Malaria Journal最新文献

Background: Restricting the placement of active ingredients (AIs) to specific panels on insecticide-treated nets (ITNs) has the potential to reduce the amount of AI required to treat a net. If the restricted placement of the AIs can exploit mosquito behaviour, particularly where they interact with the bed net interface, and not impact the net's effectiveness, then the reduction in AI could result in cost reductions.

Methods: Nine individual experimental hut trials were conducted to compare the efficacy of three different partially-treated net relative to fully treated nets; roof-only treated nets, side-only treated nets, and nets with treated roof and pyrethroid-only side panels. These trials were conducted on a range of net products with different AIs, across a range of geographies in Africa (East and West), vector species (Anopheles gambiae, Anopheles coluzzii, Anopheles arabiensis, and Anopheles funestus), hut designs (East and West African style) and hosts (cows and humans). The combined data from these trials were analysed in a meta-analysis, and odds ratios for the effect of the different net designs on mortality and blood-feeding were estimated using mixed effects logistic regression.

Results: The results of this meta-analysis demonstrated that fully treated nets provide greater mosquito killing and reduction in blood-feeding effects than any configuration of insecticide treatment restricted to specific panels.

Conclusions: This meta-analysis showed that partially-treated net that restrict the insecticide treatment to specific panels of an ITN do not give equivalency or superiority in either mortality or blood-feeding inhibition to fully treated nets. The implications of these findings are discussed.

Background: Malaria burden remains high in some Peruvian regions, especially in the Northeast Amazon rainforest state of Loreto and the tropical coastal state of Tumbes. Novel non-invasive diagnostic tools for malaria are being developed, and formative research in malaria-endemic areas with community members and health professionals who would potentially use these devices is vital for this process. This study aimed to examine the acceptability and feasibility of four new non-invasive malaria diagnostic tools in development in two regions of Peru with significant malaria burden.

Methods: The research team conducted focus group discussions and key informant interviews in Spanish to assess acceptability and ascertain questions and concerns regarding the non-invasive diagnostic tools. Focus group discussions included a range of community members (pregnant women, parents), professionals (health, education), and community leaders in Loreto. Vector control authorities and health professionals from Loreto, Tumbes, and Lima participated as key informants.

Results: Participants were initially enthusiastic about all non-invasive diagnostic tools. However, as discussions proceeded, high enthusiasm remained for two devices that were easy to use, acceptable for the communities they were intended for, feasible to carry in remote areas, and did not require new supplies nor generate waste: the skin scan and the skin odour test. The breath and saliva tests were considered less hygienic. They were less acceptable to community members and health professionals due to concerns of disease transmission and other environmental and cultural concerns. Health professionals felt the finger scan test and the skin odour test would help triage community members in endemic sites and would be valuable in remote regions with difficult access to health facilities or laboratories.

Conclusions: Novel non-invasive malaria diagnostic tools can be valuable in malaria-endemic settings. As manufacturers evaluate the efficacy and effectiveness of these non-invasive diagnostic tools, international recommendations should be created to ensure their agile integration into national malaria programmes.

Controlled human malaria infection (CHMI) involves the intentional infection of healthy individuals with malaria parasites, close observation of the volunteers, and clearance of the parasite at a predetermined endpoint. Depending on the need, CHMI can be initiated by either sporozoites or the administration of parasite-infected erythrocytes, with each of the two systems offering different advantages and caveats. Among other uses, CHMI has proven to be a useful tool for the evaluation of new malaria interventions, particularly vaccines and drugs. The majority of CHMI studies have been conducted in Europe, the USA and Australia, with only a handful of studies conducted in malaria-endemic countries. The slow adoption of CHMI in malaria-endemic countries may be attributed to a lack of infrastructure and expertise to conduct studies in malaria-endemic countries and the risk of undue influence and coercion as a result of volunteers' vulnerability due to a lack of education and financial situation. With the need to generate results relevant to the target populations, there has recently been an increase in CHMI studies that are being conducted in malaria-endemic countries. The use of CHMI models for the evaluation of preerythrocytic and blood-stage malaria interventions has been attempted in malaria-endemic countries with great success. There is a need for the adoption of a CHMI model for the evaluation of transmission-blocking interventions in malaria-endemic countries. The establishment of such a model in malaria-endemic countries will facilitate the selection of potential transmission-blocking intervention (TBI) candidates and accelerate their development. Here is an overview of CHMI, key challenges and ethical considerations in adopting CHMI for the evaluation of malaria transmission-blocking interventions in malaria-endemic countries.

Background: The increasing availability of electronic health system data and remotely-sensed environmental variables has led to the emergence of statistical models capable of producing malaria forecasts. Many of these models have been operationalized into malaria early warning systems (MEWSs), which provide predictions of malaria dynamics several months in advance at national and regional levels. However, MEWSs rarely produce predictions at the village-level, the operational scale of community health systems and the first point of contact for the majority of rural populations in malaria-endemic countries.

Methods: This study developed a hyper-local MEWS for use within a health-system strengthening intervention in rural Madagascar. It combined bias-corrected, village-level case notification data with remotely sensed environmental variables at spatial scales as fine as a 10 m resolution. A spatio-temporal hierarchical generalized linear regression model was trained on monthly malaria case data from 195 communities from 2017 to 2020 and evaluated via cross-validation. The model was then integrated into an automated workflow with environmental data updated monthly to create a continuously updating MEWS capable of predicting malaria cases up to three months in advance at the village-level. Predictions were transformed into indicators relevant to health system actors by estimating the quantities of medical supplies required at each health clinic and the number of cases remaining untreated at the community level.

Results: The statistical model was able to accurately reproduce village-level case data, performing nearly five times as well as a null model during cross-validation. The dynamic environmental variables, particularly those associated with standing water and rice field dynamics, were strongly associated with malaria incidence, allowing the model to accurately predict future incidence rates. The MEWS represented an improvement of over 50% compared to existing stock order quantification methods when applied retrospectively.

Conclusion: This study demonstrates the feasibility of developing an automatic, hyper-local MEWS leveraging remotely-sensed environmental data at fine spatial scales. As health system data become increasingly digitized, this method can be easily applied to other regions and be updated with near real-time health data to further increase performance.

Background: The availability of many tools for malaria control leads to complex decisions regarding the most cost-effective intervention package based on local epidemiology. Mosquito characteristics influence the impact of vector control, but entomological surveillance is often limited due to a lack of resources in national malaria programmes.

Methods: This study quantified the monetary value of information provided by entomological data collection for programmatic decision-making using a mathematical model of Plasmodium falciparum transmission. The 3-year impact and cost of various intervention packages was simulated in different sub-Saharan African settings, including combinations of scaling-up insecticide-treated nets (ITN), switching to next-generation ITNs, and a treatment and prevention package. The DALYs averted and their net monetary benefit were compared at different cost-effectiveness thresholds and the value of resolving uncertainty in entomological model parameters was calculated.

Results: Across transmission settings and at cost-effectiveness thresholds over US$170 per DALY averted, the most cost-effective intervention package was switching to and scaling up pyrethroid-pyrrole ITNs combined with the treatment and prevention package. The median expected value of perfect information on the entomological indicators was US$0.05 (range 0.02-0.23) and US$0.17 (range 0.09-1.43) per person at risk at thresholds of US$75 and US$1000 per DALY averted, respectively. This represented less than 2% of the net monetary benefit of implementing the most cost-effective intervention package. Value of information estimates at cost-effectiveness thresholds over US$250 were higher than current investments into entomological monitoring by the US President's Malaria Initiative.

Conclusions: These results suggest that entomological data collection should not delay implementation of interventions with demonstrated efficacy in most settings, but that sustained investments into and use of entomological surveillance are nevertheless worthwhile and have broad value to national malaria programmes.

Background: The limited efficacy of the two recently approved malaria vaccines, RTS,S/AS01 and R21/Matrix- M™, highlights the need for alternative vaccine candidate genes. Plasmodium falciparum Reticulocyte Binding Protein Homologue 5 (Pfrh5) is a promising malaria vaccine candidate, given its limited polymorphism, its essential role in parasite survival, a lack of immune selection pressure and higher efficacy against multiple parasites strains. This study evaluated the genetic diversity of Pfrh5 gene among parasites from regions with varying malaria transmission intensities in Mainland Tanzania, to generate baseline data for this potential malaria vaccine candidate.

Methods: This study utilized secondary data of 697 whole-genome sequences which were generated by the MalariaGEN Community Network. The samples which were sequenced to generated the data were collected between 2010 and 2015 from five districts within five regions of Mainland Tanzania, with varying endemicities (Morogoro-urban district in Morogoro region, Muheza in Tanga, Kigoma-Ujiji in Kigoma, Muleba in Kagera, and Nachingwea district in Lindi region). Wright's fixation index (F_ST), Wright's inbreeding coefficient (Fws), Principal component analysis (PCA), nucleotide diversity (π), haplotype network, haplotype diversity (Hd), Tajima's D, and Linkage disequilibrium (LD) were used to assess the diversity of the gene.

Results: Of the sequences used in this study, 84.5% (n = 589/697) passed quality control and 313 (53.1%) were monoclonal (contained infections from a single strain of P. falciparum) and were used for haplotype diversity and haplotype network analysis. High within-host diversity (Fws < 0.95) was reported in Kigoma-Ujiji (60.7%), Morogoro-urban (53.1%), and Nachingwea (50.8%), while Muleba (53.9%) and Muheza (61.6%) had low within-host diversity (Fws ≥ 0.95). PCA did not show any population structure and the mean F_ST value was 0.015. Low nucleotide diversity values were observed across the study sites (mean π = 0.00056). A total of 27 haplotypes were observed among the 313 monoclonal samples and under-fives exhibited higher haplotype counts. The Pf3D7 was detected as Hap_1, which occurred in 16/313 (5.1%) monoclonal sequences. Negative Tajima's D values were observed among the parasite populations in all the study sites.

Conclusion: Low levels of polymorphism in the pfrh5 gene were observed based on low nucleotide and haplotype diversity, a lack of population structure and negative Tajima's D values. This study provides essential data on the diversity of the Pfrh5 gene indicating that it can be considered in the development of the next generation malaria vaccines. Robust and intensive studies of this and other candidate genes are crucial to support the prioritization of the Pfrh5 gene for potential inclusion in a broadly cross-protective malaria vaccine.

Background: The World Health Organization conditionally recommends reactive drug administration to reduce malaria transmission in settings approaching elimination. However, few studies have evaluated the impact of reactive focal drug administration (rFDA) in sub-Saharan Africa, and none have evaluated it under programmatic conditions. In 2016, Senegal's national malaria control programme introduced rFDA, the presumptive treatment of compound members of a person with confirmed malaria, and reactive mass focal drug administration (rMFDA), an expanded effort including neighbouring compounds during an outbreak, in 10 low transmission districts in the north of the country. This evaluation sought to measure the impact of rFDA and rMFDA on malaria incidence.

Methods: An interrupted time series analysis was conducted with routine surveillance data on health post-level monthly confirmed malaria case counts from the District Health Information Software (DHIS2). The study evaluated the change in incidence following rFDA and rMFDA rollout (level change), which ranged from August 2016 to November 2019, and monthly thereafter (trend change), using an adjusted negative binomial regression model with data from January 2015 through January 2020. The model was used to estimate the number of cases averted via a counterfactual simulation.

Results: No incidence rate reductions were estimated immediately following rollout (level change: incidence rate ratio (IRR) = 1.00, 95% credible interval (CI) = 0.76, 1.33). However, rFDA and rMFDA were associated with a 4% monthly decline in incidence relative to the baseline trend (trend change: IRR = 0.96, 95% CI = 0.95, 0.98). Over the study period, RFDA and rMFDA were estimated to avert 2,070 (95% CI = 577, 4,367) of 4,108 (95% CI = 2,620, 6,425) malaria cases.

Conclusions: RFDA and rMFDA were associated with reduced malaria incidence in northern Senegal, supporting their use in malaria control in very low transmission areas. However, additional strategies are likely needed to achieve elimination in this setting.

Background: The negative impact of COVID-19 pandemic on healthcare service utilization has been reported in several countries. In Gabon, data on the preparedness for future pandemic are lacking. The aim of the present study was to assess the trends of hospital attendance, malaria and self-medication prevalences as well as ITN use before and during Covid-19 first epidemic waves in a paediatric wards of a sentinel site for malaria surveillance, in Libreville, Gabon.

Methods: This was a retrospective descriptive and hospital-based survey which was conducted at the Regional Hospital of Melen Estuaire (RHME). Census of files of patients below 18 years of age attending for fever management with a result of malaria biological diagnosis from January 2018 to December 2022 was conducted. Comparison of the prevalence of microscopic malaria, ITN use, self-medication and the fever duration prior the screening before and after year 2020 was performed using bivariate and multivariate analysis.

Results: Overall, 14428 febrile participants were screened for malaria. A 15% increase in the number of febrile patients was observed between 2019 and 2020 while this rate was above 100% in 2021 and 2022. The frequency of self-medication significantly doubled in 2020 and 2021 compared to the pre-COVID-19 period (p < 0.01). Previous self-medication was more common during the COVID-19 period compared to the COVID-19 one (aOR = 2.15 [1.91-2.42]) (p < 0.01). Among the 7259 (51.2%) patients screened after 3 days of fever onset, self-anti-malarial treatment was reported for 17.5% of them in 2019 and for more than 30% of them from 2020: 33.3% in 2020, 35.0% in 2021 and 32.3% in 2022 (p < 0.01). The median of fever duration was significantly higher in the group of participants with a previous self-medication (p < 0.01). Positive blood smears frequency was higher in the COVID-19 period (35.6%; n = 3876/10868) compared to the pre-COVID-19 period (23.6%) (OR = 1.79[1.59-2.02], (p < 0.01).

Conclusion: Malaria prevalence and care-seeking behaviours for fever management in children significantly changed during the COVID-19 epidemic phase and subsequent years in the main malaria sentinel surveillance site of Gabon.

Background: Informal Healthcare Providers (IHCPs), including Proprietary Patent Medicine Vendors (PPMVs), drug peddlers, traditional healers, and herbal drug sellers are often the first choice for malaria treatment, especially in urban slums. Unplanned urbanization significantly impacts malaria transmission by creating cities with inadequate safety nets and healthcare access, increasing reliance on IHCPs. While the World Health Organization recognizes IHCP's crucial role and emphasizes integrating them into formal healthcare for improved malaria care, they lack requisite training in malaria management and operate outside official regulations, raising concerns about the quality of care they provide. Understanding IHCPs' perceptions and practices is essential for their proper integration. This study explored the perceived malaria burden, IHCPs' competence in malaria treatment, and reasons for visiting IHCPs in various urban settlements from both community member and provider perspectives.

Methods: This qualitative cross-sectional study was carried out in Ibadan and Kano metropolises. Eighteen Focus Group Discussions among 157 adult community members and twelve Key-Informant Interviews among PPMVs, drug peddlers, traditional healers and herbal drug sellers were conducted in these cities. Participants were drawn purposively from settlements-designated as formal, informal, and slum based on local definitions-in selected wards within the cities. Data were collected using pre-tested guides and analysed thematically.

Results: This study reveals that malaria remains a significant health problem in these Nigerian cities. Patronage of IHCPs generally is driven by affordable treatment, perceived mildness of illness, and access to credit facilities. However, cultural belief was key to patronage of traditional healers and herbal drug sellers, largely among informal and slum residents. Furthermore, while IHCPs had a strong perceived competence in managing malaria cases, inadequate diagnosis and treatment were standard practices.

Conclusions: IHCPs remain consistently patronized across urban settlements. IHCPs are continuously patronized in all urban settlement. Educating and equipping IHCPs with diagnostic tools, enhancing access to affordable healthcare, and raising public awareness is crucial for proper malaria management and promoting collaborations with formal healthcare providers.

Background: Malaria remains a leading cause of death worldwide, claiming over 600,000 lives each year. Over 90% of these deaths, mostly among children under 5 years, occur in sub-Saharan Africa and are caused by Plasmodium falciparum. The merozoites stage of the parasite, crucial for asexual development invade erythrocytes through ligand-receptor interactions. Erythrocyte binding antigen (EBA)-175 is one of the key ligands facilitating invasion via interaction with glycoprotein A (GpA) receptors on the erythrocytes. EBA-175 is known to exist in two dimorphic allelic (F and C) forms with each found to infer different virulence. There is paucity of data on the prevalence of these alleles and their epidemiology in the Ghanaian malaria landscape and hence this study.

Methods: Parasite gDNA was extracted from archived Dried Blood Spots (DBS) prepared from 700 confirmed malaria-infected individuals and analysed for P. falciparum EBA-175 dimorphism. Selective eba-175 gene amplification via nested PCR and allele scoring using agarose gel electrophoresis for F, C and F/C alleles.

Results: Of the total 632 successfully genotyped samples, prevalence of F, C, and F/C allelic forms were 61.2% (n = 387), 20.7% (n = 131), and 18.0% (n = 114), respectively. Seasonality analysis did not reveal a statistically significant difference in the prevalence of dimorphic forms between the wet (n = 475) and dry (n = 157) seasons (p = 0.051). The prevalence ratio (wet/dry) for C, F and F/C were determined to be 1.0, 1.1 and 1.4, respectively. Between 2019 and 2022, the prevalence of the alleles changed significantly (χ² = 6.5427, p = 0.03). Geometric mean parasite density for the C, F, and F/C alleles were 21,477.1 [95%CI 15,749.2 - 29,288.1], 18,308.0 [95%CI 15,149.9-22,124.5] and 22,690.4[95% CI 16,891.9-30,479.2], respectively.

Conclusion: The F-allele was the most prevalent form across all age groups, followed by the C allele and mixed F/C alleles. No significant difference in allele prevalence was observed between the high malaria season (wet) and low malaria season (dry). However, a statistically significant difference in the temporal prevalence of pure alleles (F & C) between two time points was observed. The current study adds to the existing body of knowledge on eba-175 allelic dimorphism and highlights the co-circulation of alleles in high malaria endemic areas in Ghana.