Malaria Journal最新文献

Background: The World Health Organization-approved Anopheles interventions target indoor biting and resting behaviour, but are impractical or inapplicable in some settings. In Jambi Province, Sumatra, Indonesia, local indigenous populations sleep under temporary tarpaulin-roofed shelters, complicating the use of bed nets and preventing the application of indoor residual spraying. Two pyrethroid-based interventions were tested alongside a no-intervention control in the field using a Latin-square design. A volatile pyrethroid spatial emanator (SE) offers an easily deployable, simple to use intervention utilizing transfluthrin, while deltamethrin-impregnated barrier screens represents a more permanent intervention.

Methods: Human landing collection was used for mosquito collections throughout the study. Collections occurred near Bukit Duabelas National Park in central Sumatra, Indonesia, an area characterized by secondary forest undergoing widespread conversion to palm and rubber plantations. Collections occurred in three sites located roughly 150 m from each other, with a Latin-square rotational design to account for location and collector effects between experimental replicates. Three complete rotations were achieved over 27 collection nights (a total of 81 trap-nights). Results were analysed with a series of generalized linear models to analyse overall efficacy and the influence of location and device age.

Results: Anopheles host-seeking activity was reduced in the presence of the SE (RR: 0.30 [0.21-0.43], p < 0.001) and barrier screen (RR: 0.39 [0.28-0.54], p < 0.001) interventions compared to control shelters over the course of the study. Similar efficacy was observed among non-Anopheles species. Hourly differences in behaviour were observed, and device age and location were both significant predictors of efficacy in univariate analyses, with efficacy appearing to decrease with device age. However, it was not possible to differentiate between the device age and location effects, since they were correlated due to an error in the rotational design.

Conclusions: Both interventions appeared to reduce Anopheles and non-Anopheles mosquito host-seeking behaviour, highlighting the potential of these forms of outdoor mosquito control. Considerable variation was observed between collection locations, highlighting a difficulty in study design and entomological forecasting. Due to the rotational design where the device age correlated with location, it was difficult to disentangle the relative contributions of these factors. Passive SEs and insecticide-impregnated barrier screens represent interventions that may reduce exposure and hence transmission outdoors.

Background: Malaria has been surging in India for the past 3 years after reaching the recorded low in 2021. Among the possible reasons for this unexpected surge of cases, such as insufficient surveillance, slow and aggregated data reporting, endemic pockets in the tribal, dense forest areas where control programmes are difficult to reach, the role of climate change due to global warming has gained less attention. Similar to the diverse climatic conditions that prevail in different regions of India, the malaria distribution is also highly variable. Therefore, the impact of the annual average of climatic factors on the annual parasite index (API) in hyper-, high-, moderate-, and low-endemic states was analysed.

Methods: The annual malaria data provided by the National Center for Vector Borne Diseases Control, and meteorological data provided by the India Meteorological Department, Pune, and Statista, were used to make temporal trend analysis, scatter plot analysis, clustered scatter plot analysis, and Spearman & Pearson correlation coefficient to determine the impact of climatic factors on the occurrence of malaria in hyper, high, moderate and low endemic States in India.

Results: While the increasing annual temperature and rainfall negatively influenced the annual parasite index in high, moderate, and low endemic states, both had no influence on API in malaria hyperendemic states. Although minimum and maximum annual rainfall was found to be detrimental to the increase of API in low and moderate endemic states, moderate annual rainfall of high and hyperendemic states was favourable for increasing API. The increasing annual relative humidity negatively influenced the API in high and moderate endemic states and had a positive influence on the API in low endemic states. The humidity did not have any influence over the API in the hyperendemic state. Statistical analysis showed that, except in Mizoram, the annual mean temperature negatively influenced the API in all other states. The annual rainfall and average humidity were shown to be negatively associated with API only in Odisha.

Conclusion: The present study revealed the relationships between annual climatic factors such as temperature, rainfall, and humidity with API in malaria hyper-, high-, moderate- and low endemic states in India.

Background: Malaria, a mosquito-borne disease, is a serious public health issue globally and a leading cause of morbidity and mortality in many developing countries worldwide. Cambodia is in the last stages of malaria elimination and aims to eliminate all species of human malaria by 2025. Despite tremendous progress, eliminating malaria in Cambodia has proven to be challenging due to pockets of residual transmission in high-risk populations sustained by untreated asymptomatic malaria reservoirs. Understanding the extent of asymptomatic malaria reservoirs in 'last-mile' communities such as those in Mondulkiri and Kampong Speu, is vital for an effective malaria elimination strategy.

Methods: Malaria cross-sectional surveys were conducted in high-risk populations (forest dwellers, forest goers and forest rangers) at three different time points (T0, T1, T2) from October 2022 to February 2023, overlapping the rainy, malaria transmission season and into the dry season. Blood samples (n = 6350) collected on filter paper from participants from all target groups were screened for Plasmodium species using qPCR.

Results: All qPCR-diagnosed cases were asymptomatic, indicating an untreated parasite reservoir. In Mondulkiri, the prevalence of Plasmodium falciparum was 0.63% at T0, increasing to 0.81% at T1, and decreasing to 0.18% at T2. Plasmodium vivax decreased from 4.80% at T0 to 1.97% at T1 and 1.65% at T2. In Kampong Speu, overall prevalence was 7.06% at T0, declining to 5.19% at T1 and 4.59% at T2. Plasmodium falciparum prevalence was 0.30% at T0, decreasing to 0.09% at T1 and rising slightly to 0.10% at T2. The forest goers showed a prevalence increase to 1.95% at T1 and decrease to 1.46% by T2, while forest dwellers decreased to 3.25% at T1 and further to 3.13% at T2. Passively reported malaria case showed that 1.09% of cases in Mondulkiri and 0.21% of cases in Kampong Speu were rapid diagnostic test (RDT) positive.

Conclusion: Evidence generated during this study point to the continued presence of an untreated asymptomatic reservoir in high-risk populations. Targeted epidemiological and/or vector-based intervention strategies tailored to specific risk groups may enable a reduction of this sustaining reservoir of parasites, thereby leading to eliminating malaria in Cambodia.

Background: Rapid diagnostic tests (RDTs) used to diagnose Plasmodium falciparum predominantly target the antigen Histidine Rich Protein 2 (HRP2) exclusively. With the emergence of hrp2/hrp3 gene deletions, RDTs targeting other antigens such as the essential enzyme Lactate Dehydrogenase (LDH) are needed. The dynamics of LDH relative to HRP2 are currently not well described but are needed to inform the use of next-generation (NG-) LDH and HRP2 RDTs that are designed to address hrp2/hrp3 gene deletions.

Methods: A longitudinal cohort study conducted in a low transmission setting in Namibia was leveraged to compare HRP2 and LDH decay rates. Passive and active case detection were used to recruit individuals with positive HRP2-RDT results. Study participants were treated and subsequently followed weekly until they received two consecutive HRP2-RDT negative results. Blood specimens were characterized for antigen concentration and parasite density. Antigen decay rates were calculated and used to estimate time to negativity (TTN) of NG-RDTs: two HRP2 and LDH-based RDTs (Rapigen Pf and a WHO prequalified Pf/Pv RDT) and an LDH-only RDT (Rapigen Pf/Pv).

Results: In 135 participants, the starting geometric mean concentrations for HRP2 and LDH were 899 ng/mL and 344 ng/mL respectively. Both antigens followed a biphasic decay rate, with a faster decay rate in the first phase. For current RDTs with an analytical sensitivity of 1 ng/mL for HRP2 and 5 ng/mL for LDH, TTN was 44 and 4 days, respectively. With a NG-RDT with LDH analytical sensitivity of 0.37 ng/mL, average TTN was 9 days. Multiple levels of analytical sensitivity were also modeled.

Conclusions: In the detection of P. falciparum malaria, LDH versus HRP2-based RDTs had a faster TTN due to a combination of lower accumulated antigen concentrations and faster decay rates, even for more sensitive LDH-based RDTs. Detection of LDH versus HRP2 by RDT is more likely to reflect a new or very recent infection. For NG-RDTs that target both antigens, HRP2 is likely to contribute more to the test signal than LDH in recently treated infections unless the infection has hrp2/hrp3 gene deletions. Antigen decay data combined with analytical sensitivity contributes to understanding RDT performance and interpretation.

Background: This work investigated the future (2021-2050) impact of Climate Change on Malaria Prevalence in the Upper River Region of The Gambia under two representative concentration pathways, RCP4.5 and RCP8.5, comparing it with the observed evaluation period of 2011-2022.

Methods: The observed climatic variable data used was obtained from the Department of Water Resources and the corresponding malaria cases from the archive of the primary Health database, Banjul, The Gambia. Projected monthly temperature, precipitation, and relative humidity were downloaded from the coordinated Regional downscaling experiment (CORDEX) stimulation of the Rossby Centre Regional Atmospheric regional climate (RCA4). The dataset spans the decades from 2021 to 2050, providing insight into future climatic and epidemiological trends. Gradient Boost Machine Learning algorithm was utilized for the malaria projection both in the population below 5 and above five years.

Results: The result revealed an increase in malaria incidence under RCP4.5 and RCP8.5 climatic scenarios for both age categories with a clear indication in the population above five years.

Discussion and conclusion: The result pictures how climate change will impact malaria under RCP4.5 and RCP8.5 emission scenarios in the region and also clearly reveals that the upper river region of the Gambia population is at risk of malaria infection, thus, a strategic and robust intervention scheme is highly solicited.

Background: Progress in malaria elimination has been hindered by recent changes in mosquito behaviour and increased insecticide resistance in response to traditional vector control measures, such as indoor residual spraying and long-lasting insecticidal nets. There is, therefore, increasing interest in the use of larval source management (LSM) to supplement current insecticide-based interventions. However, LSM implementation requires the characterization of larval habitats at fine spatial and temporal scales to ensure interventions are well-placed and well-timed. Remotely sensed optical imagery captured via drones or satellites offers one way to monitor larval habitats remotely, but its use at large spatio-temporal scales has important limitations.

Methods: A method using radar imagery is proposed to monitor flooding dynamics in individual rice fields, a primary larval habitat, over very large geographic areas relevant to national malaria control programmes aiming to implement LSM at scale. This is demonstrated for a 3971 km² malaria-endemic district in Madagascar with over 17,000 rice fields. Rice field mapping on OpenStreetMap was combined with Sentinel-1 satellite imagery (radar, 10 m) from 2016 to 2022 to train a classification model of radar backscatter to identify rice fields with vegetated and open water, resulting in a time-series of weekly flooding dynamics for thousands of rice fields.

Results: From these time-series, over a dozen indicators useful for LSM implementation, such as the timing and frequency of flooding seasons, were obtained for each rice field. These monitoring tools were integrated into an interactive GIS dashboard for operational use by vector control programmes, with results available at multiple scales (district, sub-district, rice field) relevant for different phases of LSM intervention (e.g. prioritization of sites, implementation, follow-up).

Conclusions: Scale-up of these methods could enable wider implementation of evidence-based LSM interventions and reduce malaria burdens in contexts where irrigated agriculture is a major transmission driver.

Background: Plasmodium falciparum is the main cause of malaria in North-Eastern (NE) states of India. Artemether-lumefantrine (AL) was introduced as first-line therapy against uncomplicated P. falciparum cases in 2013 after the emergence of resistance to sulfadoxine-pyrimethamine. The aim of the study was to assess the therapeutic efficacy of AL and status of molecular markers in the circulating parasites.

Methods: Therapeutic efficacy of AL was assessed in NE states as per World Health Organization guidelines. Patients with P. falciparum positive peripheral blood smear were enrolled and treated with AL and clinical and parasitological parameters were monitored over a 28-day follow-up period. Furthermore, the pfmdr1, pfdhfr, pfdhps and pfk13 genes were amplified and sequenced for mutation analysis.

Results: A total of 231 cases were enrolled and therapeutic efficacy was determined in 215 (93.1%) patients who completed their 28 days' follow-up while 10 patients withdrew and 6 were lost to follow up during study. Overall 99.5% and 98.6% of adequate clinical and parasitological response was observed with and without PCR correction, respectively. Only three cases (1.4%) of late parasitological failure were observed in Mizoram site. One case of recrudescence and two cases of reinfection were detected by msp1 and msp2 genotyping. Mutation analysis showed the 15.8%, 100%, 90.5% mutants in pfmdr1, pfdhfr and pfdhps gene respectively and three non-synonymous mutations were also found in pfk13gene.

Conclusions: This study reports that AL is efficacious against uncomplicated P. falciparum cases in NE states of India. However, prevalence of mutations in molecular marker associated with anti-malarial resistance (pfmdr1, pfdhfr, pfdhps and pfk13) gene indicate possible emergence of drug resistance. This is to underline the fact that the drug is efficacious for now, but rising mutations indicate that continuous monitoring is essential for effective treatment regime.

Background: Malaria elimination, defined as interrupting local transmission and reducing cases to zero, is a critical public health goal. While a dual parasite-vector approach is essential, the path to elimination is complex and marked by both progress and setbacks. Despite renewed commitment and initiatives like the "High Burden High Impact" approach, challenges persist, particularly in sub-Saharan Africa. These include shifting epidemiological profiles, weak health systems, drug and insecticide resistance, and emerging global issues. Effective elimination, therefore, requires a multi-pronged approach, scaling-up a package of interventions tailored to transmission intensity, including prompt treatment with ACT, IPTp for pregnant women, vector control measures like IRS and LLINs, and robust community engagement. Ultimately, a combination of contextually appropriate strategies, implemented synergistically, will be crucial to breaking the transmission cycle and achieving sustained malaria elimination. This report aims to review the available evidence on the strategies and deployment of current tools targeting vectors and parasites in resource-limited settings, focusing on sub-Saharan Africa.

Recent findings: Combining malaria interventions can create a synergistic effect, where the combined impact is greater than the sum of individual interventions. For example, simulations show benefits from combining MDA and IRS, vaccines and bed nets, or the RTS,S vaccine with perennial malaria chemotherapy. However, synergistic effects are not always guaranteed; some combinations, like LLINs and IRS, may not provide additional benefit. Conversely, combining IRS and MDA, or SMC with seasonal malaria vaccination, has demonstrated increased protective effects. Therefore, successful elimination efforts depend on country-specific factors including malaria burden, political commitment, and health system capacity. However, significant biological and operational challenges remain, which may necessitate contextually appropriate approaches to achieve malaria elimination.

Conclusion: Synergistic intervention effects are crucial, but implementation context is paramount. While combining malaria interventions can be highly effective, not all combinations yield equal results. Thus, tailoring strategies to the specific local context and transmission dynamics is essential for maximizing impact. Moreover, successful malaria elimination is heavily reliant robust health systems and understanding the biological and operational challenges. Consequently, adaptable, evidence-based strategies are required to overcome these obstacles and achieve lasting progress toward malaria elimination.

Background: To reduce malaria burden in Côte d'Ivoire, the Ministry of Health aims for 90% of its population to possess one long-lasting insecticidal net (LLIN) for every two persons by 2025. This study evaluated LLIN coverage two years after a mass distribution in central Côte d'Ivoire.

Methods: A census was conducted in 43 villages. Data were collected on household geo-position, composition, number of sleeping units and LLINs owned. LLIN coverage was assessed using: 1/ownership; proportion of household with at least one LLIN; 2/household access; households with sufficient nets for every two persons and for every sleeping unit; and 3/population access; proportion of population with access to LLIN within households and sleeping units.

Results: 10,630 households (89.6% response rate) and 46,619 inhabitants were recruited. Household LLIN ownership was 63.8% (95% CI: 58.7-68.8). Household LLIN access was 37.6% (95% CI: 33.2-42.0) based on 1 LLIN per 2 persons and 37.1% (95% CI: 33.0-41.2) based on 1 net per sleeping unit. Population LLIN access based on 1 LLIN per 2 persons and 1 net per sleeping space was 53.3% (95% CI: 48.6-58.1) and 49.4% (95% CI: 45.1-53.6), respectively. Approximately 17% of households with access for every 2 persons did not have access by every sleeping unit and 9.7% of households with access by sleeping unit did not have access for every 2 persons. Households with adequate access by sleeping unit but not for every 2 persons tend to be larger with fewer sleeping units, and have children under 5 years old and female members. The largest households (>7 members) and households with at least one under-five member had the lowest access (20.8 and 27.3%, respectively).

Conclusion: LLIN access was low in this area of intense indoor malaria transmission, 2 years after the last mass distribution campaign. Strategies are needed to improve LLINs coverage.