Plasmodium Infection Research Articles

Assessing the burden of submicroscopic Plasmodium infections in a pre-elimination malaria setting in sub-Saharan Africa, Guinea-Bissau.

Submicroscopic Plasmodium infections can be a source of persistent malaria transmission. The aim of this study was to assess their frequency, distribution, morbidity and associated factors in a pre-elimination malaria setting in sub-Saharan Africa, Guinea-Bissau, where the Plasmodium falciparum is the predominant Plasmodium species. Dried fingerprick whole blood samples from 601 participants in the 2017 national, household-based, cross-sectional survey to estimate malaria prevalence were subjected to DNA extraction. The DNA was used in nested end-point PCR assays targeting genus- and species-specific regions of the Plasmodium 18S rRNA genes. Statistical analysis of socio-demographic, clinical and molecular data was carried out using the Statistical Package for the Social Sciences, version 29. Factors associated with submicroscopic P. falciparum infections and their magnitude were sought using Chi-square test and multiple logistic regression models, respectively. Statistically significant level was considered at P-value < 0.05. Nested PCR assays detected submicroscopic P. falciparum infections in 20.3% (95% CI = 16.8-23.8) of individuals microscopically negative for Plasmodium species in the general population and in 21.4% (95% CI = 9.9-36.5) of microscopically negative pregnant women. Submicroscopic Plasmodium malariae infections were also detected as co-infections in 3.0% individuals who were microscopically positive only for P. falciparum. Infections with other Plasmodium species were not detected. Submicroscopic P. falciparum infections were not associated with age, sex, or the presence of fever. A logistic regression model adjusted for ethnicity and health region showed that individuals from the Balanta and Bijagos ethnic groups, most of whom live in the low malaria-transmission areas of Quinara and Bissau, and the Bijagos archipelago, respectively, were less likely to have submicroscopic P. falciparum infections than individuals from the large Fula ethnic group, most of whom live in the high malaria-transmission area of Gabu. Submicroscopic P. falciparum infections were not associated with anaemia in children under 5years of age. The results obtained highlight the contribution of asymptomatic and submicroscopic P. falciparum infections to malaria transmission in high malaria-transmission areas and the need for molecular-based tools to detect submicroscopic Plasmodium species.

Impact of a large-scale fruit and vegetable irrigation scheme on the micro-epidemiology of malaria in southwest Ethiopia

BackgroundMalaria continues to represent an important public health problem in Ethiopia. The expansion of irrigated agricultural development projects turns out to be a major impediment to long-lasting and sustainable malaria prevention and control efforts in the country. The aim of this study was to determine the micro-epidemiology of malaria and associated risk factors in and around Gojeb Horizon Irrigation Plantation in southwest Ethiopia.MethodsA community-based comparative cross-sectional study was conducted from May to June 2018 in Gimbo District, southwest Ethiopia. A total of 186 households (94 from irrigated village and 92 from non-irrigated village) were randomly selected from among the communities living around the Gojeb Horizon plantation. In total, 718 individuals (368 from irrigated village and 350 from non-irrigated village) were recruited from the selected households. A finger-prick blood sample was obtained from each participant. Socio-demographic data from the households and individual study participants were collected using a semi-structured questionnaire. Multivariate regression was used to assess factors associated with micro-epidemiology of malaria. P-value < 0.05 was considered statistically significant.ResultsThe prevalence of malaria in irrigated and non-irrigated villages was 8.2% and 3.4%, respectively. Plasmodium falciparum, Plasmodium vivax and mixed infections accounted for 57.1%, 38.1%, and 4.8% of the cases, respectively. Individuals living in the irrigated villages were 2.53 (95% CI: 1.23–5.20) times at higher risk of Plasmodium infection as compared to those living in the non-irrigated village. Age (AOR = 1.03, 95% CI: 1.01–1.06) and non-use of long-lasting insecticidal net (AOR = 2.72, 95% CI: 1.03–7.22) were co-predictors of malaria infection in the area.ConclusionThis study revealed that communities living in irrigation village were at a higher risk of Plasmodium infection than those living in non-irrigated village, which necessitates the development of tailored interventions that are both targeted and customized.

Host 5-HT affects Plasmodium transmission in mosquitoes via modulating mosquito mitochondrial homeostasis.

Malaria parasites hijack the metabolism of their mammalian host during the blood-stage cycle. Anopheles mosquitoes depend on mammalian blood to lay eggs and to transmit malaria parasites. However, it remains understudied whether changes in host metabolism affect parasite transmission in mosquitoes. In this study, we discovered that Plasmodium infection significantly decreased the levels of the tryptophan metabolite, 5-hydroxytryptamine (5-HT), in both humans and mice. The reduction led to the decrease of 5-HT in mosquitoes. Oral supplementation of 5-HT to Anopheles stephensi enhanced its resistance to Plasmodium berghei infection by promoting the generation of mitochondrial reactive oxygen species. This effect was due to the accumulation of dysfunctional mitochondria caused by 5-HT-mediated inhibition of mitophagy. Elevating 5-HT levels in mouse serum significantly suppressed parasite infection in mosquitoes. In summary, our data highlight the critical role of metabolites in animal blood in determining the capacity of mosquitoes to control parasite infection.

Genotype distribution and allele frequency of thioester-containing protein 1(Tep1) and its effect on development of Plasmodium oocyst in populations of Anopheles arabiensis in Ethiopia.

Thioester-containing protein 1 (TEP1) is a crucial component of mosquitoes' natural resistance to parasites. To effectively combat malaria, there is a need to better understand how TEP1 polymorphism affects phenotypic traits during infections. Therefore, the purpose of this study was to determine the Tep1 genotype frequency in malaria vector populations from south-western Ethiopia and investigate its effect on Plasmodium oocyst development in Anopheles arabiensis populations. Using standard dippers, Anopheles mosquito larvae were collected from aquatic habitats in Asendabo, Arjo Dedessa, and Gambella in 2019 and 2020. Collected larvae were reared to adults and identified morphologically. Female An. gambiae s.l. were allowed to feed on infected blood containing the same number of gametocytes obtained from P. falciparum and P. vivax gametocyte-positive individuals using indirect membrane feeding methods. Polymerase Chain Reaction (PCR) was used to identify An. gambiae s.l. sibling species. Three hundred thirty An. gambiae s.l. were genotyped using Restricted Fragment Length Polymorphism (RFLP) PCR and sub samples were sequenced to validate the TEP1 genotyping. Among the 330 samples genotyped, two TEP1 alleles, TEP1*S1 (82% frequency) and TEP1*R1 (18% frequency), were identified. Three equivalent genotypes, TEP1*S1/S1, TEP1*R1/R1, and TEP1*S1/R1, had mean frequencies of 65.15%, 2.12%, and 32.73%, respectively. The nucleotide diversity was ranging from 0.36554 to 0. 46751 while haplotype diversity ranged from 0.48871 to 0.63161, across all loci. All sample sites had positive Tajima's D and Fu's Fs values. There was a significant difference in the TEP1 allele frequency and genotype frequency among mosquito populations (p < 0.05), except populations of Anopheles arabiensis from Asendabo and Gambella (p > 0.05). In addition, mosquitoes with the TEP1 *RR genotype were susceptible and produced fewer Plasmodium oocysts than mosquitoes with the TEP1 *SR and TEP1 *SS genotypes. The alleles identified in populations of An. arabiensis were TEP1*R1 and TEP1*S1. There was no significant variation in TEP1*R1 allele frequency between the high and low transmission areas. Furthermore, An. arabiensis carrying the TEP1*R1 allele was susceptible to Plasmodium infection. Further studies on vector-parasite interactions, particularly on the TEP1 gene, are required for vector control techniques.

A subpellicular microtubule dynein transport machinery regulates ookinete morphogenesis for mosquito transmission of Plasmodium yoelii

The cortical cytoskeleton of subpellicular microtubules (SPMTs) supports the Plasmodium ookinete morphogenesis during mosquito transmission of malaria. SPMTs are hypothesized to function as the cytoskeletal tracks in motor-driven cargo transport for apical organelle and structure assembly in ookinetes. However, the SPMT-based transport motor has not been identified in the Plasmodium. The cytoplasmic dynein is the motor moving towards the minus end of microtubules (MTs) and likely be responsible for cargo transport to the apical part in ookinetes. Here we screen 7 putative dynein heavy chain (DHC) proteins in the P. yoelii and identify DHC3 showing peripheral localization in ookinetes. DHC3 is localized at SPMTs throughout ookinete morphogenesis. We also identify five other dynein subunits localizing at SPMTs. DHC3 disruption impairs ookinete development, shape, and gliding, leading to failure in mosquito infection of Plasmodium. The DHC3-deficient ookinetes display defective formation or localization of apical organelles and structures. Rab11A and Rab11B interact with DHC3 at SPMTs in a DHC3-dependent manner, likely functioning as the receptors for the cargoes driven by SPMT-dynein. Disturbing Rab11A or Rab11B phenocopies DHC3 deficiency in ookinete morphogenesis. Our study reveals an SPMT-based dynein motor driving the transport of Rab11A- and Rab11B-labeled cargoes in the ookinete morphogenesis of Plasmodium.

Feeding habits and malaria parasite infection of Anopheles mosquitoes in selected agroecological areas of Northwestern Ethiopia

BackgroundSurveillance of the host–anopheline mosquitoes’ interaction is important for assessing malaria transmission risk and guiding vector control. We assume that changes in malaria vector species’ feeding habits, as well as the surrounding environment, have a substantial impact on varied malaria transmission. In this study, we determined the vertebrate host feeding patterns of anopheline mosquitoes to characterize entomologic risk factors for malaria in Jabi Tehnan, Northwestern Ethiopia.MethodsBlood-fed anophelines surveyed during malaria surveillance in Jabi Tehnan district of northwestern Ethiopia were utilized in this study. They were collected using Centers for Disease Control and Prevention (CDC) light traps deployed in selected households per village, placed indoors and outdoors, spanning three agroecological settings (dry mountain, plateau, and semiarid highlands) between June 2020 and May 2021. The engorged mosquitoes were analyzed for host blood meal sources and Plasmodium infection via polymerase chain reaction (PCR) and/or sequencing. Infection rates and bovine and human blood indices were calculated and compared for abundant species; between indoors and outdoors and between agroecology using a chi-squared test for equality of proportion in R package at a significant level of p ≤ 0.05.ResultsA total of 246 mosquitoes were successfully typed (indoor, 121; outdoor, 125), with greater relative abundance indoors in mountain and plateau highlands, and outdoors in semiarid areas. Despite ecological differences in blood-fed capture rates, cattle served as the most utilized blood meal source by 11 anopheline species with an overall bovine blood index (BBI) of 74.4%. This trend was dictated by Anopheles gambiae s.l. (198/246; BBI = 73.7%), which exhibited the most plastic feeding habits that included humans (human blood index = 15.7%) and other livestock and rodents. A total of five anopheline species (An. gambiae s.l., An. funestus s.l., An. coustani s.l., An. pretoriensis, and An. pharoensis) fed on humans, of which the first three were found infected with Plasmodium parasites. Most of the infected specimens were An. arabiensis (5.6%, 11/198) and had recently fed mainly on cattle (72.7%, 8/11); one each of infected An. funestus s.l. and An. coustani s.l. had fed on humans and cattle, respectively.ConclusionsThe results demonstrate communal feeding on cattle by anophelines including primary and secondary malaria vectors. This study also indicates the importance of cattle-targeted interventions for sustainable control of malaria vectors in the study areas.Graphical abstract

Avian malaria in a feral-pet pigeon: a case report

BackgroundAvian malaria is caused by diverse parasite species of the genus Plasmodium, and it affects various bird species. The occurrence of this disease in some wild bird species is sparsely documented due to the scarce availability of samples. Hence the pathogenicity in some hosts is not completely known. In addition, feral birds may act as reservoirs bridging the transmission cycle from wild migratory birds to domestic and zoo-kept bird species.Case presentationAn owner of pigeons adopted a feral pigeon (Columba livia forma domestica) and housed it together with his other pet-pigeons. The bird died unexpectedly a few weeks after a surgical procedure and necropsy revealed a severely anaemic carcass, with pale organs and hydropericardium. Histopathologic analysis revealed inflammatory infiltrates in the lung and liver, and monocytes and Kupffer cells contained haemozoin pigment indicative of phagocytosis of Plasmodium-infected erythrocytes. A high erythrocytic infection rate of 18% was evident in tissues and blood vessels in various organs. Furthermore, the thyroid had masses classified as thyroid carcinomas. Immunohistochemistry with anti- Plasmodium falciparum HSP70 antibody revealed positive signals in erythrocytes and intravascular leucocytes. Further microscopy analysis using a Hemacolor-stained impression smear revealed a high parasitaemia with an asynchronous infection showing all erythrocytic stages. Molecular diagnosis by PCR identified Plasmodium relictum, lineage GRW11 as the aetiological agent. The bird presented died most likely due to an acute infection as evidenced by the high blood parasitaemia, leading to major erythrocyte destruction. Further analyses of feral pigeons (n = 22) did not reveal any additional cases of Plasmodium infections.ConclusionThis study reports the first mortality associated with P. relictum lineage GRW11. The study supports previous studies, suggesting that Plasmodium infections are not frequent in pigeons. Host conditions like immunosuppression due to the tumour may have influenced the infection outcome in this fatal case. Use of anti-P. falciparum HSP70 antibody for detection of P. relictum antigens for immune assays in blood and tissue samples will be a useful tool for future studies.

Relationship between red blood cell polymorphisms and effectiveness of seasonal malaria chemoprevention in 2020 in Dangassa, Mali.

Treatment failure with amodiaquine was reported in Dangassa, where red blood cell (RBC) polymorphisms are found and seasonal malaria chemoprevention (SMC) is underway. Here, we aimed at assessing the influence of RBC polymorphisms on SMC effectiveness. This was a secondary analysis of data from a study conducted in Dangassa. Children aged 5 to 14years enrolled in an open randomized study were assigned either to receive SMC (intervention arm) or not (control arm). SMC was implemented from July to November. For all children, hemoglobin type and blood group were determined at enrolment in July, and parasitemia and hemoglobin level were monthly monitored by finger-prick. Overall, 166 children were enrolled among which 82 (49.40%) in the control arm and 84 (50.60%) in the SMC arm. The prevalence of HbAS was 10.24% (17/166) with 12.20% in the control and 8.33% in the SMC arm. O group was the most common overall (45%) and in the SMC arm (54%), but the control arm had more B (39.02%) than O (36.59%). In the SMC arm, no case of Plasmodium infection and malaria disease was observed in the 7 HbAS children while in Non-HbAS children, peaks of infection and disease prevalence were respectively observed in October (24.66%) and November (7.14%). For the SMC arm, in group O and Non-group O, Plasmodium infection cases were observed from August to December. Plasmodium infection and malaria disease were more frequently observed in HbAS children in the control arm than in the SMC arm. Further studies are needed to assess factors associated with the asymptomatic carriage of parasites during SMC in Dangassa. NCT04149106.

Development and longevity of naturally acquired antibody and memory B cell responses against Plasmodium vivax infection.

Plasmodium vivax malaria causes significant public health problems in endemic regions. Considering the rapid spread of drug-resistant parasite strains and the development of hypnozoites in the liver with potential for relapse, development of a safe and effective vaccine for preventing, controlling, and eliminating the infection is critical. Immunity to malaria is mediated by antibodies that inhibit sporozoite or merozoite invasion into host cells and protect against clinical disease. Epidemiologic data from malaria endemic regions show the presence of naturally acquired antibodies to P. vivax antigens during and following infection. But data on the persistence of these antibodies, development of P. vivax-specific memory B cells (MBCs), and their relation to reduction of malaria severity and risk is limited. This review provides an overview of the acquisition and persistence of naturally acquired humoral immunity to P. vivax infection. Also, we summarize and discuss current progress in assessment of immune responses to candidate vaccine antigens in P. vivax patients from different transmission settings. Longitudinal studies of MBC and antibody responses to these antigens will open new avenues for developing vaccines against malaria infection and its transmission.

Mosquito salivary apyrase regulates blood meal hemostasis and facilitates malaria parasite transmission

The evolution of hematophagy involves a series of adaptations that allow blood-feeding insects to access and consume blood efficiently while managing and circumventing the host’s hemostatic and immune responses. Mosquito, and other insects, utilize salivary proteins to regulate these responses at the bite site during and after blood feeding. We investigated the function of Anopheles gambiae salivary apyrase (AgApyrase) in regulating hemostasis in the mosquito blood meal and in Plasmodium transmission. Our results demonstrate that salivary apyrase, a known inhibitor of platelet aggregation, interacts with and activates tissue plasminogen activator, facilitating the conversion of plasminogen to plasmin, a human protease that degrades fibrin and facilitates Plasmodium transmission. We show that mosquitoes ingest a substantial amount of apyrase during blood feeding, which reduces coagulation in the blood meal by enhancing fibrin degradation and inhibiting platelet aggregation. AgApyrase significantly enhanced Plasmodium infection in the mosquito midgut, whereas AgApyrase immunization inhibited Plasmodium mosquito infection and sporozoite transmission. This study highlights a pivotal role for mosquito salivary apyrase for regulation of hemostasis in the mosquito blood meal and for Plasmodium transmission to mosquitoes and to the mammalian host, underscoring the potential for strategies to prevent malaria transmission.

Agonistic song rate positively correlates with male breeding success and avian malaria infection in Acrocephalus paludicola (Aquatic Warbler), a promiscuous songbird with female-only parental care

Abstract The link between male song and reproductive success has been explored at length in socially monogamous birds, but results were inconsistent and under-represented socially non-monogamous species with uniparental care. Here, we evaluated whether metrics of male song in Acrocephalus paludicola (Aquatic Warbler), a promiscuous songbird with female-only care and large repertoires, are associated with fitness- and quality-related traits. We showed that the number of 9-day-old nestlings fathered and probability of avian malaria infection increased with the rate of agonistic song, produced in male–male interactions, and that male-scaled mass index (proxy for energy reserves) positively correlated with the repertoire size. The male breeding success was not explained by repertoire size and song duty cycle. None of the song variables clearly explained the male return rate or change in the tarsus length (proxy for structural body size) and scaled mass index of the fathered chicks between days 2 and 9 post-hatch. No other relationships between the song characteristics and the inbreeding coefficient, scaled mass index, wing-length and Trypanosoma infection status of the males were supported, and Plasmodium infection was unrelated to the song duty cycle and repertoire size. We conclude that in male A. paludicola the repertoire size could be a signal of early developmental stress or current body condition, and the agonistic song rate could be shaped by sexual selection and signal to females a genetic makeup that enhances survival upon infection by Plasmodium.

Mathematical model and analysis for within-host dynamics of the malaria parasite infection with optimal control strategies

This study develops and analyzes the within-host dynamics of malaria parasite infection with optimal control strategies. We considered both the blood and liver stages of the malaria infection, taking into account the immunological response against the infection. The basic reproduction number, which indicates the potential spread of the parasite is evaluated. The parasite-free equilibrium point is locally and globally asymptotically stable when the basic reproduction is less than a unit. Sensitivity analysis reveals that the invention rate of red blood cells and the average number of merozoites per rupture infected red blood cell are the most influential parameters of the model. Furthermore, to investigate the most effective measurement of malaria parasite infection, we performed the optimal control strategies. The pre-erythrocytic vaccine, blood-stage vaccine, primary tissue schizontocides, blood schizontocides, and gametocytocidal drugs are incorporated as control measures. The controls are implemented to minimize the infected hepatocytes, infected red blood cells, gametocytes, and merozoites in the human host, as well as the associated costs. Pontryagin’s Minimum Principle is applied to establish optimal control strategies against infected red blood cells, infected hepatocytes, and malaria parasites. Several simulation situations are conducted to assess the analytical results and determine the effective control intervention measures. The results indicate that administering all four controls simultaneously would eradicate the prevalence of malaria infection in the human host.

Transmission-blocking activities of artesunate, chloroquine, and methylene blue on Plasmodium vivax gametocytes.

Plasmodium vivax is now the main cause of malaria outside Africa. The gametocytocidal effects of antimalarial drugs are important to reduce malaria transmissibility, particularly in low-transmission settings, but they are not well characterized for P. vivax. The transmission-blocking effects of chloroquine, artesunate, and methylene blue on P. vivax gametocytes were assessed. Blood specimens were collected from patients presenting with vivax malaria, incubated with or without the tested drugs, and then fed to mosquitos from a laboratory-adapted colony of Anopheles dirus (a major malaria vector in Southeast Asia). The effects on oocyst and sporozoite development were analyzed under a multi-level Bayesian model accounting for assay variability and the heterogeneity of mosquito Plasmodium infection. Artesunate and methylene blue, but not chloroquine, exhibited potent transmission-blocking effects. Gametocyte exposures to artesunate and methylene blue reduced the mean oocyst count 469-fold (95% CI: 345 to 650) and 1,438-fold (95% CI: 970 to 2,064), respectively. The corresponding estimates for the sporozoite stage were a 148-fold reduction (95% CI: 61 to 470) and a 536-fold reduction (95% CI: 246 to 1,311) in the mean counts, respectively. In contrast, high chloroquine exposures reduced the mean oocyst count only 1.40-fold (95% CI: 1.20 to 1.64) and the mean sporozoite count 1.34-fold (95% CI: 1.12 to 1.66). This suggests that patients with vivax malaria often remain infectious to anopheline mosquitos after treatment with chloroquine. Use of artemisinin combination therapies or immediate initiation of primaquine radical cure should reduce the transmissibility of P. vivax infections.

Insights into malaria vectors–plant interaction in a dryland ecosystem

Improved understanding of mosquito–plant feeding interactions can reveal insights into the ecological dynamics of pathogen transmission. In wild malaria vectors Anopheles gambiae s.l. and An. funestus group surveyed in selected dryland ecosystems of Kenya, we found a low level of plant feeding (2.8%) using biochemical cold anthrone test but uncovered 14-fold (41%) higher rate via DNA barcoding targeting the chloroplast rbcL gene. Plasmodium falciparum positivity was associated with either reduced or increased total sugar levels and varied by mosquito species. Gut analysis revealed the mosquitoes to frequently feed on acacia plants (~ 89%) (mainly Vachellia tortilis) in the family Fabaceae. Chemical analysis revealed 1-octen-3-ol (29.9%) as the dominant mosquito attractant, and the sugars glucose, sucrose, fructose, talose and inositol enriched in the vegetative parts, of acacia plants. Nutritional analysis of An. longipalpis C with high plant feeding rates detected fewer sugars (glucose, talose, fructose) compared to acacia plants. These results demonstrate (i) the sensitivity of DNA barcoding to detect plant feeding in malaria vectors, (ii) Plasmodium infection status affects energetic reserves of wild anopheline vectors and (iii) nutrient content and olfactory cues likely represent potent correlates of acacia preferred as a host plant by diverse malaria vectors. The results have relevance in the development of odor-bait control strategies including attractive targeted sugar-baits.

Single-cell analyses of polyclonal Plasmodium vivax infections and their consequences on parasite transmission

Most Plasmodium vivax infections contain genetically distinct parasites, but the consequences of this polyclonality on the development of asexual parasites, their sexual differentiation, and their transmission remain unknown. We describe infections of Saimiri monkeys with two strains of P. vivax and the analyses of 80,024 parasites characterized by single cell RNA sequencing and individually genotyped. In our model, consecutive inoculations fail to establish polyclonal infections. By contrast, simultaneous inoculations of two strains lead to sustained polyclonal infections, although without detectable differences in parasite regulation or sexual commitment. Analyses of sporozoites dissected from mosquitoes fed on coinfected monkeys show that all genotypes are successfully transmitted to mosquitoes. However, after sporozoite inoculation, not all genotypes contribute to the subsequent blood infections, highlighting an important bottleneck during pre-erythrocytic development. Overall, these studies provide new insights on the mechanisms regulating the establishment of polyclonal P. vivax infections and their consequences for disease transmission.

Clinical burden of Plasmodium infection and associated risk factors among the local population of Chakwal, Punjab, Pakistan (2019–2023)

BackgroundThis study aimed to determine the clinical burden, spatial dynamics, and associated risk factors of Plasmodium infection among the natives of Chakwal, Punjab Pakistan from 2019 to 2023 to guide targeted screening and treatment interventions.MethodA community-based cross-sectional study was conducted using primary and secondary data sources. Participants were recruited using a multi-stage cluster sampling by taking informed consent for the primary data sources. Whereas a secondary dataset of Plasmodium infection was obtained from the database of surveyed hospitals after ethical consideration. All the participants living in the study area for at least 3 months were included, while patients with chronic illness were excluded. Sociodemographic and environmental data were collected using a structured questionnaire. Plasmodium infection was diagnosed using microscopy, rapid diagnostic tests (RDTs), and nested polymerase chain reaction (PCR) as the reference standard. A Zero-inflated negative binomial logistic regression model and interpolation of malaria distribution to environmental variables were employed to determine the association and spatiotemporal patterns of malaria in Chakwal.ResultsAmong the 2457 participants, the prevalence of Plasmodium vivax infection (99%) was significantly higher than P. falciparum (0.8%) and mixed infection (0.2%). Females had a higher infection rate than males and the infection rate was higher in adults (21–40 years) and children (0–20 years). Age category (61–100), P. vivax species, temperature, rainfall, monsoon season, and mixed infection factors were significantly associated (p < 0.05) with increased Plasmodium infection risk. Geospatial mapping indicated potential malaria hotspots in Sarkal Kasar, Chak Baili, Mulkwal, Chohan, and other close areas of the Potohar region.ConclusionThe clinical burden of P. vivax was the highest during monsoon season in Chakwal. Age, gender, climatic factors, and mixed infection were significant risk factors for malaria transmission in this region. Targeted screening and treatment strategies should prioritize identified hotspots and high-risk groups to effectively control malaria in Potohar region of Pakistan.

Long-term blood-free rearing of Anopheles mosquitoes with no effect on fitness, Plasmodium infectivity nor microbiota composition

Mosquito-borne diseases kill millions of people each year. Therefore, many innovative research and population control strategies are being implemented but, most of them require large-scale production of mosquitoes. Mosquito rearing depends on fresh blood from human donors, experimentation animals or slaughterhouses, which constitutes a strong drawback since high blood quantities are needed, raising ethical and financial constraints. To eliminate blood dependency and the use of experimentation animals, we previously developed BLOODless, a patented diet that represents an important advance towards sustainable mosquito breeding in captivity. BLOODless diet was used to maintain a colony of Anopheles stephensi for 40 generations. Bloodmeal appetite, fitness, Plasmodium berghei infectivity, whole genome sequencing and microbiota were evaluated over time. Here we show that BLOODless can be implemented in Anopheles insectaries since it allows long-term rearing of mosquitoes in captivity, without a detectable effect on their fitness, infectivity, nor on their midgut and salivary microbiota composition.

Host-pathogen interactions in the Plasmodium-infected mouse liver at spatial and single-cell resolution

Upon infecting its vertebrate host, the malaria parasite initially invades the liver where it undergoes massive replication, whilst remaining clinically silent. The coordination of host responses across the complex liver tissue during malaria infection remains unexplored. Here, we perform spatial transcriptomics in combination with single-nuclei RNA sequencing over multiple time points to delineate host-pathogen interactions across Plasmodium berghei-infected liver tissues. Our data reveals significant changes in spatial gene expression in the malaria-infected tissues. These include changes related to lipid metabolism in the proximity to sites of Plasmodium infection, distinct inflammation programs between lobular zones, and regions with enrichment of different inflammatory cells, which we term ‘inflammatory hotspots’. We also observe significant upregulation of genes involved in inflammation in the control liver tissues of mice injected with mosquito salivary gland components. However, this response is considerably delayed compared to that observed in P. berghei-infected mice. Our study establishes a benchmark for investigating transcriptome changes during host-parasite interactions in tissues, it provides informative insights regarding in vivo study design linked to infection and offers a useful tool for the discovery and validation of de novo intervention strategies aimed at malaria liver stage infection.

Moving population is a challenge for malaria elimination in India: A cross-sectional study to assess malaria parasite infections in walking pilgrims in western Rajasthan, India

ObjectivesIndia is vigorously pursuing malaria elimination by 2030 and one of the key challenges is how to prevent the malaria risk associated with long-distance migrations of populations from endemic to non-endemic areas. Millions of pilgrims walking to the holy Ramdevra temple stay in temporary shelters along the route in district of Jaisalmer, Rajasthan state in western India. The main pilgrimage period coincides with the post-monsoon period with elevated vector densities. We investigated this situation to assess the potential risk posed by migrant pilgrims along the four highways in the temple district in disseminating malaria infections associated with their annual movements. MethodsA cross-sectional study was conducted for screening malaria in walking pilgrims from neighboring states at selected sites and a follow-up study for screening residents in Rajasthan from 2021 to 2023. The study comprises state entry routes, Ramdevra shrine, and pilgrimage route villages situated in western Rajasthan. Epidemiologic and entomologic surveillance was conducted during the “fair” period (August-September) and in pilgrimage route villages in three different seasons of the year to assess malaria in humans and the vector's infectivity. ResultsOf the 5251 individuals tested for malaria, a total of 76 (1.4%) tested positive for malaria, of whom 40.7% were infected with Plasmodium vivax (n = 31), 36.8% with P. falciparum (n = 28), and 22.3% with P. vivax and P. falciparum (n = 17). Anopheles density was highest during the fair season, peaking in August. An. stephensi exhibited a higher human blood index (0.65) than An. culicifacies (0.50). No mosquitoes were found positive for parasites. ConclusionsUp to 1.5% of pilgrims carried malaria parasites, posing a risk of spreading malaria to surrounding communities that otherwise would have low or no malaria burden. Moving populations pose the risk of local malaria transmission and reintroduction to the areas undergoing elimination. Sentinel point surveillance at the border of states will be helpful for states to share information on malaria and subsequently for the prevention of malaria transmission.

Asymptomatic Malaria Cases and Plasmodium Species among BaAka Pygmies in Central Africa.

Malaria is a significant health problem in Africa, primarily due to the Plasmodium falciparum species, but this is not the only etiological factor responsible for malaria on the continent. The goal of the present research was to describe asymptomatic malaria cases and to identify Plasmodium species responsible for malaria in the BaAka Pygmies, inhabitants of the Central African Republic (CAR). Screening was realised in the period of August-September 2021 among 308 people, including 74 children and 234 adults reporting to a healthcare facility in Monasao (southwest CAR), an area inhabited by a semi-nomadic tribe of BaAka Pygmies. The study consisted of two phases. Phase I, which was conducted in Africa, consisted of performing malaria rapid diagnostic tests (mRDTs), taking haemoglobin measurements and collecting blood samples onto Whatman FTA cards for molecular diagnostics. Phase II, which was conducted in Poland, involved molecular tests (RT-PCR) to confirm or rule out malaria infections and to identify Plasmodium species responsible for the infections. mRDTs detected Plasmodium infections in 50.3% of children and 17.1% of adults participating in the study, whereas RT-PCR assays yielded positive results for 59.5% children and 28.6% adults. Molecular tests detected multiple Plasmodium falciparum infections but also three infections with P. malariae, three with P. ovale and one with P. vivax. The obtained results have confirmed numerous asymptomatic Plasmodium infections among the BaAka Pygmies. The rates of asymptomatic malaria cases in adults were twice as high as those in children, which may be indicative of the gradual acquisition of protective immunity with age. The study findings have also demonstrated that although most cases of malaria in Africa are caused by P. falciparum, three other species are also present in the region.