Malaria Journal最新文献

Background: Malaria, caused by parasites of the Plasmodium genus and transmitted by Anopheles mosquitoes, remains a global public health issue, with a high incidence in tropical and subtropical regions. Although Plasmodium falciparum is the main cause of severe cases, Plasmodium vivax can also lead to serious complications, including cerebral malaria.

Case presentation: This case report presents the case of a 43-year-old woman from the southwestern Pacific coast, Colombia, who developed severe neurological symptoms with an initially unclear diagnosis. A thick blood smear confirmed P. vivax infection. She was treated with intravenous artesunate and subsequently with chloroquine and primaquine, and she achieved a full recovery.

Conclusions: Cerebral malaria has traditionally been associated with P. falciparum, P. vivax can also cause it through mechanical and inflammatory mechanisms, with a complex pathophysiology and potentially fatal outcomes. Early treatment with parenteral artesunate and intensive supportive care is key to improving outcomes.

Background: Recent reports documented catastrophic sensitivity failures (18%) of Abbott-Bioline™ Malaria Ag Pf/Pv rapid diagnostic tests (RDTs) at the Thailand-Myanmar border, prompting WHO to issue an information notice on quality concerns. We evaluated the same RDT lots under controlled laboratory conditions and in a high-transmission field setting in Madagascar to assess whether performance varied across epidemiological contexts.

Methods: Laboratory evaluation tested four Abbott-Bioline™ Malaria Ag Pf/Pv lots (05DDI018BH, 05DDI020BA, 05DDI041AB, 05DDI040AA) using serial dilutions of cultured Plasmodium falciparum (0-60,784 parasites/µL). Field evaluation enrolled 218 consecutive febrile patients at Ranomafana health centre, southeastern Madagascar. Performance of both RDTs (Abbott-Bioline™ Malaria Ag Pf/Pv and Parascreen® Malaria Ag Pf/Pan) was assessed against microscopy and real-time PCR as reference standards.

Results: In laboratory testing, substantial inter-lot variability was observed, with detection failures occurring between 97 and 373 parasites/µL. Incomplete blood migration and faint test lines were noted at lower densities. In the field, malaria prevalence was 70.2% by PCR and 48.6% by microscopy. Against microscopy, Abbott-Bioline™ Malaria Ag Pf/Pv achieved sensitivity of 99.1% (95% CI 94.9-100) and specificity of 93.7% (95% CI 87.4-97.4). Parascreen® Malaria Ag Pf/Pan showed sensitivity of 100% (95% CI 96.6-100) and specificity of 92.8% (95% CI 86.3-96.8). Against PCR, sensitivity decreased to 73.2% for Abbott-Bioline™ Malaria Ag Pf/Pv and 74.5% for Parascreen® Malaria Ag Pf/Pan, while specificity remained 98.5% for both tests. No significant difference was observed between RDTs (p > 0.05).

Conclusions: Despite using identical lots that showed 18% sensitivity at the Thailand-Myanmar border, Abbott-Bioline™ Malaria Ag Pf/Pv RDTs achieved 99.1% sensitivity in Madagascar. This difference likely reflects higher parasite densities in the Malagasy high-transmission setting (geometric mean 10,006 parasites/µL) compared to low-transmission elimination contexts. Both RDTs met WHO performance thresholds against microscopy but missed approximately 25% of PCR-positive infections. These findings demonstrate that RDT performance is highly context-dependent and underscore the need for enhanced post-deployment surveillance.

Background: Delays in seeking appropriate treatment for malaria in children under five remain a major contributor to poor outcomes in sub-Saharan Africa, where multiple socioeconomic, geographic, and health-system factors influence when care is accessed. This review synthesised current evidence on the prevalence and determinants of delayed malaria care-seeking, as well as the associated outcomes among children under five in sub-Saharan Africa.

Methods: This systematic review followed the guidelines by the Joanna Briggs Institute (JBI). This review was reported in accordance with following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA).

Result: The prevalence of delayed malaria care-seeking among children under five ranges from 2% to 95.8%. Factors associated with these delays include financial constraints, long travel distances, reliance on traditional treatments, and the perception of malaria as a mild illness. Additionally, health workers' attitudes and shortages of essential health facility logistics further hinder timely care-seeking by caregivers. These delays are associated with increased mortality, progression to severe malaria, and serious neurological and haematological complications.

Conclusion: Timely access to effective malaria treatment for young children can be enhanced by interventions that address financial barriers, improve access to care, and strengthen health-system readiness to respond promptly.

Background: Malaria remains a major cause of morbidity and mortality in Angola, where Plasmodium falciparum accounts for most infections. The widespread use of artemether-lumefantrine (AL) as first-line treatment and sulfadoxine-pyrimethamine (SP) for intermittent preventive treatment in pregnancy (IPTp) exerts selective pressure on local parasite populations. Molecular surveillance of drug resistance markers is essential to monitor susceptibility and anticipate changes that may influence treatment and prevention strategies. This study analyzed pfk13, pfmdr1, pfdhfr, and pfdhps polymorphisms in P. falciparum isolates from Cubal, Benguela province, to assess parasite genetic evolution under AL and SP pressure.

Methods: A cross-sectional study was conducted between 2022 and 2023 at Hospital Nossa Senhora da Paz (Cubal). A total of 139 real-time PCR-confirmed P. falciparum infections were included. Dried blood spot samples underwent sequencing of the genes involved in resistance. Mutation and haplotype frequencies associated with antimalarial resistance were determined.

Results: Among 120 pfk13 sequences, mutations were detected in 12 isolates (10%), including five nonsynonymous variants, but none corresponded to validated or candidate markers of artemisinin resistance. In pfmdr1 (100 sequences), Y184F was the most prevalent mutation (43%), N86Y was rare (1%), and D1246Y was not detected. Seven additional pfmdr1 variants were identified. Of the 101 isolates correctly sequenced for pfdhfr/pfdhps, 77.2% carried the triple pfdhfr N51I/C59R/S108N mutation. In pfdhps, A437G was nearly fixed (98%), K540E showed moderate prevalence (23.8%), and A581G was absent. The most common pfdhps haplotypes were ISGKAA (64.4%) and ISGEAA (22.8%). Combined pfdhfr/pfdhps profiles classified 58.4% of isolates as "partially resistant" (IRNG) and 17.8% as "fully resistant" (IRNGE), with no "super-resistant" haplotypes. Additional single mutations not associated with SP resistance were also detected.

Conclusions: This study provides an updated molecular profile of antimalarial resistance in a rural area of Angola. No validated or candidate pfk13 markers of artemisinin resistance were identified. However, the predominance of pfmdr1 haplotypes linked to reduced lumefantrine susceptibility raises concerns regarding AL efficacy. Although SP remains suitable for IPTp, the presence of the "fully resistant" haplotype (IRNGE) of pfdhfr/pfdhps highlight potential risks to long-term effectiveness. These findings reinforce the need for integrated molecular surveillance and periodic therapeutic efficacy studies to guide malaria control policies in rural Angola.

Background: The Plasmodium falciparum phenotypic characteristics (cytoadherence and rosetting), and the concentration of Histidine Rich Protein 2 (HRP2) in serum are associated with severe malaria in regions like Africa and Asia. Also, HRP2 has recently been associated as a P. falciparum virulence factor. Parasites lacking pfhrp2 gene were first reported in the Peruvian Amazon, however, there are not yet reports of the study of their phenotypes. For this research we decided to characterize the phenotype and genotype of P. falciparum field isolates from the Peruvian Amazon with different pfhrp2 patterns (positive or negative) cultivated in vitro.

Methods: P. falciparum field isolates (n = 5) from the Peruvian Amazon region were isolated and cultured in vitro. Three isolates had a positive result or pfhrp2 positive pattern and two of them were negatives (pfhrp2 negative pattern) by HRP2 Rapid diagnostic test. Then, these results were confirmed by conventional PCR. The following phenotypic characterization assays were tested: (i) Cytoadherence capacity (evaluated against Chondroitin Sulfate A (CSA) protein and Human umbilical vein endothelial cells (HUVEC cells)), and (ii) rosetting formation. Genotypic characterization assays were carried out by PCR (gene detection) and qPCR assays for pfhrp2 and pfhrp3 gene expression. Additionally, we evaluate the pfhrp2/3 genes and flanking genes stability using long-term cultures of these field isolates during a year.

Results: Two of the three isolates with pfhrp2 positive pattern showed rosetting formation (R + , CS-, Hu-) and cytoadherence to CSA protein (R-, CS + , Hu-), on the other hand the two field isolates with pfhrp2 negative pattern showed adhesion to HUVEC cells (R-, CS-, Hu +). 3D7 strain was used for normalization during qPCR assays. We identified that pfhrp2 gene expression levels were higher in the field isolates with pfhrp2 positive pattern, while pfhrp3 gene expression levels were similar or lower. All cultured field isolates showed genomic stability of pfhrp2 gene and flanking genes during the long-term in vitro culture. However, one field isolate showed two pfhrp3 patterns during the culture due to the presence of two parasite genotypes populations, as corroborated by microsatellite markers.

Conclusions: P. falciparum Peruvian field isolates with pfhrp2 positive pattern showed cytoadherence to Chondroitin sulfate A protein (R-, CS + , Hu-) or positive characteristics for rosetting (R + , CS-, Hu-); pfhrp2 negative parasites showed cytoadherence to HUVEC cells (R-, CS-, Hu +). In this small set of Peruvian field isolates, a clear cytoadherence and resolution profile was observed for the different pfhrp2 patterns. These findings should be interpreted as preliminary and require further verification in larger isolated panels.

Background: Malaria is a public health problem in Sudan, with more than 89% of cases caused by Plasmodium falciparum. In 2024 Sudan introduced R21/Matrix-M malaria vaccine in two states through routine immunization system. This study aimed to determine and identify the factors affecting the utilization of the vaccine.

Methods: A cross-sectional mixed -methods study was conducted in Gedarif and Blue Nile States of Sudan. Quantitative data were collected through pre-tested, pre-coded, structured questionnaire from samples of mothers or caregivers of children under the age of five. Additionally, Focus Group Discussions (FGDs) with school teachers and in-depth interviews with key Informants (KIIs) were conducted. Quantitative data were analyzed using SPSS, where univariate and multivariate analyses were performed. Qualitative thematic analysis was undertaken to identify barriers and drivers for each target group's behavior related to the malaria vaccine.

Results: A total of 416 mothers or caregivers (with a 99.0% response rate) who had children under the age of five were interviewed. The median age was 27.0 years. Of 256 children eligible for the malaria vaccine, only 36.7%, 95% CI 31.1-42.8% or 94 received it, with no difference between states or residence. Attitudes towards vaccination were generally positive. Perceptions of malaria and awareness of the vaccine were low: 53.1% of mothers perceive malaria as not a significant health problem; 57.7% were aware of the malaria vaccine; 36.7% knew the number of required doses; 25.7% knew the recommended starting dose age. FGDs and KIIs highlighted vaccine stockouts and geographic access as additional barriers, indicating the importance of sustaining supply chains.

Conclusions and recommendations: The suboptimal uptake of the malaria vaccine was not attributed to vaccine hesitancy or behavioral and social determinants, but rather to limited educational efforts and a lack of focus on the malaria vaccine as a new intervention. Reviewing the communication strategy and addressing health system barriers might help achieve the vaccine targets set by the Ministry of Health. Furthermore, assessing vaccine acceptability and identifying the enabling and inhibiting factors for vaccination before introducing the malaria vaccine in addition to engagement of higher authorities will lead to better vaccine uptake. Further research to test the effectiveness of culturally tailored communication interventions and the use of reminders or small incentives to raise the uptake is highly needed.

Background: Malaria and dengue are tropical endemic infections that can cause severe vascular and neurologic complications. Coinfection with Plasmodium vivax and dengue virus is uncommon but increasingly reported in co-endemic areas, complicating diagnosis and suggesting possible pathogenic synergy. Although each pathogen has been linked to stroke, cerebrovascular events during coinfection are exceptionally rare.

Case presentation: We describe a 23-year-old Colombian woman, who recently returned from Chocó, and developed acute right-leg monoparesis after 7 days of fever. Exam: hypotension and jaundice. Labs confirmed P. vivax malaria (8200 parasites/μL) and acute dengue (NS1 antigen positive; IgM-positive/IgG-negative). MRI revealed an acute left ACA infarct. There are no traditional stroke risk factors. She received artesunate-primaquine, supportive dengue care, and aspirin after her thrombocytopenia resolved; her neurologic function improved with rehabilitation.

Conclusions: This case highlights the potential of P. vivax-dengue coinfection to cause ischemic stroke through synergistic endothelial injury. Early recognition, targeted treatment, and coinfection screening are essential in endemic areas, especially during vector expansion.

Background: Climate change threatens maternal, and newborn health, particularly by exacerbating climate-sensitive diseases like malaria. Malaria in pregnancy (MiP) contributes to maternal anaemia, stillbirth, preterm delivery, and low birth weight. In Kenya's Lake Victoria basin, recurrent floods and droughts disrupt antenatal care (ANC), the main delivery platform for intermittent preventive treatment of MiP with sulfadoxine-pyrimethamine (IPTp-SP). The extent to which these extreme weather events affect IPTp-SP uptake through ANC attendance remains unexplored.

Methods: Data are drawn from a cross-sectional household survey conducted under the revive IPTp-SP project among women who had given birth to a live baby in the last 24 months preceding the interview in malaria-endemic counties of Kisumu and Migori. Exposure was self-reported extreme weather events in the past 12 months; the outcome was completion of three or more IPTp-SP doses (IPTp₃ +); and the mediator was attendance of ≥ 4 ANC visits (ANC4⁺). Using a counterfactual mediation framework, we decomposed the total effect of climate shock on IPTp₃ + into natural direct and indirect effects via ANC4⁺, adjusting for covariates. Models accounted for the complex survey design, with bootstrapping to estimate 95% confidence intervals (CI) for indirect effects.

Results: IPTp₃ + coverage was lower among shock-exposed pregnancies (49.5%) versus unexposed (58.8%). Extreme weather events were associated with reduction in ANC4⁺ attendance (- 0.23, 95% CI - 0.41 to - 0.05). ANC4⁺ completion strongly predicted IPTp₃ + uptake (1.71, 95% CI 1.42-2.00). The total effect of shocks on IPTp₃ + was -0.45 (95% CI - 0.68 to - 0.23), of which 76.6% was mediated through ANC. After adjustment, the total effect attenuated (-0.27, 95% CI - 0.56 to 0.02) and was no longer significant. Effects were stronger in flood-prone Kisumu than in Migori.

Conclusions: Extreme weather events reduced IPTp₃ + uptake primarily through ANC disruption in unadjusted models, with effects concentrated in Kisumu. However, these associations attenuated after adjustment, suggesting the role of underlying socioeconomic and contextual vulnerabilities.

Background: The recommendation of the RTS,S/AS01 malaria vaccine for use in children in moderate to high transmission areas by the WHO in 2021 provided another crucial tool in reducing malaria morbidity and mortality. As countries introduce the RTS,S/AS01 vaccine, there is an interest in exploring vaccination schedules that align with existing routine health touchpoints and to optimize vaccine coverage.

Methods: This study used OpenMalaria, an individual-based, stochastic model of malaria transmission and disease progression, to assess the impact of different vaccination timing schedules and coverage on uncomplicated malaria cases, severe malaria cases, and malaria-related deaths across different archetypal transmission settings. We ran simulations comparing fourth dose protection against infection and timings at 6-, 9-, 12-, 15- and 18-month intervals following the primary series, including exploring ranges of plausible protection assumptions for many of the dose timings.

Results: The primary series substantially reduces the malaria burden across transmission settings, regardless of timing of the fourth vaccine dose. For example, at a baseline Plasmodium falciparum prevalence in 2-10 year olds (PfPR_2-10) of 20%, our modeling suggests that the primary series is responsible for around 73-93% of the total uncomplicated and 74%-92% of severe cases averted regardless of fourth dose timing in perennial settings. Additionally, a fourth dose of the vaccine in this transmission setting could avert additional 8-38% of uncomplicated and 9-36% of severe malaria cases in addition to the primary series alone. While the number of cases averted varies by baseline prevalence, we find potential flexibility in timing this dose, especially when focused on 6 to 12 months following the primary series.

Conclusions: A fourth dose delivered between 15- and 21-months of age (corresponding to a 6-12 month interval after the third dose) with high population coverage will likely avert the largest proportion of cases of uncomplicated malaria, severe malaria, and deaths in perennial settings, across transmission intensities. Therefore, the delivery of the fourth dose of the RTS,S/AS01 vaccine can be tailored to country-specific context and linked to existing health touchpoints to ensure adequate coverage of this dose to optimize its impact.