Parasites & Vectors最新文献

Background: Amblyomma maculatum is a tick with a broad host range that is undergoing an expansion of its range within the USA. When feeding the predilection sites on the host are the head and ears and due to the long mouthparts, it can cause significant lesions that can lead to infection. It has also been implicated as a vector of Hepatozoon americanum, the causative agent of canine hepatozoonosis and a spotted fever group Rickettsia, Rickettsia parkeri.

Methods: Two randomized, blinded, negative controlled studies were conducted to determine whether treatment with afoxolaner (NexGard^®, Boehringer Ingelheim) or a combination of afoxolaner, moxidectin, and pyrantel (NexGard^® Plus, Boehringer Ingelheim) effectively treats and controls infestations of A. maculatum on dogs. For each study, ten healthy dogs were randomly assigned to each treatment group. In one study there were three treatment groups: an untreated control, NexGard^®-treated group, and NexGard^® Plus-treated group. The other study had an untreated control group and a NexGard^® Plus-treated group. Dogs were infested with approximately 50 unfed adult A. maculatum prior to treatment for evaluation of efficacy against existing infestations and then three times after treatment for evaluation of persistent efficacy. In each study the appropriate treatment groups were treated with either NexGard^® or NexGard^® Plus with afoxolaner targeted at 2.5 mg/kg, and ten control dogs were untreated. For evaluation of efficacy, live ticks were counted and removed from each dog at 72 h after treatment or subsequent infestations.

Results: NexGard^® and NexGard^® Plus were > 99% effective against established infestations of A. maculatum compared with the control group (P < 0.0001). NexGard^® and NexGard^® Plus were ≥ 92% effective against reinfestation with A. maculatum through Day 31 of the studies (P < 0.0001).

Conclusions: The results of these studies demonstrate that NexGard^® and NexGard^® Plus administered once at or near the minimum recommended dose of 2.5 mg/kg afoxolaner is effective for the treatment of existing A. maculatum infestations and for the control of infestations through Day 31.

Background: Cerebral malaria (CM) is the most serious and fatal neurological complication of Plasmodium falciparum infection, which can cause death or long-term neurological sequelae. Neuronal injury is a primary cause of these sequelae in patients with CM; however, the underlying mechanisms remain incompletely elucidated. Hemozoin (Hz), the metabolic byproduct of hemoglobin digested by Plasmodium parasites, is closely associated with the severity of CM. However, it is not clear whether Hz is a direct contributor to neuronal injury.

Methods: C57BL/6 J mice were infected with the Plasmodium berghei ANKA (PbA) strain to induce experimental cerebral malaria (ECM). Hz deposition and neuronal injury in ECM mice brain tissues were assessed using histopathological staining. In vitro, primary cortical neurons were stimulated with purified hemozoin (pHz). Neuronal morphology, pHz internalization, and injury severity were assessed via transmission electron microscopy (TEM), live-cell imaging, and lactate dehydrogenase (LDH) assays, respectively. Furthermore, Mito-Tracker and JC-1 probes were used to analyze mitochondrial content and membrane potential, respectively. ATP assay kits were used to quantify cellular energy metabolism levels, while reactive oxygen species (ROS)/neuronal nitric oxide synthase (nNOS) fluorescent probes were used to assess oxidative stress and inflammatory response. Neurotransmitter alterations were analyzed by measuring glutamate (Glu) levels.

Results: In the cerebral cortex of ECM mice, significant Hz deposition and reduced neuronal nuclei (NeuN) expression levels were observed. Immunofluorescence (IF) staining demonstrated that pHz adhered to primary neurons in vitro, causing reduced dendritic arborization, axon rupture, and plasma membrane disruption. TEM and live-cell imaging confirmed that pHz was internalized into the cytoplasm of neurons. Furthermore, pHz induced mitochondrial structural damage and reduced mitochondrial content. Concurrently, pHz triggered mitochondrial dysfunction, characterized by diminished mitochondrial membrane potential (MMP), reduced ATP levels, and elevated ROS. In addition, pHz upregulated intraneuronal nNOS activity and caused a decrease in neurotransmitter levels.

Conclusions: This study provided the first evidence to our knowledge that Hz directly adhered to neurons and underwent internalization into its cytoplasm, thereby leading to neuronal injury. These findings elucidate a potential mechanism underlying neuronal injury in ECM and inform the development of adjuvant therapies targeting Hz.

Background: Mosquito saliva plays a key role in arbovirus transmission and pathogenesis. It was shown that saliva contains several molecules that are essential for blood feeding. Recently, bacteria were also reported to be present in the saliva of Aedes albopictus and Anopheles mosquitoes. Nevertheless, information on the bacterial communities in Aedes and Culex saliva is still scarce.

Methods: This study isolated and identified culturable fungal and bacterial colonies from saliva harvested from Aedes aegypti (laboratory strain) and Culex pipiens (field-collected) mosquitoes. 16S metagenomic sequencing was performed to identify bacterial communities in saliva and mosquito organs. Furthermore, it was assessed how these microbial communities were affected upon blood feeding and upon oral treatment with antibiotics and an antifungal drug.

Results: The fungal species Penicillium crustosum was identified in mosquito saliva. Culturable bacteria detected in mosquito saliva included Serratia marcescens, Serratia nematodiphila, Enterobacter spp., and Klebsiella spp., which were previously identified as mosquito or insect endosymbionts in the midgut or other organs. Analysis with 16S metagenomics showed that bacterial communities in saliva were more diverse than those in the midgut. Blood feeding did not affect the fungal or bacterial load in mosquito saliva. Oral treatment of adult mosquitoes with antibiotics or an antifungal drug resulted in a significant reduction of bacteria or fungi present in the mosquito saliva. Notably, co-incubation of the mosquito-borne Semliki Forest virus with saliva from antibiotic- or antifungal-treated mosquitoes triggered a decrease in viral infection in human skin fibroblasts compared with nontreated saliva.

Conclusions: These findings indicate that bacteria and fungi can be present in mosquito saliva and provide a foundation for further exploration of the impact of salivary fungi and bacteria on both vector competence and arbovirus infection in the mammalian host.

Background: Deep amplicon sequencing of nematode internal transcribed spacer 2 (ITS2), also referred to as the "nemabiome," has been increasingly used in veterinary hosts to study gastrointestinal nematodes. While post-sequencing bioinformatic pipelines such as DADA2 and mothur have been optimized, most researchers typically use the DADA2 pipeline in R. For optimal performance, DADA2 needs parameter tuning, which is hard for novices.

Methods: In this study, we present an implementation of the DADA2 pipeline within QIIME2 for nemabiome analysis and compare its performance against the commonly used R-based DADA2 pipeline. To evaluate performance against samples with known composition, we generated simulated nemabiome datasets representing canine, ruminant, and equine nematode communities. We also tested the pipelines using publicly available datasets from ten veterinary host species. For both pipelines, we evaluated differences in amplified sequence variant (ASV) generation, taxonomic classification, and diversity metrics. We also tested different Idtaxa parameter settings within the R DADA2 pipeline (classification threshold and bootstrap iterations) to understand its effects on nemabiome outcomes.

Results: While both pipelines showed minor discrepancies in relative abundance estimates, with minimal parameter optimization, QIIME2 outputs were closer to ground truth in simulated datasets. QIIME2 using the scikit Bayes classifier produced fewer unclassified taxa and more consistent species-level identifications compared with R DADA2's Idtaxa, particularly in complex communities. Community-level differences in beta diversity were primarily driven by differences in taxonomic assignment. Parameter testing revealed that lower classification thresholds in R DADA2 reduced the number of unclassified taxa but increased the risk of misclassification, highlighting the need for careful parameter selection and reporting.

Conclusions: With minimal parameter tuning, QIIME2 outperformed the R pipeline in taxonomic resolution, and improved reproducibility by provenance tracking. Our findings emphasize how bioinformatics pipeline choices impact nemabiome outputs including the number of species detected, ranks of abundant taxa, and alpha and beta diversities. We provide a reproducible and user-friendly QIIME2 workflow suitable for researchers seeking standardized analyses of ITS2 nemabiome data.

Background: Aedes aegypti is the primary vector of arboviruses, including dengue, Zika and chikungunya, representing a major global public health concern. Owing to the lack of effective vaccines and specific therapeutic options for these infections, vector control remains the main strategy to limit their spread. Traditionally, vector control has relied on extensive use of insecticides combined with the elimination of breeding sites. However, in addition to selecting for insecticide-resistant mosquitoes, concerns have arisen about behavioural effects induced by insecticides, particularly repellency - defined as the ability of a chemical compound to trigger avoidance behaviour in insects, thereby reducing their exposure to treated surfaces. This systematic review aimed to synthesise current knowledge on repellent effects of certain insecticides on A. aegypti.

Methods: A literature search was conducted in the databases Virtual Health Library (BVS), PubMed® and Scientific Electronic Library Online (SciELO), following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) guidelines. A total of 46 original studies published between 1990 and 2023 were included.

Results: Altogether, 433 bioassays were analysed, of which 69.8% reported repellent effects. The most common methods used to assess repellency were excito-repellency chambers, HITSS assays and the arm-in-cage test. Pyrethroids were used in 86.6% of repellency assays, followed by organochlorines (9.4%). Regarding the resistance profile of tested mosquito populations, susceptible populations exhibited higher frequencies of contact (92.2%) and spatial (77.3%) repellency behaviours than resistant ones (74.1% and 44.0%, respectively).

Conclusions: Our findings indicate that insecticide-induced repellency is common and may interfere with the effectiveness of chemical control strategies. Nevertheless, studies addressing the underlying molecular and sensory mechanisms involved in repellent perception remain scarce.

Background: The potential of schistosomiasis to spread across borders, coupled with the considerable delay by which infected travellers and migrants are diagnosed in Europe, calls for better surveillance of the distribution of this disease. This study explored the geographical origin and genetic profiles of Schistosoma infections imported into Europe and diagnosed in a network of 11 European centres specialized in traveller and migrant health.

Methods: Genetic profiles were obtained from DNA extracted from concentrated Schistosoma eggs or Schistosoma-positive samples (faeces, urine, biopsy) collected during routine diagnostic procedures. The species-specific cytochrome oxidase sub-unit 1 (cox1) diagnostic region and the standard complete internal transcribed spacer (ITS) 1 + ITS2 (ITS1 + 2) ribosomal DNA region were amplified and sequenced, together with a partial region of 18S ribosomal DNA in selected cases. Prevalences of the different genetic profiles within the whole patient cohort and by country/geographical area of possible infection were analysed. A phylogenetic analysis was performed using the larger cox1 (~ 956 base pairs) sequences dataset.

Results: A total of 94 samples were available for analysis, 36 from patients with a diagnosis of intestinal schistosomiasis and 58 with urinary schistosomiasis, all acquired in a sub-Saharan African country. Mitochondrial (mt) cox1, nuclear ITS1 + 2 and/or 18S (mt/nuclear) genotypes were successfully obtained from 51/94 (54%) samples; while for 43/94 (46%) samples, only a partial mt genotype was obtained. Infections with Schistosoma haematobium and Schistosoma mansoni were identified in the majority of cases (66/94; 70%), while mixed Schistosoma spp. genetic profiles, which were identified in 30% (28/94) of the samples, were almost exclusively (27/28; 96%) associated with cases of urinary schistosomiasis. Among the urinary infections, almost half (27/58; 47%) could be identified as having a mixed genetic profile. These mostly (26/28; 93%) included genetic traits of S. haematobium and Schistosoma bovis, and all were from patients probably infected in West Africa.

Conclusions: Infections with S. haematobium and S. mansoni represent the majority of cases of schistosomiasis currently being diagnosed in Europe; however, mixed Schistosoma genetic profiles (mostly S. haematobium/S. bovis) were identified in at least 30% of samples. Our results call for a coordinated effort encompassing prompt diagnosis and treatment of Schistosoma infections, together with monitoring of the possible introduction of species of Schistosoma and establishment of their autochthonous transmission under suitable conditions in Europe.

Background: Immune thrombocytopenia (ITP) is an acquired autoimmune disease characterized by a low platelet count (< 100 × 10⁹/L) induced by an autoimmune mechanism, which increases platelet clearing by macrophages. Antigen B (AgB) is a lipoprotein derived from Echinococcus granulosus larvae and has been observed to modulate host immunity. This study evaluated the mechanistic impact of AgB on macrophage polarization in the ITP mouse model.

Methods: This study analyzed blood samples acquired from pediatric patients with ITP and healthy controls. Furthermore, the levels of inflammatory cytokines in plasma, as well as macrophage surface markers and autophagy-related markers [microtubule-associated protein 1 light chain 3 (LC3) and sequestosome-1 (p62)] in peripheral blood mononuclear cells (PBMCs) were evaluated. Moreover, the ITP model was successfully established after immunization with an anti-CD41 antibody and treatment with AgB in vivo. Platelet counts and hemorrhagic symptoms were continuously examined, while plasma inflammatory cytokine levels and the expression of pertinent indicators in the spleen were assessed. RAW264.7 macrophages and lipopolysaccharide (LPS)-stimulated RAW264.7 macrophages were treated with AgB to assess the expression of relevant markers in an in vitro experiment. The mechanism by which AgB regulates LC3 and p62 levels to inhibit LPS-induced macrophages was investigated. Lastly, autophagy inhibitors were administered to evaluate the specific stage of autophagy affected by AgB.

Results: AgB ameliorated hemorrhage and increased platelet counts in ITP murine models while decreasing the M1/M2 macrophage ratio. AgB therapy increased macrophage autophagic flux in vivo and in vitro. To elucidate the effects of AgB on various stages of autophagy, macrophages were treated with two autophagy inhibitors: 3-methyladenine (3-MA) and bafilomycin A1. This study revealed that AgB primarily acts by influencing the expression of LC3II/LC3I and p62, increasing the formation of autophagosomes and enabling lysosomes to identify and consume autophagosomes more accurately. AgB also inhibits macrophage polarization towards M1. These results suggested that AgB reduced hemorrhage in the ITP mouse model by regulating autophagy-mediated macrophage polarization.

Conclusions: This study showed that AgB alleviates ITP by restoring autophagy flux, inhibiting M1 macrophage polarization, and modulating immunity.

Background: The combination of lotilaner, moxidectin, praziquantel, and pyrantel pamoate (Credelio Quattro) is a novel systemic endectocide that provides month-long effectiveness in dogs after a single oral treatment. The safety of Credelio Quattro flavored chewable tablets was investigated when administered orally at the upper end of the recommended dosage range (20-41 mg/kg lotilaner, 0.02-0.04 mg/kg moxidectin, 5-10 mg/kg praziquantel, and 5-10 mg/kg pyrantel) and multiples thereof when administered long term.

Methods: The study was randomized and blinded, with parallel groups beginning in healthy 8-week-old Beagle dogs and continuing until they reached adulthood. A total of 32 dogs were randomized among four groups (8 dogs/group) to nontreated controls or to treated groups at target doses of 1×, 3×, or 5× the maximum dose. Treatment was administered on nine occasions to dogs in a fed state every 4 weeks, with the control group receiving placebo tablets. Assessment of safety was based on regular health observations, complete physical/neurological examinations, food consumption, clinical pathology evaluations (hematology, clinical chemistry, and urinalysis), body weight, and macroscopic and microscopic examinations of collected tissues.

Results: Credelio Quattro did not induce any serious treatment-related adverse effects based on health observations, physical/neurological examinations, food consumption, clinical pathology, body weight, or macroscopic and microscopic examinations. The only non-serious treatment-related effects of Credelio Quattro were a dose-dependent increase in the frequency of discolored feces, diarrhea, and vomiting (including hypersalivation associated with vomiting in two of the 5× dogs).

Conclusions: This study demonstrates that Credelio Quattro exhibits a wide safety margin when administered monthly to puppies and dogs at the maximum recommended commercial dose, with only transient gastrointestinal symptoms similar to other oral antiparasitic products observed. Therefore, Credelio Quattro may be safely administered to dogs each month in accordance with the approved label.

Background: Tick-borne Jingmenviruses are becoming an increasing arbovirus concern due to the rising number of reported infections in humans and animals, as well as their wide geographic distribution. The involvement of other hematophagous arthropods as vectors of Jingmenviruses is still unknown.

Methods: Mosquitoes were sampled in two different biotopes in Cameroon (Yaoundé and Garoua) during the rainy and dry seasons in 2022 and 2023. Metatranscriptomics Next Generation Sequencing was conducted using Illumina technology. Viral sequences detection revealed the presence of several contigs with high sequence identity to a human-derived Jingmenvirus (HdJV) previously discovered in plasma from an individual from Yaoundé, Cameroon. A draft viral genome was constituted for each Jingmenvirus-positive sample. Maximum likelihood phylogenetic reconstructions were used to position mosquito-associated viruses within the diversity of Jingmenviruses. Statistical analyses were conducted to estimate the prevalence of infected mosquitoes and the effect of different variables (region, season, year, mosquito species) on Jingmenvirus detection.

Results: HdJV was identified during the dry and the rainy seasons in four species of mosquitoes: Aedes albopictus, Culex quinquefasciatus, and Culex wansoni from Yaoundé, and Anopheles gambiae s.l. from Garoua. The overall prevalence of HdJV-infected mosquitoes was estimated to be 0.9% [0.4-1.7], and the unique variable significantly associated with HdJV detection was the sampling area: Yaoundé showed the highest prevalence (2.3% [0.9-4.7]) compared with Garoua (0.2% [0.01-0.8]). Mosquito-associated Jingmenviruses shared a high nucleotide identity (between 98.6 and 100% according to the segment) and clustered in the same clade in the phylogenetic analysis, indicating that they belong to the same viral species circulating in different mosquito species. The viral genome shared between 96.4 and 98.9% nucleotide identity with a HdJV detected in the plasma of a patient suffering from febrile illness originating from the same area, suggesting the possible involvement of mosquitoes as vectors of arboviral Jingmenviruses in human infections.

Conclusions: This finding provides new insights into the ecology and transmission dynamics of Jingmenviruses, highlighting mosquitoes as potential vectors, alongside ticks, in the zoonotic transmission of this virus group.

Background: Bovine babesiosis is a tick-borne disease that poses a significant economic threat to cattle industries in tropical and subtropical areas, and Babesia bovis is the most virulent causative agent of bovine babesiosis. This apicomplexan parasite infects erythrocytes of cattle, causing severe hemolytic disease, and animals that survive an acute infection become persistently infected for life. Adult cattle (> 1 year of age) are highly susceptible and often succumb to acute infection. Protective host immunity involves peripheral blood mononuclear cells (PBMCs) including monocytes, dendritic cells (DC), natural killer (NK), T cells, and B cells, all of which act to control the pathogen. Monocytes release the cytokines interleukin (IL)-1β and tumor necrosis factor (TNF) and nitric oxide, in addition to chemokines that attract immature DCs. NK cells release IL-12, IL-18, and interferon gamma (IFNγ). Mature DC migrate to secondary lymphoid tissues to present Babesia antigens to T cells. B cells will produce antibodies against Babesia.

Methods: In this study, we examined the transcriptional signatures of PBMCs from adult cattle (aged > 1.5 years) experimentally infected with the B. bovis virulent strain Vir-S74-T3Bo, during the acute phase of babesiosis, at 10 days post infection (dpi), using RNA Sequencing (RNA-Seq) technology.

Results: Transcriptional signatures evident during the acute phase of babesiosis were cytokines and chemokines, such as IL-0, TNF, IL-1B, IL-18, CSF1, CXCL10 and CXCL16; pattern recognition receptors, such as CD14, TLR and NOD2; complement components, such as C1R, C2, C3aR1, CFB, CFI and CFP; cell adhesion molecules, such as ICAM1/2 and SELL; and apoptosis markers, such as CASP, BAX and BAK. We identified 1766 upregulated and 1508 downregulated genes, with fold changes ranging from two- to 429-fold. We discuss our findings in the context of immune responses to acute disease as a mechanism for adult host survival, with a focus on the molecular functions and biological processes involved in the response to B. bovis infection.

Conclusions: In this RNA-Seq analysis, we identified genes that are up- and downregulated in response to acute B. bovis infection. Gene expression of IL-10, along with that of the inflammatory cytokines IL-1β, TNFα and IL-18, suggests a non-protective response to B. bovis at 10 dpi. These results enhance our understanding of the molecular interactions between Babesia and the host immune system.