Parasites & Vectors最新文献

Background: Malaria mosquitoes reproduce in mating swarms. Previous studies have reported a pronounced activity peak in male mosquito swarms immediately following simulated sunset, typically lasting around 20 min. This peak represents the main swarm formation, where several mosquitoes concentrate above visual markers and maintain prolonged flight activity. However, most studies rely on laboratory setups with balanced or single-sex swarms, which do not reflect the male-biased sex ratios observed in the field.

Methods: In this study, we studied swarming behavior of male and female Anopheles coluzzii mosquitoes in five sex ratios (male-only 1:0, male-biased 3:1, balanced 1:1, female-biased 1:3, female-only 0:1) using three-dimensional infrared videography to quantify spatial structure of swarms and flight speed of individual mosquitoes. For each ratio, we analyzed changes in spatial arrangement and flight speed through time and between conditions.

Results: Swarm volume varied following a quadratic trend ( $R^2=0.889$ ). As the proportion of females in the swarm increased, the volume of the swarm increased, ranging from 305.1 cm³ in male-biased swarms to 612.6 cm³ in female-only swarms. Mean flight speed also increased with female proportion, from $0.66$  m/s (1:1 balanced ratio) to $0.87$  m/s (0:1 female-only ratio), showing a moderate relationship with volume ( $R^2=0.504$ ). Swarm density and speed were negatively correlated, indicating that mixed swarms are not only smaller in volume but also exhibit higher track densities ( $R_{\text{Spline}}^2=0.712)$ suggesting tighter, slower swarms in male-rich groups. Furthermore, we used a Random Forest as an exploratory classifier to (1) identify which kinematic features most differentiate operational sex ratio (OSR) groups and (2) test, as a proof of concept, whether sex ratio can be inferred from kinematic signatures.

Conclusions: These results demonstrate the influence of sex ratio on swarm kinematics and support the use of machine learning for behavioral classification in mosquito ecology.

Background: Aedes aegypti is typically regarded as a freshwater mosquito; however, recent studies have documented its development in brackish water habitats in coastal regions, including Sri Lanka's Jaffna Peninsula. Compared with freshwater populations, brackish water samples in Jaffna display enhanced salt tolerance throughout larval-to-adult development, along with differences in gene expression, cuticle morphology and composition, and insecticide susceptibility.

Methods: To explore the genetic basis of these differences, we performed a comparative genomic analysis using 5135 genome-wide single nucleotide polymorphisms (SNPs) from Ae. aegypti inhabiting freshwater and brackish water sites in the Jaffna Peninsula. Genetic diversity, population structure, and demographic parameters were evaluated using publicly available software. Candidate genomic regions potentially involved in salinity tolerance were identified through tests for environmental associations and genetic outlier detection.

Results: After performing genotype quality control and first-degree relative removal on the initial 121 mosquitoes genotyped, the final dataset comprised 13 freshwater and 21 brackish water individuals. Ae. aegypti populations from the Jaffna Peninsula showed limited evidence of genetic structuring by collection site, with a subtle pattern associated with larval water salinity (distance-based redundancy analysis [dbRDA] P = 0.002, adjusted R² = 0.01). Brackish-water populations displayed higher linkage disequilibrium, reduced effective population size, and lower nucleotide diversity relative to freshwater populations. Genetic outlier and environmental association analyses identified loci associated with fatty acid metabolism and other cellular pathways (e.g. Toll and Imd signaling pathways) as differentiated among the groups.

Conclusions: We found subtle genetic differentiation between freshwater and brackish-water Ae. aegypti populations from the Jaffna Peninsula, suggesting that brackish-water populations may experience distinct evolutionary pressures potentially linked to adaptation to saline environments. Analyses point to fatty acid metabolism as one of the biological processes that could contribute to salinity tolerance in Ae. aegypti, possibly influencing cuticle modifications as a physiological response. Additional studies incorporating more collection sites and larger sample sizes for each salinity group are needed to further elucidate the mechanisms driving this differentiation. The ability of Ae. aegypti to adapt to brackish water substantially expands the range of potential larval sites it can occupy, particularly in coastal areas, and emphasizes the need to adjust vector control strategies accordingly.

Background: Equine piroplasmosis (EP) is a tick-borne disease of equids caused by the intraerythrocytic apicomplexan parasites Theileria equi, Babesia caballi and the recently identified Theileria haneyi. Acute cases can be severe, with anemia, jaundice, abortion or sudden death. Survivors remain lifelong carriers, serving as reservoirs for tick-borne and iatrogenic transmission. No vaccines are currently available, and control strategies rely heavily on accurate diagnostics and chemotherapeutic intervention. Imidocarb dipropionate (ID) is the current standard of care for both acute treatment and radical cure. However, growing concerns regarding ID-resistant parasite strains and its associated toxicity have highlighted the urgent need for novel, safer and more effective antiparasitic agents. Here, we assessed the in vitro efficacy of tafenoquine succinate (TFQ), a synthetic 8-aminoquinoline with broad antiparasitic activity, against T. equi and B. caballi as a potential treatment for equine piroplasmosis.

Methods: The effect of TFQ on T. equi and B. caballi was evaluated in vitro in parasite cultures. The percentage of parasitized erythrocytes was measured by flow cytometry, and the effect of TFQ on parasite growth was compared to that of ID. TFQ toxicity on horse peripheral blood mononuclear cells (PBMCs) was assessed via a colorimetric metabolic assay.

Results: TFQ reduced T. equi parasitemia in a dose-dependent manner, matching ID efficacy at 72 h. For B. caballi, TFQ had no effect at 5-10 µM but inhibited growth at 15 µM, similar to the results obtained with ID. TFQ exhibited approximately threefold greater potency against T. equi [half-maximal inhibitory concentration [IC₅₀] 5.90 μM, 95% confidence interval (CI) 4.99-5.96; 99% inhibitory concentration (IC₉₉) 60.74 μM, 95% CI 37.41-113.3] compared to B. caballi [IC₅₀ 14.5 μM, 95% CI 13.81-15.23; IC₉₉ 20.44 μM, 95% CI 17.77-28.84]. The narrower confidence intervals for T. equi suggest a more consistent antiparasitic response across replicates. Cytotoxicity assays showed no toxic effects on equine PBMCs at 2.5-5 μM (P > 0.05), while concentrations ≥ 10 μM indicated potential toxicity. These findings suggest that TFQ selectively targets parasites over host cells, supporting its therapeutic potential.

Conclusions: TFQ significantly inhibited T. equi and B. caballi growth at doses tolerated by equine PBMCs, supporting its potential as an alternative treatment for EP and warranting further in vivo study.

Background: Since 2010, dengue virus (DENV) has caused sporadic outbreaks across Europe, namely in Croatia, Spain, France, Italy and the Portuguese island of Madeira. Aedes aegypti mosquito is established in the Autonomous Region of Madeira, and along the eastern Black Sea coast of Cyprus. In Madeira Island, an outbreak of DENV serotype 1 occurred between 2012 and 2013, resulting in 1080 confirmed cases. Despite ongoing entomological surveillance, no further local transmission was detected in the following decade.

Methods: In January 2025, following two suspected dengue cases on Madeira Island, increased entomological surveillance efforts were implemented to confirm a local event transmission of DENV. A network of mosquito traps was complemented by targeted surveillance using 17 BG-PRO traps positioned in the vicinity of suspected human cases. Daily collections of adult A. aegypti, collected from 10 January to 31 March 2025, were screened by reverse transcription polymerase chain reaction (RT-PCR) for Aedes-borne viruses in the reference laboratory. Viral sequencing was performed using target enrichment and bioinformatics with INSaFLU-TELEVIR. The climate-driven suitability for dengue transmission by A. aegypti was also investigated. Serological and molecular tests were conducted on samples from suspected human cases.

Results: Out of 80 analysed A. aegypti pools (N = 393 mosquitoes), 1 pool, with 9 mosquitoes collected near the home of suspected human cases, tested positive for DENV. The dengue whole genome sequence from this sample was determined and classified as DENV-2 lineage 2II_F.1.1.3. The same virus was retrospectively confirmed in one of the clinical cases. Analysis of mosquito abundance and climate data confirmed the occurrence of this local transmission event during a period of low mosquito abundance and low climatic suitability.

Conclusions: Here, we report an in-depth analysis of a local dengue transmission event that occurred in Funchal, the capital of Madeira Island, in January 2025, with whole-genome evidence of DENV-2II_F.1.1.3 in field-caught A. aegypti mosquitoes. Retrospective analysis confirmed the presence of the same virus in one of the two clinical cases, establishing a direct link between human and mosquito infections, and highlighting the risk of off-season arboviral introductions.

Background: Although Mycoplasma spp. infection has been recently detected in other vulnerable human populations (indigenous and quilombola communities) in Brazil, no study to date has focused on traditional oceanic island communities and their dogs. To address this research gap, we assessed Mycoplasma spp. infection in humans and dogs living on the mainland seashore and oceanic islands of southern Brazil.

Methods: Humans from three oceanic islands and two coastal mainland municipalities of southern Brazil were sampled, and Mycoplasma spp. infection was determined using quantitative polymerase chain reaction (qPCR) (cycle threshold; Ct ≤ 34.4). Dog samples were collected and tested using the Canine Hemotropic Mycoplasma panel (Idexx Reference Laboratory, Sacramento, CA, USA). To ensure accurate results, samples were also subjected to targeted next-generation sequencing (tNGS), and results were used to construct phylogenetic trees. Epidemiological information was obtained to analyze associated risk factors.

Results: A total of 19/304 (6.2%) individuals tested positive to hemoplasmas, with Mycoplasma haemocanis confirmed in 3/304 (1.0%) through 16S ribosomal RNA gene and targeted next-generation sequencing. In addition, 44/290 (15.2%) dogs were positive for hemoplasmas through qPCR testing, with 13/290 (4.5%) for M. haemocanis, 23/290 (7.9%) for Candidatus Mycoplasma haematoparvum, and 8/290 (2.8%) for both. Statistical analysis revealed an association between human positivity and gender and income range, and dog positivity was associated with male gender and access to forest areas.

Conclusions: The concomitant human-dog M. haemocanis detected herein on oceanic islands together with results from previous reports on indigenous and quilombola communities, suggest that socially vulnerable populations have an increased exposure risk. Future studies should be conducted in other vulnerable populations worldwide to fully establish the extent of human-dog Mycoplasma spp.

Infection:

Background: Lipoptena cervi is a member of the Hippoboscidae family of insects and is a hematophagous ectoparasite of cervid species, commonly referred to as the deer ked. Lipoptena cervi has a wide geographical distribution and can be found from North America through Europe into East Asia. Deer keds occasionally bite humans and domestic animals and might act as disease vectors. The microbiome associated with this species of biting insect has not been investigated.

Methods: Mass sequencing of both DNA and RNA extracted from L. cervi specimens collected from two locations in southern England was conducted to characterise the complete microbiome consisting of bacterial, viral and eukaryotic species. Three specimens were collected after landing on humans in Somerset, and three specimens were collected from European roe deer (Capreolus capreolus) in Oxfordshire. Bioinformatic analysis investigated the host and microbial composition of each specimen.

Results: Near-complete mitochondrial genomes were assembled from all six specimens confirming morphological speciation as L. cervi. Bacterial endosymbionts were the most dominant organisms identified with Candidatus Arsenophonus lipoptenae being most abundant. In specimens that had fed on deer, the pathogen Bartonella schoenbuchensis was detected. A novel sigmavirus was also detected in five samples, four of which yielded near-complete genomes. The closest relative of this virus was a sigmavirus found in a sheep ked (Melophagus ovinus) sampled in the Russian Federation.

Conclusions: The data from this study will allow for a better baseline understanding of the microbiome of L. cervi and provide evidence for their role as vectors of zoonotic pathogens.

Membrane transporters play a vital role in the obligate intracellular parasite Toxoplasma gondii, mediating the acquisition of nutrients from host cells, the regulation of ion gradients, and the maintenance of metabolic homeostasis. Despite their central importance for parasite survival, pathogenesis, and drug resistance, the majority of T. gondii transporters remain poorly characterized. Key unresolved questions include the mechanisms underlying purine nucleotide transport across the plasma membrane and the import/export of metabolites for core pathways in the apicoplast (e.g., thiamine, isopentenyl diphosphate[IPP]/dimethylallyl diphosphate [DMAPP], and coproporphyrinogen III) and mitochondria (e.g., amino acids and cofactors). Recent advances in bioinformatics and CRISPR-based phenotypic screening have enabled systematic identification of transporter candidates. This review summarizes current knowledge of T. gondii transporters localized to the plasma membrane, apicoplast, mitochondria, endoplasmic reticulum, and Golgi apparatus, highlighting their roles in nutrient acquisition, metabolic crosstalk, and organellar function. Furthermore, we propose a screening strategy integrating transmembrane domain prediction, CRISPR phenotyping, and hyperLOPIT-based protein localization to prioritize uncharacterized transporters for functional study. These insights underscore the potential of transporters as therapeutic targets and provide a roadmap for future research into the physiology of T. gondii.

Background: Leishmaniasis is a parasitic disease transmitted by female sand flies and caused by protozoan parasites of the genus Leishmania. Accurate quantification of parasite load within vectors is essential for understanding transmission dynamics and vector competence. This study compares two quantitative polymerase chain reaction (qPCR) methods for detecting and quantifying Leishmania infantum in three experimentally infected sand fly species (Phlebotomus perniciosus, Phlebotomus argentipes, and Phlebotomus orientalis).

Methods: One method targets kinetoplast minicircle DNA, which offers high sensitivity but limited quantitative precision, while the other targets the single-copy Meta-1 gene, providing more precise quantification but reduced sensitivity in low-level infections.

Results: A positive correlation between the two molecular markers supports a combined approach to maximize both sensitivity and accuracy in surveillance and transmission studies. Following this methodological comparison, significant differences were observed in parasite proliferation among sand fly species and L. infantum strains, with Ph. orientalis confirmed as a highly competent vector for Leishmania donovani complex.

Conclusions: Together, these findings highlight that combining high-sensitivity (kinetoplast DNA [kDNA]) and single-copy (Meta-1) targets enables both accurate and sensitive quantification of Leishmania infections in sand flies, improving the assessment of parasite-vector interactions.

Background: The control of toxoplasmosis relies on conventional chemotherapeutics, which have hitherto unresolved concerns.

Methods: Swiss albino mice were intraperitoneally (IP) infected with 5 × 10³ tachyzoites of RH HXGPRT( -) strain of Toxoplasma gondii, then IP treated with one-fourth lethal dose 50 (one-fourth LD50) of Cerastes cerastes venom (CCV) for three consecutive days (LD = 0.535 mg/kg). The anti-Toxoplasma activity of CCV was evaluated, for the first time, in immunocompetent (IC) and immunosuppressed (IS) mice via estimation of their mortality and survival time, microscopical counting of peritoneal tachyzoites, measurement of liver parasite burdens using quantitative real-time polymerase chain reaction (qRT-PCR), detection of infectivity, and ultrastructural changes of the treated tachyzoites. The safety of the used dose was biochemically assessed by measuring liver, kidney, and oxidative stress markers in serum.

Results: CCV induced an insignificant reduction in mortality rate (MR) and a significant increase in survival time of mice. A statistically significant decrease in the mean peritoneal parasite burden with 89.8% and 90.8% reduction (%R) was observed in both IC and IS-treated subgroups compared with their controls, respectively. This reduction was consistent with 88% and 86% decrease in liver parasite load, respectively, and obvious ultrastructural alterations in treated tachyzoites. Concerning the infectivity study, the percent reduction was 78.8% and 85.5% in the peritoneal fluid and 71.1% and 60.4% in the liver tissues of IC and IS subgroups, respectively. The biochemical safety of the used dose and its high antioxidant activity were verified.

Conclusions: Thus, one-fourth LD50 of CCV can be considered a promising, effective natural alternative to standard chemotherapy for acute toxoplasmosis.

Background: The genetic variability of a large collection of European samples of the zoonotic pathogen Cryptosporidium parvum has been recently explored on the basis of a novel multi-locus sequence typing (MLST) scheme. In this work, we assessed the usefulness of this scheme to type C. parvum samples from Italy, a country where this pathogen is widespread and associated with human infections.

Methods: Polymerase chain reaction (PCR) and sequencing for the eight markers of the MLST scheme were performed on 31 human- and 21 animal-derived C. parvum samples. MLST data from 27 samples of animal origin previously sequenced at the genome level were also included. Sequence data for the glycoprotein 60 (gp60) gene were also generated. Phylogenetic and cluster analyses were conducted.

Results: Full genotyping data were obtained for 72 of 79 samples, and 39 different profiles were categorized, 28 of which were found in individual samples (singletons). A new allele was found at the marker on chromosome 2 in a human-derived sample. When compared with the 154 profiles previously described in Europe, 30 of the 39 profiles (76%) were found to be restricted to Italy, a result compatible with a model of isolation by distance, with geographically structured populations. Analysis of the gp60 sequences identified 19 different subtypes among the 55 samples belonging to family IIa, and 7 different subtypes among the 16 samples belonging to family IId. Phylogenetic and haplotype analyses did not identify clusters related to the host, the geographic origin (i.e., the Italian regions), or the time of collection of the samples but did identify two different populations, mirroring data obtained from whole genome comparative analyses.

Conclusions: The MLST scheme appears to be a promising method for genotyping C. parvum samples, as it provided higher discrimination compared with gp60 and enabled the recognition of the two major populations circulating in Europe and in Italy.