. The continuity of the studies on Anoplocephalidae will allows to advance in investigation of molecular analyses and ecological aspects that determine parasite-host-environment relationship.

ADAMTS-13 and HMGB1-induced oxidative stress in Taenia multiceps-infected animals

This study investigated the cytotoxic effects of oxidative stress (OS), high mobility group box 1 (HMGB1), ADAMTS (A disintegrin and metalloproteinase with thrombospondin motifs), and neuropathology associated with coenurus cerebralis (Taenia multiceps). ADAMTS-13, HMGB1, glutathione reductase (GR), copper/zinc superoxide dismutase (Cu/Zn SOD), and 8-hydroxy-2'-deoxyguanosine (8-OHdG) expression levels were studied. The study found that ADAMTS-13 (P < 0.005), HMGB1 (P < 0.005), GR (P < 0.005), Cu/Zn SOD (P < 0.005), and 8-OHdG (P < 0.005) levels were significantly higher in T. multiceps (c. cerebralis)-infected animals compared to healthy control animals. This study's most important finding was that HMGB1 up-regulation in neurons, endothelial cells, and glial cells can directly cause brain parenchymal destruction and that HMGB1-mediated oxidative stress plays a crucial role in the neuropathogenesis of coenurosis. The results also showed that increased levels of ADAMTS-13 may play a pivotal role in regulating and protecting the blood-brain barrier integrity and neuroprotection. These findings also suggest that ADAMTS-13 and HMGB1 compete in the prevention or formation of microthrombi, which was regarded as a remarkable finding. ADAMTS-13 and HMGB1 are valuable biomarkers for disease risk assessment, estimating host neuropathy following T. multiceps (c. cerebralis) exposure, and providing a new therapeutic target. This is the first study to show that HMGB1 and ADAMTS-13 are expressed in reactive cells and are associated with neuroimmunopathology in coenurosis.

Integrated transcriptomic and proteomic analyses of plerocercoid and adult Spirometra mansoni reveal potential important pathways in the development of the medical tapeworm

BACKGROUND

Spirometra mansoni can parasitize animals and humans through food and water, causing parasitic zoonosis. Knowledge of the developmental process of S. mansoni is crucial for effective treatment; thus, it is important to characterize differential and specific proteins and pathways associated with parasite development.

METHODS

In this study, we performed a comparative proteomic analysis of the plerocercoid and adult stages using a tandem mass tag-based quantitative proteomic approach. Additionally, integrated transcriptomic and proteomic analyses were conducted to obtain the full protein expression profiles of different life cycle stages of the tapeworm.

RESULTS

Approximately 1166 differentially expressed proteins (DEPs) were identified in adults versus plerocercoids, of which 641 DEPs were upregulated and 525 were downregulated. Gene Ontology (GO), Clusters of Orthologous groups (COG) and Kyoto Encyclopedia of Genes and Genomes (KEGG) analyses indicated that most DEPs related to genetic information processing and metabolism of energy in adults seem to be more activated. In the plerocercoid stage, compared to metabolism, genetic information processing appears more dynamic. Protein-protein interaction (PPI) revealed six key proteins (phosphomannomutase, glutathione transferase, malate dehydrogenase, cytoplasmic, 40S ribosomal protein S15, ribosomal protein L15 and 60S acidic ribosomal protein P2) that may play active roles in the growth and development of S. mansoni. Finally, the combination of transcriptomic and proteomic data suggested that three pathways (ubiquitin-mediated proteolysis, phagosome and spliceosome) and five proteins closely related to these pathways might have a significant influence in S. mansoni.

CONCLUSIONS

These findings contribute to increasing the knowledge on the protein expression profiles of S. mansoni and provide new insights into functional studies on the molecular mechanisms of the neglected medical tapeworm.

Design of ion channel blocking, toxin-like Kunitz inhibitor peptides from the tapeworm, Echinococcus granulosus, with potential anti-cancer activity

Over-expression of K+ channels has been reported in human cancers and is associated with the poor prognosis of several malignancies. EAG1, a particular potassium ion channel, is widely expressed in the brain but poorly expressed in other normal tissues. Kunitz proteins are dominant in metazoan including the dog tapeworm, Echinococcus granulosus. Using computational analyses on one A-type potassium channel, EAG1, and in vitro cellular methods, including major cancer cell biomarkers expression, immunocytochemistry and whole-cell patch clamp, we demonstrated the anti-tumor activity of three synthetic small peptides derived from E. granulosus Kunitz4 protease inhibitors. Experiments showed induced significant apoptosis and inhibition of proliferation in both cancer cell lines via disruption in cell-cycle transition from the G0/G1 to S phase. Western blotting showed that the levels of cell cycle-related proteins including P27 and P53 were altered upon kunitz4-a and kunitz4-c treatment. Patch clamp analysis demonstrated a significant increase in spontaneous firing frequency in Purkinje neurons, and exposure to kunitz4-c was associated with an increase in the number of rebound action potentials after hyperpolarized current. This noteworthy component in nature could act as an ion channel blocker and is a potential candidate for cancer chemotherapy based on potassium channel blockage.

Better sturdy or slender? Eurasian otter skull plasticity in response to feeding ecology

Otters are semi-aquatic mammals specialized in feeding on aquatic prey. The Eurasian otter Lutra lutra is the most widely distributed otter species. Despite a low degree of genetic variation across its European range, the population from Great Britain exhibits distinct genetic structuring. We examined 43 skulls of adult Eurasian otters belonging to 18 sampling localities and three genetic clusters (Shetlands, Wales and Scotland). For each sample location, information regarding climate was described using bioclimatic variables from WorldClim, and information on otter diet was extracted from the literature. By using photogrammetry, 3D models were obtained for each skull. To explore any evidence of adaptive divergence within these areas we used a three dimensional geometric morphometric approach to test differences in skull size and shape between areas with genetically distinct populations, as well as the influence of diet, isolation by distance and climate. Males were significantly larger in skull size than females across all the three genetic clusters. Skull shape, but not size, appeared to differ significantly among genetic clusters, with otters from Shetland exhibiting wider zygomatic arches and longer snouts compared to otters from Wales, whereas otters from Scotland displayed intermediate traits. A significant relationship could also be found between skull shape variation, diet as well as climate. Specifically, otters feeding on freshwater fish had more slender and short-snouted skulls compared to otters feeding mostly on marine fish. Individuals living along the coast are characterised by a mixed feeding regime based on marine fish and crustaceans and their skull showed an intermediate shape. Coastal and island otters also had larger orbits and eyes more oriented toward the ground, a larger nasal cavity, and a larger distance between postorbital processes and zygomatic arch. These functional traits could also represent an adaptation to favour the duration and depth of diving, while the slender skull of freshwater feeding otters could improve the hydrodynamics.

Diplogonoporiasis Following the Consumption of Raw Juvenile Japanese Anchovy

Human diplogonoporiasis caused by the tapeworm Diplogonoporus balaenopterae has been rarely reported in Japan in the last decade. A 38-year-old man complained of a fever, diarrhea, intermittent abdominal pain, and worm excretion. He had a history of consuming raw juvenile Japanese anchovy one month earlier. On admission, the patient had acute enteritis and received intravenous fluids. During hospitalization, he excreted a white worm in his stool. On a macroscopic examination, the worm was found to be a tapeworm with scolexes. His health improved spontaneously without taking anthelmintic agents. Based on the genetic analysis, the tapeworm was identified as Diplogonoporus balaenopterae.

Transcriptome profiling of plerocercoid and adult developmental stages of the neglected medical tapeworm Spirometra erinaceieuropaei

The plerocercoid larvae of the tapeworm Spirometra erinaceieuropaei can parasitize humans and animals and cause serious parasitic zoonosis. However, our knowledge of the developmental process of S. erinaceieuropaei is still inadequate. To better characterize differential and specific genes and pathways associated with parasite development, a comparative transcriptomic analysis of the plerocercoid stage and the adult stage was performed using RNA-seq and de novo analysis. Approximately 13,659 differentially expressed genes (DEGs) were identified in plerocercoids versus adults, of which 6455 DEGs were upregulated and 7204 were downregulated. DEGs involved in parasite immunoevasion were more active in plerocercoid larvae than in adults, while DEGs associated with metabolic activity were upregulated in adults. Gene Ontology (GO) and Kyoto Encyclopedia of Genes (KEGG) analyses revealed that most DEGs involved in protein phosphorylation/dephosphorylation and the Wnt signalling pathway were much more active in plerocercoid larvae. The molecular functions of upregulated unigenes in adults were mainly enriched for metabolic activities. qPCR validated that the expression levels of 10 selected DEGs were consistent with those in RNA-seq, confirming the accuracy of the RNA-seq results. Our results contributed to increasing the knowledge on the S. erinaceieuropaei gene repertoire and expression profile and also provide valuable resources for functional studies on the molecular mechanisms of S. erinaceieuropaei.

Unique genetic structure of the human tapeworm Dibothriocephalus latus from the Alpine lakes region - a successful adaptation?

Dibothriocephalus latus is the most frequent causative agent of fish-borne zoonosis (diphyllobothriosis) in Europe, where it is currently circulating mainly in the Alpine lakes region (ALR) and Russia. Three mitochondrial genes (cox1, cob and nad3) and 6 microsatellite loci were analysed to determine how is the recently detected triploidy/parthenogenesis in tapeworms from ALR displayed at the DNA level. A geographically distant population from the Krasnoyarsk Reservoir in Russia (RU-KR) was analysed as a comparative population. One or 2 alleles of each microsatellite locus was detected in plerocercoids from RU-KR, corresponding to the microsatellite pattern of a diploid organism. In contrast, 1–3 alleles were observed in tapeworms from ALR, in accordance with their triploidy. The high diversity of mitochondrial haplotypes in D. latus from RU-KR implied an original and relatively stable population, but the identical structure of mitochondrial genes of tapeworms from ALR was probably a consequence of a bottleneck typical of introduced populations. These results indicated that the diploid/sexually reproducing population from RU-KR was ancestral, located within the centre of the distribution of the species, and the triploid/parthenogenetically reproducing subalpine population was at the margin of the distribution. The current study revealed the allelic structure of the microsatellite loci in the triploid tapeworm for the first time.

Branchiopodataenia bazaletica sp. n., a Parasite of the Black Tern (Chlidonias niger) from Georgia

INTRODUCTION

Branchiopodataenia bazaletica sp. n. (Cestoda, Cyclophyllidea) is described from the black tern, Chlidonias niger L., after re-examination of material deposited in the helminthological collection of the Institute of Zoology, Ilia State University, Institute of Zoology in Tbilisi, Georgia.

METHODS

The cestodes were collected from Bazaleti Lake in Georgia and originally identified as Wardium cirrosa, as labeled on the slides. Cestodes were examined using light microscopy.

RESULTS

Detailed examination of the morphology of these specimens showed that they belong to the genus Branchiopodataenia and are described as a new species. The presence of 10 aploparaksoid hooks with an elongate handle, three testes, and chitinoid latch-like structure in the copulative part of the vagina support the assignment of the new species to Branchiopodataenia. The new species has rostellar hooks 48-52 in length, a long, armed cirrus, and long copulative part of the vagina. Branchiopodataenia bazaletica sp. n. differs from its congeners by the size of rostellar hooks and by the shape of the cirrus and vagina.

A synergistic, global approach to revising the trypanorhynch tapeworm family Rhinoptericolidae (Trypanobatoida)

Since 2010, the trypanorhynch tapeworm family Rhinoptericolidae Carvajal & Campbell, 1975 has housed just two distinctive, monotypic genera (Rhinoptericola Carvajal & Campbell, 1975 and Nataliella Palm, 2010). However, global collections of tapeworms from sharks and rays over the last more than three decades brought to light the need for major revision of the family by suggesting a much greater species-level diversity for the nominal genus Rhinoptericola. Through synonymy and the description of new species, the number of species in the genus is increased from one to eight. A phylogenetic analysis of the D1-D3 gene region of 28S rRNA (28S), including seven of the now nine species of rhinoptericolids, and a broad sampling of the other Trypanobatoida is the first to recover a monophyletic Rhinoptericolidae. In addition to systematic revision, this study allowed for the first evaluation of the degree of intraspecific vs interspecific variation in 28S for adult trypanorhynchs across the various hosts and geographic localities from which they have been reported, suggesting a relatively consistent boundary for Rhinoptericola. It is further suggested that detailed scanning electron microscopy (SEM) images of both the basal and metabasal armatures greatly aid in the interpretation of hook arrangement and shape. A schematic to streamline determination of the tentacular surface presented in scanning electron micrographs and line drawings of trypanorhynchs is presented for species with both two and four bothria. In combination, these methodological refinements can now be used as a model to resolve issues of classification and non-monophyly within both major lineages of the Trypanorhyncha. As a result of the taxonomic work, Rhinoptericola megacantha Carvajal & Campbell, 1975 (previously only known from the American cownose ray from the Chesapeake Bay and the Ticon cownose ray from the Gulf of Mexico, Venezuela, and Brazil) is now known from an additional species of cownose ray and a species of stingray, and is revealed to have a transatlantic distribution. Data from SEM suggest a simpler interpretation of hook arrangement in the metabasal armature for Rhinoptercola and-in combination with 28S sequence data-support Shirleyrhynchus Beveridge & Campbell, 1988 (a former rhinoptericolid) as its junior synonym. The three species formerly assigned to Shirleyrhynchus are thus transferred to Rhinoptericola. Data from light microscopy on whole-mounted specimens and histological sections, SEM, and 28S showed the eutetrarhynchid Prochristianella jensenae Schaeffner & Beveridge, 2012b to be morphologically consistent with species of Rhinoptericola and it is thus transferred to the genus. The type series of P. jensenae was determined to be mixed, representing two distinct species which are here redescribed and described as new, respectively. Two additional novel species of Rhinoptericola are described from cownose rays from off Mozambique and the Gulf of California.

Dipylidium caninum draft genome - a new resource for comparative genomic and genetic explorations of flatworms

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.

The potential for histone deacetylase (HDAC) inhibitors as cestocidal drugs

Background

Echinococcosis and cysticercosis are neglected tropical diseases caused by cestode parasites (family Taeniidae). Not only there is a small number of approved anthelmintics for the treatment of these cestodiases, but also some of them are not highly effective against larval stages, such that identifying novel drug targets and their associated compounds is critical. Histone deacetylase (HDAC) enzymes are validated drug targets in cancers and other diseases, and have been gaining relevance for developing new potential anti-parasitic treatments in the last years. Here, we present the anthelmintic profile for a panel of recently developed HDAC inhibitors against the model cestode Mesocestoides vogae (syn. M. corti).

Methodology/Principal findings

Phenotypic screening was performed on M. vogae by motility measurements and optical microscopic observations. Some HDAC inhibitors showed potent anthelmintic activities; three of them -entinostat, TH65, and TH92- had pronounced anthelmintic effects, reducing parasite viability by ~100% at concentrations of ≤ 20 μM. These compounds were selected for further characterization and showed anthelmintic effects in the micromolar range and in a time- and dose-dependent manner. Moreover, these compounds induced major alterations on the morphology and ultrastructural features of M. vogae. The potencies of these compounds were higher than albendazole and the anthelmintic effects were irreversible. Additionally, we evaluated pairwise drug combinations of these HDAC inhibitors and albendazole. The results suggested a positive interaction in the anthelmintic effect for individual pairs of compounds. Due to the maximum dose approved for entinostat, adjustments in the dose regime and/or combinations with currently-used anthelmintic drugs are needed, and the selectivity of TH65 and TH92 towards parasite targets should be assessed.

Conclusion, significance

The results presented here suggest that HDAC inhibitors represent novel and potent drug candidates against cestodes and pave the way to understanding the roles of HDACs in these parasites.

Neglected tropical diseases, such as echinococcosis and cysticercosis, which are caused by taeniid cestodes (tapeworms), represent serious public health problems in many countries around the world. Given that there is only a small number of approved anthelmintics for the treatment of cestodiases, and that most of them are not highly effective against larval stages, identifying novel drug targets and their associated compounds is critical. Histone deacetylases (HDACs) are enzymes that produce epigenetic modifications of chromatin, thus modifying cellular gene expression. In this study, we evaluate and characterize a number of HDAC inhibitors on the model cestode Mesocestoides vogae and report the anthelmintic profile of these compounds. Some of the HDAC inhibitors tested showed potent anthelmintic effects, particularly entinostat, TH65 and TH92. These compounds were selected as the most promising candidates due to their high potencies, which were superior to the commercially-available anthelmintic drug albendazole. We also evaluated pairwise drug combinations of HDAC inhibitors and albendazole. The findings of this study provide a starting point for the development of new HDAC-based cestocidal compounds.

Climate change facilitates a parasite's host exploitation via temperature-mediated immunometabolic processes

Global climate change can influence organismic interactions like those between hosts and parasites. Rising temperatures may exacerbate the exploitation of hosts by parasites, especially in ectothermic systems. The metabolic activity of ectotherms is strongly linked to temperature and generally increases when temperatures rise. We hypothesized that temperature change in combination with parasite infection interferes with the host's immunometabolism. We used a parasite, the avian cestode Schistocephalus solidus, which taps most of its resources from the metabolism of an ectothermic intermediate host, the three-spined stickleback. We experimentally exposed sticklebacks to this parasite, and studied liver transcriptomes 50 days after infection at 13°C and 24°C, to assess their immunometabolic responses. Furthermore, we monitored fitness parameters of the parasite and examined immunity and body condition of the sticklebacks at 13°C, 18°C and 24°C after 36, 50 and 64 days of infection. At low temperatures (13°C), S. solidus growth was constrained, presumably also by the more active stickleback's immune system, thus delaying its infectivity for the final host to 64 days. Warmer temperature (18°C and 24°C) enhanced S. solidus growth, and it became infective to the final host already after 36 days. Overall, S. solidus produced many more viable offspring after development at elevated temperatures. In contrast, stickleback hosts had lower body conditions, and their immune system was less active at warm temperature. The stickleback's liver transcriptome revealed that mainly metabolic processes were differentially regulated between temperatures, whereas immune genes were not strongly affected. Temperature effects on gene expression were strongly enhanced in infected sticklebacks, and even in exposed-but-not-infected hosts. These data suggest that the parasite exposure in concert with rising temperature, as to be expected with global climate change, shifted the host's immunometabolism, thus providing nutrients for the enormous growth of the parasite and, at the same time suppressing immune defence.

[Potential hazard of zoonotic parasites present in canine feces in Puerto Escondido, Oaxaca]

OBJECTIVE

To estimate the zoonotic parasites prevalence in feral dog feces in Puerto Escondido.

MATERIAL AND METHODS

The fecalism frecuency was estimated in ten zones. To identify the parasites parasitological flotation and direct smear methods were used. The parasitic prevalence was estimated in the canine feces.

RESULTS

All the zones presented canine fecalism. The parasitic prevalence in the feces was 73.33%. The parasites with the highest prevalence were Toxocara canis (47.78%), Ancylostoma caninum (17.88%), and Dipylidium caninum (13.89%).

CONCLUSION

Canine fecalism comes from strayed and owned dogs. 66.66% of the parasites found in the dog feces are zoonotics. The factors associated to this problem are the suburban habitat, waste mishandling and nil tenure of stray dogs.

[Peculiarities of the biology and parasite fauna of juvenile Atlantic salmon (Salmo salar L.) in the Pista River (White Sea Basin), according to the Gyrodactylus salaris infestation]

Juvenile salmon Salmo salar m. sebago Girard from the Pista River system (the White Sea Basin) was investigated. The data on species composition and occurrence peculiarities of Gyrodactylus salaris Malmberg, 1957 are given. This monogenean is the alien species for the river system and it is recorded for the first time. It is shown that the distribution of the parasite abundance is can be described as the negative binomial distribution; variations of its parameters (k and p) were also characterized. Parasitological data obtained, as well as the data describing the characteristics of growth and age structure of juvenile salmon population, suggest the potential influence of G. salaris infection on the degree of survival of fishes in the lake-river system examined.

Early infection of discus Symphysodon aequifasciatus altricial larvae by Sciadicleithrum variabilum (Monogenea)

The occurrence of Sciadicleithrum variabilum on the gills of discus Symphysodon aequifasciatus larvae 7 days after hatching is reported for the first time. This suggests that altricial larvae are susceptible to Monogenea following gill differentiation and before complete yolk resorption.

On the Species of Diphyllobothrium occurring in Birds, and their Relation to Man and other Hosts

A comparative study has been made of certain species of Diphyllobothrium which are primarily parasites of birds, but which have been obtained from man and other hosts, both naturally and experimentally. As a result of this work it appears that only two valid species are known in birds, namely: Diphyllobothrium dendriticum (Nitzsch, 1824) and D. ditremum (Creplin, 1825). These species differ markedly from each other in certain morphological features and there appears to be a noticeable difference in their host-adaptation, inasmuch as D. ditremum occurs only in birds belonging to the families Phalacrocoracidae, Ardeidae, Colymbidae and Anatidae, while D. dendriticum occurs naturally in birds belonging to the Laridae and other families, and experimentally also in mammals.

A Survey of the Intestinal Helminths Parasitic in British Domestic Fowl

1. Examination of 289 fowl showed that 69·2% were infected with intestinal helminths. The following 6 species were identified: Ascaridia galli (33·6%), Capillaria anatis (10·4%), C. caudinflata (15·9%), C. obsignata (45·3%), Davainea proglottina (0·7%) and Heterakis gallinarum (60·9%).

2. No parasites were found in the upper intestines of 151 fowl.

3. The results are compared with those of previous surveys and are discussed in relation to the age and management of the birds.

The First Record of Human Infection with Bertiella studeri in Malaya

1. A six year old child living in Singapore was found to be infected with the cestode Bertiella studeri.

2. Apparent cure was affected by use of Dichlorophen.

The anatomy of Cysticercus taeniae-taeniaeformis (Batsch 1786) (Cysticercus fasciolaris Rud. 1808), from the liver of Rattus norvegicus (Erx.), including an account of spiral torsion in the species and some minor abnormalities in structure

1. The musculature and excretory and nervous systems of Cysticercus taeniae-taeniaeformis are described.

2. The nervous system consists often longitudinal nerve cords in the strobila and of a brain and complicated system of nerves in the scolex. The nervous system of the scolex shows several variations on the earlier description by Bartels (1902).

3. Minor abnormalities have been found in the form of multiplication of the lateral margins and duplication of the ventral excretory vessels.

4. Three specimens showed spiral torsion of the internal organs involving the musculature and excretory and nervous systems of the strobila. The number of turns of the spiral and the positions of the chiasmata are variable. It is suggested that the spiral twisting occurs before growth and strobilation in the neck region has begun, the chiasmata being carried back as new segments are formed.

Some new and little known cestodes from Australian elasmobranchs with a brief discussion on their possible use in problems of host taxonomy

One diphyllidean and five tetraphyllidean cestodes from Australian elasmobranchs are described and figured.Echinobothrium heroniensissp.nov., fromHimantura granulata(Macleay, 1883) possesses two groups each of 42 apical hooks, eight rows each of 25 hooks on the cephalic peduncle and ten testes in each proglottid. InAnthobothrium sexorchidumsp.nov. fromT. lymna(Forskal, 1775) there are only six testes and the bothridium is irregularly divided into a number of shallow areolae while inRhinebothrium himanturisp.nov. fromHimantura granulatathere are 22 proglottids, 52 loculi and 19–20 testes. Comments are made on the taxonomy ofRhinebothriumsp.,Spiniloculus mavensisandYorkeria parva.The value of some helminths, especially cestodes from elasmobranchs, as an aid to the study of the taxonomy, biology and zoogeography of their hosts is briefly discussed with reference to some previous papers on this topic. Previous work on the cestodes of Australasian marine fishes is summarized briefly.

Some cyclophyllidean cestodes from carnivores in Southern Rhodesia

Three new species of cestodes are described. They are: Joyeuxiella paucitestis sp.nov. from the Rusty Spotted Genet, Genetta rubiginosa; Diplopylidium paurodex sp.nov. from the Rusty Spotted Genet, Genetta rubiginosa; Taenia crocutae sp.nov. from the Spotted Hyaena, Crocuta crocuta.

Re-descriptions are given of Joyeuxiella fuhrmanni (Baer, 1924), Fuhrmann, 1935, and Taenia ingwei Ortlepp, 1938, with particular reference to differences between the original descriptions and those based upon the present material.

Observations on the occurrence of the plerocercoids of Triaenophorus nodulosus (Pallas, 1781) (Cestoda: Pseudophyllidea) in the perch Perca fluviatilis L. of Llyn Tegid (Bala Lake), Merionethshire

The perch was the principal host for the plerocercoid of Triaenophorus nodulosus in Llyn Tegid.

Three stages of plerocercoid development were recognized: non-encapsuled developing plerocercoids, encapsuled but living mature plerocercoids, and dead encapsuled degenerate plerocercoids.

The stomach contents of the perch were analysed and planktonic crustaceans were found to be a significant part of the food from May to December. No change in diet in relation to length was found.

The period of occurrence of developing plerocercoids in the perch livers was March to June. This in relation to other evidence was shown to indicate the period of infection of the perch by the procercoids.

The three stages of plerocercoid development recognized were found to occur simultaneously in a few perch, and thus may represent infections acquired over three successive seasons.

There was no seasonal periodicity of occurrence of the plerocercoids in the perch.

All the perch examined were more or less equally infected by plerocercoids. There was no tendency for older, longer perch to be more heavily infected.

One to five capsules, normally containing one plerocercoid each, occurred in the livers of the infected perch.

For the perch examined there was a dynamic equilibrium between establishment of procercoids from the copepod host, and loss of plerocercoids by degeneration within the perch.

The mature plerocercoids form the reservoir of infection for the definitive host of T. nodulosus, the pike.

Certain aspects of the host-parasite relationship of Nematospiroides dubius (Baylis). I. Resistance of male and female mice to experimental infections

1. It has been shown that there is a difference between the resistance of male and female mice to infection withNematospiroides dubius.

2. More parasites were harboured, during both the larval and adult parasitic phases, by male mice.

3. These worms were found to occupy a similar relative length of the intestine between the stomach and the caecum in male and female mice infected for either 5 or 10 days.

4. The relative length of the intestine infected on the fifth day was significantly greater than that infected on the tenth day.

This investigation was carried out during the tenure of a Research Studentship from the Department of Scientific and Industrial Research. I should like to thank Professor I. Chester Jones, in whose department the work was done, for the facilities provided and Dr E. T. B. Francis for his helpful and critical supervision.

Studies on the tapeworm Anoplocephala perfoliata (Goeze, 1782)

1. The exrectory system of Anoplocephala perfoliata has been re-described and shown to consist of a dorsal ‘network’ system of vessels to which the flame cells are connected and a ventral pair of longitudinal vessels linked only by a transverse vessel in each proglottid.

2. The two excretory systems unite only in the apical ramifying vessels of the scolex.

3. Alkaline phosphatase activity was demonstrated in the cuticular microvilli, the subcuticular region and in the excretory vessels.

4. Non-specific esterase, insensitive to 10−4m E 600, was located in the lappets and embryonated eggs and esterases, inhibited by 10−4m E600, in parts of the cuticle and subcuticular region and parenchyma.

5. Cholinesterases were found in the nervous system and in the reproductive ducts.

6. Aminopeptidase was found in the neck region, in the undifferentiated proglottids, the active testes and ovaries, the male reproductive ducts and in the region of high metabolic activity in the fringe of the proglottid.

On the transmission, biology and morphology of Echinococcus granulosus equinus, a new subspecies of hydatid tapeworm in horses in Great Britain

1. A 12·8% incidence of hydatid infections occurred in 709 horses examined in England. By contrast, hydatid cysts do not occur in horses in New Zealand where Echinococcus granulosus granulosus is common in sheep, cattle and swine.

2. Experimentally, scolices from hydatid cysts from English horses reached a gravid state in laboratory dogs. It was not possible to infect horses with E. g. granulosus of sheep-dog origin, and only one of two sheep became infected with two cysts following the ingestion of eggs of English horse-dog origin.

3. Our observations, together with those of others on secondary hydatid cyst formation, indicate that the two types are not only biologically but morphologically distinct.

4. In the horse-dog worms, the cirrus sac tilts anteriorly at an acute angle; the testes (about 35) are distributed throughout the proglottid with two or three rows posterior to the vitelline gland, and persist in proglottids when some mature eggs are present; the average length of the rostellar hooks is greater than in E. g. granulosus.

5. It is proposed that the horse-dog material be named E. g. equinus subsp. nov.

6. Rostellar hooks from cysts in British cattle resembled morphologically those from horses, while those from a British sheep and from man were like the hooks from hydatid cysts in man and livestock in New Zealand.

7. A red deer, hedgehog and European rabbit were not infected artificially following the ingestion of eggs of E. g. equinus.

Mr J. T. Briggs, Chief Public Health Inspector, Public Health Department, Bently, Doncaster, England, was responsible for the inspection of the British horses reported in this paper. We are indebted to Mr Briggs for this courtesy and for sending us fresh hydatid cysts from horses for experimental purposes. Mr N. Aitken was responsible for maintaining the experimental horses in an area of New Zealand known to be free of E. granulosus. Our thanks are also due to Messrs G. D. Page, D. V. Weston, Miss L. A. Duncan and Mrs B. R. Clarke for their able technical assistance.

Cytological and histochemical criteria for evaluating development of trematodes and pseudophyllidean cestodesin vivoandin vitro

1. Maturation of the plerocercoid of the pseudophyllidean cestodeDiphyllobothriumsp. and the metacercaria of the strigeid trematodeDiplostomum phoxinifollow a similar pattern, which may be divided into the following phases: (1) cell multiplication; (2) segmentation or body shaping; (3) organogeny; (4) early gametogeny; (5) late gametogeny; (6) egg-shell formation and vitellogenesis; (7) oviposition.

2. Cytological or histochemical criteria have been developed by means of which each developmental phase may be recognized. Developmentin vitromay be considered comparable with that occurringin vivoif the same phases are completed with the same incubation time and without the appearance of cytological abnormalities.

3. The cell multiplication phase is characterized by high mitotic activity. This activityin vitrocan be evaluated by incubating larvae after 24 hr. culture for a standard time (5 hr.Diphyllobothrium; 4 hr.Diplostomum) in 10−4colchicine and comparing the number of mitoses seen in a defined area of an aceto-orcein squash with those found in tissue maturedin vivofor the same period. Use of this criterion enables the growth-producing properties of a medium to be assessed after 24 hr. culture.

4. Phases 2–4 are characterized by the appearance of the tubular genitalia, the rudiments of which are readily recognized in aceto-orcein squashes or whole mount preparations.

5. The presence of spermatids and mature spermatozoa (phases 4–5) may be detected in aceto-orcein squashes or in fresh tissue teases. The quantity and activity of spermatozoa also serve as important criteria.

6. Recognition of phase 6, egg-shell formation, is carried out by means of diazo reagents which give orange or orange-red reactions with the phenolic egg-shell precursors in the vitellaria, as seen in whole mount preparations. Abnormal egg-shell development is reflected in the failure of vitellaria to give a normal diazo reaction.

7. The appearance of eggs which are macroscopically normal constitutes the final maturation phase. Early detection of eggs (especially abnormal ones) is facilitated by the use of the diazo reaction or the catechol test for polyphenol oxidase.

8. Embryonation and hatching of eggs to produce morphologically normal infective coracidia or miracidia serve as a final criteria.

9. Criteria for the maintenance of the adult condition are also considered.

A review of the species of Dinobothrium (Cestoda), with a description of a new species

A critical review is presented of the species of Dinobothrium and their probable synonyms. D. septaria v. Beneden and D. planum Linton are accepted as valid species. D. keilini Sproston and D. plicitum Linton are regarded as of doubtful status, the former being probably a synonym of D. septaria, while D. plicitum may be a synonym of D. planum. The type-specimens of D. keilini and of D. paciferum Sproston have been re-examined. A new interpretation is offered of the structure of the scolex of D. paciferum, and some other details of its anatomy are redescribed. A small species from Cetorhinus maximus is described, which is very similar to, and may prove to be identical with, Dinobothrium paciferum. As it apparently differs in having the neck and parts of the bothria covered with spines, it is treated as a distinct species and named D. spinosum. The question of the specific identity of the known larval forms of Dinobothrium is briefly discussed.

On six new avian cestodes from India

Six new species of cestodes from birds have been described. These are: Ophryocotyle indicus from the Rufous Babbler, Turdoides subrufus; Biuterina dicruri from the Grey Drongo, Dicrurus leucophaeus longicaudatus; Choanotaenia tandani from the Himalayan Whistling Thrush, Myiophoneus caeruleus temminckii; Choanotaenia picusi from the Scalybellied Green Woodpecker, Picus squamatus; Panuwa stylicirrosa from the Little Scalybellied Green Woodpecker, Picus xanthopygaeus; and Anoncotaenia indica from the Rufous-bellied Niltava, Muscicapa sundara.

Parasitic zoonoses in Papua New Guinea

Relatively few species of zoonotic parasites have been recorded in humans in Papua New Guinea. A greater number of potentially zoonotic species, mostly nematodes, occur in animals but are yet to be reported from humans. Protozoa is the best represented group of those infecting man, withGiardia duodenalis,Cryptosporidium parvum,Cyclospora cayetanesis,Toxoplasma gondii,Sarcocystisspp.,Entamoeba polecki,Balantidium coliand, possibly,Blastocystis hominis. The only zoonotic helminths infecting humans include the trematodeParagonimus westermani, the cestodesHymenolepis nana,H. diminutaand the sparganum larva ofSpirometra erinacea, and the nematodesTrichinella papuaeandAngiostrongylus cantonensisand, possibly,Ascaris suum. Other groups represented are Acanthocephala (Macracanthorhynchus hirudinaceus)), insects (Chrysomya bezziana,Cimexsp.,Ctenocephalidesspp.), and mites (Leptotrombidiumspp. and, possiblySarcoptes scabiei, andDemodexsp.). One leech (Phytobdella lineata) may also be considered as being zoonotic. The paucity of zoonotic parasite species can be attributed to long historical isolation of the island of New Guinea and its people, and the absence until recent times of large placental mammals other than pig and dog. Some zoonotic helminths have entered the country with recent importation of domestic animals, in spite of quarantine regulations, and a few more (two cestodes, one nematode and one tick) are poised to enter from neighbouring countries, given the opportunity. Improvement in water supplies, human hygiene and sanitation would reduce the prevalence of many of these parasites, and thorough cooking of meat would lessen the risk of infection by some others.

Insight into the role of cetaceans in the life cycle of the tetraphyllideans (Platyhelminthes: Cestoda)

Four types of tetraphyllidean larvae infect cetaceans worldwide: two plerocercoids differing in size, 'small' (SP) and 'large' (LP), and two merocercoids referred to as Phyllobothrium delphini and Monorygma grimaldii. The latter merocercoid larvae parasitize marine mammals exclusively and exhibit a specialised cystic structure. Adult stages are unknown for any of the larvae and thus the role of cetaceans in the life cycle of these species has been a long-standing problem. The SP and LP forms are thought to be earlier stages of P. delphini and M. grimaldii that are presumed to infect large pelagic sharks that feed on cetaceans. A molecular analysis of the D2 variable region of the large subunit ribosomal DNA gene based on several individuals of each larval type collected from three Mediterranean species of cetaceans showed consistent and unique molecular signatures for each type regardless of host species or site of infection. The degree of divergence suggested that LP, P. delphini and M. grimaldii larvae may represent separate species, whereas SP may be conspecific with M. grimaldii. In all host species, individuals of SP accumulated in the gut areas in which the lymphoid tissue was especially developed. We suggest therefore that these larvae use the lymphatic system to migrate to the abdominal peritoneum and mesenteries where they develop into forms recognizable as M. grimaldii. The plerocercoid stage of P. delphini remains unknown. In a partial phylogenetic tree of the Tetraphyllidea, all larvae formed a clade that included a representative of the genus Clistobothrium, some species of which parasitize sharks such as the great white which is known to feed on cetaceans. A bibliographic examination of tetraphyllidean infections in marine mammals indicated that these larvae are acquired mostly offshore. In summary, the evidence suggests that cetaceans play a significant role in the life cycle of these larvae. In addition, it seems clear that cetaceans act as natural intermediate hosts for P. delphini and M. grimaldii, as within these hosts they undergo development from the plerocercoid stage to the merocercoid stage. Because tetraphyllidean species use fish, cephalopods and other marine invertebrates as intermediate hosts, the inclusion of cetaceans in the life cycle would have facilitated their transmission to apex predators such as the large, lamnid sharks. The biological significance of infections of LP in cetaceans is unclear, but infections do not seem to be accidental as such larvae show high prevalence and abundance as well as a high degree of site specificity, particularly in the anal crypts and bile ducts.