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Plasmodium and other vector-borne pathogens have evolved mechanisms to hijack the mammalian fibrinolytic system to facilitate infection of the human host and the invertebrate vector. Plasmin, the effector protease of fibrinolysis, maintains homeostasis in the blood vasculature by degrading the fibrin that forms blood clots. Plasmin also degrades proteins from extracellular matrices, the complement system, and immunoglobulins. Here, we review some of the mechanisms by which vector-borne pathogens interact with components of the fibrinolytic system and co-opt its functions to facilitate transmission and infection in the host and the vector. Further, we discuss innovative strategies beyond conventional therapeutics that could be developed to target the interaction of vector-borne pathogens with the fibrinolytic proteins and prevent their transmission.

Asymptomatic malaria parasite carriers do not seek anti-malarial treatment and may constitute a silent infectious reservoir. In order to assess the level of asymptomatic and symptomatic carriage amongst adolescents in a highly endemic area, and to identify the risk factors associated with such carriage, we conducted a cross-sectional survey of 1032 adolescents (ages 10–19 years) from eight schools located in Ibadan, southwestern Nigeria in 2016. Blood films and blood spot filter paper samples were prepared for microscopy and DNA analysis. The prevalence of asymptomatic malaria was determined using microscopy, rapid diagnostic tests and PCR for 658 randomly selected samples. Of these, we found that 80% of asymptomatic schoolchildren were positive for malaria parasites by PCR, compared with 47% and 9%, determined by rapid diagnostic tests and microscopy, respectively. Malaria parasite species typing was performed using PCR targeting the mitochondrial CoxIII gene, and revealed high rates of carriage of Plasmodium malariae (53%) and Plasmodium ovale (24%). Most asymptomatic infections were co-infections of two or more species (62%), with Plasmodium falciparum + P. malariae the most common (35%), followed by P. falciparum + P. malariae + P. ovale (21%) and P. falciparum + P. ovale (6%). Single infections of P. falciparum, P. malariae and P. ovale accounted for 24%, 10% and 4% of all asymptomatic infections, respectively. To compare the species composition of asymptomatic and symptomatic infections, further sample collection was carried out in 2017 at one of the previously sampled schools, and at a nearby hospital. Whilst the species composition of the asymptomatic infections was similar to that observed in 2016, the symptomatic infections were markedly different, with single infections of P. falciparum observed in 91% of patients, P. falciparum + P. malariae in 5% and P. falciparum + P. ovale in 4%.

Malaria inflicts the highest rate of morbidity and mortality among the vector-borne diseases. The dramatic bottleneck of parasite numbers that occurs in the gut of the obligatory mosquito vector provides a promising target for novel control strategies. Using single-cell transcriptomics, we analyzed Plasmodium falciparum development in the mosquito gut, from unfertilized female gametes through the first 20 hours post blood feeding, including the zygote and ookinete stages. This study revealed the temporal gene expression of the ApiAP2 family of transcription factors, and of parasite stress genes in response to the harsh environment of the mosquito midgut. Further, employing structural protein prediction analyses we found several upregulated genes predicted to encode intrinsically disordered proteins (IDPs), a category of proteins known for their importance in regulation of transcription, translation and protein-protein interactions. IDPs are known for their antigenic properties and may serve as suitable targets for antibody or peptide-based transmission suppression strategies. In total, this study uncovers the P. falciparum transcriptome from early-to-late parasite development in the mosquito midgut, inside its natural vector, which provides an important resource for future malaria transmission-blocking initiatives. This repository contains original data such as raw sequencing data (fastq files), count matrices, metadata files, images parameters, GO term files, etc.isolated time points of P.falciparum single parasite from mosquito midgut experiments usingmicro-manipulation performed in this study.These folders contain input data for the R markdown script, which can be found in this GitHub repository:Github link. The filescontains all data necessary to reproduce the results of the study and raw_seq_filesis a directory for all of the fastq files and their metadata. processed_datafiles.zip have the expression matrix reads counts and metadata toreproduce the data of this study can also be found in the same GitHub repository (https://github.com/ANKARKLEVLAB/Single-cell-P.falciparum-midgut). for data interactive Visualizationplease go toScRNA-seq data Visualization Experiment design:Plasmodium falciparum NF54 gametocyte producing cell line were committed to sexual stages (gametocytes) and pooled to 1% gametocytaemia and 50% hematocrit. Gametocyte were membrane fed to Anopheles gambiae adult mosquito and dissected at time points; 2, 4, 8, 12 and 20 hours post infection, parasites were then isolated using Micro-maniupulation based on Anti-Pfs25 antibody conjugated to Alexa-488 flour and Hoechststain. cDNA library were prepared using SMART-seq2 and illumina sequenced. ScRNA-seq data were then analyzed using various computational tools, including Seurat toolkit and Slingshot for Pseudotime analyses. directories structure: Processed_datafiles.zip: metadata.txt (cell IDs + clusters + Time points + Pseudotime modules) zygote_raw_expressionmatrix.txt (columns = cell Ids , rows = gene accession number) img_data.txt ( imaging data ,The fluorescence intensity + Volume) metadata_NFFG.txt ( cell IDs + clusters + Time points including unfertilized female gametes) metadata_without_NFFG.txt (cell IDs + clusters + Pseudotime modules without unfertilized female gametes) raw seq data files and metadata batch_1.zip(RNA-seq fastq files linked to metadata_batch_1.csv) batch_2.zip(RNA-seq fastq files linked to metadata_batch_2.csv) raw_seq_metadata.zip folder RNA-seq metadata files information sheet: Sc_Pfalciparum_midgut_stages_Mohammed et al.xlsx (information about the study and experimental design)&nbsp

Background Malaria rapid diagnostic tests have become a primary and critical tool for malaria diagnosis in malaria-endemic countries where Plasmodium falciparum Histidine Rich Protein 2-based rapid diagnostic tests (PfHRP2-based RDTs) are widely used. However, in the last decade, the accuracy of PfHRP2-based RDTs has been challenged by the emergence of P. falciparum strains harbouring deletions of the P. falciparum histidine rich protein 2 (pfhrp2) gene, resulting in false-negative results. In the Democratic Republic of Congo (D.R. Congo), little is known about the prevalence of the pfhrp2 gene deletion among P. falciparum isolates infecting symptomatic patients, especially in low to moderate transmission areas where pfhrp2 deletion parasites are assumed to emerge and spread. Here we determine the local prevalence and factors associated with pfhrp2 gene deletions among symptomatic malaria patients in the Kwilu Province of the D.R. Congo. Methods We used secondary data from a prospective health facility-based cross-sectional study conducted in 2018. Blood was collected for microscopy, PfHRP2-RDT, and spotted onto Whatman filter paper for downstream genetic analysis. Genomic DNA was extracted and used to perform PCR assays for the detection and confirmation of pfhrp2 gene deletions. Fischer’s exact and the Kruskal–Wallis tests were applied to look for associations between potential explanatory variables and the pfhrp2 gene deletion with a level of statistical significance set at P Results Of the 684 enrolled symptomatic patients, 391 (57.7%) were female. The majority (87.7%) reported the presence of mosquito breeding sites within the household’s compound, and fever was the most reported symptom (81.6%). The overall prevalence of the pfhrp2 gene deletion was 9.2% (95% CI: 6.7%–12.1%). The deletion of the pfhrp2 gene was associated with health zone of origin (P = 0.012) and age (P = 0.019). Among false-negative PfHRP2-RDT results, only 9.9% were due to pfhrp2 gene deletion. Conclusions P. falciparum isolates with pfhrp2 gene deletions are relatively common among symptomatic patients in Kwilu province. Further investigations are needed to provide enough evidence for policy change. Meanwhile, the use of RDTs targeting PfHRP2 and parasite lactate dehydrogenase (pLDH) antigens could limit the spread of deleted isolates. Graphic Abstract

Anopheles mosquitoes feed on plant nectars as their main source of sugar. Wang et al. show that Asaia bacteria proliferate in the midgut of mosquitoes that feed on glucose or trehalose. Asaia increases the lumenal pH by downregulating mosquito vacuolar ATPase expression, therefore increasing Plasmodium gametogenesis and vector competence.

Asymptomatic malaria parasite carriers do not seek anti-malarial treatment and may constitute a silent infectious reservoir. In order to assess the level of asymptomatic and symptomatic carriage amongst adolescents in a highly endemic area, and to identify the risk factors associated with such carriage, we conducted a cross sectional survey of 1032 adolescents (ages 10-19) from eight schools located in Ibadan, Southwest Nigeria in 2016. Blood films and blood spot filter paper samples were prepared for microscopy and DNA analysis. The prevalence of asymptomatic malaria was determined using microscopy, rapid diagnostic tests and PCR for 658 randomly selected samples. Of these, we found that 80% of asymptomatic schoolchildren were positive for malaria parasites by PCR, compared to 47% and 9% determined by RDT and microscopy, respectively. Malaria parasite species typing was performed using PCR targeting the mitochondrial CoxIII gene, and revealed high rates of carriage of Plasmodium malariae (53%) and Plasmodium ovale (24%). Most asymptomatic infections were co-infections of two or more species (62%), with P. falciparum + P. malariae the most common (35%), followed by P. falciparum + P. malariae + P. ovale (21%) and P. falciparum + P. ovale (6%). Single infections of P. falciparum, P. malariae and P. ovale accounted for 24%, 10% and 4% of all asymptomatic infections respectively. To compare the species composition of asymptomatic and symptomatic infections, further sample collection was carried out in 2017 at one of the previously sampled schools, and at a nearby hospital. Whilst the species composition of the asymptomatic infections was similar to that observed in 2016, the symptomatic infections were markedly different, with single infections of P. falciparum observed in 91% of patients, P. falciparum + P. malariae in 5% and P. falciparum + P. ovale in 4%.

BackgroundMalaria rapid diagnostic tests have become a primary and critical tool for malaria diagnosis in malaria-endemic countries where PfHRP2-based RDTs are widely used. However, in the last decade, the accuracy of PfHRP2-based RDTs has been challenged by the emergence of P. falciparum strains harbouring deletions of the pfhrp2 gene, resulting in false-negative results. In DR. Congo, little is known about the prevalence of the pfhrp2 gene deletion among P. falciparum isolates infecting symptomatic patients, especially in low to moderate transmission areas where pfhrp2 deletion parasites are assumed to emerge and spread. Here we determine the local prevalence and factors associated with pfhrp2 gene deletions among symptomatic malaria patients in the Kwilu province of the Democratic Republic of Congo, a low to moderate malaria transmission area.MethodsWe used secondary data from a prospective health facility-based cross-sectional study conducted on 684 individuals of all ages, seeking healthcare with symptoms suggestive of malaria from October to December 2018 in 34 randomly selected health facilities. Sociodemographic, malaria prevention and treatment practices, and clinical variables were collected using a pre-tested structured questionnaire. Patients’ medical records were used to collect additional clinical data. Blood was collected for microscopy, PfHRP2-RDT, and spotted onto Whatman filter paper for downstream genetic analysis. Genomic DNA was extracted and used to perform PCR assays for the detection and confirmation of pfhrp2 gene deletions. Data were entered and analysed using STATA15. Fischer’s exact and the Kruskal-Wallis tests were applied to look for associations between exposures and the pfhrp2 gene deletion with a level of statistical significance set at p < 0.05. ResultsThe overall prevalence of the pfhrp2 gene deletion was 9.2% (95% CI 6.7% – 12.1%). The deletion of the pfhrp2 gene was associated with health zone of origin (p=0.012) and age (p=0.019). Among false-negative PfHRP2-RDT results, only 9.9% were due to pfhrp2 gene deletion.ConclusionP. falciparum isolates with pfhrp2 gene deletions are relatively common among symptomatic patients in Kwilu province. Further investigations are needed to provide enough evidence for policy change. Meanwhile, the use of RDTs targeting PfHRP2 and pLDH antigens could limit the spread of deleted isolates.