Search Results (55)

Background: Malaria remains a major public health concern in Africa, due to the persistence of Plasmodium falciparum gametocytes that sustain transmission post treatment. This study evaluated the effects of artemether–lumefantrine (AL) alone compared with AL combined with a single low-dose of primaquine (SLD-PQ) on gametocyte clearance and infectivity to Anopheles arabiensis post treatment. Methods: A prospective cohort and entomological study were conducted from January to September 2025 in Northwest Ethiopia. Ninety-six microscopically confirmed cases of P. falciparum gametocytemia mono-infection were proportionally assigned to both treatment groups. Follow-up assessments were conducted on days 3, 7, 14, and 28, and mixed-species infections were assessed using molecular diagnostic assays. Additionally, membrane feeding assays (MFAs) were performed to evaluate mosquito infectivity post treatment. Results: Gametocyte prevalence declined faster with AL + SLD-PQ (15.2% on day 3; 0% by day 7) compared to AL alone (28.9% on day 3: p = 0.001; 12.2% by day 7: p = 0.033). Higher baseline gametocyte density strongly predicted mosquito infection (95% in high vs. 59% moderate and 33% low). On day 3 post treatment, 28.6% of cases treated with AL only showed confirmed mosquito infection, compared to 6.8% in the AL + SLD-PQ group (p = 0.001). By day 7, 7.3% of cases remained infectious in the AL-only group, while none were detected in the AL+ SLD-PQ group (p = 0.01). Conclusions: High baseline gametocyte density strongly correlated with increased infectivity. Adding SLD-PQ markedly accelerates gametocyte clearance and completely blocks post-treatment transmission. Submicroscopic gametocytemia contributed to residual transmission in the AL-only group. Incorporation of SLD-PQ alongside AL, in line with WHO recommendations, is advised to enhance post-treatment transmission blocking, with continued surveillance. Full article

SSB proteins play essential roles in DNA replication, recombination, and repair in bacteria, archaea, and eukarya. This study investigates the transcript levels, identification, expression and purification, subcellular localization, and immune protective potential of the SSB-like proteins of Eimeria necatrix (EnSSB), exploring its role in the development of E. necatrix and its potential as a candidate antigen for a subunit vaccine against avian coccidiosis. The level of EnSSB gene transcription was highest in unsporulated oocysts (UO), followed by gametocytes (GAM) (p < 0.05). The gene consisted of an open reading frame of 1488 nucleotides encoding a protein of 495 amino acid residues with a predicted molecular weight of 53.31 kDa. EnSSB contained a SSB domain with a conserved OB (oligonucleotide/oligosaccharide binding) fold. The molecular mass of the native protein, as determined by Western blot analysis, was ~58 kDa in second-generation merozoites (MZ-2) and UO. In addition to the 58 kDa band, four other bands (~98 kDa, ~82 kDa, ~36 kDa and ~28 kDa) were detected in GAM. No bands were detected in MZ-3. Indirect immunofluorescence and immuno-electron microscopy localized EnSSB in the cytoplasm of macrogametocytes but not in wall-forming bodies and oocyst wall. Animal challenge experiments demonstrated that rEnSSB elicited robust IgY responses, increased splenic T lymphocytes and body weight gain, reduced intestinal lesion scores and oocyst shedding, and presented anticoccidial index (ACI) more than 160. These findings not only offer a foundation for understanding the role of EnSSB protein in regulating the development of E. necatrix, but also present a potential protective antigen of E. necatrix for the development of a subunit vaccine against avian coccidiosis. Full article

With the increasing detection of artemisinin resistance to front-line antimalarials in Africa and notwithstanding the planned roll-out of RTS’S and R21 in Africa, the search for new vaccines with high efficacy remains an imperative. Towards this endeavour, we performed in silico screening to identify Plasmodium falciparum gametocyte stage genes that could be targets of protection or diagnosis. Through the analysis we identified a gene, Pf3D7_1105800, coding for a Plasmodium falciparum subtilisin-like domain-containing protein (PfSDP) and thus dubbed the gene Pfsdp. Genetic diversity assessment revealed the Pfsdp gene to be relatively conserved across continents with signs of directional selection. Using RT qPCR and Western blots, we observed that Pfsdp is expressed in all developmental stages of the parasite both at the transcript and protein level. Immunofluorescence assays found PfSDP protein co-localizing with PfMSP-1 and partially with Pfs48/45 at the asexual and sexual stages, respectively. Further, we demonstrated that anti-PfSDP peptide-specific antibodies inhibited erythrocyte invasion by 20–60% in a dose-dependent manner, suggesting that PfSDP protein might play a role in merozoite invasion. We also discovered that PfSDP protein is immunogenic in children from different endemic areas with antibody levels increasing from acute infection to day 7 post-treatment, followed by a gradual decay. The limited effect of antibodies on erythrocyte invasion could imply that it might be more involved in other processes in the development of the parasite. Full article

Small rodents are known hosts of various pathogens, including Hepatozoon, but until now, in Brazil, only Hepatozoon milleri has been described in these animals. In this study, liver samples and blood smears were obtained from 289 rodents belonging to 14 Cricetidae and two Muridae species that had been captured in municipalities of the states of Paraná and Rio de Janeiro. Smears were stained with Giemsa, and gametocytes were detected via microscopy in 10.72% (n = 31/289) of samples, with these individuals representing three rodent species. Significant morphometric differences were observed in gametocyte measurements in Akodon rodents. Using conventional PCR, Hepatozoon spp. 18S rDNA fragments were amplified in 24.91% (n = 72/289) of samples, with those individuals representing seven rodent species. Phylogenetic analyses clustered 41 sequences from this study into a subclade with other sequences from small mammals in Brazil, identifying four distinct haplotypes, and, for the first time, a relationship between Hepatozoon haplotype and gametocyte length was observed. Based on phylogenetic analysis, this study reinforces the trophic relationship between rodents and reptiles as a possible link in the Hepatozoon transmission cycle in South America. Furthermore, our findings expand knowledge on Hepatozoon spp. hosts, describing Oxymycterus nasutus and Oxymycterus quaestor as new host species and identifying two novel circulating haplotypes in rodents from Paraná State, southern Brazil. Full article

Plasmodium vivax malaria continues to pose a significant and enduring public health challenge across the Americas. Transmission-blocking vaccines (TBVs), which target gametocyte surface antigens such as Pvs47 and Pvs48/45, are being investigated as promising tools to interrupt transmission and advance toward disease elimination. To investigate the genetic diversity and phylogeographic structure of the pvs47 and pvs48/45 genes in P. vivax, we conducted molecular analyses on samples collected from seven malaria-endemic regions of Honduras using PCR-based sequencing, population genetics, and phylogenetic approaches. This study presents the first complete characterization of the pvs47 gene and expands the available data on pvs48/45 in P. vivax from Honduras. We observed a low level of genetic diversity with no evidence of geographic structuring within the country. At a global scale, Honduran sequences shared variants with other Latin American strains and exhibited region-specific amino acid signatures. These findings suggest that local selective pressures, possibly driven by mosquito vector compatibility, are shaping the evolution of these TBV candidate genes. Our results underscore the importance of regional surveillance to inform the development and deployment of effective transmission-blocking strategies. Full article

Coccidiosis, caused by Eimeria spp., significantly reduces poultry productivity and causes major economic losses. Traditional control methods are limited by drug resistance and high production costs. Recent genomic and bioinformatic advances have enabled the identification of novel antigens, making recombinant subunit vaccines a promising next-generation strategy by eliciting robust cellular and humoral immune responses. This study investigates the E. necatrix gametocyte protein 56 (EnGAM56) as a potential candidate for recombinant subunit vaccines. The full-length E. necatrix gametocyte gam56 gene (Engam56-F) was amplified, expressed in vitro, and characterized via SDS-PAGE and Western blot. Immunofluorescence assays revealed that EnGAM56-F is specifically localized in gametocytes and unsporulated oocysts. Chickens immunized with recombinant proteins (rEnGAM56-F and rEnGAM56-T) were evaluated for immunoprotection against E. necatrix infection through lesion scores, weight gain, oocyst production, anticoccidial index (ACI), and antibody and cytokine levels. The synergistic effects were evaluated by employing various combinations of recombinant proteins, including rEtGAM22, rEtGAM56-T, and rEtGAM59. Results showed that EnGAM56-F encodes a 468-amino acid protein with distinct tyrosine-serine-rich and proline-methionine-rich regions. rEnGAM56-F was specifically recognized by both anti-6 × His tag antibodies and convalescent serum from chickens infected with E. necatrix. Both rEnGAM56-F and rEnGAM56-T provided immune protection, with rEnGAM56-T showing superior efficacy. The combination of rEnGAM (22 + 59 + 56-T) yielded the strongest immune response, followed by rEnGAM (22 + 56-T). These findings highlight the potential of EnGAM56 as a candidate for recombinant subunit anticoccidial vaccines. Full article

RNA-binding E3 ubiquitin ligases (RBULs) provide a link between RNA metabolic processes and the ubiquitin proteasome system (UPS). In humans, RBULs are involved in various biological processes, such as cell proliferation and differentiation, as well as sexual development. To date, little is known about their role in the protozoan parasite Plasmodium falciparum, the causative agent of malaria tropica. We previously identified a novel P. falciparum RBUL, the RING finger E3 ligase PfRNF1, which is highly expressed during gametocyte development. Here, we conducted BioID-based proximity interaction studies to unveil the PfRNF1 interactome. We show that in immature gametocytes, PfRNF1 forms an interaction network that is mainly composed of RNA-binding proteins, including the translational repressors DOZI and CITH and members of the CCR4-NOT complex, as well as UPS-related proteins. In particular, PfRNF1 interacts with recently identified regulators of sexual development like the zinc finger protein PfMD3, with which it shares the majority of interactors. The common interactome of PfRNF1 and PfMD3 comprises several uncharacterized proteins predominantly expressed in male or female gametocytes. Our results demonstrate that PfRNF1 engages with RNA-binding proteins crucial for sex determination in gametocytes, thereby linking posttranscriptional regulation with the UPS. Full article

Coccidian parasites possess complex life cycles involving asexual proliferation followed by sexual development, producing oocysts that are transmitted from host to host through feces, guaranteeing disease transmission. Eimeria necatrix is a highly pathogenic coccidian causing high mortality in birds. This study examined ultrastructural changes occurring during the third merogony, microgametogenesis, and macrogametogenesis of E. necatrix. The third-generation meront contained eight merozoites, each with coccidian-specific features like conoid, rhoptries, micronemes, and dense granules. Microgametes had a nucleus, mitochondrion, two flagella, and a basal apparatus. Macrogametes surrounded by two membranes (M1 and M2), contained organelles like WFB1, WFB2, endoplasmic reticulum, mitochondria, and tubular structures. Oocyst wall formation began with M2 separating from M1 and forming a loose veil around the organism. The WFB1 fused together to form the outer layer of the oocyst wall between M1 and M2, while M4 formed beneath M1. The WFB2 fused with the M4 to discharge its contents external to M4, which fused together to form the inner layer of the oocyst wall. Immunogold electron microscopy co-localization result showed that EnGAM22 localized to WFB1 and the outer wall, while EnGAM59 localized to WFB2 and the inner wall, suggesting they are key structural components of the oocyst wall. Full article

Haemosporidian parasites (Apicomplexa, Haemosporida) are diverse obligatory heteroxenous protists, which infect all major groups of terrestrial vertebrates and use dipterous blood-sucking insects as vectors. These pathogens are responsible for various diseases, including malaria, which remains an important human and animal illness. In the wild, haemosporidians are particularly diverse in reptiles and birds in tropical countries, where they are flourishing. Avian haemosporidians have been particularly extensively investigated, especially due to their high prevalence and global distribution, including the countries with cold climates. The general scheme of the life cycle of haemosporidians is known, but the details of development remain insufficiently investigated or even unknown in most of the described parasite species, suggesting the existence of knowledge gaps. This attracts attention to some recent observations, which remain fragmentary but suggest the existence of formerly neglected or underestimated modes of the haemosporidians’ survival in vertebrates. Such findings are worth discussion as they indicate the novel directions in wildlife haemosporidian research. This article overviews some recent findings, which call for broadening of the orthodox views on modes of existence of haemosporidian parasites in avian hosts. Among them are the role of blood merogony in the long-lasting persistence of malaria parasites in birds, the role of gametocytes in the long-lasting survival of Haemoproteus species in vertebrates, the possible reasons of undetectable avian Haemoproteus infections due to peculiarities of exo-erythrocytic development, and the plausible factors driving the narrow vertebrate host specificity of Haemoproteus species. Full article

Croton sylvaticus, a tropical African plant, is traditionally used to treat several diseases, including fever, inflammation, and malaria. Essential oils (EOs) from the plant’s leaves, roots, and trunk bark were obtained by hydrodistillation, and their chemical composition was analyzed by gas chromatography–mass spectrometry (GC-MS). The major constituents identified were virdiflorene (18.13 ± 0.46%) in root EO, (E)-β-caryophyllene (18.40 ± 0.60%) in trunk bark EO, and farnesyl acetone (15.26 ± 0.25%) in leaf EO. Notably, Cameroonian C. sylvaticus leaf EO exhibited a distinct and newly described chemotype with high levels of farnesyl acetone, β-copaene-4-α-ol, β-cadinene, α-humulene, and trans-longipinocarveol. In vitro testing revealed significant antiplasmodial activity against Plasmodium falciparum asexual (Pf3D7) and sexual (NF-54 strain) stages, with trunk bark EO showing the highest potency (IC₅₀: 9.06 ± 2.15 µg/mL for Pf3D7 and 0.56 µg/mL for gametocytes). These findings support the traditional antimalarial use of C. sylvaticus and represent the first chemical profile and antiplasmodial efficacy report for its root and trunk bark EOs against both parasite stages. To the best of our knowledge, we also report for the first time the antiplasmodial activity of an EO that exerts significant activity against both the asexual and sexual forms of P. falciparum. Full article

Malaria remains a global health concern, with 249 million cases and 608,000 deaths being reported by the WHO in 2022. Traditional diagnostic methods often struggle with inconsistent stain quality, lighting variations, and limited resources in endemic regions, making manual detection time-intensive and error-prone. This study introduces an automated system for analyzing Romanowsky-stained thick blood smears, focusing on image quality evaluation, leukocyte detection, and malaria parasite classification. Using a dataset of 1000 clinically diagnosed images, we applied feature extraction techniques, including histogram bins and texture analysis with the gray level co-occurrence matrix (GLCM), alongside support vector machines (SVMs), for image quality assessment. Leukocyte detection employed optimal thresholding segmentation utility (OTSU) thresholding, binary masking, and erosion, followed by the connected components algorithm. Parasite detection used high-intensity region selection and adaptive bounding boxes, followed by a custom convolutional neural network (CNN) for candidate identification. A second CNN classified parasites into trophozoites, schizonts, and gametocytes. The system achieved an F1-score of 95% for image quality evaluation, 88.92% for leukocyte detection, and 82.10% for parasite detection. The F1-score—a metric balancing precision (correctly identified positives) and recall (correctly detected instances out of actual positives)—is especially valuable for assessing models on imbalanced datasets. In parasite stage classification, CNN achieved F1-scores of 85% for trophozoites, 88% for schizonts, and 83% for gametocytes. This study introduces a robust and scalable automated system that addresses critical challenges in malaria diagnosis by integrating advanced image quality assessment and deep learning techniques for parasite detection and classification. This system’s adaptability to low-resource settings underscores its potential to improve malaria diagnostics globally. Full article

Malaria is a leading cause of morbidity and mortality in tropical and sub-tropical regions. This research proposed a malaria diagnosis system based on the you only look once algorithm for malaria parasite detection and the convolutional neural network algorithm for malaria parasite life stage classification. Two public datasets are utilized: MBB and MP-IDB. The MBB dataset includes human blood smears infected with Plasmodium vivax (P. vivax). While the MP-IDB dataset comprises 4 species of malaria parasites: P. vivax, P. ovale, P. malariae, and P. falciparum. Four distinct stages of life exist in every species, including ring, trophozoite, schizont, and gametocyte. For the MBB dataset, detection and classification accuracies of 0.92 and 0.93, respectively, were achieved. For the MP-IDB dataset, the proposed algorithms yielded the accuracies for detection and classification as follows: 0.84 and 0.94 for P. vivax; 0.82 and 0.93 for P. ovale; 0.79 and 0.93 for P. malariae; and 0.92 and 0.96 for P. falciparum. The detection results showed the models trained by P. vivax alone provide good detection capabilities also for other species of malaria parasites. The classification performance showed the proposed algorithms yielded good malaria parasite life stage classification performance. The future directions include collecting more data and exploring more sophisticated algorithms. Full article

The Plasmodium falciparum mitochondrial electron transport chain (mETC) is responsible for essential metabolic pathways such as de novo pyrimidine synthesis and ATP synthesis. The mETC complex III (cytochrome bc₁ complex) is responsible for transferring electrons from ubiquinol to cytochrome c and generating a proton gradient across the inner mitochondrial membrane, which is necessary for the function of ATP synthase. Recent studies have revealed that the composition of Plasmodium falciparum complex III (PfCIII) is divergent from humans, highlighting its suitability as a target for specific inhibition. Indeed, PfCIII is the target of the clinically used anti-malarial atovaquone and of several inhibitors undergoing pre-clinical trials, yet its role in parasite biology has not been thoroughly studied. We provide evidence that the universally conserved subunit, PfRieske, and the new parasite subunit, PfC3AP2, are part of PfCIII, with the latter providing support for the prediction of its divergent composition. Using inducible depletion, we show that PfRieske, and therefore, PfCIII as a whole, is essential for asexual blood stage parasite survival, in line with previous observations. We further found that depletion of PfRieske results in gametocyte maturation defects. These phenotypes are linked to defects in mitochondrial functions upon PfRieske depletion, including increased sensitivity to mETC inhibitors in asexual stages and decreased cristae abundance alongside abnormal mitochondrial morphology in gametocytes. This is the first study that explores the direct role of the PfCIII in gametogenesis via genetic disruption, paving the way for a better understanding of the role of mETC in the complex life cycle of these important parasites and providing further support for the focus of antimalarial drug development on this pathway. Full article

Malaria is a serious health problem worldwide affecting mainly children and socially vulnerable people. The biological particularities of P. vivax, such as the ability to generate dormant liver stages, the rapid maturation of gametocytes, and the emergence of drug resistance, have contributed to difficulties in disease control. In this context, developing an effective vaccine has been considered a fundamental tool for the efficient control and/or elimination of vivax malaria. Although recombinant proteins have been the main strategy used in designing vaccine prototypes, synthetic immunogenic peptides have emerged as a viable alternative for this purpose. Considering, therefore, that in the Brazilian endemic population, little is known about the profile of the humoral immune response directed to synthetic peptides that represent different P. vivax proteins, the present work aimed to map the epitope-specific antibodies’ profiles to synthetic peptides representing the linear portions of the ookinete and sporozoite cell passage protein (CelTOS), thrombospondin-related adhesive protein (TRAP), and cysteine-rich protective antigen (CyRPA) proteins in the acute (AC) and convalescent phases (Conv30 and Conv180 after infection) of vivax malaria. The results showed that the studied subjects responded to all proteins for at least six months following infection. For IgM, a few individuals (3–21%) were positive during the acute phase of the disease; the highest frequencies were observed for IgG (28–57%). Regarding the subclasses, IgG2 and IgG3 stood out as the most prevalent for all peptides. During the follow-up, the stability of IgG was observed for all peptides. Only one significant positive correlation was observed between IgM and exposure time. We conclude that for all the peptides, the immunodominant epitopes are recognized in the exposed population, with similar frequency and magnitude. However, if the antibodies detected in this study are potential protectors, this needs to be investigated. Full article

Malaria drug research and development efforts have resurged in the last decade following the decelerating rate of mortality and malaria cases in endemic regions. The inefficiency of malaria interventions is largely driven by the spreading resistance of the Plasmodium falciparum parasite to current drug regimens and that of the malaria vector, the Anopheles mosquito, to insecticides. In response to the new eradication agenda, drugs that act by breaking the malaria transmission cycle (transmission-blocking drugs), which has been recognized as an important and additional target for intervention, are being developed. These drugs take advantage of the susceptibility of Plasmodium during population bottlenecks before transmission (gametocytes) and in the mosquito vector (gametes, zygotes, ookinetes, oocysts, sporozoites). To date, compounds targeting stage V gametocytes predominate in the chemical library of transmission-blocking drugs, and some of them have entered clinical trials. The targeting of Plasmodium mosquito stages has recently renewed interest in the development of innovative malaria control tools, which hold promise for the application of compounds effective at these stages. In this review, we highlight the major achievements and provide an update on the research of transmission-blocking drugs, with a particular focus on their chemical scaffolds, antiplasmodial activity, and transmission-blocking potential. Full article