Parasites & Vectors最新文献

Background: Aedes aegypti is the primary vector of dengue, chikungunya, and Zika viruses in Colombia. Various insecticides, including pyrethroid, organophosphate, and carbamate insecticides; growth regulators; and biological insecticides, such as Bacillus thuringiensis var. israelensis, have been used to control Ae. aegypti populations. However, organophosphates such as malathion, pirimiphos-methyl, and temephos have been used over the last decade owing to the high resistance to pyrethroids.

Methods: This study assessed the susceptibility to organophosphates in 14 Ae. aegypti populations from the Córdoba department in northern Colombia. Moreover, possible resistance mechanisms were investigated by determining the activity levels of α-esterases, β-esterases, mixed function oxidases (MFOs), glutathione S-transferases (GSTs), and insensitive acetylcholinesterase (iAChE). Additionally, the Ace-1 gene was sequenced to identify mutations at the target site of action.

Results: The populations were susceptible to temephos and malathion but resistant to fenitrothion, and in three of them, to pirimiphos-methyl. Alterations in the enzyme activity levels of α-esterases and β-esterases, GST, and iAChE were observed among the populations, with high enzyme activity levels of α and β esterases associated with resistance to fenitrothion. No mutations were identified in the Ace-1 gene.

Conclusions: These findings are highly relevant for vector control programs in the region, as they allow for adjustments in resistance management strategies and improve the effectiveness of interventions against these arboviruses.

Background: A fundamental tenet of the hygiene theory is the inverse association between helminth infections and the emergence of immune-mediated diseases. Research has been done to clarify the processes by which helminth-derived molecules can inhibit immunological disorders. This study aimed to evaluate the ability of Trichinella spiralis chitinase (Ts-chit) to ameliorate the symptoms of allergic airway inflammation.

Methods: Recombinant Trichinella spiralis chitinase (rTs-chit) was expressed in Escherichia coli BL21, and its structural homology to murine acidic mammalian chitinase (AMCase) was comprehensively analyzed. The expression of Ts-chit was examined across all T. spiralis life stages. To explore its immunomodulatory potential, a murine model of allergen-induced airway inflammation was established. The effects of rTs-chit were evaluated by assessing airway hyperresponsiveness and cytokine profiles in bronchoalveolar lavage fluid and performing detailed histopathological and immunohistochemical analyses.

Results: Recombinant Ts-chit (rTs-chit) was successfully expressed in E. coli BL21, showing strong structural similarity to murine acidic mammalian chitinase (AMCase). Expression profiling revealed that Ts-chit is present throughout all stages of the T. spiralis life cycle. In an allergic airway inflammation model, rTs-chit reduced weight loss and lung inflammation, lowering inflammatory cell infiltration and Th2 cytokines (IL-4, IL-5, IL-13) while increasing the immunosuppressive cytokine IL-10. Additionally, rTs-chit treatment decreased the expression of GATA3, arginase-1, MCP-1, CCL-11, and AMCase, along with reducing OVA-specific IgE, IgG, and IgG1 levels, suggesting its potential as an immunomodulatory agent.

Conclusions: This study highlights rTs-chit's potential as a therapeutic agent for allergic airway diseases, leveraging its structural similarity to host chitinases to regulate Th2 responses and inflammatory pathways. The findings provide new insights into helminth-derived proteins as promising candidates for immune-based therapies.

Background: Faecal egg counts (FECs) are essential for diagnosing helminth infections and guiding treatment decisions. For camels, no evaluations of coproscopic methods regarding precision, sensitivity and correlation between individual and pooled faecal samples are currently available.

Methods: Here, 410 camel faecal samples were collected in 2022 from South Darfur State, Sudan, and analysed to compare the semi-quantitative flotation, McMaster and Mini-FLOTAC methods in terms of precision, sensitivity, inter-rater reliability and helminth egg count correlations, as well as the effects of pooling samples. Six samples were used to assess precision for McMaster and Mini-FLOTAC, while the remaining 404 samples were evaluated for sensitivity, inter-rater reliability and egg count correlations. Of these, 80 samples were used in pooling experiments.

Results: Six analyses of each sample (n = 6) using the McMaster and Mini-FLOTAC methods revealed no significant difference in the coefficient of variation between the two. For strongyle eggs, 48.8%, 52.7% and 68.6% were positive for McMaster, semi-quantitative flotation and Mini-FLOTAC, respectively. The sensitivity of the three methods showed only minimal improvement when three egg counts were performed on the same sample. McMaster and Mini-FLOTAC had similar sensitivity for Strongyloides spp. (3.5% frequency), while it was lower for semi-quantitative flotation at 2.5%. Mini-FLOTAC was more sensitive for Moniezia spp., detecting 7.7% of positives compared with 4.5% for semi-quantitative flotation and 2.2% for McMaster. For Trichuris spp., frequencies were 0.3% with Mini-FLOTAC, 0.7% with McMaster and 1.7% with semi-quantitative flotation. Mini-FLOTAC also detected higher strongyle eggs per gram (EPG) of faeces (mean 537.4) compared with McMaster (330.1). More samples exceeded treatment thresholds with Mini-FLOTAC, with 28.5% of animals having EPG ≥ 200 compared with 19.3% for McMaster, while 19.1% showed EPG ≥ 500 with Mini-FLOTAC compared with 12.1% with McMaster. There was no significant correlation between individual and pooled strongyle FECs, as indicated by Pearson correlation coefficients of r ≥ 0.368 (P ≥ 0.113) and Spearman correlation.

Conclusions: Mini-FLOTAC outperformed semi-quantitative flotation and McMaster in diagnosing helminth infections in camels, offering greater sensitivity and detecting higher EPGs, particularly for strongyles, Strongyloides spp. and Moniezia spp. Thus, treatment decisions based on Mini-FLOTAC EPGs will lead to more treatments.

Background: Elimination of lymphatic filariasis (LF) is a World Health Organization goal, with several countries at or near prevalence thresholds. Where LF cases remain after mass drug administration, they tend to be spatially clustered, with an overdispersed individual worm burden. Both individual and spatial heterogeneities can cause aggregation of infection; however, few studies have investigated the drivers of heterogeneity and implications for disease elimination.

Methods: We used a spatially explicit lymphatic filariasis model to investigate LF transmission in American Samoa at three spatial scales - a territory-level model, a village model with 64 groups and a subvillage model with 316 groups.

Results: To reproduce American Samoan survey data, models with less spatial structure required increased individual-level bite aggregation. Threshold behaviour was present in the territory model but less evident in the models with spatial structure. As such, mass drug administration was most effective in the territory model, while in the spatially structured models, successive rounds of mass drug administration only gradually increased the likelihood of elimination. With the addition of spatial structure, residual infections remained in limited groups, and infection resurgence was slowed.

Conclusions: Due to the impacts on potential intervention and surveillance strategies, it is critical that studies incorporate individual and spatial sources of heterogeneity to accurately model transmission and inform potential policy decisions.

Rapid urbanization and migration in Latin America have intensified exposure to insect-borne diseases. Malaria, Chagas disease, yellow fever, and leishmaniasis have historically afflicted the region, while dengue, chikungunya, and Zika have been described and expanded more recently. The increased presence of synanthropic vector species and spread into previously unaffected areas due to urbanization and climate warming have intensified pathogen transmission risks. This review examines recent outbreaks and reemergence of insect-borne diseases through five case studies: (i) malaria transmission linked to political instability and large-scale migration through the Amazon jungle; (ii) the expansion of triatomine bug habitats into overcrowded, substandard urban settlements, increasing Chagas disease incidence; (iii) the influence of movement and ecotourism in the Amazonia on yellow fever transmission in peri-urban areas; (iv) the spread of visceral leishmaniasis driven by deforestation and human-canine movement; and (v) dengue outbreaks in rural Amazon regions, spurred by urbanization and rural development. The findings underscore the complex interactions among vectors, pathogens, and shifting environmental and social conditions, complicating predictability and control. Addressing the social, economic, and political determinants of health is crucial to reducing disease transmission. Key measures include scaling vaccine coverage, especially for dengue and yellow fever; developing vaccines and treatments for neglected diseases; improving housing and sanitation; strengthening vector surveillance and control; fostering community engagement; enhancing data-driven interventions.

Background: We standardized two recombinase polymerase amplification (RPA) assays coupled with lateral flow (LF) strips for the detection of Leishmania braziliensis and Leishmania infantum kinetoplast DNA (kDNA).

Methods: The RPA-LF assays were tested at different temperatures and reaction times, using DNA from cultured L. braziliensis and L. infantum. The L. infantum RPA-LF was also tested using clinical samples (bone marrow and skin) from infected and uninfected dogs.

Results: The detection limits (analytical sensitivity) of the assays were 0.04 pg/μl and 0.04 ng/μl for L. braziliensis and L. infantum kDNA, respectively. Using clinical samples, the L. infantum RPA-LF successfully detected the parasite kDNA in bone marrow (21/30; 70.0%) and skin samples (23/30, 76.6%) from naturally infected dogs. We found an almost perfect agreement (kappa = 0.807) between RPA-LF for L. infantum and our reference quantitative real-time polymerase chain reaction (qPCR), considering clinical samples with a quantification cycle (C_q) < 30, whereas the agreement with samples with a C_q > 30 (lower parasite loads) was moderate (kappa = 0.440).

Conclusions: The RPA-LF assays developed here may be promising diagnostic tools for point-of-care diagnosis of L. infantum and L. braziliensis infection in dogs, particularly in remote rural areas lacking laboratory infrastructure.

Background: The subfamily Phlebotominae comprises 1028 species of sand fly, of which only 90 are recognized as vectors of pathogenic agents such as Trypanosoma, Leishmania, and Bartonella. In Thailand, leishmaniasis-a sand fly-borne disease-is currently endemic, with 36 documented sand fly species. However, many cryptic species likely remain unidentified. To improve our understanding of the distribution, habitat preferences, and role in disease transmission of these sand flies, further research is necessary.

Methods: Sand flies were collected using CDC light traps from 13 locations across four provinces in Thailand between October 2022 and October 2023. Initially, species identification was based on morphological characteristics, employing identification keys, and subsequently confirmed through mitochondrial cytochrome oxidase c subunit I (COI) and cytochrome b (Cytb) sequencing. Species identities were verified using BLASTN and BOLD searches. Species delimitation was conducted using Automatic Barcode Gap Discovery (ABGD) and Assemble Species by Automatic Partitioning (ASAP) with three substitution models. Additionally, intraspecific and interspecific genetic variation, neutrality tests (including Tajima's and Fu and Li's D* tests), phylogenetic analyses, and TCS haplotype network analysis were performed using the obtained sequences.

Results: A total of 3693 phlebotomine sand flies were collected, with 2261 (61.22%) identified as female. Integrative analyses combining morphological data, BLASTN searches, phylogenetic assessments, and species delimitation confirmed the identification of four genera: Sergentomyia, Grassomyia, Phlebotomus, and Idiophlebotomus, encompassing 12 species: Sergentomyia anodontis, Se. sylvatica, Se. perturbans, Se. barraudi, Se. hivernus, Se. khawi, Se. siamensis, Grassomyia indica, Phlebotomus barguesae, Ph. stantoni, Idiophlebotomus asperulus, and Id. longiforceps. Furthermore, molecular analysis revealed cryptic and complex species, including two putatively novel species, Se. sp. 1 and Se. sp. 2, as well as a unique haplotype.

Conclusions: This study, which integrated genetic and morphological identification techniques, identified 12 sand fly species and unveiled cryptic and complex species, including two putatively novel species (Se. sp. 1 and Se. sp. 2) and a unique haplotype. The findings underscore the utility of mitochondrial genes, combined with species delimitation methodologies, as reliable approaches for identifying diverse sand fly species.

Background: Echinococcosis is a zoonotic disease caused by an Echinococcus tapeworm infection. While diagnostic methods for humans often rely on ultrasound imaging and immunodiagnostic techniques, diagnosis in intermediate hosts typically has no widely used diagnostic markers, hampering disease control efforts.

Methods: The differences in serum metabolites of sheep infected with Echinococcus granulosus and a control group were analyzed using ultrahigh-performance liquid chromatography (UHPLC) separation with tandem mass spectrometry (MS/MS) detection. This provided a basis for the early diagnosis and pathogenetic study of cystic echinococcosis (CE) in intermediate hosts at the metabolomics level. Orthogonal projections to latent structures-discriminant analysis (OPLS-DA) were used to analyze different metabolites in the serum of the two groups. The differentially abundant metabolites were entered into the MetaboAnalyst 5.0 online analysis website for processing, and the top-15-ranked metabolic pathways were set to produce bubble plots and differential abundance score plots, with a significant difference of P < 0.05 and a false discovery rate (FDR) < 0.1 as the screening conditions.

Results: Data analyses of serum samples from both groups identified a total of 1905 significantly different metabolites, where 841 metabolites were upregulated and 1064 metabolites were downregulated. Twelve metabolites were significantly upregulated and 21 metabolites were significantly downregulated in the experimental group. Then, the 1,7-dihydroxyxanthone, 2-methylbutyrylglycine, 3,3-dimethylglutaric acid, 5,12-dihydroxy-6,8,10,14,17-eicosapentaenoic acid, 9-hydroperoxy-10E,12Z,15Z-octadecatrienoic acid, and trimethylamine N-oxide 6 metabolites were selected as diagnostically valuable candidate biomarkers (area under the curve [AUC] > 0.7). These differential metabolites are involved in various metabolic pathways, including amino acid metabolites (arginine, L-isoleucine, L-valine) and fatty acid metabolism (fenugreek, arachidonic acid, linolenic acid). Compared with the control group, sheep in the CE group had increased serum levels of fenugreek acid, while all other metabolites such as glycine showed significantly reduced serum levels (P < 0.01).

Conclusions: Through non-targeted metabolomic analysis of the serum of CE-infected sheep, differential metabolites closely related to amino acid metabolism and the fatty acid metabolism pathway were identified. These differentially abundant metabolites can serve as biomarkers for diagnosing CE infection in intermediate sheep hosts.

Background: Fleas are insect vectors that transmit several Gram-negative bacterial pathogens acquired by ingesting infected vertebrate blood. To combat foodborne illness, insect midgut epithelial cells are armed with efficient microbial recognition and control systems, such as the immune deficiency (IMD) pathway that regulates the expression of antimicrobial peptides (AMPs). However, despite their medical and veterinary importance, relatively little is known about the IMD signaling pathway and production of AMPs in the digestive tract of cat fleas (Ctenocephalides felis).

Methods: In the present study, we measured the expression of target genes comprising the IMD pathway, as well as corresponding AMP transcripts, in the digestive tract of C. felis following exposure to three different species of bacteria: Gram-negative Bartonella henselae (a flea-borne pathogen), Gram-negative Serratia marcescens (a model laboratory species), and Gram-positive Micrococcus luteus (a model laboratory species). Additionally, we examined the antibacterial activity of proteins isolated from the flea digestive tract in vitro following bacterial challenge and at different days post adult emergence to determine if feeding-induced antibacterial activity varies with age.

Results: In our analysis of C. felis, we observed an increase in the expression of representative IMD pathway genes and associated AMP transcripts, indicating the activation of the IMD pathway. Furthermore, our results revealed that different bacterial species elicit distinct transcriptional profiles of IMD pathway genes, suggesting a species-specific response to bacterial invasion. We found that the gut of C. felis produces antibacterial molecules as a localized defense mechanism. Additionally, we observed that proteins with antimicrobial properties are synthesized as part of local defense mechanisms in the gut, with differential patterns of antibacterial activity related to infection status and age.

Conclusions: Our findings provide essential insights into the potential mechanisms by which cat fleas regulate immune responses in their digestive tract against different bacterial species.