Acta tropica最新文献

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.

Dengue transmission varies markedly across Mexico, posing challenges for short-term operational planning. We propose a two-layer framework that (i) constructs incidence-free eco-epidemiological clusters for the 32 Mexican states and (ii) produces one-week-ahead forecasts of weekly dengue cases at the cluster level with quantified uncertainty, expressed through P10-P90 prediction bands. Our analysis covers 283 epidemiological weeks per state from 2020 to 2025, with all 32 states retained after meteorological quality control. Clusters are identified using full-covariance Gaussian mixture models applied to seasonal summaries of temperature, relative humidity and vapour-pressure deficit, precipitation, solar radiation, and wind, together with descriptors of weekly seasonality. We select the number of clusters, k, using the Bayesian information criterion or integrated complete likelihood, and we confirm robustness with bootstrap adjusted Rand index, favoring k = 5. For forecasting, we train cluster-specific HistGradientBoosting (Poisson) models using leak-free lagged incidence and lagged or rolling meteorological data, fitting quantile variants (α=0.10, 0.90) to create P10-P90 bands. Over the last 20 weeks, the overall performance measures are a mean absolute error of 17.1 and a root mean square error of 27.7, outperforming a seasonal-naïve baseline in several clusters. The best-performing cluster achieves a mean absolute error of about 5.6 and a root mean square error of about 10.2, while the most variable cluster reaches a mean absolute error of about 38.1 and a root mean square error of about 55.1. Residuals center around zero but show heavy tails during rapid changes. Ablation studies show that climate contributes small, regime-specific improvements at h = 1 (mean absolute error +1.8%, root mean square error -1.4% without climate), whereas removing autoregressive terms more than doubles the error (mean absolute error +109.7%, root mean square error +106.9%). Based on open surveillance and NASA POWER data, this framework provides understandable spatial types and practical, uncertainty-aware forecasts to aid in subnational dengue preparedness.

Visceral leishmaniasis (VL) is a highly debilitating parasitic disease that primarily affects people living in poverty. In northern Baringo County, Kenya, VL contributes greatly to the overall burden of disease. The aim of this study was to identify hotspots of VL transmission and regional environmental associations in this area. Data was obtained from Chemolingot Sub-County Hospital's laboratory records and VL prevalence was assessed at the sub-location level. Monthly environmental covariates-mean, maximum, and minimum temperature, total precipitation, relative humidity, normalized difference vegetation index (NDVI), and elevation-were retrieved from Google Earth Engine. Spatial clustering was assessed with Getis-Ord GI* hotspot analysis in ArcGIS Pro. VL prevalence were modelled at the sub-location level with negative binomial regression to identify environmental risk factors for transmission. Between July 2019 and December 2024, 637 confirmed cases translated to an overall period prevalence of 2.71 per 1000 residents across Tiaty East and West. Four sub-locations were identified as VL hotspots; Losikiriamoi recorded the highest prevalence, 43.4 per 1000. The final model after excluding collinear variables included mean monthly temperature, precipitation, elevation, and NDVI. Mean monthly temperature and precipitation were significantly associated with VL prevalence at the sub-location level. Elevation and NDVI were not significant predictors. These findings can inform targeted VL surveillance and control strategies, which is particularly important in a resource-limited field. Changes in temperature and precipitation should be monitored by local public health officials to anticipate changes in VL transmission.

This study describes a new species of myxozoan, Myxidium pantanalense n. sp., parasitizing the gallbladder of the freshwater fish Pimelodus pantaneiro Souza-Filho and Shibatta, 2007, collected in the Brazilian Pantanal wetland, Mato Grosso do Sul State. The identification was based on morphological and molecular analyses. Myxospores exhibited a fusiform shape, 7-8 striations on the valvular surface, measuring 16.5 μm in length and 4.4 μm in width, with equally sized pyriform nematocysts measuring 5.5 μm in length and 2.8 μm in width, each containing a tubule making 4 to 5 turns. Phylogenetic analysis, based on small subunit ribosomal DNA sequences, positioned M. pantanalense n. sp. as the sister species to Myxidium amazonense. Morphological, genetic, and phylogenetic data support the designation of M. pantanalense n. sp. as a new taxon and expand the known diversity and geographic distribution of the genus Myxidium in South America.

The causative protozoan of Chagas disease, Trypanosoma cruzi, undergoes a complex life cycle involving cell cycle regulation and differentiation. However, the connection between these processes remains unclear. Here, we investigated the cell cycle phase in which commitment to metacyclogenesis occurs. Using synchronized populations, CFSE labeling, and cytokinesis inhibition, we show that differentiation stimuli can be perceived from G2/M to G1, but execution takes place exclusively in G1. CFSE results revealed that parasites already in G1 differentiate without division, whereas inhibition of cytokinesis assays demonstrated that post-G1 cells must complete cytokinesis before producing metacyclics. Together, these findings support a two-step model, stimulus perception followed by execution in G1, providing new insights into T. cruzi differentiation and advancing our understanding of parasite development and transmission.

Background: Aedes aegypti is a primary vector of dengue, chikungunya, Zika, and yellow fever diseases. Despite its global invasion, little is known about how populations from climatically contrasting regions adapt to varied thermal environments. Understanding survival strategies is critical for predicting population dynamics and disease transmission under climate change. To address this gap, we assessed ecological adaptations in terms of development, survival, and wing length, along with molecular variations, in the Thar Desert (Jodhpur) and the east coastal (Kolkata) strains of Ae. aegypti.

Methods: Mosquito eggs (3rd generation) of the coastal and desert Ae. aegypti strains were subjected to 20, 26, 30, and 35 °C to assess the impact on developmental time, survival rate, and wing length. The mitochondrial COI gene was analysed to examine nucleotide sequence variation and protein physicochemical properties.

Results: The desert strain developed faster, but showed inferior survival compared to the coastal strain at all temperatures tested. Temperature also affected wing length in both strains, showing significant differences between strains at 35 °C for males and at 30 °C for females. Wing length of the desert strain was less impacted by temperature increase (30 to 35 °C) compared to the coastal strain for both males and females. The COI gene formed two distinct clades. Three transition nucleotide mutations (Adenosine with Guanosine) altered physicochemical and structural properties of the COI protein (i.e., molecular weight, theoretical isoelectric point, total number of positively charged residues, and the number of atoms). Additionally, the bad angles, instability index, and GRAVY affected the protein.

Conclusion: This study provides a comparative analysis linking life-history traits with genetic variation in Aedes aegypti mosquitoes from climatically distinct regions of India. Temperature affects the survival, developmental rates, and wing length of genetically varied Ae. aegypti from different ecological areas. This may refine the understanding of population dynamics and management.

Sand fly vectors harbor and transmit Leishmania parasites and other pathogens, including arboviruses, to vertebrate hosts. The geographical distribution of phleboviruses transmitted by sand flies in areas affected by leishmaniasis has prompted research into coinfection in vectors and in Leishmania reservoirs in Europe and Africa. Despite the widespread occurrence of canine visceral Leishmaniasis in Brazil and the identification of several viruses carried by sand flies, the issue of coinfection remains unclear. We developed an RT-PCR-based assay to detect segmented (-) RNA arboviruses from the families Phenuiviridae and Peribunyaviridae in the Americas. This assay was based on a phylogenetic analysis of the genomes of 29 American species within these families. We processed serum and bone marrow samples from 25 dogs with confirmed cases of visceral leishmaniasis in Rio de Janeiro City, Brazil. Samples from two of the dogs were amplified using a set of primers tailored to the predicted amplicon size. DNA sequencing analysis revealed a high identity to members of the Peribunyaviridae family, specifically within the genus Pacuvirus. We successfully cultivated the virus from one of the samples and sequenced its genome, confirming the identification of a virus belonging to the species Pacuvirus pacuiense or a closely related variant. The implications of our results are discussed.

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of Johne's disease (paratuberculosis), a chronic enteritis affecting domestic and wild ruminants worldwide. While MAP transmission primarily occurs among livestock, increasing attention has been given to the role of wildlife in the maintenance and spread of this pathogen. Invasive species, such as the American mink (Neogale vison), may serve as unexpected source of infection or mechanical vectors for MAP, especially in regions where wildlife and domestic animals share habitats. In this study, we performed a specific MAP-IS900 real-time PCR assay to detect bacterial DNA in mesenteric lymph nodes (MesLN) (n = 401) and colonic/rectal fecal swabs (n = 346) from minks in Los Ríos region, Chile. We detected MAP DNA in 16 % and 10 % of minks in MesLN and fecal swabs, respectively, while 4 % of minks were MAP qPCR-positive in both MesLN and fecal swab samples. Considering specimens with known sex and age, we detected MAP DNA in 22 % of minks in either MesLN or fecal swabs, where 21 % of males and 22 % of females were MAP qPCR-positives, and 15 % of juveniles, 25 % of subadults, and 21 % of adults were MAP DNA-positive in at least one sample type. Our study is the first report on MAP detection in this non-ruminant carnivore in Chile, raising further questions about interspecies transmission dynamics and the potential environmental dissemination of this bacterial agent. These findings highlight the need for broader surveillance strategies that incorporate wildlife, particularly invasive species, into MAP control programs.