Parasitology最新文献

A new genus and species of trematode, Paratestophis gelicolus gen. nov., sp. nov., is described from the large intestine of the rainbow water snake, Enhydris enhydris, collected from several provinces in southern Thailand. Morphological analyses reveal distinct characteristics that differentiate P. gelicolus gen. nov., sp. nov. from related echinochasmid taxa, specifically its elongated bottle-shaped body, presence of 22 collar spines, parallel testes and parasitism of snakes-features not observed in other echinochasmid genera. Multi-marker phylogenetic analyses (28S rRNA, 18S rRNA, ITS2 and COI) strongly support its taxonomic placement within Echinochasmidae while confirming its genetic distinction from known genera such as Echinochasmus, Stephanoprora, and Microparyphium, thereby warranting the establishment of Paratestophis gen. nov. The species exhibited a 24% prevalence of infection (25/106) in E. enhydris, and was found co-infecting with four other helminths, including Tanqua siamensis, Encyclometra bungara, and two additional trematode species currently under examination, all occupy distinct ecological niches. Principal Component Analysis based on 19 morphological characters revealed morphological homogeneity among the specimens. This study represents the first record of a new genus and species within Echinochasmidae infecting snakes, and provides an updated systematic framework for the family, including a revised key to genera. The findings emphasise the need for further research into parasite taxonomy, host specificity and evolutionary relationships in Southeast Asian ecosystems.

Accurate characterization of helminth communities in amphibian hosts is essential for understanding host-parasite dynamics in changing environments. This study presents an integrative parasitological survey of Bufotes viridis populations in eastern Slovakia, using both morphological and molecular methods. A total of 61 road-killed individuals collected across 13 localities were examined for helminth presence. Only nematodes were detected, encompassing 3 families, Rhabdiasidae, Molineidae and Cosmocercidae. Four nematode species were recorded, Rhabdias rubrovenosa, Oswaldocruzia filiformis, O. ukrainae and Aplectana linstowi, and a further unidentified Cosmocerca species. Notably, R. rubrovenosa seems to be a new or previously misidentified helminth species found in Slovakia. Cosmocercidae represented the most abundant family, while Molineidae occurred scarcely. Each species was characterized genetically - for the members of Rhabdiasidae and Cosmocercidae, partial 18S rDNA, complete ITS1, complete 5.8S rRNA, complete ITS2 and partial 28S rDNA sequences were amplified, whereas for representatives of Molineidae, partial COI sequences were obtained. These results underscore the utility of combining molecular and morphological tools in helminth biodiversity studies and provide updated baseline data on nematode infections in B. viridis within an anthropogenically influenced landscape. Despite visual patterns indicating differences in the community compositions of nematode families between urban and rural localities, multivariate analyses testing revealed no significant differences.

Freshwater parasitic copepods appear to exhibit great taxonomic diversity. However, little is known about gene flow between species or whether there is incongruence between morphological and phylogenetic species definitions. Additionally, little is known about what evolutionary factors may contribute to speciation across various lineages. The copepod genus Salmincola, which includes common ectoparasites of fishes in the family Salmonidae, is distributed throughout the northern hemisphere and is a good model to demonstrate limited taxonomic understanding. Much of the regular scholarly output regarding Salmincola copepods comes from fisheries management agencies, where they are considered a pest species. Within a geographic region, Salmincola copepods of the same species are often found infecting their hosts at substantially different rates across different water bodies. However, present taxonomic definitions of Salmincola are based on decades old morphological descriptions, which were limited in geographic scope and number of specimens examined. There is a strong possibility that traditional species definitions in this genus, based on host species along with morphology, are missing cryptic diversity that may explain differences in infection intensity across environments. This review outlines the current scientific limitations of understanding of this genus and provides suggestions for how adding genetic data could inform taxonomic revisions, as well as clarifying connections between genetic differentiation and infection dynamics across localities.

Myxozoans are parasitic cnidarians that can cause severe damage to fish, resulting in economic losses to aquaculture and fisheries. In Israel, only a few taxonomic studies have been conducted on Myxozoa infecting freshwater fish and none on barb parasites. Here, we describe two new myxozoan species - Myxidium grauri n. sp. and Myxidium sharmai n. sp. - from the gallbladder of the barbs Carasobarbus canis and Luciobarbus longiceps, respectively, from the Sea of Galilee (Lake Kinneret). The prevalence of infection was 42.2% (19/45) for M. grauri n. sp. and 25% (5/20) for M. sharmai n. sp. We obtained 18S rRNA sequences for both species, providing the first molecular data on Myxidium infecting barbs from the Sea of Galilee. Phylogenetic analysis confirmed that the genera Myxidium and Zschokkella are not monophyletic. The δ-statistic was used to assess the phylogenetic signal of categorical traits within the Biliary Tract Clade IV lineage, which includes the species studied. The analysis revealed a significant phylogenetic signal associated with the host clade, the parasite's geographic origin and the type of environment it inhabits. However, some of these statistical results may be influenced by sampling bias, as Percomorpha and Otomorpha fish are disproportionately represented in marine and freshwater environments, respectively. The newly obtained sequences form a distinct lineage within a clade of freshwater-infecting myxozoans. Our findings suggest that myxozoan infections are widespread in the Sea of Galilee. Given their potential impact on fisheries and the lake's ecosystem, further research is needed to assess their distribution, dynamics and ecological consequences.

Recently introduced parasites are predicted to cause more severe infections because of a lack of host-parasite co-evolution. When new parasites co-occur with similar parasites they may compete for resources within a host, with mixed species infections potentially resulting in antagonistic, synergistic or additive effects. We tested Ostrea chilensis flat oysters in New Zealand for infections by two species of haplosporidian oyster parasites. Bonamia exitiosa is an endemic parasite to New Zealand, whereas Bonamia ostreae is an introduced species first detected in New Zealand in 2015. We investigated the infection intensity of each parasite by estimating gene copy numbers using species-specific digital droplet PCR (ddPCR) across Bonamia spp. allopatric and sympatric ranges. Our results showed that B. ostreae had significantly higher gene copy numbers than B. exitiosa. However, concurrent infections of both Bonamia parasites had similar intensities (based on gene copy number) to single-species infections, with no detectable interactive effects. Collectively, the results indicate that B. ostreae remains a significant risk to O. chilensis, although coinfections may not exacerbate disease. This study demonstrates the value of ddPCR screening and the importance of considering evolutionary ecology in the management of commercially important marine diseases.

Egg hatching is a critical stage in the life cycle of parasitic nematodes and is strongly influenced by abiotic factors. This study investigates, under in vitro condition, the effects of temperature (5 °C, 10 °C, 20 °C, 30 °C) and salinity (0-70 psu) on egg hatching success in the two sibling species Contracaecum rudolphii sp. A and C. rudolphii sp. B, which have been hypothesized to be adapted to brackish/marine and freshwater environments, respectively. Hatching was completely inhibited at 5 °C in both species. At temperature of 10 °C and above, both taxa showed successful hatching with largely overlapping thermal profiles; however, C. rudolphii sp. A achieved a marginally significantly higher success, with maximum hatching observed at 30 °C - a value chosen to simulate a potential heatwave scenario. Temperature also influenced developmental timing, with faster hatching occurring at higher temperatures. In contrast, significant marked differences were observed along the salinity gradient: C. rudolphii sp. A hatched across a wide range (0-70 psu); while C. rudolphii sp. B was restricted to 0-20 psu, with a steep decline above 10 psu. The observed species-specific hatching dynamics, primarily driven by salinity factor, support differential ecological adaptation of the two taxa in their respective aquatic habitats. These findings also provide a basis for predicting parasite responses to environmental change, including rising temperatures and salinity shifts in aquatic ecosystems.

An extensive survey of North American catostomid fishes yielded insights into the diversity, host specificity and phylogenetic relationships of monopisthocotylans belonging to Pseudomurraytrematidae. Parasites were recorded from 14 of 16 host species surveyed. In total, 22 species of Anonchohaptor, Icelanonchohaptor and Pseudomurraytrema were collected, including 7 new species. Most species were recovered from gills, whereas two Icelanonchohaptor species were found on fins. Phylogenetic analyses based on 28S rDNA support the monophyly of Pseudomurraytrematidae and its sister relationship to Diplectanidae. Within the family, Pseudomurraytrema asiaticum - a parasite of the East Asian fish Myxocyprinus asiaticus - was recovered as sister to the clade of Nearctic pseudomurraytrematids, a placement that may reflect geographic and host-associated separation. The remaining Pseudomurraytrema species parasitize North American Catostominae and form a well-supported clade sister to the clade comprising species of Anonchohaptor and Icelanonchohaptor, primarily associated with Ictiobinae. Under this topology, Pseudomurraytrema, as currently circumscribed, may be paraphyletic. Relationships between morphologically similar species of Anonchohaptor and Icelanonchohaptor remain unresolved: in the 28S tree, Anonchohaptor is paraphyletic (with Icelanonchohaptor nested within it), whereas the concatenated 18S-ITS1-28S analyses recover a single clade with Icelanonchohaptor (2 spp.) sister to the remaining species of Anonchohaptor. The parasite phylogeny broadly reflects host relationships, though several incongruences point to historical host switching. Morphological data also support the monophyly of Pseudomurraytrematidae via a synapomorphic male copulatory organ (U-shaped copulatory tube with a submedial spine, 3-ramus accessory piece), indicating structural conservatism within this family.

Trypanosoma (Megatrypanum) pestanai is a parasite of the Eurasian badger (Meles meles), reported in various European countries. However, its presence in the Iberian Peninsula had not been previously investigated. To address this knowledge gap and to assess its occurrence and potential risk factors associated with infection, we analyzed DNA from the spleens of 145 badgers sampled across 4 autonomous regions in northern Spain. Two real-time PCR assays using a reference 18S rRNA partial sequence of T. pestanai (92 bp) were developed: one based on SYBR Green chemistry and the other employing a TaqMan probe. Both protocols demonstrated excellent concordance. Defining a sample as positive when at least 1 assay yielded a positive result, the overall prevalence was 35%, consistent with values previously reported in other European populations. A logistic regression model indicated a significantly higher occurrence in badgers from the Eurosiberian bioregion (42%) compared to those from the Mediterranean bioregion (19%). No significant associations were found with age or sex. A subset of positive samples was further analyzed by conventional PCR targeting approximately 900 bp of the 18S rRNA gene and sequenced. All 9 high-quality sequences shared 99.75-100% identity with known T. pestanai sequences. These findings confirm that T. pestanai is a common parasite of Iberian badgers and suggest that more humid climatic conditions may favour its persistence, potentially through effects on host ecology or vector dynamics.

While the interaction between humans and their parasites is well studied today, taking a long view of infection throughout human evolution helps to place the current picture in context and identify trends in infection over time. After considering how early technologies may have facilitated the transmission of parasites to humans, we examine the association between humans and parasites through time using archaeological and genetic evidence. Techniques such as microscopy, immunoenzymatic assays and DNA analysis have identified a range of protozoa, helminths and ectoparasites in our ancestors. Evidence is discussed for the origins and impact upon societies through time for protozoa causing malaria, leishmaniasis, Chagas' Disease and diarrhoeal illnesses, helminths such as schistosomiasis, soil-transmitted helminths, Taenia tapeworms, fish tapeworms and liver flukes, and ectoparasites such as fleas, body lice and pubic lice. Prevalence studies show widespread infection for some parasites, such as 36% with falciparum malaria in ancient Egypt, and 40% with Chagas disease in prehistoric Peru and northern Chile. Humans have been responsible for the inadvertent spread of a range of parasites around the world, ranging from African heirloom parasites with early human migrations to the introduction of malaria and schistosomiasis to the Americas with the transatlantic slave trade in the 1600s-1800s. It is clear that the epidemics due to bacterial pathogens spread by ectoparasites since the Bronze Age must have had major impacts upon past societies, particularly for bubonic plague and epidemic typhus.

Giardiasis is the most common enteric protozoan infection notifiable in New South Wales (NSW), Australia. Surveillance by NSW Health had shown a steady increase (prior to the COVID-19 pandemic) in the number of cases reported since 2012 and the reasons for this currently remain unknown. This study aimed to investigate the occurrence of Giardia intestinalis assemblages causing human infection in NSW. Individual faecal specimens were collected from participating hospitals and private laboratories, and the presence of Giardia and co-infections was confirmed by real-time multiplex-polymerase chain reaction (PCR). Samples were genotyped by sequence analysis of the triose phosphate isomerase (tpi) gene and the small subunit rDNA. Combined genotyping showed that most samples belong to assemblage B, and only a small percentage were infected with only assemblage A. Mixtures of assemblages A and B in individuals were relatively common. Co-infections were observed in ∼ half of the cases, with the most common co-infection being Blastocystis hominis and Dientamoeba fragilis. Although giardiasis was more prevalent in males, the assemblage distribution between the sexes appeared uniform. The age distribution was bimodal, with peaks in 0-15-year-olds and in adults in their 30s. The overall largest number of cases was collected from patients aged 30-49 years. Interestingly, females aged 5 years old and under had a greater risk of assemblage B infection than their male counterparts. No significant correlation was found between assemblage and clinical symptoms. This study provides new insights into the molecular diversity of giardiasis in NSW and helps inform enhanced surveillance and prevention strategies in Sydney.