Parasites & Vectors最新文献

Background: Drug-resistant strains of Leishmania infantum challenge the effectiveness of treatments for clinical leishmaniosis and may lead to more frequent relapses. Copy number variation (CNV) at specific genetic loci is associated with drug resistance and virulence, but information about its prevalence in endemic regions is limited. This study examines the drug resistance and virulence status of Leishmania strains in human and canine isolates from the Mediterranean region.

Methods: Forty-eight Leishmania infantum isolates were whole-genome sequenced with nanopore long reads, followed by de novo assembly. We analyzed chromosomal aneuploidies and gene copy number variation in loci linked to drug resistance and virulence in Leishmania, alongside the genomic structure and rearrangements responsible for these variations.

Results: Complete genomes were de novo assembled for 35 L. infantum isolates (22 from dogs and 13 from humans), revealing significant chromosomal variability. We assessed copy number variation for 22 potential biomarkers: 15 genes related to drug resistance to first-line drugs (METK for allopurinol; LdSMT for amphotericin B; AQP1 and H-locus for antimonials; LdMT, LdRos3, and MSL for miltefosine; and PPM for paramomycin) and 7 genes related to virulence (lipophosphoglycan and proteophosphoglycan biosynthesis, and the Lack protein). Drug-resistance biomarkers were identified in 80% of the isolates. Canine strains primarily showed resistance to allopurinol and antimonials, while human isolates exhibited a broader resistance spectrum, especially to antimonials and paromomycin. The co-occurrence of resistance biomarkers was common, especially for allopurinol and antimonial resistance. Distinct mechanisms underlie the observed copy number variations. Virulence-associated genes were less variable among isolates.

Conclusions: The prevalence of drug-resistance biomarkers in Leishmania infantum strains from the Mediterranean region, as revealed by this study, underscores the critical need for routine resistance surveillance in managing clinical leishmaniosis. These findings not only inform current clinical practice but also pave the way for more effective management strategies in the future.

Background: Sand flies are vectors of the protozoan Leishmania spp. and phleboviruses. In Europe, several species are widely distributed in the Mediterranean region and a northward spread can be observed. They can be found regularly also in some regions of Central Europe, with Phlebotomus mascittii being the most cold-tolerant and northerly distributed species, but the knowledge on their distribution in countries such as Germany, Austria, Czechia, Slovakia, and Hungary remains fragmentary because of a lack of comprehensive field studies and a poor understanding of the ecological requirements and phylogeographic history.

Methods: A comprehensive literature review of sand fly occurrence in five Central European countries was complemented by entomological surveys, including sand fly and rodent screening for sand fly-borne pathogens. Nucleic acid extraction, COI barcoding, blood meal analysis, and phylogenetic and environmental analyses incorporating unsupervised machine learning techniques were conducted.

Results: This study significantly advances the understanding of the current distribution of six sand fly species in Central Europe. Among them, only Ph. mascittii was present in all analyzed countries, except Czechia, with its seasonal activity peaking in July. Phlebotomus papatasi, Ph. perfiliewi and Ph. neglectus were recorded in Hungary, while Ph. perniciosus and Phlebotomus simici were found in Germany and Austria, respectively. Although Leishmania DNA was absent in sand flies and rodents, DNA from two distinct Trypanosoma lineages was detected in several specimens, suggesting Ph. mascittii feeds on both birds and ruminants. Trypanosomatid lineages identified in local rodents differed, indicating distinct lineages between sand flies and rodents. Environmental analysis identified 15 Corine land cover classes associated with sand fly presence, with urban locations being the most frequently occupied. Linear regression models comparing presence versus absence revealed significantly higher sand fly presence in forested and urban landscapes. Furthermore, Ph. mascittii populations formed four distinct ecological clusters, which broadly grouped into two main geographic groups: one in the Upper Rhine Valley of southwestern Germany and the other spanning the Carpathian Basin.

Conclusions: This study provides new insights into the current distribution, ecological preferences, seasonal activity, and potential vector capacity of sand fly species in Central Europe.

Background: Globally, the disease ecology of reptiles remains understudied, even for threatened and iconic species such as the Galápagos marine iguana (Amblyrhynchus cristatus). Although marine iguanas are parasitized by distinct species of ticks and mites, research on vector-borne diseases for this species is limited.

Methods: In this study, we detected 16S ribosomal RNA (rRNA) sequences of Candidatus Allocryptoplasma in transcriptomic data from marine iguana blood samples. These 16S rRNA sequences were further characterized through phylogenetic analysis and a haplotype network.

Results: Our analysis revealed the first molecular evidence for the infection of marine iguanas with Candidatus Allocryptoplasma, a candidate genus in the family Anaplasmataceae with unknown pathogenic potential, likely transmitted by ticks. Phylogenetic analysis of the novel 16S rRNA sequences together with available Anaplasmataceae sequences confirmed their assignment to this candidate genus. A haplotype network analysis indicated that the agent infecting the marine iguana represents a distinct lineage within the known Ca. Allocryptoplasma diversity.

Conclusions: Candidatus Allocryptoplasma had a high prevalence within marine iguanas, infecting individuals across most of the geographical range of this species. To elucidate the transmission dynamics of this bacterium in the Galápagos ecosystem, ectoparasites of the marine iguana and shared vertebrate hosts should be screened for infection with Ca. Allocryptoplasma.

Background: Cyclospora is an emerging intestinal pathogenic protozoan transmitted through foodborne and waterborne routes. At least 19 countries in the world have recorded outbreaks of cyclosporiasis, mainly associated with the consumption of contaminated fresh agricultural products. The lack of a sensitive immediate test is one of the major obstacles to the rapid diagnosis of cyclosporiasis. The target interference mechanisms of clustered regularly interspaced short palindromic repeats (CRISPR) and CRISPR-associated (Cas) protein systems have been adapted into versatile and efficient genome manipulation and disease-curing technologies, while also being promising for point-of-care testing (POCT) applications. It can serve as an excellent rapid and specific detection tool.

Methods: The recombinase polymerase amplification (RPA) and the CRISPR/Cas12a system were combined to develop a detection method for C. cayetanensis (termed RECCT-Cay) via visual observation of fluorescent readings under blue light and field diagnosis using lateral flow strip (LFS) biosensors.

Results: The detection limit of the established RECCT-Cay was 7 copies/μL. Under simulated clinical conditions, the detection limit was 30 oocysts per gram of stool. At the same time, the established detection platform can distinguish C. cayetanensis from the closely related Eimeria spp. The results of our constructed assay were compared with nested PCR, and the detection results of 30 clinical stool samples were consistent, with three samples positive for C. cayetanensis. Based on the RECCT-Cay detection principle, a portable suitcase-sized device has been designed, which can conduct rapid on-site detection of clinical samples.

Conclusions: The RECCT-Cay platform features rapid speed, high sensitivity, and the capability for field detection, making it a promising tool for use in remote areas.

Background: Arboviruses continue to threaten global health because of their rapid geographical expansion and significant disease burden. Of the over 500 recognized arboviruses, approximately 150 affect humans, and around 50 affect domestic animals and wildlife. The spread and impact of these viruses have increased significantly over the past three decades, driven by the proliferation of their vectors and the rise of global trade and travel.

Methods: In this study, we used molecular methods to characterize mosquito species diversity and host feeding preferences across Ethiopia's Great Rift Valley. Mosquitoes were collected from diverse habitats in the Great Rift Valley of Ethiopia using Centers for Disease Control and Prevention (CDC) light traps, BG-Sentinel traps, and hand aspirators. The area was chosen for its high vector diversity, suitable breeding habitats, and the epidemiological importance of arboviruses. Morphological identification was conducted, and 204 blood-fed mosquitoes were selected. Genomic DNA was extracted, followed by polymerase chain reaction (PCR) amplification targeting the COI gene. Blood meal analysis was performed using vertebrate-specific primers targeting the 12S rRNA gene. Mosquito species identification, genetic diversity analysis, and phylogenetic analyses were conducted.

Results: Of 6601 collected mosquitoes, 4977 were identified morphologically, comprising 399 Aedes, 2861 Culex, 1841 Anopheles, and 275 Mansonia species. COI DNA barcode analysis identified 142 mosquito specimens belonging to 16 species, with Anopheles coustani, Cx. tritaeniorhynchus, Cx. pipiens complex, Mansonia africana, and Ma. uniformis being the predominant species. Blood meal analysis (n = 71 successful amplifications) revealed a primary reliance on humans and cattle. Cx. pipiens complex showed a strong anthropophilic tendency, while Cx. tritaeniorhynchus and Ma. uniformis exhibited broader host ranges. Genetic diversity indices showed significant Fu's F_s statistics for Cx. pipiens complex, Cx. tritaeniorhynchus, Ma. africana, and Ma. uniformis.

Conclusions: This study offers valuable preliminary insights into the diversity of mosquito species, genetic variation, and host-feeding preferences within the Ethiopian Rift Valley. The findings emphasize the potential of molecular techniques to enhance traditional entomological methods and improve the accuracy of mosquito identification. While the study is limited in both geographic and temporal scope, it highlights mosquito species of medical and veterinary significance and suggests implications for arboviral disease surveillance.

Background: The risk of developing Lyme borreliosis (LB) following a tick bite is influenced by several independent factors, including the promptness of tick removal, host immune response, and regional variability in pathogen prevalence. This study employed a citizen science approach to investigate the incidence of LB following Ixodes ricinus bites in Poland and to assess the relationship between Borrelia spirochete load, tick attachment duration, and subsequent LB development in humans.

Methods: The study was conducted over 2 years (2021-2022). Participants were instructed to submit removed ticks and to complete questionnaires at enrollment and 8 weeks post-bite. All LB cases were physician-confirmed on the basis of national clinical criteria. Tick attachment duration was estimated using scutal and coxal indices. Genomic DNA extracted from ticks was subjected to molecular screening for Borrelia spp., and spirochete load was quantified using droplet digital polymerase chain reaction (PCR).

Results: The prevalence of Borrelia infection in I. ricinus ticks was 15.7% (n = 2079). The overall risk of developing LB following a tick bite was 3.1% (n = 1757). Among confirmed LB cases (n = 54), erythema migrans was reported in 64.9%. In cases involving Borrelia-positive ticks (n = 250), the risk of LB increased with attachment duration-from 10.0% for ticks removed within 24 h to 30.0% for those removed after 48 h. Among Borrelia-infected ticks removed from the skin of the patients with LB, Borrelia afzelii was the most frequently detected species, however co-infection with Borrelia miyamotoi was also observed. Notably, both Borrelia prevalence and spirochete load in ticks decreased significantly with prolonged attachment duration.

Conclusions: The overall risk of LB following an I. ricinus bite was relatively low. While B. afzelii was the dominant species detected, the potential risk posed by B. miyamotoi warrants attention, given its significantly higher spirochete load compared with the B. burgdorferi sensu lato complex, potentially indicating greater transmission efficiency. The observed decline in spirochete load with increasing attachment time suggests a complex dynamic that may influence transmission risk, meriting further investigation. This study highlights the utility of citizen science as a viable method for collecting large-scale data on human-tick encounters, despite methodological constraints inherent in volunteer-based research.

Background: Entomopathogenic fungi like Metarhizium are emerging as effective biopesticides against malaria vectors. They reduce mosquito survival, fecundity, and flight ability, and reverse insecticide susceptibility in resistant Anopheles gambiae sensu lato strains. To elucidate the unclear underlying mechanisms, this study investigates the effects of fungal infections and insecticide exposure on the mosquito's energy reserves and the expression of key metabolic and immune genes.

Methods: Three mosquito types: (i) pyrethroid-resistant An. gambiae sensu lato and two laboratory colonies: (ii) pyrethroid-resistant An. coluzzii VKPER and (iii) insecticide-susceptible An. gambiae sensu stricto Kisumu were used. They were infected with Metarhizium pingshaense S10 strain at a concentration of 10⁷ spores/mL (treatment groups) and with solvent only (0.05% Tween^® 80; control groups). Live mosquitoes were collected on days 0, 4, and 8 post-infection. They were used to quantify glucose, glycogen, and lipid via Van Handel's protocol and to assess insecticide resistance. For resistance testing, mosquitoes underwent a standard WHO insecticide susceptibility test using deltamethrin (0.05%) or a control. Survival was measured 1 h after exposure, and surviving mosquitoes were analyzed by RT-qPCR for the expression of defensin and CYP6P3, CYP6Z1, and GSTe2.

Results: Susceptible An. gambiae Kisumu were eliminated by deltamethrin, while resistant An. coluzzii VKPER and wild An. gambiae s.l. mosquitoes survived. However, deltamethrin exposure following Metarhizium infection significantly reduced survival in these resistant strains compared to the controls. This also resulted in reduced expression levels of defensin, GSTe2, and CYP6Z1 compared to deltamethrin exposure alone, but no difference was found in the expression levels of CYP6P3. These results collectively indicate that Metarhizium infection reduces mosquito survival by impairing their energetic reserves and ability to sustain vital physiological processes, including immune function and metabolic homeostasis.

Conclusions: We demonstrate that Metarhizium infection reverses insecticide resistance in An. gambiae s.l. by depleting energy reserves and suppressing the expression of detoxification genes. This mechanistic insight is crucial for optimizing the future integration of Metarhizium alongside conventional insecticides for malaria vector control.

Background: Malaria vectors reproduce through in-flight copulation within swarms, which remains poorly understood. Gaining insights into swarming and mating behavior is essential for optimizing novel vector control strategies including sterile insect technique, genetically modified mosquitoes, and behavior based intervention. This study investigates the factors influencing swarm dynamics and mating efficiency in Anopheles coluzzii.

Methods: We surveyed swarms across 40 residential compounds in Burkina Faso, georeferencing swarming sites and recording swarming times and height. In a subset of three compounds selected for detailed characterization, we also measured inter-swarm distances, counted swarm size from photography, and mating pairs through direct observation during swarming. Furthermore, we collected 30% of male mosquitoes from swarms to measure wing length and perform PCR analyses. We monitored environmental variables including temperature, humidity, wind speed, and luminosity. Finally, we performed spatial and statistical analysis using ArcGIS and R to determine how swarm and mating dynamics are correlated and how they depend on biological and environmental conditions.

Results: We identified 169 Anopheles coluzzii swarms and found strong evidence of spatial clustering (General G: P < 0.001; Moran's I = 0.2, P < 0.001), with localized hotspots. Swarming occurred between 18:05 h and 18:45 h, extending into darkness at ~19:15 h. Swarms had an average height of 2.87 m (range: 1.0-3.2 m) and consisted of 83-2783 mosquitoes. Swarm size strongly predicted pairing success in Anopheles coluzzii (t = 9.16, P < 0.001) with larger swarms producing more pairs. However, individual pairing efficiency decreased with swarm size (t = -3.515, P < 0.001). Male size positively influenced individual pairing efficiency (t = 3.25, P = 0.002) but did not affect swarm size or total pairing frequency. Inter-swarm distances varied nonrandomly, suggesting interactions between neighboring and/or swarm markers.

Conclusions: This study shows that An. coluzzii swarming is shaped by both biological and environmental factors. While larger males achieved higher individual mating efficiency, swarm size was the strongest predictor of mating success. Larger swarms yielded more mating pairs overall, although efficiency declined with increasing density. In addition, swarms formed in clustered nonrandom patterns within compounds. These results highlight the interplay between male traits and environment in shaping swarming dynamics.

Background: VectoMax FG (Valent BioSciences, Libertyville, IL, USA) is a biological mosquito larvicide, combining Bacillus thuringiensis var. israelensis and Lysinibacillus sphaericus. Bacillus thuringiensis var. israelensis demonstrates a low propensity for resistance development, whereas L. sphaericus exhibits prolonged residual effectiveness in organically polluted aquatic environments. The manufacturer recommends treatments at least every 4 weeks; however, recent evidence suggests that less frequent applications may achieve comparable effectiveness, which is important for reducing operational costs related to larvicide volume and labour as well as reduced environmental exposure.

Methods: To provide data-driven guidance for vector control programmes targeting Aedes albopictus in catch basins, we conducted a randomised controlled trial in Basel, Switzerland, from May to October 2024. A total of 180 catch basins, randomly selected from 768 basins in an urban area infested with Ae. albopictus, were assigned to treatment intervals of 2, 4, 6, 8 or 10 weeks, alongside untreated controls. Emergence traps were used to capture adult mosquitoes developing from larvae within the basins, allowing comparison of mosquito abundance reductions across treatment frequencies. Generalised additive and linear mixed effects models were applied to quantify the effects of larvicide application frequency, temperature, precipitation and time since treatment on mosquito and non-target dipteran populations.

Results: Suppression of all taxa peaked within 20-30 days post-treatment. Over 50% reductions in mosquito abundance were sustained for up to 10 weeks following treatment, with Culex spp. exhibiting persistent suppression exceeding 90% for up to 6 weeks, and Ae. albopictus maintaining comparably high levels of suppression for up to 4 weeks.

Conclusions: While Culex spp. responded well even at longer intervals, Ae. albopictus required more frequent treatment to avoid rebound. Our findings show effective (> 90%) suppression in both Ae. albopictus and Culex spp. when VectoMax FG was reapplied at 4-week intervals. Increased application frequency not only enhanced overall effectiveness but also reduced variability in mosquito abundance, contributing to more stable vector control.

Background: The cestode Dipylidium caninum is known to infect dogs via the ingestion of an intermediate flea host, typically Ctenocephalides felis. Simparica Trio^® is an oral combination drug product for dogs effective in the treatment and prevention of fleas, including C. felis. Here, we report two laboratory studies evaluating the efficacy of a single administration of Simparica Trio at the minimum label dosage of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, and 5 mg/kg pyrantel (as pamoate salt) in preventing D. caninum infection in dogs for 1 month through killing of C. felis.

Methods: A total of 20 dogs (n = 10 per group) proven to be suitable hosts for C. felis were used in each of the two studies. Treatment occurred on day 0, with each dog given either the placebo or Simparica Trio. On days 0 (after treatment), 7, 14, 21, and 30, dogs were infested using 200 (± 5) unfed D. caninum-infected C. felis. Live flea counts were conducted on day 33 (72 ± 2 h after day 30 infestation). All dogs were euthanized on day 58, and each dog was necropsied for the recovery of D. caninum scolexes from the gastrointestinal tract.

Results: Placebo-treated dogs had adequate flea infestations and cestode infections in both studies. Simparica-Trio-treated dogs were free of fleas on day 33 (100% efficacy) and had significantly lower mean flea counts compared with placebo-treated dogs (P ≤ 0.0007). Scolex counts in Simparica-Trio-treated dogs were also significantly decreased compared with placebo-treated dogs in both studies. The efficacy of Simparica Trio against D. caninum based on least squares mean scolex counts was 100% (P < 0.0001) in study 1 and 92.1% (P = 0.0033) in study 2.

Conclusions: The efficacy provided by Simparica Trio against C. felis at the minimum dosage of 1.2 mg/kg sarolaner, 24 µg/kg moxidectin, and 5 mg/kg pyrantel (as pamoate salt) prevented D. caninum infection in dogs for 1 month.