Clinical forms of peritoneal larval cestodiasis by Mesocestoides spp. in dogs: diagnosis, treatment and long term follow-up.

Canine peritoneal larval cestodiasis (CPLC) is a little-known parasitological infestation of the peritoneal cavity of wild and domestic carnivores with Mesocestoides spp. larvae. While adult Mesocestoides tapeworms reside within the small intestine, the larvae occasionally penetrate the host's intestinal wall, causing a potentially life-threatening peritonitis. Severity of infection as well as the host response influences the prognosis significantly, and early diagnosis and treatment are essential. However, due to the lack of specific symptoms, this condition is underdiagnosed and, furthermore, no clear effective treatment has yet been described. The aim of this study is therefore to report two clinical cases of CPLC in dogs and to illustrate their clinical presentation and follow-up to serve as a reference for clinicians and researchers alike. Both animals were presented with abdominal distention as their main complaint. They underwent clinical examination, abdominal ultrasonography, abdominocentesis, and laparotomy followed by biochemical, cytological, parasitological, and molecular examination of the collected samples. After surgical lavage, the dogs received anthelmintic treatment with either fenbendazole (FBZ) or praziquantel (PZQ). Overall, timely and prolonged administration of high doses of FBZ seems to be the most effective treatment method. Irrespective, to date, no treatment capable of complete eradication of the infection and prevention of recurrence of disease has been found. In conclusion, further investigation into appropriate treatment plans as well as diagnostic development is needed.

Rodents as intermediate hosts of cestode parasites of mammalian carnivores and birds of prey in Poland, with the first data on the life-cycle of Mesocestoides melesi.

BACKGROUND: Rodents constitute an important part of the diet of many carnivore species. This predator-prey food chain is exploited by helminth parasites, such as cestodes, whose larval stages develop in rodents and then mature to the adult stage in predators. The main aim of our study was to use molecular techniques for identification of cestode species recovered from both intermediate and definitive hosts, with a particular focus on the genus Mesocestoides. METHODS: Larval cestodes were obtained during our long-term studies on rodent helminth communities in the Mazury Lake District in the north-east Poland in 2000-2018. Cestode larvae/cysts were collected from body cavities or internal organs (e.g. liver) during autopsies. Adult tapeworms were derived from nine red foxes, three Eurasian badgers and one Eurasian lynx. PCR amplification, sequencing and phylogenetic analyses were conducted employing three genetic markers: 18S rDNA, mitochondrial (mt) 12S rDNA and the mt cytochrome c oxydase subunit 1 (cox1) gene fragment. RESULTS: Altogether 19 Mesocestoides samples were analyzed, including 13 adult tapeworms from definitive hosts and six larval samples from 4 bank voles and 2 yellow-necked mice. Phylogenetic analyses revealed three well-supported trees of similar topology. In each case the Mesocestoides samples formed two separate clades. All isolates from foxes, the lynx isolate and two isolates from rodents grouped with Mesocestoides litteratus. Four isolates from rodents and all three isolates from Eurasian badgers were resolved in a separate clade, most similar to North American M. vogae (syn. M. corti). Examination of fixed, stained adult specimens from Eurasian badgers revealed consistency with the morphology of Mesocestoides melesi. Therefore, this clade is likely to represent M. melesi, a species first described in 1985 from the Eurasian badger Meles meles. Molecular analysis allowed also the identification of Taenia crassiceps, Hydatigera kamiyai and Cladotaenia globifera among larvae derived from rodents. CONCLUSIONS: Molecular and phylogenetic analyses support the recognition of M. melesi as a valid species. Our data represent the first record of the larvae of this species in rodents. This is the first report on the occurrence of H. kamiyai in rodents from Poland.

Transcriptomic profile of two developmental stages of the cestode parasite Mesocestoides corti.

Cestode development involves complex morphological and physiological changes. Here, we performed a differential expression analysis of gene transcripts between two developmental stages of the model cestode Mesocestoides corti. A RNA-seq-based approach was used to compare the transcriptomes of the tetrathyridium (larval, TT) and strobilated worm (ST) stages of the parasite. We found 19,053 transcripts, from which ∼45% were complete matches to genes previously annotated in the available M. corti draft genome sequence, ∼24% were considered novel isoforms, and ∼24% were considered potential novel transcripts. Stage-specific transcripts were found for both TTs (66) and STs (136), along with shared transcripts significantly overrepresented in one stage (342 in TTs, and 559 in STs). Differential expression and Gene Ontology term enrichment analyzes provided evidence of upregulation of different sets of transcripts associated with 'cytoskeleton', 'metabolism' and 'oxidation-reduction' processes in each stage, suggesting functional involvement of the corresponding genes with stage-specific features. Transcripts and processes enriched in the TT reflect typical larval processes that occur with the parasite in the intermediate host, such as asexual reproduction and budding, as well as active migration from the peritoneum to the liver and vice versa. In STs, transcripts associated with 'development', 'cell growth', and 'morphogenesis' were enriched, along with processes related to sexual reproduction, represented by the upregulation of numerous transcription factors, protein kinases, and histones. Overall, our results contributed to significantly increase the knowledge on the M. corti gene repertoire and expression profile in two developmental stages. Functional implications for the biology of larval and adult cestode parasites and for host-parasite interactions are discussed.

Unique pharmacological properties of serotoninergic G-protein coupled receptors from cestodes.

BACKGROUND: Cestodes are a diverse group of parasites, some of them being agents of neglected diseases. In cestodes, little is known about the functional properties of G protein coupled receptors (GPCRs) which have proved to be highly druggable targets in other organisms. Notably, serotoninergic G-protein coupled receptors (5-HT GPCRs) play major roles in key functions like movement, development and reproduction in parasites. METHODOLOGY/PRINCIPAL FINDINGS: Three 5-HT GPCRs from Echinococcus granulosus and Mesocestoides corti were cloned, sequenced, bioinformatically analyzed and functionally characterized. Multiple sequence alignment with other GPCRs showed the presence of seven transmembrane segments and conserved motifs but interesting differences were also observed. Phylogenetic analysis grouped these new sequences within the 5-HT7 clade of GPCRs. Molecular modeling showed a striking resemblance in the spatial localization of key residues with their mammalian counterparts. Expression analysis using available RNAseq data showed that both E. granulosus sequences are expressed in larval and adult stages. Localization studies performed in E. granulosus larvae with a fluorescent probe produced a punctiform pattern concentrated in suckers. E. granulosus and M. corti larvae showed an increase in motility in response to serotonin. Heterologous expression revealed elevated levels of cAMP production in response to 5-HT and two of the GPCRs showed extremely high sensitivity to 5-HT (picomolar range). While each of these GPCRs was activated by 5-HT, they exhibit distinct pharmacological properties (5-HT sensitivity, differential responsiveness to ligands). CONCLUSIONS/SIGNIFICANCE: These data provide the first functional report of GPCRs in parasitic cestodes. The serotoninergic GPCRs characterized here may represent novel druggable targets for antiparasitic intervention.

Spatio-temporal expression of Mesocestoides corti McVAL2 during strobilar development.

VAL proteins belong to a diverse superfamily containing the CAP domain, with members described for various eukaryotic organisms, including parasites. They are implicated in diverse biological activities and, as secreted proteins, may be related in host - parasite interactions. For this reason they have been proposed as vaccine candidates against nematode infections. However, little is known about their function in cestodes. In M. corti, four partial cDNA sequences coding for members of the CAP superfamily were previously isolated. In this work we characterize the expression of McVAL2 in the larvae and segmented worms of M. corti, describing mRNA and protein localization using fluorescent microscopy. We also optimized real time PCR analysis for quantification of mRNA expression through the different stages of strobilar development. We show that McVAL2 is differentially located, depending on the developmental stage, and can be used as a molecular marker for the neuroendocrine system in the larvae. The dynamic and stage-specific expression patterns of McVAL2, combined with the large number of VAL proteins found in the genomes of parasitic flatworms, suggest varied roles for the VAL protein family in the biology of these parasites.

Identification and profiling of microRNAs in two developmental stages of the model cestode parasite Mesocestoides corti.

MicroRNAs (miRNAs), a class of small non-coding RNAs, are key regulators of gene expression at post-transcriptional level and play essential roles in fundamental biological processes such as metabolism and development. The particular developmental characteristics of cestode parasites highlight the importance of studying miRNA gene regulation in these organisms. Here, we performed a comprehensive analysis of miRNAs in two developmental stages of the model cestode Mesocestoides corti. Using a high-throughput sequencing approach, we found transcriptional evidence of 42 miRNA loci in tetrathyridia larvae and strobilated worms. Tetrathyridium and strobilated worm-specific miRNAs were found, as well as differentialy expressed miRNAs between these developmental stages, suggesting miRNA regulation of stage-specific features. Moreover, it was shown that uridylation is a differential mechanism of post-transcriptional modification of M. corti miRNAs. The whole set of M. corti miRNAs represent 33 unique miRNA families, and confirm the remarkable loss of conserved miRNA families within platyhelminth parasites, reflecting their relatively low morphological complexity and high adaptation to parasitism. Overall, the presented results provide a valuable platform to studies aiming to identify and characterize novel miRNA-based molecular mechanisms of post-transcriptional gene regulation in cestodes, necessary for the elucidation of developmental aspects of the complex biology of these parasites.

In vitro culture of Mesocestoides corti metacestodes and isolation of immunomodulatory excretory-secretory products.

Cestode-mediated diseases hold the interesting feature of persisting metacestode larvae dwelling within the host tissues, in the midst of the immune response. Excretory-secretory (ES) products of the metacestode larval stage modulate the host immune response and modify the outcome of the disease. Therefore, isolation and analysis of axenic metacestode ES products are crucial to study their properties. Here, we report the development of a system for long-term in vitro cultivation of the metacestode of the parasitic cestode Mesocestoides corti (syn. Mesocestoides vogae). Although feeder cells and host serum supported the early growth of the parasite, long-term survival was not dependent on host serum or host-derived factors enabling the collection of parasite released products in serum-free medium. Functionally, these axenic ES products recapitulated M. corti tetrathyridia's ability to inhibit LPS-driven IL-12p70 secretion by dendritic cells. Thus, our new axenic culture system will simplify the identification and characterization of M. corti-derived immunomodulatory factors that will indirectly enable the identification and characterization of corresponding factors in the metacestode larvae of medically relevant cestodes such as Echinococcus multilocularis that are not yet amenable to serum-free cultivation.

Occurrence of Mesocestoides canislagopodis (Rudolphi, 1810) (Krabbe, 1865) in mammals and birds in Iceland and its molecular discrimination within the Mesocestoides species complex.

The life cycle of Mesocestoides tapeworms (Cestoda: Cyclophyllidea: Mesocestoididae) requires three hosts. The first intermediate host is unknown but believed to be an arthropod. The second intermediate host is a vertebrate. The primary definitive host is a carnivore mammal, or a bird of prey, that eats the tetrathyridium-infected second intermediate host. One representative of the genus, Mesocestoides canislagopodis, has been reported from Iceland. It is common in the arctic fox (Vulpes lagopus) and has also been detected in domestic dogs (Canis familiaris) and cats (Felis domestica). Recently, scolices of a non-maturing Mesocestoides sp. have also been detected in gyrfalcon (Falco rusticolus) intestines, and tetrathyridia in the body cavity of rock ptarmigan (Lagopus muta). We examined the taxonomic relationship of Mesocestoides from arctic fox, gyrfalcon, and rock ptarmigan using molecular methods, both at the generic level (D1 domain LSU ribosomal DNA) and at the specific level (cytochrome c oxidase subunit I (COI) and 12S mitochondrial DNA). All stages belonged to Mesocestoides canislagopodis. Phylogenetic analysis of the combined 12S-COI at the specific level confirmed that M. canislagopodis forms a distinct clade, well separated from three other recognized representatives of the genus, M. litteratus, M. lineatus, and M. corti/vogae. This is the first molecular description of this species. The rock ptarmigan is a new second intermediate host record, and the gyrfalcon a new primary definitive host record. However, the adult stage seemed not to be able to mature in the gyrfalcon, and successful development is probably restricted to mammalian hosts.

A new approach for the characterization of proliferative cells in cestodes.

Cestodes show a remarkable proliferative capability that sustains the constant growth and differentiation of proglottids essential for their lifestyle. It is believed that a separate population of undifferentiated stem cells (the so-called germinative cells) are the only cells capable of proliferation during growth and development. The study of this particular cell subpopulation is hampered by the current lack of methods to isolate it. In this work, we developed a reproducible flow cytometry and cell sorting method to quantify and isolate the proliferating cells in the tetrathyridia larvae of the model cestode Mesocestoides corti, based on the DNA content of the cells. The isolated cells display the typical germinative cell morphology, and can be used for RNA isolation with a yield in the ng to µg range. We expect that this approach may facilitate the characterization of the germinative cells in M. corti and other model tapeworms.

Proteomic survey of the cestode Mesocestoides corti during the first 24 hours of strobilar development.

Despite the fact that cestodes represent major etiological agents of both human and domestic animal diseases, little is known about the molecular aspects of cestode development. In this work, Mesocestoides corti, a model cestode species, was studied from the early development of its larval form (tetrathyridium) into adult worms (strobilation) using different proteomic approaches. The protein profiles of M. corti tetrathyridia induced or not induced to undergo strobilation were compared. Proteomic mapping by two-dimensional gel electrophoresis showed the resolution of 248 and 154 spots from tetrathyridia that were subjected or not subjected to strobilation induction, respectively, allowing for the detection of at least nine spots exclusive to each group. Spot analysis by matrix-assisted laser desorption/ionization time-of-flight (MALDI-TOF) mass spectrometry (MS) or MALDI-TOF MS/MS identified four reference proteins (six spots). LC-MS/MS analyses of protein extracts identified 66 proteins, eight of which were found exclusively in non-induced tetrathyridia, while 13 were found exclusively in strobilation-induced tetrathyridia. Among the proteins exclusively identified in strobilation-induced worms, there was a predominance of proteins with functions relating to chaperone activity and protein synthesis and turnover. Quantitative differential expression analysis between M. corti tetrathyridia prior to and after strobilation induction revealed six proteins upregulated in strobilation-induced worms; these proteins were involved in metabolic pathways, cell proliferation, and cytoskeletal rearrangement. Overall, despite the absence of a sequenced M. corti genome, using sequences from other platyhelminthes, we were able to establish comprehensive protein profiles for tetrathyridia prior to and after strobilation induction and identify several proteins potentially involved in the early events leading to strobilation.

Developmental expression of high molecular weight tropomyosin isoforms in Mesocestoides corti.

Tropomyosins are a family of actin-binding proteins with diverse roles in actin filament function. One of the best characterized roles is the regulation of muscle contraction. Tropomyosin isoforms can be generated from different genes, and from alternative promoters and alternative splicing from the same gene. In this work, we have isolated sequences for tropomyosin isoforms from the cestode Mesocestoides corti, and searched for tropomyosin genes and isoforms in other flatworms. Two genes are conserved in the cestodes M. corti and Echinococcus multilocularis, and in the trematode Schistosoma mansoni. Both genes have the same structure, and each gene gives rise to at least two different isoforms, a high molecular weight (HMW) and a low molecular weight (LMW) one. Because most exons are duplicated and spliced in a mutually exclusive fashion, isoforms from one gene only share one exon and are highly divergent. The gene duplication preceded the divergence of neodermatans and the planarian Schmidtea mediterranea. Further duplications occurred in Schmidtea, coupled to the selective loss of duplicated exons, resulting in genes that only code for HMW or LMW isoforms. A polyclonal antibody raised against a HMW tropomyosin from Echinococcus granulosus was demonstrated to specifically recognize HMW tropomyosin isoforms of M. corti, and used to study their expression during segmentation. HMW tropomyosins are expressed in muscle layers, with very low or absent levels in other tissues. No expression of HMW tropomyosins is present in early or late genital primordia, and expression only begins once muscle fibers develop in the genital ducts. Therefore, HMW tropomyosins are markers for the development of muscles during the final differentiation of genital primordia.

Effectiveness of praziquantel for treatment of peritoneal larval cestodiasis in dogs: a case report.

Peritoneal larval cestodiasis (PLC) was incidentally identified in an adult female mixed-breed dog by explorative celiotomy done in response to abnormal blood values found during a routine work-up in preparation for an ovariohysterectomy. Ten days after ovariohysterectomy, treatment with fenbendazole began (50mg/kg, per os, every 12h, for 21 days). Two weeks after the end of treatment, samples of peritoneal fluid were obtained by paracentesis and examined. Motile peritoneal tetrathyridia were still evident. Fenbendazole was discontinued. After 10 days of withdrawal from fenbendazole, the dog was treated with a subcutaneous administration of injectable praziquantel (5mg/kg). The administration was repeated after a 15 days interval. Two weeks after the second administration, samples of peritoneal fluid were obtained again by paracentesis. Motile peritoneal tetrathyridia were not detected. Fourteen months after the last administration of praziquantel, the dog remained still free of peritoneal tetrathyridia as determined by abdominal ecography. Therefore, praziquantel was effective to eliminate peritoneal tetrathyridia definitely. Practitioners should be aware of PLC in order to early recognize this condition in case of incidental finding and implement adequate therapy as soon as possible.

Mesocestoides corti: morphological features and glycogen mobilization during in vitro differentiation from larva to adult worm.

Mesocestodes corti has the capacity to develop from the tetrathyridium (larva) stage to adult worm in vitro by trypsin and serum stimulation. Consequently, it has been used as an experimental model system for studying cestode development, host-parasite relationships and anthelmintic drugs. We describe morphological features in 5 different developmental stages of M. corti obtained in vitro, including larvae from the peritoneal cavity of infected mice, trypsin- and serum-stimulated larvae, elongated parasites as well as segmented and mature worms. It is unambiguously confirmed that sexually mature worms are obtained as a result of this in vitro process of differentiation. Defined cellular regions are present in all stages of development studied, some of them surrounded by a basal lamina. Glycogen is present in the larvae obtained from the mouse peritoneal cavity and in parasites encapsulated in the mouse host liver. Glycogen distribution in the parasite changes on trypsin and serum stimulation to differentiate. We propose that changes in the distribution of neutral polysaccharides in the parenchyma of the parasite at different stages of development and degradation of polysaccharides in the transition from segmented to adult worm are related to energy needs necessary for the cellular processes leading to the mature specimen.

In vivo response of Mesocestoides vogae to human insulin.

SUMMARY: Successful host invasion by parasitic helminths involves detection and appropriate response to a range of host-derived signals. Insulin signal response pathways are ancient and highly-conserved throughout the metazoans. However, very little is known about helminth insulin signalling and the potential role it may play in host-parasite interactions. The response of Mesocestoides vogae (Cestoda: Cyclophyllidea) larvae to human insulin was investigated, focusing on tyrosine-phosphorylation status, glucose content, survival and asexual reproduction rate. Parasite larvae were challenged with different levels of insulin for variable periods. The parameters tested were influenced by human insulin, and suggested a host-parasite molecular dialogue.

Preliminary analysis of cold stress responsive proteins in Mesocestoides corti larvae.

Many parasites undergo sudden changes in environmental conditions at some stage during their life cycle. The molecular response to this variation is characterised by a rapid transcriptional activation of a specific set of genes coding for proteins generically known as stress proteins. They appear to be also involved in various biological processes including cell proliferation and differentiation. The platyhelminth parasite, Mesocestoides corti (Cestoda) presents important properties as a model organism. Under stress conditions, key molecules involved in metabolic pathways as well as in the growth and differentiation of the parasite can be identified. 2D protein expression profile of tetrathyridia of M. corti, submitted to nutritional starvation and cold stress is described, as well as the recovery pattern. A set of specifically expressed proteins was observed in each experimental condition. Quantitative and qualitative differences and stress recovery pattern are also reported. This work makes evident the high plasticity and resistance to extreme environmental conditions of these parasites at the molecular level.

Developmental expression pattern of histone H4 gene associated to DNA synthesis in the endoparasitic platyhelminth Mesocestoides corti.

In higher eukaryotes, histone gene expression is coupled to DNA replication during the S-phase of the cell cycle. This coupling is primarily controlled at the transcriptional level. Considering the basal phylogenic position of platyhelminthes in the bilateria phylum, we have cloned a partial sequence of the histone H4 gene of Mesocestoides corti and studied its expression during the post larval development of this endoparasitic platyhelminth. In in vitro trypsin-induced tetrathyridia development to segmented adult worm, we found that histone H4 is expressed concomitantly with DNA synthesis throughout all stages of development. DNA synthesis and histone H4 mRNA levels were sharply increased at 24 h after inducing development. Afterwards, tetrathyridia grew in length from days 4 to 12 of development as proliferative cells gradually increased in number. Consequently, during this period of development histone H4 mRNA levels were upregulated. Taken together these results suggest that a replication-dependent expression pattern of histone H4 occurs in ancient bilateria, such as platyhelminthes, as previously observed in higher eukaryotes.

Localization, specific activity, and molecular forms of acetylcholinesterase in developmental stages of the cestode Mesocestoides corti.

The nervous system of flatworms is quite simple although there is increasing evidence indicating that it is chemically complex. Studies of the nervous system in these animals have only been performed in the larval stage or in the adult worms, which are easy to obtain in nature, while the description of the nervous system in developing stages of these organisms is missing. Mesocestoides corti is a parasitic platyhelminth whose larvae can be induced in vitro to develop to adult, sexually mature worms, opening the possibility of studying the nervous system of a flatworm in different stages of development. Here, we describe the presence, activity, location, and molecular forms of acetylcholinesterase (AChE) in different stages of development of M. corti, from the larvae to adult forms of this endoparasite, obtained in in vitro cultures after induction of the larval stage with trypsin. Our results point to AChE as a molecular marker of the nervous system in platyhelminthes. The change in molecular forms of this enzyme and the increase in its activity during development from larvae to adult worm may reflect the presence of a more complex nervous system, necessary to adjust and coordinate the movement of a much bigger structure. A relationship between the development of the reproductive apparatus in segmented and adult worms with a more complex nervous system in these stages is also apparent. Finally, our study opens the possibility of applying anti-AChE as more effective therapeutic strategies against cestode parasites.

Praziquantel and albendazole damaging action on in vitro developing Mesocestoides corti (Platyhelminthes: Cestoda).

Parasitic flatworms present several steps of body architecture rearrangement during their fast transition from one developmental stage to another, which are, at least in part, responsible for their evasion from host immune response. Besides, different developmental stages present different degrees of susceptibility to drug action, and the identification of more susceptible stages is of importance for the definition of therapeutical approaches. Mesocestoides corti (syn. Mesocestoides vogae) is considered a good model to study cestode biology because it can be easily manipulated both in vivo and in vitro and due to its relatively close relationship to cestodes of medical relevance, such as those from genera Echinococcus or Taenia. We have analyzed the damaging action of two broad spectrum anthelmintic drugs (praziquantel and albendazole) throughout the in vitro strobilization process of M. corti in order to identify developmental stages or body structures more susceptible to these drugs. Tetrathyridia (larval stage) and segmented-induced worms were cultivated and treated with praziquantel and albendazole. Whole mounted samples, taken from different developmental stages, were fixed and stained with fluorophore-labeled WGA lectin and phalloidin for the analysis of tegument and muscles, respectively. Confocal laser scanning microscopy was used to identify anatomical changes and lesions caused by each anthelmintic drug in a 3D view. We demonstrated that both praziquantel and albendazole cause extensive tissue damage, especially on tegument, and that adult forms were the most susceptible to drug exposure.