Parasitology最新文献

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.

Recent research on zoonotic diseases has increasingly focused on tick-borne illnesses due to their high prevalence in northwestern China. This study aimed to determine the prevalence of tick-borne pathogens in yaks (Bos grunniens) within Qinghai Province. A total of 299 blood samples were collected from yaks in Xining City of Qinghai Province and analysed using polymerase chain reaction. Results indicated the absence of several significant zoonotic pathogens, including Borrelia burgdorferi sensu lato, Anaplasma spp. and Coxiella burnetii. However, rickettsiae were detected in the sampled yaks. The overall prevalence of spotted fever group rickettsiae was 46·5%, with a significant difference between females (68·3%) and males (9·09%). Age was also identified as a significant factor influencing infection rates. Furthermore, sequencing analysis revealed that the obtained rickettsial sequences shared 99·04-100% nucleotide identity with Rickettsia raoultii, a species endemic to Qinghai, China. Phylogenetic analysis based on the ompA and gltA genes confirmed that these sequences clustered within the R. raoultii clade. This study demonstrates a high prevalence of R. raoultii infection in yaks from Qinghai. Consequently, the implementation of preventive and therapeutic measures for yaks is recommended to mitigate the risk of transmission. This study did not collect tick samples simultaneously, so the transmission vector cannot be identified. Additionally, uneven sample distribution across some age groups may affect the representativeness of the results.

In sub-Saharan Africa's endemic areas for urogenital schistosomiasis, male genital schistosomiasis (MGS) can cause significant morbidity. As part of the Hybridization in UroGenital Schistosomiasis investigation, an MGS sub-study examined a cohort of adult men over a calendar year to better ascertain general infection dynamics and putative zoonotic schistosome transmission. During follow-up, demographic, health and socio-economic data were collected through individual questionnaire interviews. Collected urine and semen were analysed using urine filtration, urine and semen microscopy and molecular DNA analyses of semen. Ten participants with reported MGS-associated symptoms had Schistosoma eggs in their urine and semen at 6-month follow-up, with seven at 12 months. Ten out of 11 participants with Schistosoma haematobium eggs on semen microscopy at baseline had persistent infection at 6-month follow-up, together with 6 new participants, giving an MGS prevalence of 84·2% (n = 19). Two also had Schistosoma mattheei eggs co-infection. Four of the 13 participants at 12-month follow-up had S. haematobium eggs in their semen which were persistent at all the time points. Using semen PCR, 14 participants (73·7%) had Schistosoma infection at 6 months, with only 2 participants being infected for first time. Upon DNA analysis, three participants also had hybrid co-infection at this time point. At 12 months, only 6 participants had Schistosoma infection with no hybrids detected. In summary, like S. haematobium and despite praziquantel treatment, both zoonotic and hybrid schistosomes can continue to cause MGS, which pose a further tangible challenge in future management and control measures.

The species boundary between the paramyxid parasitic protists Marteilia refringens sensu stricto and Marteilia pararefringens has been disputed, and their classification as separate species has been a topic of debate for the past 2 decades. Originally described as separate species, they were later synonymized based on limited evidence and referred to as 2 types of M. refringens (O-type and M-type). In 2018, longer rRNA gene sequences from a small number of samples supported their reclassification as distinct species. However, limited sample sizes and incomplete array coverage left questions regarding the robustness of this separation. We present full transcribed ribosomal RNA (rRNA) gene arrays from a broad set of Marteilia samples collected across their known host and geographic ranges. Phylogenetic and species delimitation analysis of these sequences robustly distinguished M. refringens sensu stricto from M. pararefringens. We identified sites across the entire rRNA array with consistent sequence differences between species and carried out phylogenetic analyses on the most variable regions of the rRNA array (ITS1 and ETS), which also distinguished between the 2 species. We also provide new evidence for distinct host preference profiles for M. refringens sensu stricto and M. pararefringens. The results support the recognition of M. refringens sensu stricto and M. pararefringens as separate species and identify robust markers for their detection, allowing a better understanding of their respective ecologies, host preference, pathogenicity and life cycle. The study also lays a foundation for future genomic comparisons to explore evolutionary divergence and diagnostic marker development beyond the rRNA array.