Interplay between liver and blood stages of Plasmodium infection dictates malaria severity via γδ T cells and IL-17-promoted stress erythropoiesis.

Plasmodium replicates within the liver prior to reaching the bloodstream and infecting red blood cells. Because clinical manifestations of malaria only arise during the blood stage of infection, a perception exists that liver infection does not impact disease pathology. By developing a murine model where the liver and blood stages of infection are uncoupled, we showed that the integration of signals from both stages dictated mortality outcomes. This dichotomy relied on liver stage-dependent activation of Vγ4+ γδ T cells. Subsequent blood stage parasite loads dictated their cytokine profiles, where low parasite loads preferentially expanded IL-17-producing γδ T cells. IL-17 drove extra-medullary erythropoiesis and concomitant reticulocytosis, which protected mice from lethal experimental cerebral malaria (ECM). Adoptive transfer of erythroid precursors could rescue mice from ECM. Modeling of γδ T cell dynamics suggests that this protective mechanism may be key for the establishment of naturally acquired malaria immunity among frequently exposed individuals.

Detection of Duffy blood group genotypes and submicroscopic Plasmodium infections using molecular diagnostic assays in febrile malaria patients.

BACKGROUND: Malaria remains a severe parasitic disease, posing a significant threat to public health and hindering economic development in sub-Saharan Africa. Ethiopia, a malaria endemic country, is facing a resurgence of the disease with a steadily rising incidence. Conventional diagnostic methods, such as microscopy, have become less effective due to low parasite density, particularly among Duffy-negative human populations in Africa. To develop comprehensive control strategies, it is crucial to generate data on the distribution and clinical occurrence of Plasmodium vivax and Plasmodium falciparum infections in regions where the disease is prevalent. This study assessed Plasmodium infections and Duffy antigen genotypes in febrile patients in Ethiopia. METHODS: Three hundred febrile patients visiting four health facilities in Jimma town of southwestern Ethiopia were randomly selected during the malaria transmission season (Apr-Oct). Sociodemographic information was collected, and microscopic examination was performed for all study participants. Plasmodium species and parasitaemia as well as the Duffy genotype were assessed by quantitative polymerase chain reaction (qPCR) for all samples. Data were analysed using Fisher's exact test and kappa statistics. RESULTS: The Plasmodium infection rate by qPCR was 16% (48/300) among febrile patients, of which 19 (39.6%) were P. vivax, 25 (52.1%) were P. falciparum, and 4 (8.3%) were mixed (P. vivax and P. falciparum) infections. Among the 48 qPCR-positive samples, 39 (13%) were negative by microscopy. The results of bivariate logistic regression analysis showed that agriculture-related occupation, relapse and recurrence were significantly associated with Plasmodium infection (P < 0.001). Of the 300 febrile patients, 85 (28.3%) were Duffy negative, of whom two had P. vivax, six had P. falciparum, and one had mixed infections. Except for one patient with P. falciparum infection, Plasmodium infections in Duffy-negative individuals were all submicroscopic with low parasitaemia. CONCLUSIONS: The present study revealed a high prevalence of submicroscopic malaria infections. Plasmodium vivax infections in Duffy-negative individuals were not detected due to low parasitaemia. In this study, an improved molecular diagnostic tool was used to detect and characterize Plasmodium infections, with the goal of quantifying P. vivax infection in Duffy-negative individuals. Advanced molecular diagnostic techniques, such as multiplex real-time PCR, loop-mediated isothermal amplification (LAMP), and CRISPR-based diagnostic methods. These techniques offer increased sensitivity, specificity, and the ability to detect low-parasite-density infections compared to the employed methodologies.

TLR9 signalling inhibits Plasmodium liver infection by macrophage activation.

Recognition of pathogen-associated molecular patterns (PAMPs) through Toll-like receptors (TLRs) plays a pivotal role in first-line pathogen defense. TLRs are also likely triggered during a Plasmodium infection in vivo by parasite-derived components. However, the contribution of innate responses to liver infection and to the subsequent clinical outcome of a blood infection is not well understood. To assess the potential effects of enhanced TLR-signalling on Plasmodium infection, we systematically examined the effect of agonist-primed immune responses to sporozoite inoculation in the P. berghei/C57Bl/6 murine malaria model. We could identify distinct stage-specific effects on the course of infection after stimulation with two out of four TLR-ligands tested. Priming with a TLR9 agonist induced killing of pre-erythrocytic stages in the liver that depended on macrophages and the expression of inducible nitric oxide synthase (iNOS). These factors have previously not been recognized as antigen-independent effector mechanisms against Plasmodium liver stages. Priming with TLR4 and -9 agonists also translated into blood stage-specific protection against experimental cerebral malaria (ECM). These insights are relevant to the activation of TLR signalling pathways by adjuvant systems of antimalaria vaccine strategies. The protective role of TLR4-activation against ECM might also explain some unexpected clinical effects observed with pre-erythrocytic vaccine approaches.

Plasmodium infection and dysbiosis: A new paradigm in the host-parasite interaction.

The mucosal immune system contributes for the largest component of the tissue immune system due to its massive surface area and constant exposure to the microbiota. The gut microbiota comprises a complex micro-ecosystem in the intestine and plays a major role in regulating innate and adaptive immunity. Several studies revealed that infectious diseases involve bidirectional interactions in the gut microenvironment, including changes in the gut microbiota composition. During Plasmodium infection, an increase of pro-inflammatory cells in the lamina propria and a shift in the composition of the gut microbiota contribute to intestinal ecosystem dysbiosis. Although the mechanisms of this dysbiosis is still uncertain, it is thought to be associated with the sequestration of infected red blood cells in the intestinal microvascular system, leading to endothelial villous disruption, and thus activating effector immune cells scattered in the intestinal epithelium and lamina propria. This review provides information on this conjoint interaction which will be beneficial to modulate the host immune response in malaria through manipulation of the gut microbiota composition.

Plasmodium infections and associated risk factors among parturients in Jawi district, northwest Ethiopia: a cross-sectional study.

BACKGROUND: Pregnant women have an increased risk of Plasmodium infections and disease. Malaria in pregnancy is a major public health problem in endemic areas. Assessment of the burden and risk factors of malaria in pregnancy across different malaria transmission settings is required to guide control strategies and for malaria elimination. Thus, the current study is generating such evidence from parturient women in northwest Ethiopia. METHODS: A cross-sectional study was conducted among 526 pregnant women admitted to the delivery rooms of selected health facilities in Jawi district, northwest Ethiopia, between November 2021 and July 2022. Data on the socio-demographic, clinical, obstetric, and malaria prevention practices of pregnant women were collected using interviewer-administered questionnaires and from women's treatment cards. Malaria was diagnosed by light microscopy, rapid diagnostic test, and multiplex real-time polymerase chain reaction. Risk factors for malaria were evaluated using bivariable and multivariable logistic regression models. A P-value of < 0.05 was considered statistically significant. RESULTS: Among the examined parturient women, 14.3% (95% CI 11.4-17.5%) had Plasmodium infections. The prevalence of peripheral, placental, and congenital malaria was 12.2% (95% CI 9.5-15.3%), 10.9% (95% CI 8.2-14.1%), and 3.7% (95% CI 2.3-6.1%), respectively. About 90.6% of peripheral and 92% of placental Plasmodium infections were asymptomatic. Plasmodium infection at parturiency was independently predicted by maternal illiteracy (AOR = 2.03, 95% CI 1.11-3.74), primigravidity (AOR = 1.88, 95% CI 1.01-3.49), lack of antenatal care follow-up (AOR = 2.28, 95% CI 1.04-5.03), and history of symptomatic malaria during pregnancy (AOR = 4.2, 95% CI 2.32-7.59). Moreover, the blood group O phenotype was significantly associated with placental malaria among the primiparae. CONCLUSIONS: Overall, asymptomatic Plasmodium infections were prevalent among parturients in northwest Ethiopia. Maternal illiteracy, primigravidity, lack of antenatal care follow-up, and history of symptomatic malaria during pregnancy were the risk factors for malaria during parturiency. Thus, promotion of a healthy pregnancy through ANC follow-up, strengthening malaria prevention and control practices, and screening of malaria in asymptomatic pregnant women are suggested to reduce its burden in pregnancy.

Escaping the enemy's bullets: an update on how malaria parasites evade host immune response.

Malaria continues to cause untold hardship to inhabitants of malaria-endemic regions, causing significant morbidity and mortality that severely impact global health and the economy. Considering the complex life cycle of malaria parasites (MPs) and malaria biology, continued research efforts are ongoing to improve our understanding of the pathogenesis of the diseases. Female Anopheles mosquito injects MPs into its hosts during a blood meal, and MPs invade the host skin and the hepatocytes without causing any serious symptoms. Symptomatic infections occur only during the erythrocytic stage. In most cases, the host's innate immunity (for malaria-naïve individuals) and adaptive immunity (for pre-exposed individuals) mount severe attacks and destroy most MPs. It is increasingly understood that MPs have developed several mechanisms to escape from the host's immune destruction. This review presents recent knowledge on how the host's immune system destroys invading MPs as well as MPs survival or host immune evasion mechanisms. On the invasion of host cells, MPs release molecules that bind to cell surface receptors to reprogram the host in a way to lose the capacity to destroy them. MPs also hide from the host immune cells by inducing the clustering of both infected and uninfected erythrocytes (rosettes), as well as inducing endothelial activation. We hope this review will inspire more research to provide a complete understanding of malaria biology and promote interventions to eradicate the notorious disease.

Irrigation-Induced Environmental Changes Sustain Malaria Transmission and Compromise Intervention Effectiveness.

BACKGROUND: Irrigated agriculture enhances food security, but it potentially promotes mosquito-borne disease transmission and affects vector intervention effectiveness. This study was conducted in the irrigated and nonirrigated areas of rural Homa Bay and Kisumu Counties, Kenya. METHODS: We performed cross-sectional and longitudinal surveys to determine Plasmodium infection prevalence, clinical malaria incidence, molecular force of infection (molFOI), and multiplicity of infection. We examined the impact of irrigation on the effectiveness of the new interventions. RESULTS: We found that irrigation was associated with >2-fold higher Plasmodium infection prevalence and 3-fold higher clinical malaria incidence compared to the nonirrigated area. Residents in the irrigated area experienced persistent, low-density parasite infections and higher molFOI. Addition of indoor residual spraying was effective in reducing malaria burden, but the reduction was more pronounced in the nonirrigated area than in the irrigated area. CONCLUSIONS: Our findings collectively suggest that irrigation may sustain and enhance Plasmodium transmission and affects intervention effectiveness.

Preparation of Decoquinate Solid Dispersion by Hot-Melt Extrusion as an Oral Dosage Form Targeting Liver-Stage Plasmodium Infection.

Liver-stage Plasmodium in humans is an early stage of malarial infection. Decoquinate (DQ) has a potent multistage antimalarial activity. However, it is practically water insoluble. In this study, the hot-melt extrusion (HME) approach was employed to prepare solid dispersions of DQ to improve oral bioavailability. The DQ dispersions were homogeneous in an aqueous suspension that contained most DQ (>90%) in the aqueous phase. Soluplus, a solubilizer, was found compatible with DQ in forming nanoparticle formulations during the HME process. Another excipient HPMC AS-126 was also proven to be suitable for making DQ nanoparticles through HME. Particle size and antimalarial activity of HME DQ suspensions remained almost unchanged after storage at 4°C for over a year. HME DQ was highly effective at inhibiting Plasmodium infection in vitro at both the liver stage and blood stage. HME DQ at 3 mg/kg by oral administration effectively prevented Plasmodium infection in mice inoculated with Plasmodium berghei sporozoites. Orally administered HME DQ at 2,000 mg/kg to mice showed no obvious adverse effects. HME DQ at 20 mg/kg orally administered to rats displayed characteristic distributions of DQ in the blood with most DQ in the blood cells, revealing the permeability of HME DQ into the cells in relation to its antimalarial activity. The DQ dispersions may be further developed as an oral formulation targeting Plasmodium infection at the liver stage.

Prevalence of malaria and its risk factors in Lake Tana and surrounding areas, northwest Ethiopia.

BACKGROUND: In Ethiopia, malaria is a major concern to the health, and socio-economic development of the country because of its occurrence at the peak agricultural activities. Factors such as environmental, human host, parasite, and vector determine malaria transmission. Therefore, the present study was conducted to determine the prevalence and associated factors of malaria among febrile patients who visited selected health centres. METHODS: Institutional-based cross-sectional study was conducted between October 2020 to July 2021 in eight selected health centres located in Lake Tana and its surrounding areas. A simple random sampling technique was used to select febrile patients. Thick and thin blood films were prepared and processed according to the WHO guidelines. Socio-demographic and malaria risk factors were collected from study participants who could read and write using a self-administered questionnaire, whereas face-to-face interview was used to collect information from those participants who could not write and read. The strength of association between risk factors and malaria was assessed using univariate and multivariate logistic regression models. RESULTS: Of the total (531) febrile patients, 75.3% were malaria negative and 24.7% (overall prevalence) were malaria confirmed cases. Most of the infections were caused by Plasmodium falciparum (72.5%) followed by Plasmodium vivax (23.7%) and mixed-species (3.8%). The highest prevalence was recorded in Kidist Hana (51.5%) followed by Robit (34.8%), Gorgora (30.3%), and Wusha Tiris (25%) health centres. In terms of months, the highest prevalence (37.5%) was detected in October whereas the lowest (14%) was in March. Logistic regression analysis revealed that gender (p = 0.023), educational level (p = 0.025), study month (p = 0.036), presence of eave in the house (p = 0.002) and wall openings (p = 0.041), not using bed nets (p = 0.001), sleeping in the same house with cattle (p = 0.031) and the distance between mosquito-breeding site and living house (p = 0.020) were explanatory risk factors significantly associated with malaria among studied participants. CONCLUSIONS: In this study, we confirmed that the occurrence of malaria prevalence was high and continued against the Ethiopian malaria elimination plan of 2021-2025. Therefore, to meet the goals of this plan, the current prevention and control efforts should be stepped up even better in the coming years.

The mechanisms of action of Plasmodium infection against cancer.

Our murine cancer model studies have demonstrated that Plasmodium infection activates the immune system that has been inhibited by cancer cells, counteracts tumor immunosuppressive microenvironment, inhibits tumor angiogenesis, inhibits tumor growth and metastasis, and prolongs the survival time of tumor-bearing mice. Based on these studies, three clinical trials of Plasmodium immunotherapy for advanced cancers have been approved and are ongoing in China. After comparing the mechanisms of action of Plasmodium immunotherapy with those of immune checkpoint blockade therapy, we propose the notion that cancer is an ecological disease and that Plasmodium immunotherapy is a systemic ecological counterattack therapy for this ecological disease, with limited side effects and without danger to public health based on the use of artesunate and other measures. Recent reports of tolerance to treatment and limitations in majority of patients associated with the use of checkpoint blockers further support this notion. We advocate further studies on the mechanisms of action of Plasmodium infection against cancer and investigations on Plasmodium-based combination therapy in the coming future. Video Abstract.

The epidemiology and detectability of asymptomatic plasmodium vivax and plasmodium falciparum infections in low, moderate and high transmission settings in Ethiopia.

BACKGROUND: As countries move to malaria elimination, detecting and targeting asymptomatic malaria infections might be needed. Here, the epidemiology and detectability of asymptomatic Plasmodium falciparum and Plasmodium vivax infections were investigated in different transmission settings in Ethiopia. METHOD: A total of 1093 dried blood spot (DBS) samples were collected from afebrile and apparently healthy individuals across ten study sites in Ethiopia from 2016 to 2020. Of these, 862 were from community and 231 from school based cross-sectional surveys. Malaria infection status was determined by microscopy or rapid diagnostics tests (RDT) and 18S rRNA-based nested PCR (nPCR). The annual parasite index (API) was used to classify endemicity as low (API > 0 and < 5), moderate (API ≥ 5 and < 100) and high transmission (API ≥ 100) and detectability of infections was assessed in these settings. RESULTS: In community surveys, the overall prevalence of asymptomatic Plasmodium infections by microscopy/RDT, nPCR and all methods combined was 12.2% (105/860), 21.6% (183/846) and 24.1% (208/862), respectively. The proportion of nPCR positive infections that was detectable by microscopy/RDT was 48.7% (73/150) for P. falciparum and 4.6% (2/44) for P. vivax. Compared to low transmission settings, the likelihood of detecting infections by microscopy/RDT was increased in moderate (Adjusted odds ratio [AOR]: 3.4; 95% confidence interval [95% CI] 1.6-7.2, P = 0.002) and high endemic settings (AOR = 5.1; 95% CI 2.6-9.9, P < 0.001). After adjustment for site and correlation between observations from the same survey, the likelihood of detecting asymptomatic infections by microscopy/RDT (AOR per year increase = 0.95, 95% CI 0.9-1.0, P = 0.013) declined with age. CONCLUSIONS: Conventional diagnostics missed nearly half of the asymptomatic Plasmodium reservoir detected by nPCR. The detectability of infections was particularly low in older age groups and low transmission settings. These findings highlight the need for sensitive diagnostic tools to detect the entire parasite reservoir and potential infection transmitters.

Hyper-prevalence of submicroscopic Plasmodium falciparum infections in a rural area of western Kenya with declining malaria cases.

BACKGROUND: The gold standard for diagnosing Plasmodium falciparum infection is microscopic examination of Giemsa-stained peripheral blood smears. The effectiveness of this procedure for infection surveillance and malaria control may be limited by a relatively high parasitaemia detection threshold. Persons with microscopically undetectable infections may go untreated, contributing to ongoing transmission to mosquito vectors. The purpose of this study was to determine the magnitude and determinants of undiagnosed submicroscopic P. falciparum infections in a rural area of western Kenya. METHODS: A health facility-based survey was conducted, and 367 patients seeking treatment for symptoms consistent with uncomplicated malaria in Homa Bay County were enrolled. The frequency of submicroscopic P. falciparum infection was measured by comparing the prevalence of infection based on light microscopic inspection of thick blood smears versus real-time polymerase chain reaction (RT-PCR) targeting P. falciparum 18S rRNA gene. Long-lasting insecticidal net (LLIN) use, participation in nocturnal outdoor activities, and gender were considered as potential determinants of submicroscopic infections. RESULTS: Microscopic inspection of blood smears was positive for asexual P. falciparum parasites in 14.7% (54/367) of cases. All of these samples were confirmed by RT-PCR. 35.8% (112/313) of blood smear negative cases were positive by RT-PCR, i.e., submicroscopic infection, resulting in an overall prevalence by RT-PCR alone of 45.2% compared to 14.7% for blood smear alone. Females had a higher prevalence of submicroscopic infections (35.6% or 72 out of 202 individuals, 95% CI 28.9-42.3) compared to males (24.2%, 40 of 165 individuals, 95% CI 17.6-30.8). The risk of submicroscopic infections in LLIN users was about half that of non-LLIN users (OR = 0.59). There was no difference in the prevalence of submicroscopic infections of study participants who were active in nocturnal outdoor activities versus those who were not active (OR = 0.91). Patients who participated in nocturnal outdoor activities and use LLINs while indoors had a slightly higher risk of submicroscopic infection than those who did not use LLINs (OR = 1.48). CONCLUSION: Microscopic inspection of blood smears from persons with malaria symptoms for asexual stage P. falciparum should be supplemented by more sensitive diagnostic tests in order to reduce ongoing transmission of P. falciparum parasites to local mosquito vectors.

Plasmodium infection inhibits tumor angiogenesis through effects on tumor-associated macrophages in a murine implanted hepatoma model.

BACKGROUND: Hepatocellular carcinoma (HCC) is one of the leading causes of cancer-related death in China. The lack of an effective treatment for this disease results in a high recurrence rate in patients who undergo radical tumor resection, and the 5-year survival rate of these patients remains low. Our previous studies demonstrated that Plasmodium infection provides a potent antitumor effect by inducing innate and adaptive immunity in a murine Lewis lung carcinoma (LLC) model. METHODS: This study aimed to investigate the inhibitory effect of Plasmodium infection on hepatocellular carcinoma in mice, and various techniques for gene expression analysis were used to identify possible signal regulation mechanisms. RESULTS: We found that Plasmodium infection efficiently inhibited tumor progression and prolonged survival in tumor-bearing mice, which served as a murine implanted hepatoma model. The inhibition of tumor progression by Plasmodium infection was related to suppression of tumor angiogenesis within the tumor tissue and decreased infiltration of tumor-associated macrophages (TAMs). Further study demonstrated that matrix metalloprotease 9 (MMP-9) produced by TAMs contributed to tumor angiogenesis in the tumor tissue and that the parasite-induced reduction in MMP-9 expression in TAMs resulted in the suppression of tumor angiogenesis. A mechanistic study revealed that the Plasmodium-derived hemozoin (HZ) that accumulated in TAMs inhibited IGF-1 signaling through the PI3-K and MAPK signaling pathways and thereby decreased the expression of MMP-9 in TAMs. CONCLUSIONS: Our study suggests that this novel approach of inhibiting tumor angiogenesis by Plasmodium infection is of high importance for the development of new therapies for cancer patients. Video abstract.

New insights into malaria vector bionomics in Lao PDR: a nationwide entomology survey.

BACKGROUND: In Laos, the malaria burden remains high despite a significant reduction of cases during the last decade. In the context of the disease elimination by 2030, a nationwide entomological survey was conducted to better understand the distribution, abundance and behaviour of major malaria vectors (Anopheles spp.) in the country. METHODS: Mosquito collections were implemented in ten villages from ten provinces during the rainy and dry seasons of 2014 and 2015 by using human landing catch (HLC) and cow bait collection (CBC) methods. After morphological identification in the field, molecular identification of the sibling species of Anopheles mosquitoes from the Funestus, Leucosphyrus, and Maculatus groups were determined using PCR specific alleles. A screening of Plasmodium falciparum and Plasmodium vivax infections in the vectors was carried out by quantitative PCR assays. RESULTS: A total of 14,146 adult mosquitoes representing 25 different Anopheles species were collected and morphologically identified. Molecular identification revealed the presence of 12 sibling species within the main primary vector groups, including Anopheles maculatus, Anopheles rampae, Anopheles sawadwongporni, Anopheles pseudowillmori, Anopheles dravidicus, Anopheles minimus, Anopheles aconitus, Anopheles pampanai, Anopheles harrisoni, Anopheles dirus, Anopheles baimaii, Anopheles nemophilous. Anopheles maculatus and An. minimus were predominant during both the dry and rainy seasons, but showed highly zoophilic preferences (Zoophilic index of 98% and 95%, respectively). Overall, 22% of the total malaria vectors were collected between 10:00 PM and 5:00 AM indoors when people are sleeping. Twenty-seven percent of primary and secondary vectors were collected outdoors before 10:00 PM or after 5:00 AM, times when people are usually awake and outdoors. Only two specimens were positive for P. falciparum, one An. aconitus from Phongsaly and one An. minimus from Vientiane Province CONCLUSIONS: The results indicate that people living in rural areas in Laos are constantly exposed to malaria vectors throughout the year and specifically outdoors. The use of LLINs/IRS remains important but innovative tools and new strategies are needed to address locally, the early and outdoor malaria transmission. Lack of expertise in general entomological methods may further exacerbate the situation.

Circulating microRNAs in malaria infection: bench to bedside.

Severe malaria has a poor prognosis with a morbidity rate of 80% in tropical areas. The early parasite detection is one of the effective means to prevent severe malaria of which specific treatment strategies are limited. Many clinical characteristics and laboratory testings have been used for the early diagnosis and prediction of severe disease. However, a few of these factors could be applied to clinical practice. MicroRNAs (miRNAs) were demonstrated as useful biomarkers in many diseases such as malignant diseases and cardiovascular diseases. Recently it was found that plasma miR-451 and miR-16 were downregulated in malaria infection at parasitic stages or with multi-organ failure involvement. MiR-125b, -27a, -23a, -150, 17-92 and -24 are deregulated in malaria patients with multiple organ failures. Here, the current findings of miRNAs were reviewed in relation to clinical severity of malaria infection and emphasized that miRNAs are potential biomarkers for severe malaria infection.

Non-random distribution of Plasmodium Species infections and associated clinical features in children in the lake Victoria region, Kenya, 2012-2018.

BACKGROUND: While Plasmodium falciparum (Pf) stands out as the most lethal malaria parasite species in humans, the impact of other species should not be dismissed. Moreover, there is a notable lack of understanding of mixed-species infections and their clinical implications. METHODS: We conducted eight school-based cross-sectional malariometric surveys in the Lake Victoria region of western Kenya between January-February 2012 and September-October 2018. In each survey, a minimum of 100 children aged 3 to 15 years were randomly chosen from a school in Ungoye village on the mainland and as well as from each school selected in every catchment area on Mfangano island. Plasmodium infection was determined by microscopy and nested polymerase chain reaction (PCR). The multiple-kind lottery (MKL) model calculated the expected distribution of Plasmodium infections in the population and compared it to observed values using a chi-squared test (χ2). RESULTS: The Plasmodium prevalence was 25.9% (2521/9724) by microscopy and 51.1% (4969/9724) by PCR. Among all infections detected by PCR, Pf, P. malariae (Pm), and P. ovale (Po) mono-infections were 58.6%, 3.1%, and 1.8%, respectively. Pf/Pm, Pf/Po, Pm/Po, and Pf/Pm/Po co-infections were 23.5%, 4.3%, 0.1%, and 8.6%, respectively. MKL modelling revealed non-random distributions, with frequencies of Pf/Pm and Pf/Pm/Po co-infections being significantly higher than expected (χ2 = 3385.60, p < 0.001). Pf co-infections with Pm and Po were associated with a decreased risk of fever (aOR 0.64, 95% CI 0.46-0.83; p = 0.01) and increased risks of splenomegaly (aOR 12.79, 95% CI 9.69-16.9; p < 0.001) and anaemia (aOR 2.57, 95% CI 2.09-3.15; p < 0.001), compared to single-species infections. CONCLUSION: This study sheds light on the potential interaction between Pf and Pm and/or Po. Given the clinical significance of mixed-species infections, improved diagnostics, and case management of Pm and Po are urgently needed.

Imported malaria in pregnancy in Europe: A systematic review of the literature of the last 25 years.

BACKGROUND: Malaria during pregnancy is associated with a greater risk of complications for the mother and fetus. The aim of the study is to analyze the features of imported cases of malaria in pregnant women in Europe and evaluate which factors are associated with a non-favourable outcome. METHODS: A computerized search of the literature was performed combining the terms plasmod*, malaria, pregnan*, maternal, gravid, parturient, expectant, and congenital, from January 1997 to July 2023. RESULTS: 28 articles reporting 57 cases of malaria in pregnant women immigrant in non-endemic areas were included. The patients mainly came from Sub-Saharan Africa. There were 10 asymptomatic cases, while the predominant clinical syndrome among the symptomatic women was fever associated with anaemia. The median latency period from permanence in endemic areas and diagnosis in European countries was 180 days (IQR 15-730). Pregnancy outcomes were favourable in 35 cases (61 %): all term pregnancies, no low-birth-weight newborns. There were 4 abortions; 1 child was delivered pre-term; 7 babies were reported to have a low birth weight; 10 cases of congenital malaria were documented. P. falciparum was found with a higher frequency in women with a favourable outcome, while P. vivax was, in all cases, associated with a worse prognosis. CONCLUSIONS: Diagnosis of malaria in pregnant woman in non-endemic countries may be challenging and a delay in diagnosis may lead to an adverse outcome. Screening for malaria should be performed in pregnant women from endemic areas, especially if they present anaemia or fever.

Knowledge, attitude, and adherence to malaria control guidelines and the prevalence of Plasmodium species infection in localities across transmission and ecological zones in Cameroon.

Background: Despite a scale up of control interventions over the years, malaria remains a major public health and economic concern in Cameroon, contributing considerably to hospitalization and deaths. The effectiveness of control strategies depends on the extent of adherence by the population to national guidelines. This study assessed the influence of human knowledge, attitudes, and practices related to malaria and its control on the prevalence of malaria parasite infection, with implications for the elimination of the disease. Methodology: This is a cross-sectional community and hospital-based study, covering the five ecological and three malaria transmission zones in Cameroon. A pre-tested semi-structured questionnaire was used to document socio-demographic and clinical parameters as well as knowledge, attitudes, and practices toward malaria control and management. Consenting participants were screened for malaria parasite with rapid diagnostic test (mRDT) of the peripheral blood. Association between qualitative variables was determined using the chi-square test and logistic regression analysis. Results: A total of 3,360 participants were enrolled, 45.0% (1,513) of whom were mRDT positive, with 14.0% (451/3,216) and 29.6% (951/3,216) having asymptomatic parasitaemia and malaria, respectively. Although most participants knew the cause, symptoms, and control strategies, with 53.6% (1,000/1,867) expertly knowledgeable about malaria overall, only 0.1% (2/1,763) individuals were fully adherent to malaria control measures. Conclusion: The risk of malaria in Cameroon remains high, with the population considerably knowledgeable about the disease but poorly adherent to national malaria control guidelines. Concerted and more effective strategies aimed at improving knowledge about malaria and adherences to control interventions are necessary to ultimately eliminate the disease.

Asymptomatic Malaria During Pregnancy: Prevalence, Influence on Anemia and Associated Factors in West Guji Zone, Ethiopia - A Community-Based Study.

Background: Pregnant women with asymptomatic malaria parasitemia are at increased risk of anaemia, stillbirth, miscarriage, and preterm delivery. The asymptomatic nature of the population makes diagnosis difficult, and there is generally a lack of urgency to address this specific outcome. Objective: This study aimed to determine the prevalence of asymptomatic malaria and associated factors among pregnant women in West Guji Zone, Oromia, Ethiopia. Methods: A community-based cross-sectional study was conducted among randomly selected 557 asymptomatic pregnant women in the West Guji Zone from February to March 2022. A standardized questionnaire was used to collect information on socio-demographic and obstetric characteristics. Approximately 2 milliliters of peripheral blood was collected for microscopy to identify species and parasite density. Epi-Data and SPSS were used for data entry and analysis respectively. Binary logistic regression was used to identify risk factors. Results: The prevalence of malaria among asymptomatic pregnant women was 24.10% (95% CI: 20.55%-27.65%). The prevalence of Plasmodium vivax and falciparum prevalence was 73 (54.5%) and 61 (45.5%), respectively. Of the study subjects, 105 (78.4%) had mild parasitemia and 29 (21.6%) had moderate parasitemia. Pregnant women with Plasmodium infection were anaemic in two-thirds (66.5%) of cases. Living near standing water (AOR=2.6, 95% CI: 1.74-3.96), having a history of Plasmodium species infection (AOR=2.12, 95% CI: 1.36-3.31), not using indoor residual spraying (AOR=2.0, 95% CI: 1.32-3.14), and not using insecticide-treated bed nets (AOR=1.62, 95% CI: 1.02-2.55) were all factors that were significantly associated with asymptomatic infection. Pregnant women with Plasmodium infection had a significantly higher rate of anaemia than those who were not infected (OR = 6.31, p = 0.000). Conclusion: Pregnant women had a significant prevalence of asymptomatic Plasmodium infection. Regular screening, appropriate treatment for those who test positive, and health education for pregnant women should be provided by the West Guji Zone Health Bureau.

Limited association between Wolbachia and Plasmodium falciparum infections in natural populations of the major malaria mosquito Anopheles moucheti.

Since the discovery of natural malaria vector populations infected by the endosymbiont bacterium Wolbachia, a renewed interest has arisen for using this bacterium as an alternative for malaria control. Among naturally infected mosquitoes, Anopheles moucheti, a major malaria mosquito in Central Africa, exhibits one of the highest prevalences of Wolbachia infection. To better understand whether this maternally inherited bacterium could be used for malaria control, we investigated Wolbachia influence in An. moucheti populations naturally infected by the malaria parasite Plasmodium falciparum. To this end, we collected mosquitoes in a village from Cameroon, Central Africa, where this mosquito is the main malaria vector. We found that the prevalence of Wolbachia bacterium was almost fixed in the studied mosquito population, and was higher than previously recorded. We also quantified Wolbachia in whole mosquitoes and dissected abdomens, confirming that the bacterium is also elsewhere than in the abdomen, but at lower density. Finally, we analyzed the association of Wolbachia presence and density on P. falciparum infection. Wolbachia density was slightly higher in mosquitoes infected with the malaria parasite than in uninfected mosquitoes. However, we observed no correlation between the P. falciparum and Wolbachia densities. In conclusion, our study indicates that naturally occurring Wolbachia infection is not associated to P. falciparum development within An. moucheti mosquitoes.