Acta tropica最新文献

Although the current therapeutic regimens for acute toxoplasmosis, most commonly a combination of pyrimethamine and sulfadiazine, are still considered the standard of care, they are associated with numerous drawbacks, such as bone marrow suppression, and hepatotoxicity. Given these challenges, there is an urgent need to explore and find safer and more effective therapeutic alternatives. Acetazolamide has been widely used in clinical practice for non-infectious illnesses. Lately, increasing attention has been directed toward its repurposing as an antiparasitic agent. Thirty-six mice were infected with Toxoplasma gondii (RH strain) tachyzoites, and divided into three groups: non-treated group, Acetazolamide-treated group and Septrin- treated group. In the present study, the anti - Toxoplasma efficacy of Acetazolamide was assessed in comparison to Septrin using parasitological, ultrastructural, biochemical, immunological, and histopathological studies. Treatment with Acetazolamide significantly prolonged the mice's survival time and reduced tachyzoites count with percentages of reduction of 83.12% and 79.84 % in the peritoneal fluids and hepatic impression smears, respectively. Furthermore, Acetazolamide has dramatically altered the ultrastructure of the tachyzoites, decreased the liver and kidney malondialdehyde levels and suppressed serum cytokines (tumor necrosis factor alpha and interleukin-1β). Histopathological examination of hepatic and renal tissue sections showed amelioration of parenchymal inflammation and scanty parasite. In conclusion, Acetazolamide demonstrated a significant promise as a therapeutic agent for combating acute murine toxoplasmosis with anti-inflammatory and antioxidant effects.

Background: Severe Fever with Thrombocytopenia Syndrome (SFTS) is a severe tick-borne viral infection with high mortality, making the timely prediction of clinical deterioration critical. Current predictive models lack timeliness and generalizability. Therefore, this study aimed to develop and validate an interpretable machine learning model for the early prediction of deterioration in SFTS patients.

Methods: We retrospectively analyzed 560 SFTS patients from two hospitals. Using clinical and laboratory data from a training set (n = 407), we developed eight ML models. An independent test set (n = 153) was used for external validation. Model performance was assessed via area under the ROC curve (AUC), calibration, decision curve analysis (DCA), and SHapley Additive exPlanations (SHAP).

Results: The RF model outperformed others with an external validation AUC of 0.825. Key predictors included viral load, serum creatinine, D-dimer, procalcitonin, platelets, blood urea nitrogen, age, and lymphocytes. SHAP analysis revealed significant interactions, especially between blood urea nitrogen and viral load. The RF model provided reliable risk stratification, with net benefits surpassing no-treatment or all-treatment strategies when the threshold probability was between 0.09 and 0.76. An interactive web-based application was developed for real-time individualized risk prediction.

Conclusion: We successfully developed and validated a robust ML model using RF, integrating eight readily measurable clinical variables to predict early deterioration in SFTS patients. This model offers improved timeliness and interpretability, facilitating early clinical interventions. Future multi-center studies will further validate its robustness and reliability, enhancing its clinical utility.

Freshwater species of the myxozoan genus Ceratomyxa have recently emerged as a diverse group of parasites infecting fish in South America, many of which exhibit vermiform plasmodia with dynamic motility. In this integrative taxonomic study, we describe Ceratomyxa souzapintorum n. sp., a novel species infecting the gallbladder of the Amazonian clupeiform fish Pellona castelnaeana. The prevalence of infection was 73%, and the parasite displayed worm-like plasmodia exhibiting nematode-like motility. Arcuate myxospores measured 14.8 ± 1.7 µm in thickness and 6.1 ± 0.7 µm in length, with a posterior angle of 59° (42-78°). The two spherical nematocysts measured 2.0 µm and contained filaments with 3-4 coils. Ultrastructural analyses revealed plasmodia consisting of an outer cytoplasmic region containing sporogonic stages and numerous tubular mitochondria, and internally a large central vacuole. Mature plasmodia exhibited a thin cytoplasmic layer, with mature myxospores apparently free within the central vacuole. Phylogenetic analyses positioned C. souzapintorum n. sp. within the clade of Amazonian Ceratomyxa species.

Understanding mosquito host-feeding patterns is essential for elucidating the transmission dynamics of mosquito-borne pathogens and informing targeted control strategies. In this study, we investigated the host-feeding patterns of mosquitoes collected in 2022 and 2023 across three land use types (urban, rural, and forest) in four geographical regions of Vietnam (North, South, Central Coast, and Central Highlands). Mosquitoes were sampled using BG-Pro traps, and host identification was performed via DNA barcoding of the cytochrome b and 16S rRNA genes. A total of 349 blood-fed mosquito specimens, representing 13 species and three undifferentiated taxa, were analyzed. The dominant species were Culex tritaeniorhynchus, Cx. quinquefasciatus, and Cx. vishnui. Host-DNA was successfully identified in 267 specimens (77%), revealing blood meals from 18 mammal and 4 bird species. Chickens (45%), humans (28%), and dogs (12%) were the most frequent hosts. Mixed blood meals were detected in 23% of successfully analyzed specimens, indicating potential for bridge vector transmission between host groups. No statistically significant effect of land use on host-feeding patterns was observed for the three dominant mosquito species. These findings highlight the diverse feeding behaviour of mosquitoes in Vietnam, characterize by broad host species and frequent mixed blood meals, and emphasize the need for continued research to better understand mosquito-host interactions and their implications for vector-borne pathogen transmission.

Emerging evidence suggests the development of malaria parasites in the human bone marrow. Whether glucose-6-phosphate dehydrogenase (G6PD) deficiency affects parasite growth in erythroblast has yet to be determined. Here, we examine the invasion and development of Plasmodium falciparum in human erythroblasts of subjects carrying the most common variant of G6PD Viangchan (871G>A) in Southeast Asia. Erythroblasts were generated by differentiation of erythroids of human CD34-positive hematopoietic stem and progenitor cells isolated from peripheral blood. The results showed that P. falciparum parasites invade polychromatic erythroblasts and develop into mature trophozoites. The percentages and stages of parasitized erythroblasts were not different between the subjects with G6PD normal, heterozygous, or hemizygous G6PD Viangchan. While the sample size (n = 6) limited statistical analysis, these preliminary findings suggest that protection against malaria is not observed in this in vitro erythroblast model, supporting further validation in expanded cohorts.

Toxoplasma gondii has been reported to exert antitumor effects by inducing apoptosis and cell cycle arrest; however, the biological roles of small extracellular vesicles released by the parasite remain poorly understood. Small extracellular vesicles derived from parasite-host coculture systems may encapsulate molecular signals that reflect interactions between T. gondii and distinct epithelial microenvironments. In this study, tachyzoites of the T. gondii RH strain were cocultured with human cervical adenocarcinoma HeLa cells or normal cervical epithelial H8 cells, and small extracellular vesicles were isolated from coculture supernatants. High-throughput small RNA sequencing and liquid chromatography-tandem mass spectrometry were used to profile microRNA and protein cargo, followed by differential expression and functional enrichment analyses. Vesicles from both coculture systems contained components of both parasite and host origin, indicating bidirectional molecular exchange. Compared with vesicles derived from coculture with normal epithelial cells, those obtained from tumor cell coculture showed distinct enrichment of microRNAs and proteins associated with cell proliferation, DNA damage responses, and apoptotic regulation. Pathway analyses highlighted the involvement of cell cycle checkpoints, p53-related signaling, and programmed cell death. Overall, the molecular composition of parasite-derived vesicles varied according to the epithelial feeder layer, with tumor cell-associated vesicles exhibiting a stronger association with tumor-related regulatory pathways. These findings provide insight into parasite-host communication mediated by extracellular vesicles and suggest a potential role for T. gondii-derived vesicles in modulating tumor-associated biological processes.

Myxozoans belonging to the genus Ellipsomyxa have been described in the gallbladders of fish from marine, brackish, and freshwater environments worldwide. Recent research suggests substantial speciation in South America freshwater environments. This study enhances our understanding of the diversity of freshwater Ellipsomyxa in the Amazon Basin, with the description of two new species. It also provides novel life history insights, expands host ranges, and proposes taxonomic revision. Ellipsomyxa filiformis n. sp. was identified infecting the gallbladder of the pimelodid Amazonian fish Hypophthalmus marginatus. Ellipsomyxa granulosa n. sp. was found in the gallbladder of the curimatid Curimata inornata. Ellipsomyxa amazonensis is here reported to parasitise two pimelodids - Pinirampus pirinampu and Platynematichthys notatus. Ellipsomyxa paraensis is reported to parasitize the cichlid Satanoperca jurupari and the prochilodontid Prochilodus nigricans. Morphological and small subunit ribosomal DNA sequence data support the reclassification of Ellipsomyxa santarenensis as a junior synonym of E. paraensis. Molecular phylogenetic analyses indicate that E. filiformis n. sp. and E. granulosa n. sp. comprise a sister lineage to Ellipsomyxa papantla. Ultrastrucutural analyses of E. filiformis n. sp. and E. granulosa n. sp. revealed details of the plasmodia, including numerous filopodial and pseudopodial projections of the ectoplasm, and a concentration of actin associated with the cytoskeleton.

Accurate quantification of Plasmodium vivax parasitemia and identification of glucose-6-phosphate dehydrogenase (G6PD) deficiency, particularly the Viangchan variant, the most prevalent in Southeast Asia, are crucial for effective malaria case management. This study developed, validated, and implemented droplet digital PCR (ddPCR) assays for precise quantification of P. vivax parasitemia and genotyping of the G6PD Viangchan variant. Duplex ddPCR assays targeting the P. vivax tubulin gene and the human RHCE gene were designed to accurately determine parasitemia, with precision and accuracy comprehensively evaluated. In parallel, a duplex ddPCR assay targeting the G6PD Viangchan (871G>A) variant was optimized and assessed for sensitivity and specificity. These assays were applied to clinical samples in Kanchanaburi Province, Thailand. The parasitemia assay demonstrated a limit of detection of 3.2 parasites/µL and a limit of quantification of 400 parasites/µL, at which it exhibited accuracy greater than 90% relative to reference values and coefficients of variation below 20%. For G6PD genotyping, the ddPCR assay clearly distinguished normal, heterozygous, and homozygous/hemizygous individuals, achieving 100% sensitivity and specificity. Parasite densities in clinical samples ranged from 315 to 82,429 parasites/µL. Monitoring parasitemia during chloroquine treatment showed a 99.2-99.9% reduction from day 0 to day 2, with complete clearance by day 3, confirming drug efficacy. G6PD Viangchan genotyping revealed a predominance of the wild-type allele (98.9%), with a single heterozygous female (1.1%) carrying the variant. Collectively, these novel ddPCR assays provide robust tools for accurate parasitemia quantification, treatment monitoring, and rapid, reliable G6PD genetic screening in clinical and epidemiological settings.

This study developed a quantitative real-time PCR (qPCR)-based strategy for the differential molecular diagnosis of visceral and cutaneous leishmaniasis in humans and dogs, using blood, skin biopsy, and conjunctival swab samples. The assay demonstrated satisfactory sensitivity and specificity, reaching 93.3% and 100% in human samples and 90.48% and 100% in canine samples, across the evaluated species (Leishmania infantum, L. braziliensis, and L. amazonensis). Detection of L. amazonensis required an adapted protocol incorporating SYTO9 intercalating dye and melting curve analysis. Although exploratory, these results indicate that the proposed method is feasible and support its potential for further validation in larger cohorts and future studies.