Parasitology Research最新文献

Parasitic infection is a complex process involving interactions among various immune cells. Regulatory B cells (Breg cells), a subset of B lymphocytes with immunosuppressive functions, play a role in modulating immune responses during infection to prevent excessive immune activation. This article reviews the origin, phenotype, and immunoregulatory mechanisms of Breg cells. We summarize the immunomodulatory roles of Breg cells in various parasitic infections. We also discuss the potential applications of activating Breg cells through parasitic infections and their derived molecules in the treatment of certain allergic, autoimmune, and inflammatory diseases. The aim is to provide new perspectives for the future treatment of parasitic diseases and other related conditions.

The European catfish (Silurus glanis) is an important species with high economic value, and its growing demand has led to intensive farming practices for it. However, this species is increasingly challenged by parasitic infections, particularly from a specific gill monopisthocotylan parasite called Thaparocleidus vistulensis. To establish effective management strategies, it is crucial to comprehend the fundamental environmental variables that could influence the reproductive and survival behavior of T. vistulensis. The present study conducted controlled in vitro experiments to observe the fecundity, hatching rate, and survival ability of T. vistulensis under varying light-dark conditions, as well as across a range of water temperatures from 5 to 35 °C. Interestingly, light exposure led to a threefold increase in egg production by adult T. vistulensis compared to constant darkness. While light or dark conditions did not significantly affect the hatching and survival rate of adults, they did significantly affect the survival rate of oncomiracidia. The parasite's fecundity was optimal at 15 °C. Eggs hatched fastest at 30 °C, whereas no hatching occurred at 5 °C and 35 °C. The survival rate for both oncomiracidia and adults showed a negative correlation with increasing water temperatures. These findings provide fundamental insights into how varying environmental variables impact the life cycle of the parasite. The improved understanding of these findings provides a valuable basis for the management of T. vistulensis in cultured European catfish stocks in fish farms.

This study set out to characterise the in vitro development, including musculature, of the microphallid parasite of the barnacle Semibalanus balanoides (Linnaeus, 1767), Maritrema gratiosum Nicoll, 1907 collected in Scotland. An in vitro culture model was developed to obtain ovigerous adults of M. gratiosum and their morphology was observed. Different media were tested and NCTC-109 was chosen as the best medium. The effects of different concentrations of serum upon adult longevity, size and egg production was measured. Survival for 10-days was achieved when flukes were cultured in NCTC-109 plus chicken serum and antibiotics. Forty percent chicken serum seemed to provide better results in terms of survival time and producing flukes with the largest body lengths. Both normal and abnormal eggs were observed from adults cultured in vitro. Confocal microscopy was undertaken to provide details of the development of the parasite's ultrastructure, including musculature, during the course of in vitro culture. While the musculature of M. gratiosum was similar to that of other microphallids, some additional novel structures were observed, most notably a ligament connecting pars prostatica and seminal vesicle and a racket-shaped excretory bladder. This study has provided greater insight into the biology M. gratiosum, and also developed a good in vitro model which might be applied to ecological or medical research in the future.

Haemosporidians, a group of vector-borne parasites that parasitize the blood cells and internal organs of various animal species, are reported to cause severe pathology in raptors. Species belonging to the genera Plasmodium, Haemoproteus and Leucocytozoon are the ones of greatest wildlife importance. The common buzzard (Buteo buteo) and the Eurasian sparrowhawk (Accipiter nisus) are the most numerous raptor species in Europe. Reliable data is lacking for many raptor species in Greece. The aim of this study was to assess, for the first time, the prevalence and geographical distribution of haemosporidian infection (mainly Leucocytozoon and Plasmodium) in these two avian species in Greece, in correlation with the risk factors of age and sex. In total, 62 common buzzards and 26 Eurasian sparrowhawks were included in this study, all being admitted for treatment at a Greek Wildlife Rehabilitation Center. Blood samples were collected and microscopical analysis was performed after staining blood smears with Giemsa. DNA was extracted from each sample and a fraction of the mitochondrial cytochrome b gene was amplified by a nested PCR protocol. All positive samples were subjected to sequencing. Total prevalence of haemosporidian infection by morphological and molecular examination was 59% and 73.9%, respectively. Binary logistic regression was carried out. The most prevalent infection was by Leucocytozoon spp. Most of the samples had mixed infections. The isolated genetic lineages of Leucocytozoon spp. were BUBT2, BUBT3, MILVUS01, ACNI1, BUBO01 and MILANS04. The detected genetic lineages of Plasmodium spp. were TURDUS1, BT7 and DONANA02. A new genetic lineage, BUTBUT17, was also identified.

Babesia bigemina is an apicomplexan parasite responsible for causing "Texas fever" in bovines. Current treatments for bovine babesiosis are hindered by several limitations, including toxicity, insufficient efficacy in eliminating the parasite, and the potential for resistance development. A promising approach to overcome these challenges is the identification of compounds that specifically target essential metabolic pathways unique to the parasite. One such target is lactate dehydrogenase (LDH), a critical enzyme involved in the regulation of anaerobic glycolysis. Notably, Babesia bigemina LDH (BbigLDH) exhibits a five-amino acid insertion in the active site, a feature that differentiates it from the host's LDH. This structural divergence makes apicomplexan LDH an attractive and potentially selective drug target for therapeutic intervention. In this study, a structure-based drug discovery approach was implemented to find novel inhibitor candidates. Potential candidates were identified using a virtual screening workflow. The compounds with favorable docking scores were filtered using the QM-polarized ligand docking and induced fit docking methods. As a result, 20 novel compounds were identified that bind to the active site of BbigLDH but show low affinity to the host LDHs. Molecular dynamics simulations of the complexes (8.8 µs in total) were performed, and binding free energies were calculated. As a result, protein structures containing compounds C9, C16 and C18 maintained their stability throughout 1 µs simulations with low binding free energies and conserved interactions with known catalytic residues. Therefore, these three compounds deserve further investigation to better understand their mode of action and therapeutic potential for babesiosis. The results of this study elucidate the structural features of the BbigLDH enzyme and provide novel LDH binders that may pave the way for further research into the development of parasite-specific LDH inhibitors.

Coccidiosis is caused by apicomplexan parasites of the genus Eimeria, which infect epithelial cells of the intestinal tract causing diarrhea and negatively impacting production in the poultry industry. The self-limiting and highly immunogenic nature of infection by Eimeria spp. make live vaccination an effective means of coccidiosis control. Paramount to vaccine efficacy is the ability to administer precise numbers of viable oocysts. Unfortunately, no rapid and accurate method for determination of oocyst viability is available presently. This study presents the development of a qPCR-based assay for assessment of Eimeria tenella Tyzzer, 1929 oocyst viability. Transcriptome sequencing supported identification of three viability assay target transcripts based on significant increase in abundance with heat-stimulation. Measurement of shifts in target abundances in response to heat stimulation in oocysts, that ranged from high viability to non-infectious, was achieved via qPCR. Omission of DNase treatment supported use of background DNA in RNA samples for normalization for parasite numbers and oocyst disruption efficiency, while spike in of exogenous RNA supported normalization for variations in RNA recovery and reverse transcription efficiency. The assay demonstrated strong correlation with oocyst viability as confirmed through live infection trials, showing the highest predictive value for a transcript encoding a putative partial translationally controlled tumor protein, XM_013379639.1. This assay provides results in hours and could reduce the reliance on time-consuming and expensive live-infection trials in oocyst viability testing and could improve the accessibility and efficacy of coccidiosis vaccines. Future iterations may facilitate multivalent vaccine quality control and environmental monitoring.

The superfamily Ascaridoidea are parasitic nematodes in vertebrates, including birds and humans. In order to investigate the presence and distribution of these parasitic nematodes in birds acting as the definitive host, 157 birds of 64 bird species belonging to 16 orders were collected and necropsied in the Kızılırmak Delta area in the Bafra district of Samsun province. The parasites collected were fixed in 70% ethyl alcohol and identified under a light microscope, and morphologically important regions were photographed for identification. The parasitological examination determined morphologically that Ardea purpurea was infected with Contracaecum rudolphii; Accipiter nisus, Buteo buteo, and B. rufinus with Porrocaecum angusticolle; Aythya ferina with P. crassum; Egretta garzetta with P. depressum; and Turdus merula with P. ensicaudatum. ITS-1 gene region was preferred for molecular analyses of all identified species, and morphological findings were confirmed. C. rudolphii, P. depressum, and P. ensicaudatum were described molecularly for the first time in Turkey, while P. angusticolle and P. crassum were described both molecularly and morphologically.

Naegleria fowleri is a free-living amoeba and the causative agent of Primary Amebic Meningoencephalitis (PAM), a rare yet almost always fatal disease that primarily affects children. While only 431 PAM cases have been reported worldwide, the southern states of the United States, including Texas, report the highest number of cases. Despite the high mortality of the disease, studies have identified antibodies to N. fowleri in healthy individuals suggesting that exposure to this pathogen is common, but disease is rare. Here, we investigated the seroprevalence of N. fowleri in the general population of individuals residing in an area of Texas to identify population characteristics or water-based activity levels that may be associated with seropositivity. For this, healthy human participants were surveyed, and blood samples were collected to test their sera against N. fowleri lysate by indirect ELISA. A seropositivity rate of 89% was observed with 40% of participants demonstrating a titer of up to 1:500. Demographic and water-activity level differences among subjects did not correlate with antibody titers. The high seropositivity suggests environmental exposure and the development of humoral immunity against this pathogen.

Opisthorchiasis, caused by the liver fluke Opisthorchis viverrini, is endemic to Southeast Asian countries and constitutes a major health problem as it increases the risk of cholangiocarcinoma. However, owing to the complicated life cycle of O. viverrini, there is no rapid method for monitoring the risk of infection in the environment. The inability to identify water sources at risk of infection presents a challenge in implementing preventive measures in areas where fish are a significant component of the local diet. Using the environmental DNA (eDNA) approach to detect parasitic DNA in water samples, it is possible to understand the distribution of O. viverrini and the dynamics of infection with high accuracy. However, the sensitivity of environmental samples remains a bottleneck. In this study, we developed a highly sensitive method for detecting O. viverrini eDNA by designing a multi-marker assay targeting two mitochondrial and two nuclear genes. We compared its performance with single-marker assays using tissue-derived DNA. The multi-marker assay exhibited the highest detection sensitivity. We also collected data from 56 sites in Sakon Nakhon, Thailand, in October 2022, and tested them for eDNA detection of O. viverrini. Eleven sites were positive in the multi-marker assay, whereas five sites were positive in the single-marker assay. This multi-marker assay can be used in the field to detect small organisms and rare species, other than parasites, that are expected to have low levels of eDNA.

Toxoplasmosis is a foodborne zoonotic parasitic disease caused by Toxoplasma gondii, which seriously threatens to human health and causes economic losses. At present, there is no effective vaccine strategy for the prevention and control of toxoplasmosis. T. gondii rhoptry proteins (ROPs) are important proteins secreted by the parasite during the early stage of invasion into host cells. In this study, we constructed six individual plasmids (pVAX1-ROP2, pVAX1-ROP5, pVAX1-ROP9, pVAX1-ROP16, pVAX1-ROP17, and pVAX1-ROP18) encoding T. gondii rhoptry proteins and then used an equimolar amount of each as a vaccine cocktail. Following booster immunization, serum antibody levels, splenic lymphocyte proliferation, cytokine production, and survival time after infection with T. gondii RH strain were measured in immunized mice. The results showed that the mice immunized with the DNA vaccine cocktail developed a higher level of the specific anti-T. gondii IgG in serum and the cytokines such as IFN-γ, IL-2, IL-12, and IL-4 (P < 0.01). The stimulation index (SI) of spleen lymphocytes (P < 0.01), the frequencies of CD4⁺ T lymphocytes (P < 0.01), and the ratio of CD4⁺/CD8⁺ T lymphocytes (P < 0.05 or P < 0.01) in the vaccine-immunized mice were significantly increased compared to the control group. After challenge with the virulent T. gondii RH strain tachyzoites, the survival time of mice in the DNA vaccine cocktail group (18.1 ± 1.81 d) was significantly longer (P < 0.01) than that in the control group (8.4 ± 1.02 or 7.9 ± 0.83 d). The results indicated that the DNA vaccine cocktail could elicit strong humoral and cellular immune responses in mice and could also improve the resistance of mice to acute T. gondii infection.