Journal of Helminthology最新文献

The diversity of Rhabdias includes 101 species, 71 of which parasitize the lungs of anurans, caudates, gymnophionans, and some occur in reptiles worldwide. Currently, 26 species are found in the Neotropical region, and in Brazil, there are 16 nominal species, a relatively low number considering the high diversity of potential hosts. Here, we describe a new species of Rhabdias found in Physalaemus albonotatus, with morphological and molecular data, as well as phylogenetic analyses using sequences of the mitochondrial gene Cytochrome Oxidase Subunit I (COI). Rhabdias taquariensis n. sp. differs from other known species by a set of morphometric traits and by presenting a well-defined internal shape of the cephalic dilation. Molecular analyses revealed that R. taquariensis n. sp. exhibits a significant divergence of 13.6% in COI compared to the Rhabdias cf. stenocephala species complex. Additionally, phylogenetic reconstructions indicate that the new species represents a distinct lineage, external to a clade formed by species such as Rhabdias fuelleborni, Rhabdias cf. stenocephala, and Rhabdias waiapi. Rhabdias taquariensis n. sp. is the 27th species described in the Neotropical region and the 16th in Brazil, the first description of a species of the genus Rhabdias for Physalaemus albonotatus, and one of the few Rhabdias species described for the Cerrado biome.

This study provides the description of a new species of Anisakidae, Contracaecum cocoi sp. nov., as well as the record of Contracaecum jorgei, both species parasitizing the Cocoi heron Ardea cocoi (Ardeidae) in a locality from the Buenos Aires Province, Argentina. An integrative taxonomic approach was used, involving phylogenetic analyses and the examination of diagnostic morphological features in the studied specimens. Among other features, the new species can be morphologically distinguished by the papillae arrangement on the male tail: while C. jorgei exhibits a simple morphotype A, C. cocoi sp. nov. presents an intermediate morphotype B. Mainly, the possession of three adcloacal papillae pairs is a diagnostic feature separating this new species from the rest of the Contracaecum species. The cox2 mtDNA isolates exhibited C. cocoi sp. nov. as a single node and grouped close to the clade formed by both species Contracaecum micropapillatum and C. bancrofti. The other cox2 mtDNA sequences showed a great concordance with C. jorgei. The K2P distances calculated for the cox2 mtDNA isolates of C. cocoi sp. nov. displayed a distance of 0.12 with C. bancrofti, 0.13 with C. micropapillatum, and 0.16 with C. jorgei. Contracaecum cocoi sp. nov. is proposed as a new taxon clearly supported by both phylogenetic analysis and distinctive morphological features that distinguish it from its congeners. The occurrence of C. cocoi sp. nov. together with C. jorgei in sympatric and syntopic conditions suggests that ecological or reproductive isolating mechanisms may be acting to maintain distinct lineages in shared environments. New records, particularly those involving intermediate and definitive hosts, will contribute to elucidating the distribution of these parasites in the Americas and potentially lead to the discovery of new species.

Many parasitic nematodes exhibit a range of behavioural responses to host-associated stimuli, especially chemicals. The infective juveniles (IJs) of specialized insect-infecting nematodes, i.e., entomopathogenic nematodes (EPNs), can show directed movement (taxis) or other behaviours in response to odorants. However, relatively little is known in terms of IJ responses in the context of increases in non-directed movement (kinesis) resulting from physical contact with host chemicals, or the effects of insect semiochemicals on EPN behaviours. We individually exposed IJs of the EPN Steinernema carpocapsae to solutions representing five different treatments, including those containing the macerated tissues of a suitable insect host (greater wax moth larvae - waxworms) or a semiochemical (1-pentadecene) secreted by various insects. We conducted behavioural observations at six time points over an 8-h period, measuring the total number of movements by each IJ (orthokinesis), along with the occurrence of side-to-side movements (klinokinesis) or head-waving. We found that IJs in the waxworm or 1-pentadecene solutions showed high levels of overall movement, but waxworm-exposed IJs also exhibited the most sinusoidal movement, whereas IJs exposed to 1-pentadecene exhibited far more head-waving than nematodes in the other treatments. These results indicate that S. carpocapsae shows behavioural responses through kinesis when exposed to host chemical cues in an aqueous medium. As our study is only the second report of EPNs responding to an insect semiochemical, this is a promising area for future studies to better understand host-finding strategies by these nematodes, with possible applications for their use in insect biocontrol.

Human strongyloidiasis, caused by Strongyloides stercoralis, is a neglected disease of high worldwide prevalence, with considerable potential for severe, fatal outcomes in complicated cases. Studies using the rodent parasite Strongyloides venezuelensis as a model have provided valuable insights into strongyloidiasis, yet efficient, standardised methods for isolating large quantities of viable parasite eggs for biomedical research remain scarce. This study revisits and modernises the classical flotation principle, presenting a saturated-solution centrifugation protocol for egg recovery from infected clawed jirds (Meriones unguiculatus). Saturated NaCl outperformed sucrose, primarily due to enhanced egg visualisation and reduced microbial contamination, achieving mean recovery of 84.8 ± 6.7% (peaks to 94%). Key variables - including faecal suspension volume, solution concentration, reprocessing, and the NaCl gradient - were systematically optimised to maximise recovery and viability. The resulting protocol is cost-effective, rapid, and practical, enabling scalable collection of viable S. venezuelensis eggs (and likely other nematodes) for different applications, including hatching studies, larval development, microenvironmental assays, and drug screening. By integrating classical diagnostics with parametric optimisation, this study exemplifies how methodological advances preserve and renew foundational knowledge, underscoring its epistemological value in experimental parasitology.

The alternation between wet and dry seasons in tropical regions can dramatically affect parasite infection dynamics by influencing larval survival, intermediate-host density, definitive-host foraging behaviour, and host immune function. Freshwater chelonians are excellent models for studying parasite-host ecology. Their longevity, site fidelity, and dietary breadth make them valuable sentinel species for aquatic ecosystem health. Here, we identified the gastrointestinal helminth fauna of scorpion mud turtle (Kinosternon scorpioides) from Marajó Island and evaluated seasonal effects on parasite community dynamics. We observed a 71% reduction in parasite load during the dry season and substantial compositional shifts, in addition to species-specific responses: Spiroxys figueiredoi exclusively during floods and Nematophila grandis peaking during dry periods. Parasite species with flexible transmission pathways may thrive while specialists decline. Kinosternon scorpioides and its parasites function as sentinels, and monitoring helminth community composition could more accurately track ecosystem health than measuring host abundance alone.

Marsupials have been the subject of experimental and natural parasitological studies on helminths in the Americas. Brazil has a significant proportion of the American marsupial fauna, with approximately 15 genera and 69 species out of 95 extant. Helminths have been reported for approximately one-third of the Brazilian marsupial species. Consequently, an update of this information is necessary to ensure the correct identification of the species. This work represents the first comprehensive review of the helminths of the Brazilian marsupials, including taxonomic information on both parasites and hosts. The data were extracted and compiled from references published from 1819 to 2023 and organised according to the classification of the helminths by the host name of the original description, followed by the updated host species nomenclature, geographical distribution, site of infection, and references. In total, 1,047 records of helminths parasitising 22 marsupial species in Brazil were compiled. The list included 93 identified species, including five of the phylum Acanthocephala, 58 of the phylum Nematoda, and 30 of the phylum Platyhelminthes. In addition, 51 other morphospecies were reported. This work may serve as a reference for future studies.

Metacercariae of Diplostomum spp. are globally distributed pathogens that infect the eyes and brains of fish and lampreys, including populations in northern latitudes. This study investigated the species diversity and distribution of Diplostomum in juvenile Atlantic salmon Salmo salar and brown trout Salmo trutta from 11 rivers in northwestern Russia. Phylogenetic analyses revealed two diplostomid species: 'D. mergi' Lineage 3 and D. numericum. It is the first record of these species in the Russian part of the Arctic. These species, previously recorded in Western/Central Europe and Russian Karelia, likely spread via major migratory flyways of their avian definitive hosts. The species composition of Diplostomum metacercariae in riverine salmonids of the studied region was notably poorer than in lacustrine salmonids from other Arctic localities. The haplotype distributions of recorded Diplostomum species showed no spatial structuring, consistent with broad-scale dispersal processes.

This study provides the first integrative analysis of Megacoelium spinicavum Thatcher & Varella, 1981 (Digenea: Haploporidae) from the Amazon sailfin catfish Pterygoplichthys pardalis Castelnau, 1855 (Siluriformes: Loricariidae) in the Peruvian Amazon. A detailed morphological description is presented, including the first scanning electron microscopy (SEM) images of tegumental structures, which revealed two distinct types of tegumental spines: (1) small, button-like spines and (2) sharply pointed spines. Partial sequences of the 28S rDNA and mitochondrial cox1 genes were generated and analysed to investigate the phylogenetic position of Megacoelium Szidat, 1954, within the Haploporidae Nicoll, 1914. Phylogenetic analyses placed M. spinicavum within the 'robust species' clade of Saccocoelioides Szidat, 1954, clustering with S. bacilliformis Szidat, 1973, although with weak support. These results provide additional evidence that Saccocoelioides is not monophyletic and support restricting the genus to the 'minute species' clade containing the type species. The 'robust species' clade appears to comprise at least three divergent lineages, potentially representing distinct genera, one of which includes M. spinicavum. The absence of molecular data for M. plecostomi Szidat, 1954, the type species of Megacoelium, continues to obscure its phylogenetic placement. We highlight the need for comprehensive morphological and multilocus molecular analyses, including SEM, to clarify the taxonomic status of Megacoelium and to resolve the evolutionary relationships of chalcinotrematine digeneans in Neotropical fishes.

An adult female great curassow (Crax rubra) and an adult female crested guan (Penelope purpurascens) were examined post-mortem and found to harbour trematode flukes in their pulmonary air sacs and coelom, with severe pathological changes. Seven trematode specimens (four from C. rubra and three from P. purpurascens) were stained with hydrochloric acid-carmine for optical microscopy, while four specimens (two from each bird species) were submitted to molecular analysis. Morphological and molecular analyses identified the specimens as Circumvitellatrema momota. Phylogenetic analysis showed that C. momota from different geographical origins constitutes a single species within the subfamily Cyclocoelinae and is clearly distinct from other cyclocoelid genera. This is the first documented case of C. momota infecting members of the Cracidae family. These findings highlight the importance of monitoring parasitic infections in captive and free-ranging cracids under conservation programmes.

TEM analyses of germinal elements in miracidia and 6-day-old mother sporocysts of Echinostoma caproni were performed. Germinal elements in miracidia are represented by undifferentiated cells and germinal cells. They are localised in the posterior half of the body and form the primordium of the germinal mass, which plays the role of the gonad. In mother sporocysts the germinal mass is located caudally and plays the dual role of the gonad and the uterus. In addition to the undifferentiated cells and germinal cells, it contains embryos, which develop there up to the stage of germinal balls and then move into the sporocyst's schizocoel, which plays the role of the brood chamber. New germinal cells are formed only by division of undifferentiated cells. No differences between undifferentiated and germinal cells in miracidia and those in sporocysts were found.