Malaria resurgence: a systematic review and assessment of its causes

Hematological changes due to malaria - An update

Malaria, a parasitic infection caused by the genus Plasmodium, results to over 20 million reported cases annually worldwide. Most individuals exhibit various symptoms, and blood analysis plays a crucial role in determining the appropriate treatment approach. This study discusses various hematologic complications associated with different Plasmodium species. A review of scientific databases including PubMed, Science Direct, Web of Science, Scopus, EMBASE, Magiran, SID, IranMedex was conducted using standard keywords such as Plasmodium, malaria, anemia and blood disorders (hematologic disorder) between 2000 and 2024. The review focused on articles pertaining to clinical trials, prospective cohort, retrospective, cross-sectional and case-control studies. Articles evaluating the effects of malaria on blood cells and indices, with target groups including human and animals, were included. Articles not written in English or Farsi were excluded. Our review revealed that, apart from iron deficiency anemia and vascular dysfunction contributed in part by adhesion of infected RBC to endothelium, decreases in hematocrit and hemoglobin levels, as part of pancytopenia and thrombocytopenia, are characteristic of Plasmodium infection. Additionally, the occurrence of inflammation due to the release of inflammatory cytokines and complement activation can complicate the clinical features of malaria in individuals with hematologic conditions.

Hyper-diverse antigenic variation and resilience to transmission-reducing intervention in falciparum malaria

Intervention efforts against falciparum malaria in high-transmission regions remain challenging, with rapid resurgence typically following their relaxation. Such resilience co-occurs with incomplete immunity and a large transmission reservoir from high asymptomatic prevalence. Incomplete immunity relates to the large antigenic variation of the parasite, with the major surface antigen of the blood stage of infection encoded by the multigene and recombinant family known as var. With a stochastic agent-based model, we investigate the existence of a sharp transition in resurgence ability with intervention intensity and identify molecular indicators informative of its proximity. Their application to survey data with deep sampling of var sequences from individual isolates in northern Ghana suggests that the transmission system was brought close to transition by intervention with indoor residual spraying. These results indicate that sustaining and intensifying intervention would have pushed malaria dynamics to a slow-rebound regime with an increased probability of local parasite extinction.

Patterns and predictors of malaria among head porters: a mobile population in Ghana

BACKGROUND

Head porters popularly known as 'Kayayeis in Ghana, face challenges in accessing essential health care services due to the mobile nature of their trade, low formal education, poor settlements, low-income among others. Kayayeis are predominantly females and form part of the mobile population who are at increased risk of malaria infection. Despite their increased risk of malaria, mobile populations are difficult to target for malaria interventions, hence serving as potential drivers of transmission even if malaria in the general population is controlled. The study, therefore, assessed the patterns and predictors of malaria among the Kayayei population in Ghana to inform policy decisions.

METHODS

A mixed methods study was conducted among Head-porters and their leaders in the three main hubs of Head-porters in Ghana; namely Accra, Kumasi, and Tamale. Blood samples were collected from participants and tested for malaria parasites using Rapid Diagnostic Test (RDT). Additionally, data including socio-demographics, malaria knowledge, attitude and practice were collected using a semi-structured questionnaire. Associations between malaria status and participants characteristics were determined by logistic regression (p < 0.05). Thematic analysis was used to analyse transcripts from the key informant interviews.

RESULTS

Out of 754 head porters studied, 10.48% (79) tested positive for malaria. The majority 43.10% (325/754) of the head porters were twenty years and below, and most 67.11% (506/754) had no formal education. Nearly half (50.4%) were not on any health insurance. Receiving malaria education in the past 6 months [AOR = 0.48, (0.26-0.88), p-value 0.02], and having poor knowledge of malaria [AOR = 2.23, (1.26-4.27), p < 0.02], were the factors significantly associated with malaria infection.

CONCLUSION

The prevalence of malaria among 'Kayayei's was estimated at 10.46%. A majority of them sleeps outside and in structures without mosquito screens. Receiving malaria education in the past 6 months reduced the odds of malaria infection whilst poor knowledge of malaria increased the odds of malaria infection among the porters. The authors recommend that the National Malaria Elimination Programme and partners should provide long-lasting insecticidal nets (LLIN) and other outdoor interventions for use by this special group. Designated state institutions should arrange free National Health Insurance Scheme (NHIS) registration for 'Kayayeis' to narrow the health access gap.

Influence of environmental, geographic, socio-demographic, and epidemiological factors on presence of malaria at the community level in two continents

The interactions of environmental, geographic, socio-demographic, and epidemiological factors in shaping mosquito-borne disease transmission dynamics are complex and changeable, influencing the abundance and distribution of vectors and the pathogens they transmit. In this study, 27 years of cross-sectional malaria survey data (1990-2017) were used to examine the effects of these factors on Plasmodium falciparum and Plasmodium vivax malaria presence at the community level in Africa and Asia. Monthly long-term, open-source data for each factor were compiled and analyzed using generalized linear models and classification and regression trees. Both temperature and precipitation exhibited unimodal relationships with malaria, with a positive effect up to a point after which a negative effect was observed as temperature and precipitation increased. Overall decline in malaria from 2000 to 2012 was well captured by the models, as was the resurgence after that. The models also indicated higher malaria in regions with lower economic and development indicators. Malaria is driven by a combination of environmental, geographic, socioeconomic, and epidemiological factors, and in this study, we demonstrated two approaches to capturing this complexity of drivers within models. Identifying these key drivers, and describing their associations with malaria, provides key information to inform planning and prevention strategies and interventions to reduce malaria burden.

Occupational exposure to malaria, leishmaniasis and arbovirus vectors in endemic regions: A systematic review

Vector-borne diseases, including dengue, leishmaniasis and malaria, may be more common among individuals whose occupations or behaviours bring them into frequent contact with these disease vectors outside of their homes. A systematic review was conducted to ascertain at-risk occupations and situations that put individuals at increased risk of exposure to these disease vectors in endemic regions and identify the most suitable interventions for each exposure. The review was conducted in accordance with PRISMA guidelines on articles published between 1945 and October 2021, searched in 16 online databases. The primary outcome was incidence or prevalence of dengue, leishmaniasis or malaria. The review excluded ecological and qualitative studies, abstracts only, letters, commentaries, reviews, and studies of laboratory-acquired infections. Studies were appraised, data extracted, and a descriptive analysis conducted. Bite interventions for each risk group were assessed. A total of 1170 articles were screened and 99 included. Malaria, leishmaniasis and dengue were presented in 47, 41 and 24 articles, respectively; some articles presented multiple conditions. The most represented populations were soldiers, 38% (43 of 112 studies); refugees and travellers, 15% (17) each; migrant workers, 12.5% (14); miners, 9% (10); farmers, 5% (6); rubber tappers and missionaries, 1.8% (2) each; and forest workers, 0.9% (1). Risk of exposure was categorised into round-the-clock or specific times of day/night dependent on occupation. Exposure to these vectors presents a critical and understudied concern for outdoor workers and mobile populations. When devising interventions to provide round-the-clock vector bite protection, two populations are considered. First, mobile populations, characterized by their high mobility, may find potential benefits in insecticide-treated clothing, though more research and optimization are essential. Treated clothing offers personal vector protection and holds promise for economically disadvantaged individuals, especially when enabling them to self-treat their clothing to repel vectors. Secondly, semi-permanent and permanent settlement populations can receive a combination of interventions that offer both personal and community protection, including spatial repellents, suitable for extended stays. Existing research is heavily biased towards tourism and the military, diverting attention and resources from vulnerable populations where these interventions are most required like refugee populations as well as those residing in sub-Saharan Africa.

Recent advances, challenges and updates on the development of therapeutics for malaria

Malaria has developed as a serious worldwide health issue as a result of the introduction of resistant Plasmodium species strains. Because of the common chemo resistance to most of the existing drugs on the market, it poses a severe health problem and significant obstacles in drug research. Malaria treatment has evolved during the last two decades in response to Plasmodium falciparum drug sensitivity and a return of the disease in tropical areas. Plasmodium falciparum is now highly resistant to the majority of antimalarial drugs. The parasite resistance drew focus to developing novel antimalarials to combat parasite resistance. The requirement for many novel antimalarial drugs in the future year necessitates adopting various drug development methodologies. Different innovative strategies for discovering antimalarial drugs are now being examined here. This review is primarily concerned with the description of newly synthesized antimalarial compounds, i.e. Tafenoquine, Cipargamin, Ferroquine, Artefenomel, DSM265, MMV390048 designed to improve the activity of pure antimalarial enantiomers. In this review, we selected the representative malarial drugs in clinical trials, classified them with detailed targets according to their action, discussed the relationship within the human trials, and generated a summative discussion with prospective expectations.

Updates on traditional methods for combating malaria and emerging Wolbachia-based interventions

The escalating challenge of malaria control necessitates innovative approaches that extend beyond traditional control strategies. This review explores the incorporation of traditional vector control techniques with emerging Wolbachia-based interventions. Wolbachia, a naturally occurring bacteria, offers a novel approach for combatting vector-borne diseases, including malaria, by reducing the mosquitoes' ability to transmit these diseases. The study explores the rationale for this integration, presenting various case studies and pilot projects that have exhibited significant success. Employing a multi-dimensional approach that includes community mobilization, environmental modifications, and new biological methods, the paper posits that integrated efforts could mark a turning point in the struggle against malaria. Our findings indicate that incorporating Wolbachia-based strategies into existing vector management programs not only is feasible but also heightens the efficacy of malaria control initiatives in different countries especially in Pakistan. The paper concludes that continued research and international collaboration are imperative for translating these promising methods from the laboratory to the field, thereby offering a more sustainable and effective malaria control strategy.

2,4-disubstituted 6-fluoroquinolines as potent antiplasmodial agents: QSAR, homology modeling, molecular docking and ADMET studies

Objective

This work was designed to study 2,4-disubstituted 6-fluoroquinolines as antiplasmodial agents by using in silico techniques, to aid in the design of novel analogs with high potency against malaria and high inhibition of Plasmodium falciparum translation elongation factor 2 (PfeEF2), a novel drug target.

Methods

Quantitative structure-activity relationships (QSAR) of 2,4-disubstituted 6-fluoroquinolines were studied with the genetic function approximation technique in Material Studio software. The 3D structure of PfeEF2 was modeled in the SWISS-MODEL workspace through homology modeling. A molecular docking study of the modeled PfeEF2 and 2,4-disubstituted 6-fluoroquinolines was conducted with Autodock Vina in Pyrx software. Furthermore, the in silico pharmacokinetic properties of selected compounds were investigated.

Results

A robust, reliable and predictive QSAR model was developed that related the chemical structures of 2,4-disubstituted 6-fluoroquinolines to their antiplasmodium activities. The model had an internal squared correlation coefficient R2 of 0.921, adjusted squared correlation coefficient R2adj of 0.878, leave-one-out cross-validation coefficient Q2cv of 0.801 and predictive squared correlation coefficient R2pred of 0.901. The antiplasmodium activity of 6-fluoroquinolines was found to depend on the n5Ring, GGI9, TDB7u, TDB8u and RDF75i physicochemical properties: n5Ring, TDB8u and RDF75i were positively associated, whereas GGI9 and TDB7u were negatively associated, with the antiplasmodium activity of the compounds. Stable complexes formed between the compounds and modeled PfeEF2, with binding affinity ranging from -8.200 to -10.700 kcal/mol. Compounds 5, 11, 16, 22 and 24 had better binding affinities than quinoline-4-carboxamide (DDD107498), as well as good pharmacokinetic properties, and therefore may be better inhibitors of this novel target.

Conclusion

QSAR and docking studies provided insight into designing novel 2,4-disubstituted 6-fluoroquinolines with high antiplasmodial activity and good structural properties for inhibiting a novel antimalarial drug target.

Brazilian plants with antimalarial activity: A review of the period from 2011 to 2022

ETHNOPHARMACOLOGICAL RELEVANCE

Malaria continues to be a serious global public health problem in subtropical and tropical countries of the world. The main drugs used in the treatment of human malaria, quinine and artemisinin, are isolates of medicinal plants, making the use of plants a widespread practice in countries where malaria is endemic. Over the years, due to the increased resistance of the parasite to chloroquine and artemisinin in certain regions, new strategies for combating malaria have been employed, including research with medicinal plants.

AIM

This review focuses on the scientific production regarding medicinal plants from Brazil whose antimalarial activity was evaluated during the period from 2011 to 2022. 2.

METHODOLOGY

For this review, four electronic databases were selected for research: Pubmed, ScienceDirect, Scielo and Periódicos CAPES. Searches were made for full texts published in the form of scientific articles written in Portuguese or English and in a digital format. In addition, prospects for new treatments as well as future research that encourages the search for natural products and antimalarial derivatives are also presented.

RESULTS

A total of 61 publications were encountered, which cited 36 botanical families and 92 species using different Plasmodium strains in in vitro and in vivo assays. The botanical families with the most expressive number of species found were Rubiaceae, Apocynaceae, Fabaceae and Asteraceae (14, 14, 9 and 6 species, respectively), and the most frequently cited species were of the genera Psychotria L. (8) and Aspidosperma Mart. (12), which belong to the families Rubiaceae and Apocynaceae. Altogether, 75 compounds were identified or isolated from 28 different species, 31 of which are alkaloids. In addition, the extracts of the analyzed species, including the isolated compounds, showed a significant reduction of parasitemia in P. falciparum and P. berghei, especially in the clones W2 CQ-R (in vitro) and ANKA (in vivo), respectively. The Brazilian regions with the highest number of species analyzed were those of the north, especially the states of Pará and Amazonas, and the southeast, especially the state of Minas Gerais.

CONCLUSION

Although many plant species with antimalarial potential have been identified in Brazil, studies of new antimalarial molecules are slow and have not evolved to the production of a phytotherapeutic medicine. Given this, investigations of plants of traditional use and biotechnological approaches are necessary for the discovery of natural antimalarial products that contribute to the treatment of the disease in the country and in other endemic regions.

N-Substituted Phenylhydrazones Kill the Ring Stage of Plasmodium falciparum

Antimalarial resistance has hampered the effective treatment of malaria, a parasitic disease caused by Plasmodium species. As part of our campaign on phenotypic screening of phenylhydrazones, a library of six phenylhydrazones was reconstructed and evaluated for their in vitro antimalarial and in silico receptor binding and pharmacokinetic properties. The structures of the phenylhydrazone hybrids were largely confirmed using nuclear magnetic resonance techniques. We identified two compounds which exhibited significant antimalarial potential against the ring stage (trophozoite) of 3D7 chloroquine-sensitive (CS) strain and DD2 chloroquine-resistant (CR) strains of Plasmodium falciparum with monosubstituted analogs bearing meta or para electron-donating groups showing significant activity in the single-digit micromolar range. Structure activity relationship is presented showing that electron-donating groups on the substituent hydrophobic pharmacophore are required for antimalarial activity. Compounds PHN6 and PHN3 were found to be the most potent with pIC50s (calculated form in vitro IC50s) of 5.37 and 5.18 against 3D7 CS and DD2 CR strains, respectively. Our selected ligands (PHN3 and PHN6) performed better when compared to chloroquine regarding binding affinity and molecular stability with the regulatory proteins of Plasmodium falciparum, hence predicted to be largely responsible for their in vitro activity. Pharmacokinetic prediction demonstrated that the phenylhydrazones may not cross the blood-brain barrier and are not P-glycoprotein (P-gp) substrates, a good absorption of 62% to 69%, and classified as a category IV compound based on toxicity grading.

Hyper-diverse antigenic variation and resilience to transmission-reducing intervention in falciparum malaria

Intervention against falciparum malaria in high transmission regions remains challenging, with relaxation of control efforts typically followed by rapid resurgence. Resilience to intervention co-occurs with incomplete immunity, whereby children eventually become protected from severe disease but not infection and a large transmission reservoir results from high asymptomatic prevalence across all ages. Incomplete immunity relates to the vast antigenic variation of the parasite, with the major surface antigen of the blood stage of infection encoded by the multigene family known as var. Recent deep sampling of var sequences from individual isolates in northern Ghana showed that parasite population structure exhibited persistent features of high-transmission regions despite the considerable decrease in prevalence during transient intervention with indoor residual spraying (IRS). We ask whether despite such apparent limited impact, the transmission system had been brought close to a transition in both prevalence and resurgence ability. With a stochastic agent-based model, we investigate the existence of such a transition to pre-elimination with intervention intensity, and of molecular indicators informative of its approach. We show that resurgence ability decreases sharply and nonlinearly across a narrow region of intervention intensities in model simulations, and identify informative molecular indicators based on var gene sequences. Their application to the survey data indicates that the transmission system in northern Ghana was brought close to transition by IRS. These results suggest that sustaining and intensifying intervention would have pushed malaria dynamics to a slow-rebound regime with an increased probability of local parasite extinction.

Recent advances in the synthesis and antimalarial activity of 1,2,4-trioxanes

The increasing resistance of various malarial parasite strains to drugs has made the production of a new, rapid-acting, and efficient antimalarial drug more necessary, as the demand for such drugs is growing rapidly. As a major global health concern, various methods have been implemented to address the problem of drug resistance, including the hybrid drug concept, combination therapy, the development of analogues of existing medicines, and the use of drug resistance reversal agents. Artemisinin and its derivatives are currently used against multidrug- resistant P. falciparum species. However, due to its natural origin, its use has been limited by its scarcity in natural resources. As a result, finding a substitute becomes more crucial, and the peroxide group in artemisinin, responsible for the drugs biological action in the form of 1,2,4-trioxane, may hold the key to resolving this issue. The literature suggests that 1,2,4-trioxanes have the potential to become an alternative to current malaria drugs, as highlighted in this review. This is why 1,2,4-trioxanes and their derivatives have been synthesized on a large scale worldwide, as they have shown promising antimalarial activity in vivo and in vitro against Plasmodium species. Consequently, the search for a more convenient, environment friendly, sustainable, efficient, and effective synthetic pathway for the synthesis of 1,2,4-trioxanes continues. The aim of this work is to provide a comprehensive analysis of the synthesis and mechanism of action of 1,2,4-trioxanes. This systematic review highlights the most recent summaries of derivatives of 1,2,4-trioxane compounds and dimers with potential antimalarial activity from January 1988 to 2023.

Analysing the six-year malaria trends at Metehara Health Centre in Central Ethiopia: the impact of resurgence on the 2030 elimination goals

BACKGROUND

Despite Ethiopia's concerted efforts to eliminate malaria by 2030, the disease continues to pose a significant public health and socioeconomic challenge in the country. The year 2021 witnessed 2.78 million malaria cases and 8041 associated deaths, emphasizing the persistent threat. Monitoring the prevalence trend of malaria is crucial for devising effective control and elimination strategies. This study aims to assess the trend of malaria prevalence at the Metehara Health Centre in the East Shoa Zone, Ethiopia.

METHODS

A retrospective study, spanning from February to September 2023, utilized malaria registration laboratory logbooks at Metehara Health Centre to evaluate the prevalence of malaria from 2017/18 to 2022/23. Malaria and related data were collected using a pre-designed data collection sheet. Descriptive statistics were employed for data summarization, presented through graphs and tables.

RESULTS

Out of 59,250 examined blood films, 17.4% confirmed the presence of Plasmodium infections. Among the confirmed cases, 74.3%, 23.8%, and 1.84% were attributed to Plasmodium falciparum, Plasmodium vivax, and mixed infections, respectively. The trend of malaria exhibited a steady decline from 2017/18 to 2021/22, reaching 9.8% prevalence. However, an abrupt increase to 26.5% was observed in 2022/23. Males accounted for a higher proportion (66%) of cases compared to females (34%). The age group 15-24 years experienced the highest malaria incidence at 42%. Notably, malaria cases peaked during autumn (September to November) at 43% and reached the lowest percentage during spring (March to May) at 13%.

CONCLUSION

Malaria persists as a significant health challenge in and around Metehara, central Ethiopia, predominantly driven by Plasmodium falciparum. The five-year declining trend was interrupted by a notable upsurge in 2022/23, indicating a resurgence of malaria in the study area. It is imperative to adopt a reverse strategy to sustain the progress achieved by the national malaria control plan.

Mobilizing resources with an investment case to mitigate cross-border malaria transmission and achieve malaria elimination in South Africa

South Africa's effort to eliminate malaria is significantly challenged by a large number of imported malaria cases, especially from neighbouring Mozambique. The country has a funding gap to achieve its malaria elimination goals (prior to 2019) and is ineligible to receive a national allocation from the Global Fund. The findings of an IC were utilised to successfully mobilise resources for malaria elimination in South Africa in 2018. A five-step resource mobilisation strategy was implemented to highlight financing challenges and leverage the economic evidence from an IC for malaria elimination in South Africa. South Africa's malaria programme implements control and elimination activities in three malaria-endemic provinces (KwaZulu Natal, Limpopo, and Mpumalanga). Driven by the IC findings, the South African government took an unprecedented step and increased total domestic malaria financing by approximately 36%, from the 2018/19 to the 2019/20 financial years through the creation of a new conditional grant for malaria. The IC findings predicted that malaria control in southern Mozambique is a prerequisite to eliminate malaria in South Africa. Based on this, the South African government also allocated funding towards a co-financing mechanism to support malaria control efforts in southern Mozambique. The IC findings assisted the South African National Department of Health to make a convincing case to key government decision-makers to invest in national malaria elimination and maximise economic returns in the long run. The South African government is the first in Southern Africa to mobilise a significant increase in domestic malaria financing to address the financial sustainability of both national and regional malaria elimination efforts. Continued surveillance activities will be required to prevent the re-establishment of malaria transmission even after malaria elimination is achieved in South Africa. Information sharing and close collaboration with provincial and national government officials were key to the successful outcome.

An immune memory-structured SIS epidemiological model for hyperdiverse pathogens

A hyperdiverse class of pathogens of humans and wildlife, including the malaria parasite Plasmodium falciparum, relies on multigene families to encode antigenic variation. As a result, high (asymptomatic) prevalence is observed despite high immunity in local populations under high-transmission settings. The vast diversity of "strains" and genes encoding this variation challenges the application of established models for the population dynamics of such infectious diseases. Agent-based models have been formulated to address theory on strain coexistence and structure, but their complexity can limit application to gain insights into population dynamics. Motivated by P. falciparum malaria, we develop an alternative formulation in the form of a structured susceptible-infected-susceptible population model in continuous time, where individuals are classified not only by age, as is standard, but also by the diversity of parasites they have been exposed to and retain in their specific immune memory. We analyze the population dynamics and bifurcation structure of this system of partial-differential equations, showing the existence of alternative steady states and an associated tipping point with transmission intensity. We attribute the critical transition to the positive feedback between parasite genetic diversity and force of infection. Basins of attraction show that intervention must drastically reduce diversity to prevent a rebound to high infection levels. Results emphasize the importance of explicitly considering pathogen diversity and associated specific immune memory in the population dynamics of hyperdiverse epidemiological systems. This statement is discussed in a more general context for ecological competition systems with hyperdiverse trait spaces.

Plasmodium falciparum resistant to artemisinin and diagnostics have emerged in Ethiopia

Diagnosis and treatment of Plasmodium falciparum infections are required for effective malaria control and are pre-requisites for malaria elimination efforts; hence we need to monitor emergence, evolution and spread of drug- and diagnostics-resistant parasites. We deep sequenced key drug-resistance mutations and 1,832 SNPs in the parasite genomes of 609 malaria cases collected during a diagnostic-resistance surveillance study in Ethiopia. We found that 8.0% (95% CI 7.0-9.0) of malaria cases were caused by P. falciparum carrying the candidate artemisinin partial-resistance kelch13 (K13) 622I mutation, which was less common in diagnostic-resistant parasites mediated by histidine-rich proteins 2 and 3 (pfhrp2/3) deletions than in wild-type parasites (P = 0.03). Identity-by-descent analyses showed that K13 622I parasites were significantly more related to each other than to wild type (P < 0.001), consistent with recent expansion and spread of this mutation. Pfhrp2/3-deleted parasites were also highly related, with evidence of clonal transmissions at the district level. Of concern, 8.2% of K13 622I parasites also carried the pfhrp2/3 deletions. Close monitoring of the spread of combined drug- and diagnostic-resistant parasites is needed.

Predicting the risk of malaria re-introduction in countries certified malaria-free: a systematic review

BACKGROUND

Predicting the risk of malaria in countries certified malaria-free is crucial for the prevention of re-introduction. This review aimed to identify and describe existing prediction models for malaria re-introduction risk in eliminated settings.

METHODS

A systematic literature search following the PRISMA guidelines was carried out. Studies that developed or validated a malaria risk prediction model in eliminated settings were included. At least two authors independently extracted data using a pre-defined checklist developed by experts in the field. The risk of bias was assessed using both the prediction model risk of bias assessment tool (PROBAST) and the adapted Newcastle-Ottawa Scale (aNOS).

RESULTS

A total 10,075 references were screened and 10 articles describing 11 malaria re-introduction risk prediction models in 6 countries certified malaria free. Three-fifths of the included prediction models were developed for the European region. Identified parameters predicting malaria re-introduction risk included environmental and meteorological, vectorial, population migration, and surveillance and response related factors. Substantial heterogeneity in predictors was observed among the models. All studies were rated at a high risk of bias by PROBAST, mostly because of a lack of internal and external validation of the models. Some studies were rated at a low risk of bias by the aNOS scale.

CONCLUSIONS

Malaria re-introduction risk remains substantial in many countries that have eliminated malaria. Multiple factors were identified which could predict malaria risk in eliminated settings. Although the population movement is well acknowledged as a risk factor associated with the malaria re-introduction risk in eliminated settings, it is not frequently incorporated in the risk prediction models. This review indicated that the proposed models were generally poorly validated. Therefore, future emphasis should be first placed on the validation of existing models.

HM, Brady OJ, Guerra CA, García GA, Carter AR, Ferguson HM, Afolabi BE, Hay SI, Reiner RC, Kiware S, Smith DL. Spatial dynamics of malaria transmission

The Ross-Macdonald model has exerted enormous influence over the study of malaria transmission dynamics and control, but it lacked features to describe parasite dispersal, travel, and other important aspects of heterogeneous transmission. Here, we present a patch-based differential equation modeling framework that extends the Ross-Macdonald model with sufficient skill and complexity to support planning, monitoring and evaluation for Plasmodium falciparum malaria control. We designed a generic interface for building structured, spatial models of malaria transmission based on a new algorithm for mosquito blood feeding. We developed new algorithms to simulate adult mosquito demography, dispersal, and egg laying in response to resource availability. The core dynamical components describing mosquito ecology and malaria transmission were decomposed, redesigned and reassembled into a modular framework. Structural elements in the framework-human population strata, patches, and aquatic habitats-interact through a flexible design that facilitates construction of ensembles of models with scalable complexity to support robust analytics for malaria policy and adaptive malaria control. We propose updated definitions for the human biting rate and entomological inoculation rates. We present new formulas to describe parasite dispersal and spatial dynamics under steady state conditions, including the human biting rates, parasite dispersal, the "vectorial capacity matrix," a human transmitting capacity distribution matrix, and threshold conditions. An [Formula: see text] package that implements the framework, solves the differential equations, and computes spatial metrics for models developed in this framework has been developed. Development of the model and metrics have focused on malaria, but since the framework is modular, the same ideas and software can be applied to other mosquito-borne pathogen systems.

How can the complex epidemiology of malaria in India impact its elimination?

Malaria is a human health hazard in the tropical and subtropical zones of the globe and is poised to be eliminated by the year 2030. Despite a decrease in incidence in the past two decades, many endemic countries, including India, report cases regularly. The epidemiology of malaria in India is unique owing to several features of the Plasmodium parasites, Anopheles vectors, ecoepidemiological situations conducive to disease transmission, and susceptible humans living in rural and forested areas. Limitations in public health reach, and poor health-seeking behaviour of vulnerable populations living in hard-to-reach areas, add to the problem. We bring all of these factors together in a comprehensive framework and opine that, in spite of complexities, targeted elimination of malaria in India is achievable with planned programmatic approaches.

The impact of sustained malaria control in the Loreto region of Peru: a retrospective, observational, spatially-varying interrupted time series analysis of the PAMAFRO program

Background

Although malaria control investments worldwide have resulted in dramatic declines in transmission since 2000, progress has stalled. In the Amazon, malaria resurgence has followed withdrawal of Global Fund support of the Project for Malaria Control in Andean Border Areas (PAMAFRO). We estimate intervention-specific and spatially-explicit effects of the PAMAFRO program on malaria incidence across the Loreto region of Peru, and consider the influence of the environmental risk factors in the presence of interventions.

Methods

We conducted a retrospective, observational, spatial interrupted time series analysis of malaria incidence rates among people reporting to health posts across Loreto, Peru between the first epidemiological week of January 2001 and the last epidemiological week of December 2016. Model inference is at the smallest administrative unit (district), where the weekly number of diagnosed cases of Plasmodium vivax and Plasmodium falciparum were determined by microscopy. Census data provided population at risk. We include as covariates weekly estimates of minimum temperature and cumulative precipitation in each district, as well as spatially- and temporally-lagged malaria incidence rates. Environmental data were derived from a hydrometeorological model designed for the Amazon. We used Bayesian spatiotemporal modeling techniques to estimate the impact of the PAMAFRO program, variability in environmental effects, and the role of climate anomalies on transmission after PAMAFRO withdrawal.

Findings

During the PAMAFRO program, incidence of P. vivax declined from 42.8 to 10.1 cases/1000 people/year. Incidence for P. falciparum declined from 14.3 to 2.5 cases/1000 people/year over this same period. The effects of PAMAFRO-supported interventions varied both by geography and species of malaria. Interventions were only effective in districts where interventions were also deployed in surrounding districts. Further, interventions diminished the effects of other prevailing demographic and environmental risk factors. Withdrawal of the program led to a resurgence in transmission. Increasing minimum temperatures and variability and intensity of rainfall events from 2011 onward and accompanying population displacements contributed to this resurgence.

Interpretation

Malaria control programs must consider the climate and environmental scope of interventions to maximize effectiveness. They must also ensure financial sustainability to maintain local progress and commitment to malaria prevention and elimination efforts, as well as to offset the effects of environmental change that increase transmission risk.

Funding

National Aeronautics and Space Administration, National Institutes of Health, Bill and Melinda Gates Foundation.

Gaps in research and capacity development for malaria surveillance and response in the Asia-Pacific: meeting report

BACKGROUND

This report is based on the 2021 annual meeting of the Asia-Pacific Malaria Elimination Network Surveillance and Response Working Group held online on November 1-3, 2021. In light of the 2030 regional malaria elimination goal, there is an urgency for Asia-Pacific countries to accelerate progress towards national elimination and prevent re-establishment. The Asia Pacific Malaria Elimination Network (APMEN) Surveillance Response Working Group (SRWG) supports elimination goals of national malaria control programmes (NMCPs) by expanding the knowledge base, guiding the region-specific operational research agenda and addressing evidence gaps to improve surveillance and response activities.

METHODS

An online annual meeting was hosted from 1 to 3 November 2021, to reflect on research needed to support malaria elimination in the region, challenges with malaria data quality and integration, current surveillance-related technical tools, and training needs of NMCPs to support surveillance and response activities. Facilitator-led breakout groups were held during meeting sessions to encourage discussion and share experience. A list of identified research priorities was voted on by attendees and non-attending NMCP APMEN contacts.

FINDINGS

127 participants from 13 country partners and 44 partner institutions attended the meeting, identifying strategies to address malaria transmission amongst mobile and migrant populations as the top research priority, followed by cost effective surveillance strategies in low resource settings, and integration of malaria surveillance into broader health systems. Key challenges, solutions and best practices for improving data quality and integrating epidemiology and entomology data were identified, including technical solutions to improve surveillance activities, guiding priority themes for hosting informative webinars, training workshops and technical support initiatives. Inter-regional partnerships and SRWG-led training plans were developed in consultation with members to be launched from 2022 onwards.

CONCLUSION

The 2021 SRWG annual meeting provided an opportunity for regional stakeholders, both NMCPs and APMEN partner institutions, to highlight remaining challenges and barriers and identify research priorities pertaining to surveillance and response in the region, and advocate for strengthening capacity through training and supportive partnerships.

Larval habitat stability and productivity in two sites in Southern Ghana

BACKGROUND

Mosquito larval source management (LSM) is a valuable additional tool for malaria vector control. Understanding the characteristics of mosquito larval habitats and its ecology in different land use types can give valuable insight for an effective larval control strategy. This study determined the stability and productivity of potential anopheline larval habitats in two different ecological sites: Anyakpor and Dodowa in southern Ghana.

METHODS

A total of 59 aquatic habitats positive for anopheline larvae were identified, and sampled every two weeks for a period of 30 weeks using a standard dipping method. Larvae were collected using standard dippers and were raised in the insectary for identification. Sibling species of the Anopheles gambiae sensu lato (s.l.) were further identified by polymerase chain reaction. The presence of larval habitats, their stability and larvae positive habitats were compared between the two sites using Mann-Whitney U and the Kruskal-Wallis test. Factors affecting the presence of An. gambiae larvae and physicochemical properties at the sites were determined using multiple logistic regression analysis and Spearman's correlation.

RESULTS

Out of a total of 13,681 mosquito immatures collected, 22.6% (3095) were anophelines and 77.38% (10,586) were culicines. Out of the 3095 anophelines collected, An. gambiae s.l. was predominant (99.48%, n = 3079), followed by Anopheles rufipes (0.45%, n = 14), and Anopheles pharoensis (0.064%, n = 2). Sibling species of the An. gambiae consisted of Anopheles coluzzii (71%), followed by An. gambiae s.s. (23%), and Anopheles melas (6%). Anopheles mean larval density was highest in wells [6.44 (95% CI 5.0-8.31) larvae/dip], lowest in furrows [4.18 (95% CI 2.75-6.36) larvae/dip] and man-made ponds [1.20 (95% CI 0.671-2.131) larvae/dip].The results also revealed habitat stability was highly dependent on rainfall intensity, and Anopheles larval densities were also dependent on elevated levels of pH, conductivity and TDS.

CONCLUSION

The presence of larvae in the habitats was dependent on rainfall intensity and proximity to human settlements. To optimize the vector control measures of malaria interventions in southern Ghana, larval control should be focused on larval habitats that are fed by underground water, as these are more productive habitats.

Magnesium Oxide Nanoparticles: Effective Antilarvicidal and Antibacterial Agents

People are vulnerable to mosquito-borne infections in tropical and subtropical climate countries. Due to resistive issues, vector control is an immediate concern in today's environment. The current study describes the synthesis of magnesium oxide by four different approaches including green, microwave, sol-gel, and hydrothermal methods. The synthesized magnesium oxide (MgO) nanoparticles were characterized using Fourier transform infrared spectroscopy (FT-IR), X-ray diffraction (XRD), high-resolution scanning electron microscopy (HRSEM), and energy-dispersive X-ray analysis (EDAX) techniques. The FT-IR studies reveal the presence of functional groups in the synthesized nanoparticles. The structural and morphological studies were investigated using XRD and HRSEM. EDAX reveals the presence of Mg and O in the prepared samples. The synthesized MgO NPs were screened for antibacterial studies against Gram-positive strains, Enterococcus faecalis and Staphylococcus aureus, two Gram-negative cultures, Escherichia coli and Klebsiella pneumoniae, using different concentrations. The results indicated excellent antibacterial activity against both Gram-positive and Gram-negative bacteria at 50 mg/mL hydrothermally produced MgO nanoparticles, with a maximal zone of inhibition (ZOI) of 5 mm for S. aureus, 7 mm for E. faecalis, and 6 mm for K. pneumoniae. The ZOI of E. coli was found to be the greatest at 9 mm when 50 mg/mL sol-gel-produced MgO nanoparticles were used. The synthesized MgO nanostructures were tested against fourth-instar larvae of Aedes aegypti and Aedes albopictus, and the hydrothermally synthesized MgO nanostructures exhibited better results when compared with other methods of synthesis. The reports show that A. aegypti and A. albopictus mortality rates were reported to be the lowest with green-manufactured MgO nanoparticles (7.5 g mL-1) and the highest with hydrothermally synthesized MgO nanoparticles (120 g mL-1). The research indicates that MgO nanostructures are promising drugs for antibacterial and mosquitocidal larvae control properties.

Livelihood activities, human mobility, and risk of malaria infection in elimination settings: a case-control study

BACKGROUND

Livelihood activities and human movements participate in the epidemiology of vector-borne diseases and influence malaria risk in elimination settings. In Saudi Arabia, where malaria transmission intensity varies geographically, it is vital to understand the components driving transmission within specific areas. In addition, shared social, behavioural, and occupational characteristics within communities may provoke the risk of malaria infection. This study aims to understand the relationship between human mobility, livelihood activities, and the risk of malaria infection in the border region of Jazan to facilitate further strategic malaria interventions. In addition, the study will complement and reinforce the existing efforts to eliminate malaria on the Saudi and Yemen border by providing a deeper understanding of human movement and livelihood activities.

METHODS

An unmatched case-control study was conducted. A total of 261 participants were recruited for the study, including 81 cases of confirmed malaria through rapid diagnostic tests (RDTs) and microscopy and 180 controls in the Baish Governorate in Jazan Provinces, Saudi Arabia. Individuals who received malaria tests were interviewed regarding their livelihood activities and recent movement (travel history). A questionnaire was administered, and the data was captured electronically. STATA software version 16 was used to analyse the data. Bivariate and multivariate analyses were conducted to determine if engaging in agricultural activities such as farming and animal husbandry, recent travel history outside of the home village within the last 30 days and participating in spiritual gatherings were related to malaria infection status.

RESULTS

A logistical regression model was used to investigate components associated with malaria infection. After adjusting several confounding factors, individuals who reported travelling away from their home village in the last 30 days OR 11.5 (95% CI 4.43-29.9), and those who attended a seasonal night spiritual gathering OR 3.04 (95% CI 1.10-8.42), involved in animal husbandry OR 2.52 (95% CI 1.10-5.82), and identified as male OR 4.57 (95% CI 1.43-14.7), were more likely to test positive for malaria infection.

CONCLUSION

Human movement and livelihood activities, especially at nighttime, should be considered malaria risk factors in malaria elimination settings, mainly when the targeted area is limited to a confined borderland area.

Efficacy of pyriproxyfen-pyrethroid long-lasting insecticidal nets (LLINs) and chlorfenapyr-pyrethroid LLINs compared with pyrethroid-only LLINs for malaria control in Benin: a cluster-randomised, superiority trial

BACKGROUND

New classes of long-lasting insecticidal nets (LLINs) combining mixtures of insecticides with different modes of action could put malaria control back on track after rebounds in transmission across sub-Saharan Africa. We evaluated the relative efficacy of pyriproxyfen-pyrethroid LLINs and chlorfenapyr-pyrethroid LLINs compared with standard LLINs against malaria transmission in an area of high pyrethroid resistance in Benin.

METHODS

We conducted a cluster-randomised, superiority trial in Zou Department, Benin. Clusters were villages or groups of villages with a minimum of 100 houses. We used restricted randomisation to randomly assign 60 clusters to one of three LLIN groups (1:1:1): to receive nets containing either pyriproxyfen and alpha-cypermethrin (pyrethroid), chlorfenapyr and alpha-cypermethrin, or alpha-cypermethrin only (reference). Households received one LLIN for every two people. The field team, laboratory staff, analyses team, and community members were masked to the group allocation. The primary outcome was malaria case incidence measured over 2 years after net distribution in a cohort of children aged 6 months-10 years, in the intention-to-treat population. This study is ongoing and is registered with ClinicalTrials.gov, NCT03931473.

FINDINGS

Between May 23 and June 24, 2019, 53 854 households and 216 289 inhabitants were accounted for in the initial census and included in the study. Between March 19 and 22, 2020, 115 323 LLINs were distributed to 54 030 households in an updated census. A cross-sectional survey showed that study LLIN usage was highest at 9 months after distribution (5532 [76·8%] of 7206 participants), but decreased by 24 months (4032 [60·6%] of 6654). Mean malaria incidence over 2 years after LLIN distribution was 1·03 cases per child-year (95% CI 0·96-1·09) in the pyrethroid-only LLIN reference group, 0·84 cases per child-year (0·78-0·90) in the pyriproxyfen-pyrethroid LLIN group (hazard ratio [HR] 0·86, 95% CI 0·65-1·14; p=0·28), and 0·56 cases per child-year (0·51-0·61) in the chlorfenapyr-pyrethroid LLIN group (HR 0·54, 95% CI 0·42-0·70; p<0·0001).

INTERPRETATION

Over 2 years, chlorfenapyr-pyrethroid LLINs provided greater protection from malaria than pyrethroid-only LLINs in an area with pyrethroid-resistant mosquitoes. Pyriproxyfen-pyrethroid LLINs conferred protection similar to pyrethroid-only LLINs. These findings provide crucial second-trial evidence to enable WHO to make policy recommendations on these new LLIN classes. This study confirms the importance of chlorfenapyr as an LLIN treatment to control malaria in areas with pyrethroid-resistant vectors. However, an arsenal of new active ingredients is required for successful long-term resistance management, and additional innovations, including pyriproxyfen, need to be further investigated for effective vector control strategies.

FUNDING

UNITAID, The Global Fund.

An insight to better understanding cross border malaria in Saudi Arabia

BACKGROUND

Border malaria is a major obstacle for the malaria elimination in Saudi Arabia. Today, the southern border of Saudi Arabia is a region where malaria cases are resurging, and malaria control is dwindling mainly due to the humanitarian crisis and the conflict in Yemen. This study analyses the current border malaria epidemiology along the southern border of Saudi Arabia from 2015 to 2018.

METHODS

All reported cases maintained by the malaria elimination centres in Aledabi and Baish, Jazan Province, Saudi Arabia, from 2015 to 2018 were analysed to examine the epidemiological changes over time. Pearson's Chi-Square test of differences was utilized to assess differences between the characteristics of imported and local causes and between border cases. A logistic regression model was used to predict imported status was related to living along side of the border area.

RESULTS

A total of 3210 malaria cases were reported in Baish and Aledabi malaria centres between 2015 and 2018, of which 170 were classified as local cases and 3040 were classified as imported cases. Reported malaria cases were mainly among males, within the imported cases 61.5% (1868/3039) were residents of the border areas.

CONCLUSIONS

Given the complexity of cross-border malaria, creating a malaria buffer zone that covers a certain margin from both sides of the border would allow for a joint force, cross-border malaria elimination programme. To initiate a malaria elimination activity and cases reported as belonging to this zone, rather than being pushed from one country to the other, would allow malaria elimination staff to work collaboratively with local borderland residents and other stakeholders to come up with innovative solutions to combat malaria and reach malaria-free borders.

Impact of the COVID-19 Pandemic on Malaria Control in Africa: A Preliminary Analysis

Malaria remains a significant public health concern in Africa, and the emerging coronavirus disease 2019 (COVID-19) pandemic may have negatively impacted malaria control. Here, we conducted a descriptive epidemiological analysis of malaria globally, and preliminarily explored the impact of COVID-19 on the malaria elimination program in regions of Africa (AFR). The present analysis found that there was a vast heterogeneity of incidence of deaths caused by malaria globally in different continents, and the highest malaria burden was observed in AFR. In 2020, there was an obviously increasing trend in the malaria epidemic in AFR, while the other four continents exhibited stable and declining patterns. Historically, malaria has been largely concentrated in high-malaria-burden regions, such as West Africa, and there has been an obvious increasing trend in Nigeria. These data suggest that dynamic changes in the malaria epidemic situation worldwide have primarily originated from AFR, and West Africa has played an important role in the global malaria increase in recent years. Under the coercion of COVID-19, multiple factors have co-driven the increase in malaria in AFR, including insufficient financial investments, a high native malaria burden, weak surveillance systems, limited medical resources, and low socioeconomic development levels. In addition, the shift of medical resources (e.g., health workers and personal protective equipment (PPE), the manufacturing of diagnostic reagents, and drugs) from malaria control to emergency COVID-19 response in the pandemic's early stage caused disruptions, reductions, and delays in pillar malaria control measures, leading to a significant negative impact on malaria control. In particular, a funding shortfall at both the international and domestic levels led to a "significant threat," resulting in vast gaps in access to proven malaria control tools. Although there has been a declining trend in malaria control over time due to COVID-19, the effect still cannot be ignored. Hence, we recommend the implementation of medical and technical resource assistance as a priority strategy to support Africa (West Africa) in order to curb further transmission.

Neutral vs. non-neutral genetic footprints of Plasmodium falciparum multiclonal infections

At a time when effective tools for monitoring malaria control and eradication efforts are crucial, the increasing availability of molecular data motivates their application to epidemiology. The multiplicity of infection (MOI), defined as the number of genetically distinct parasite strains co-infecting a host, is one key epidemiological parameter for evaluating malaria interventions. Estimating MOI remains a challenge for high-transmission settings where individuals typically carry multiple co-occurring infections. Several quantitative approaches have been developed to estimate MOI, including two cost-effective ones relying on molecular data: i) THE REAL McCOIL method is based on putatively neutral single nucleotide polymorphism loci, and ii) the varcoding method is a fingerprinting approach that relies on the diversity and limited repertoire overlap of the var multigene family encoding the major Plasmodium falciparum blood-stage antigen PfEMP1 and is therefore under selection. In this study, we assess the robustness of the MOI estimates generated with these two approaches by simulating P. falciparum malaria dynamics under three transmission conditions using an extension of a previously developed stochastic agent-based model. We demonstrate that these approaches are complementary and best considered across distinct transmission intensities. While varcoding can underestimate MOI, it allows robust estimation, especially under high transmission where repertoire overlap is extremely limited from frequency-dependent selection. In contrast, THE REAL McCOIL often considerably overestimates MOI, but still provides reasonable estimates for low and moderate transmission. Regardless of transmission intensity, results for THE REAL McCOIL indicate that an inaccurate tail at high MOI values is generated, and that at high transmission, an apparently reasonable estimated MOI distribution can arise from some degree of compensation between overestimation and underestimation. As many countries pursue malaria elimination targets, defining the most suitable approach to estimate MOI based on sample size and local transmission intensity is highly recommended for monitoring the impact of intervention programs.

Characterizing human movement patterns using GPS data loggers in an area of persistent malaria in Zimbabwe along the Mozambique border

BACKGROUND

Human mobility is a driver for the reemergence or resurgence of malaria and has been identified as a source of cross-border transmission. However, movement patterns are difficult to measure in rural areas where malaria risk is high. In countries with malaria elimination goals, it is essential to determine the role of mobility on malaria transmission to implement appropriate interventions.

METHODS

A study was conducted in Mutasa District, Zimbabwe, to investigate human movement patterns in an area of persistent transmission along the Mozambique border. Over 1 year, a convenience sample of 20 participants/month was recruited from active malaria surveillance cohorts to carry an IgotU^® GT-600 global positioning system (GPS) data logger during all daily activities. Consenting participants were tested for malaria at data logger distribution using rapid antigen diagnostic tests and completed a survey questionnaire. GPS data were analyzed using a trajectory analysis tool, and participant movement patterns were characterized throughout the study area and across the border into Mozambique using movement intensity maps, activity space plots, and statistical analyses.

RESULTS

From June 2016-May 2017, 184 participants provided movement tracks encompassing > 350,000 data points and nearly 8000 person-days. Malaria prevalence at logger distribution was 3.7%. Participants traveled a median of 2.8 km/day and spent a median of 4.6 h/day away from home. Movement was widespread within and outside the study area, with participants traveling up to 500 km from their homes. Indices of mobility were higher in the dry season than the rainy season (median km traveled/day = 3.5 vs. 2.2, P = 0.03), among male compared to female participants (median km traveled/day = 3.8 vs. 2.0, P = 0.0008), and among adults compared to adolescents (median total km traveled = 104.6 vs. 59.5, P = 0.05). Half of participants traveled outside the study area, and 30% traveled into Mozambique, including 15 who stayed in Mozambique overnight.

CONCLUSIONS

Study participants in Mutasa District, Zimbabwe, were highly mobile throughout the year. Many participants traveled long distances from home, including overnight trips into Mozambique, with clear implications for malaria control. Interventions targeted at mobile populations and cross-border transmission may be effective in preventing malaria introductions in this region.

A world free of malaria: It is time for Africa to actively champion and take leadership of elimination and eradication strategies

The global burden of malaria seems unabated. Africa carries the greatest burden accounting for over 95% of the annual cases of malaria. For the vision of a world free of malaria by Global Technical Strategy to be achieved, Africa must take up the stakeholder's role. It is therefore imperative that Africa rises up to the challenge of malaria and champion the fight against it. The fight against malaria may just be a futile or mere academic venture if Africans are not directly and fully involved. This work reviews the roles playable by Africans in order to curb the malaria in Africa and the world at large.

The impact of reactive case detection on malaria transmission in Zanzibar in the presence of human mobility

Malaria persists at low levels on Zanzibar despite the use of vector control and case management. We use a metapopulation model to investigate the role of human mobility in malaria persistence on Zanzibar, and the impact of reactive case detection. The model was parameterized using survey data on malaria prevalence, reactive case detection, and travel history. We find that in the absence of imported cases from mainland Tanzania, malaria would likely cease to persist on Zanzibar. We also investigate potential intervention scenarios that may lead to elimination, especially through changes to reactive case detection. While we find that some additional cases are removed by reactive case detection, a large proportion of cases are missed due to many infections having a low parasite density that go undetected by rapid diagnostic tests, a low rate of those infected with malaria seeking treatment, and a low rate of follow up at the household level of malaria cases detected at health facilities. While improvements in reactive case detection would lead to a reduction in malaria prevalence, none of the intervention scenarios tested here were sufficient to reach elimination. Imported cases need to be treated to have a substantial impact on prevalence.

A review of malaria epidemiology and control in Papua New Guinea 1900 to 2021: Progress made and future directions

The research and control of malaria has a long history in Papua New Guinea, sometimes resulting in substantial changes to the distribution of infection and transmission dynamics in the country. There have been four major periods of malaria control in PNG, with the current control programme having commenced in 2004. Each previous control programme was successful in reducing malaria burden in the country, but multiple factors led to programme failures and eventual breakdown. A comprehensive review of the literature dating from 1900 to 2021 was undertaken to summarize control strategies, epidemiology, vector ecology and environmental drivers of malaria transmission in PNG. Evaluations of historical control programs reveal poor planning and communication, and difficulty in sustaining financial investment once malaria burden had decreased as common themes in the breakdown of previous programs. Success of current and future malaria control programs in PNG is contingent on adequate planning and management of control programs, effective communication and engagement with at-risk populations, and cohesive targeted approaches to sub-national and national control and elimination.

Malaria Research for Tailored Control and Elimination Strategies in the Greater Mekong Subregion

The malaria landscape in the Greater Mekong Subregion has experienced drastic changes with the ramp-up of the control efforts, revealing formidable challenges that slowed down the progress toward malaria elimination. Problems such as border malaria and cross-border malaria introduction, multidrug resistance in Plasmodium falciparum, the persistence of Plasmodium vivax, the asymptomatic parasite reservoirs, and insecticide resistance in primary vectors require integrated strategies tailored for individual nations in the region. In recognition of these challenges and the need for research, the Southeast Asian International Center of Excellence for Malaria Research has established a network of researchers and stakeholders and conducted basic and translational research to identify existing and emerging problems and develop new countermeasures. The installation of a comprehensive disease and vector surveillance system at sentinel sites in border areas with the implementation of passive/active case detection and cross-sectional surveys allowed timely detection and management of malaria cases, provided updated knowledge for effective vector control measures, and facilitated the efficacy studies of antimalarials. Incorporating sensitive molecular diagnosis to expose the significance of asymptomatic parasite reservoirs for sustaining transmission helped establish the necessary evidence to guide targeted control to eliminate residual transmission. In addition, this program has developed point-of-care diagnostics to monitor the quality of artemisinin combination therapies, delivering the needed information to the drug regulatory authorities to take measures against falsified and substandard antimalarials. To accelerate malaria elimination, this program has actively engaged with stakeholders of all levels, fostered vertical and horizontal collaborations, and enabled the effective dissemination of research findings.

Global Cross-Border Malaria Control Collaborative Initiatives: A Scoping Review

Malaria remains a global disease of public health concern. Malaria control collaborative initiatives are widely being adopted to reduce malaria burden by various countries. This review sought to describe current and past cross-border malaria control initiatives focusing on key activities, outcomes and challenges. An exhaustive search was conducted in Web of Science, PubMed, Google Scholar and EBSCOhost using the following key words: cross-border malaria control, cross-border malaria elimination, bi-national malaria control and multinational malaria control, in combination with Boolean operators "AND" and "OR". Eleven studies satisfied the inclusion criteria for this review. The majority of collaborative initiatives have been formed within regional developmental and continental bodies with support from political leadership. The studies revealed that joint vector control, cases management, epidemiological data sharing along border regions as well as resource sharing and capacity building are some of the key collaborative initiatives being implemented globally. Collaborative initiatives have led to significant reduction in malaria burden and mortality. The majority of collaborative initiatives are underfunded and rely on donor support. We concluded that cross-border malaria collaborative initiatives have the capacity to reduce malaria burden and mortality along border regions; however, inadequate internal funding and over-reliance on donor funding remain the biggest threats to the survival of collaborative initiatives.

Introduction to the special section: Histories of Global Health in Africa

Global health is a multidisciplinary field, yet rarely productively incorporates historical knowledge. Local historical processes, interactions with past biomedical campaigns, and dynamic ecological narratives shape how disease outbreaks, health crises, and international interventions are received and remembered. The residues and afterlives of past interactions influence contemporary understandings. We argue for a broadening of the types of knowledge that are integrated into global health research, interventions, and policymaking by paying attention to project afterlives and better integrating forms of vernacular knowledge. Recognizing, understanding, respecting, and incorporating this knowledge is critical to the efficacy of global health-related interventions and the resulting outcomes.

Efficacy of metal nanoparticles as a control tool against adult mosquito vectors: A review

Presently, there is a need to develop effective and novel modes of control for mosquitoes, which remain a key driver of infectious disease transmission throughout the world. Control methods for these vectors have historically relied on a limited number of active ingredients (AIs) that have not experienced significant change in usage since the mid-20th century. The resulting development of widespread insecticide resistance has consequently increased the risk for future vector-borne disease outbreaks. Recently, metal nanoparticles have been explored for potential use in mosquito control due to their demonstrated toxicity against mosquitoes at all life stages. However, the majority of studies to date have focused on the larvicidal efficacy of metal nanoparticles with few studies examining their adulticidal potential. In this review, we analyze the current literature on green synthesized metal nanoparticles and their effect on adult mosquitoes.

Lessons for improved COVID-19 surveillance from the scale-up of malaria testing strategies

Effective control of infectious diseases is facilitated by informed decisions that require accurate and timely diagnosis of disease. For malaria, improved access to malaria diagnostics has revolutionized malaria control and elimination programmes. However, for COVID-19, diagnosis currently remains largely centralized and puts many low- and middle-income countries (LMICs) at a disadvantage. Malaria and COVID-19 are infectious diseases that share overlapping symptoms. While the strategic responses to disease control for malaria and COVID-19 are dependent on the disease ecologies of each disease, the fundamental need for accurate and timely testing remains paramount to inform accurate responses. This review highlights how the roll-out of rapid diagnostic tests has been fundamental in the fight against malaria, primarily within the Asia Pacific and along the Greater Mekong Subregion. By learning from the successful elements of malaria control programmes, it is clear that improving access to point-of-care testing strategies for COVID-19 will provide a suitable framework for COVID-19 diagnosis in not only the Asia Pacific, but all malarious countries. In malaria-endemic countries, an integrated approach to point-of-care testing for COVID-19 and malaria would provide bi-directional benefits for COVID-19 and malaria control, particularly due to their paralleled likeness of symptoms, infection control strategies and at-risk individuals. This is especially important, as previous disease pandemics have disrupted malaria control infrastructure, resulting in malaria re-emergence and halting elimination progress. Understanding and combining strategies may help to both limit disruptions to malaria control and support COVID-19 control.

The resting behavior of malaria vectors in different ecological zones of Ghana and its implications for vector control

BACKGROUND

In sub-Saharan Africa there is widespread use of long-lasting insecticidal nets and indoor residual spraying to help control the densities of malaria vectors and decrease the incidence of malaria. This study was carried out to investigate the resting behavior, host preference and infection with Plasmodium falciparum of malaria vectors in Ghana in the context of the increasing insecticide resistance of malaria vectors in sub-Saharan Africa.

METHODS

Indoor and outdoor resting anopheline mosquitoes were sampled during the dry and rainy seasons in five sites in three ecological zones [Sahel savannah (Kpalsogo, Pagaza, Libga); coastal savannah (Anyakpor); and forest (Konongo)]. Polymerase chain reaction-based molecular diagnostics were used to determine speciation, genotypes for knockdown resistance mutations (L1014S and L1014F) and the G119S ace1 mutation, specific host blood meal origins and sporozoite infection in the field-collected mosquitoes.

RESULTS

Anopheles gambiae sensu lato (s.l.) predominated (89.95%, n = 1718), followed by Anopheles rufipes (8.48%, n = 162) and Anopheles funestus s.l. (1.57%, n = 30). Sibling species of the Anopheles gambiae s.l. revealed Anopheles coluzzii accounted for 63% (95% confidence interval = 57.10-68.91) and 27% (95% confidence interval = 21.66-32.55) was Anopheles gambiae s. s.. The mean resting density of An. gambiae s.l. was higher outdoors (79.63%; 1368/1718) than indoors (20.37%; 350/1718) (Wilcoxon rank sum test, Z = - 4.815, P < 0.0001). The kdr west L1014F and the ace1 mutation frequencies were higher in indoor resting An. coluzzii and An. gambiae in the Sahel savannah sites than in the forest and coastal savannah sites. Overall, the blood meal analyses revealed that a larger proportion of the malaria vectors preferred feeding on humans (70.2%) than on animals (29.8%) in all of the sites. Sporozoites were only detected in indoor resting An. coluzzii from the Sahel savannah (5.0%) and forest (2.5%) zones.

CONCLUSIONS

This study reports high outdoor resting densities of An. gambiae and An. coluzzii with high kdr west mutation frequencies, and the presence of malaria vectors indoors despite the use of long-lasting insecticidal nets and indoor residual spraying. Continuous monitoring of changes in the resting behavior of mosquitoes and the implementation of complementary malaria control interventions that target outdoor resting Anopheles mosquitoes are necessary in Ghana.

The fight against malaria: Diminishing gains and growing challenges

Since the year 2000, historic reductions in malaria incidence and mortality have been driven by the widespread distribution of bed nets, drugs, and insecticides for the prevention and treatment of malaria. Scale-up of these tools has been enabled by an increase in malaria financing compounded by price reductions, yet these trends are unlikely to continue at the same rate. Rapid population growth in high-endemic areas requires procurement of more of these tools just to maintain current coverage, even as prices are likely to increase as resistance to drugs and insecticides forces shifts to newer products. Further progress toward the long-term goal of malaria eradication requires a combination of greater funding, more cost-effective resource allocation, and fundamental changes to the global malaria control strategy.

Implementation and challenges to preventing the re-establishment of malaria in China in the COVID-19 era

BACKGROUND

The rapid emergence and global spread of COVID-19 have caused substantial global disruptions that have impacted malaria programs worldwide. Innovative strategies to enable countries aiming to eliminate malaria as well as those that are already certified as malaria-free, are needed to address malaria importation in the context of the COVID-19 pandemic. China was certified as malaria-free in 2021 and now aims to prevent the malaria re-establishment. Nonpharmaceutical interventions such as entry screening, quarantining, and health education for individuals returning from international travel during the COVID-19 pandemic present both opportunities and challenges to the management of imported malaria. This study aimed to describe and analyze the operational challenges associated with an integrated surveillance and case management program in which malaria re-establishment prevention measures were incorporated into the COVID-19 program in China.

METHODS

After the integration of malaria re-establishment prevention activities into the COVID-19 program for 10 months in Jiangsu Province, China, a focus-group discussion of public health workers working on preventing malaria re-establishment and controlling COVID-19 was held in June 2021, aiming to explore the operational challenges and lessons learned from the integrated approach.

RESULTS

From 01 August 2020 to 31 May 2021, 8,947 overseas travelers with Yangzhou as the final destination underwent 14-day managed quarantine and 14-day home isolation. Of these travelers, 5,562 were from malaria-endemic regions. A total of 26,026 education booklets and materials were distributed to expand malaria-related knowledge. Twenty-two patients with unknown fever were screened for malaria with rapid diagnostic tests, and one patient was confirmed to have imported malaria. The challenges associated with the implementation of the integrated malaria surveillance and case management program include neglect of malaria due to COVID-19, lack of a standard operating procedure for malaria screening, mobility of public health providers, and difficulties in respecting the timeline of the "1-3-7" surveillance strategy.

CONCLUSIONS

China's experience highlights the feasibility of integrated case surveillance and management of existing infectious diseases and new emerging infections. It also demonstrates the importance of a sound public health infrastructure with adequate, trained field staff for screening, testing, contact tracing, and providing health education, all of which are crucial for the success of both malaria re-establishment prevention program and the effective control of COVID-19.

Rebounding Malaria and the failures of eradication in Zanzibar: The World Health Organization campaign and the after effects, 1957-1985

This article presents a case study of the WHO's malaria elimination attempt in Zanzibar and the decades after the program's conclusion in 1968. Drawing on archival, ethnographic, and interview data, we find that Zanzibar experienced a rebound malaria epidemic in the 1970s-1980s when prevalence rates surged higher than they were prior to the WHO's intervention. We show that scientists were aware of the risks of rebound before it happened and recognized the rebound epidemic as it was happening. We argue that many of the challenges facing Zanzibar in the 1960s remain dilemmas today, and many of the ethical questions about rebound malaria remain unaddressed.

Case-based malaria surveillance and response: implementation of 1-3-7 approach in Jiangsu Province, China

Following initiation of China's National Malaria Elimination Action Plan (NMEAP) in 2010, China's 1-3-7 surveillance and response approach was developed and rolled out in China to facilitate the malaria control programme and accelerate the progress of malaria elimination. Innovative strategies and interventions have been developed and implemented in Jiangsu Province to facilitate case-based malaria surveillance and response. A total of 9879 malaria cases were reported in Jiangsu Province from 2001 to 2020. Since 2012, no indigenous malaria cases have been reported in Jiangsu Province. However, in recent years, there has been a substantial increase of imported cases from abroad. To continue improving the malaria surveillance and response system, Jiangsu Province has conducted population-based health education to improve the healthcare seeking behaviour of malaria patients, strengthened the capacity of health facilities to improve the performance of malaria diagnosis and treatment, and strengthened health workforce capacity to improve the implementation of 1-3-7 approach. Continually improving surveillance and response system can play a critical role in the early detection and rapid response of individual malaria cases and prevent the re-establishment of malaria.

Development of New Strategies for Malaria Chemoprophylaxis: From Monoclonal Antibodies to Long-Acting Injectable Drugs

Drug discovery for malaria has traditionally focused on orally available drugs that kill the abundant, parasitic blood stage. Recently, there has also been an interest in injectable medicines, in the form of monoclonal antibodies (mAbs) with long-lasting plasma half-lives or long-lasting depot formulations of small molecules. These could act as prophylactic drugs, targeting the sporozoites and other earlier parasitic stages in the liver, when the parasites are less numerous, or as another intervention strategy targeting the formation of infectious gametocytes. Generally speaking, the development of mAbs is less risky (costly) than small-molecule drugs, and they have an excellent safety profile with few or no off-target effects. Therefore, populations who are the most vulnerable to malaria, i.e., pregnant women and young children would have access to such new treatments much faster than is presently the case for new antimalarials. An analysis of mAbs that were successfully developed for oncology illustrates some of the feasibility aspects, and their potential as affordable drugs in low- and middle-income countries.

Tafenoquine for the treatment of Plasmodium vivax malaria

INTRODUCTION

Plasmodium vivax malaria causes significant disease burden worldwide, especially in Latin America, Southeast Asia, and Oceania. P. vivax is characterized by the production of liver hypnozoites that cause clinical relapses upon periodic activation. Primaquine, an 8-aminoquinoline drug, has been the standard of care for decades to treat liver-stage P. vivax malaria; however, it requires long treatment regimens (one to two weeks) that lead to poor adherence and thus clinical relapses. Tafenoquine (TFQ), a newly available and efficacious single-dose 8-aminoquinoline, aims to address this challenge. Safe administration is possible when paired with the use of glucose-6-phosphate dehydrogenase (G6PD) diagnostics to prevent 8-aminoquinoline-induced hemolysis in patients with underlying G6PD deficiency (G6PDd).

AREAS COVERED

In this review, the authors present the recent literature regarding the pharmacology, efficacy, safety, and tolerability of TFQ and highlight regional differences in these areas. The authors also discuss the potential for TFQ, complemented with primaquine PQ and effective screening for G6PDd, to improve P. vivax clinical management and facilitate targeted mass drug administration in communities to decrease transmission.

EXPERT OPINION

Clinical studies show therapeutic efficacy of TFQ as well as a good performance in terms of safety and tolerability. Additional research regarding the effectiveness and safety TFQ in malaria elimination strategies such as targeted or mass drug administration are needed.

Predicting the impact of climate change on the re-emergence of malaria cases in China using LSTMSeq2Seq deep learning model: a modelling and prediction analysis study

OBJECTIVES

Malaria is a vector-borne disease that remains a serious public health problem due to its climatic sensitivity. Accurate prediction of malaria re-emergence is very important in taking corresponding effective measures. This study aims to investigate the impact of climatic factors on the re-emergence of malaria in mainland China.

DESIGN

A modelling study.

SETTING AND PARTICIPANTS

Monthly malaria cases for four Plasmodium species (P. falciparum, P. malariae, P. vivax and other Plasmodium) and monthly climate data were collected for 31 provinces; malaria cases from 2004 to 2016 were obtained from the Chinese centre for disease control and prevention and climate parameters from China meteorological data service centre. We conducted analyses at the aggregate level, and there was no involvement of confidential information.

PRIMARY AND SECONDARY OUTCOME MEASURES

The long short-term memory sequence-to-sequence (LSTMSeq2Seq) deep neural network model was used to predict the re-emergence of malaria cases from 2004 to 2016, based on the influence of climatic factors. We trained and tested the extreme gradient boosting (XGBoost), gated recurrent unit, LSTM, LSTMSeq2Seq models using monthly malaria cases and corresponding meteorological data in 31 provinces of China. Then we compared the predictive performance of models using root mean squared error (RMSE) and mean absolute error evaluation measures.

RESULTS

The proposed LSTMSeq2Seq model reduced the mean RMSE of the predictions by 19.05% to 33.93%, 18.4% to 33.59%, 17.6% to 26.67% and 13.28% to 21.34%, for P. falciparum, P. vivax, P. malariae, and other plasmodia, respectively, as compared with other candidate models. The LSTMSeq2Seq model achieved an average prediction accuracy of 87.3%.

CONCLUSIONS

The LSTMSeq2Seq model significantly improved the prediction of malaria re-emergence based on the influence of climatic factors. Therefore, the LSTMSeq2Seq model can be effectively applied in the malaria re-emergence prediction.

Malaria chemoprevention and drug resistance: a review of the literature and policy implications

Chemoprevention strategies reduce malaria disease and death, but the efficacy of anti-malarial drugs used for chemoprevention is perennially threatened by drug resistance. This review examines the current impact of chemoprevention on the emergence and spread of drug resistant malaria, and the impact of drug resistance on the efficacy of each of the chemoprevention strategies currently recommended by the World Health Organization, namely, intermittent preventive treatment in pregnancy (IPTp); intermittent preventive treatment in infants (IPTi); seasonal malaria chemoprevention (SMC); and mass drug administration (MDA) for the reduction of disease burden in emergency situations. While the use of drugs to prevent malaria often results in increased prevalence of genetic mutations associated with resistance, malaria chemoprevention interventions do not inevitably lead to meaningful increases in resistance, and even high rates of resistance do not necessarily impair chemoprevention efficacy. At the same time, it can reasonably be anticipated that, over time, as drugs are widely used, resistance will generally increase and efficacy will eventually be lost. Decisions about whether, where and when chemoprevention strategies should be deployed or changed will continue to need to be made on the basis of imperfect evidence, but practical considerations such as prevalence patterns of resistance markers can help guide policy recommendations.

Resurgent and delayed malaria

The populations of moderate or highly malaria endemic areas gradually acquire some immunity to malaria as a result of repeated exposure to the infection. When this exposure is reduced as a result of effective malaria control measures, subjects who benefitted from the intervention may consequently be at increased risk of malaria if the intervention is withdrawn, especially if this is done abruptly, and an effective malaria vector remains. There have been many examples of this occurring in the past, a phenomenon often termed ‘rebound malaria’, with the incidence of malaria rebounding to the level present before the intervention was introduced. Because the main clinical burden of malaria in areas with a high level of malaria transmission is in young children, malaria control efforts have, in recent decades, focussed on this group, with substantial success being obtained with interventions such as insecticide treated mosquito nets, chemoprevention and, most recently, malaria vaccines. These are interventions whose administration may not be sustained. This has led to concerns that in these circumstances, the overall burden of malaria in children may not be reduced but just delayed, with the main period of risk being in the period shortly after the intervention is no longer given. Although dependent on the same underlying process as classical ‘resurgent’ malaria, it may be helpful to differentiate the two conditions, describing the later as ‘delayed malaria’. In this paper, some of the evidence that delayed malaria occurs is discussed and potential measures for reducing its impact are suggested.

Blood-feeding patterns of Anopheles vectors of human malaria in Malawi: implications for malaria transmission and effectiveness of LLIN interventions

Background

Access to human hosts by Anopheles mosquitoes is a key determinant of vectorial capacity for malaria, but it can be limited by use of long-lasting insecticidal nets (LLINs). In Malawi, pyrethroid-treated LLINs with and without the synergist piperonyl butoxide (PBO) were distributed to control malaria. This study investigated the blood-feeding patterns of malaria vectors and whether LLINs containing pyrethroid and PBO led to a reduction of human blood feeding than those containing only pyrethroids.

Methods

Mosquitoes were sampled inside houses from May 2019 through April 2020 by aspiration, pyrethrum spray catch, and light trap methods in two sites. One site (Namanolo, Balaka district) had LLINs containing only pyrethroids whereas the other (Ntaja, Machinga district) had LLINs with both pyrethroids and PBO. Anopheles species, their blood-meal host, and infection with Plasmodium falciparum were determined using PCR methods.

Results

A total of 6585 female Anopheles were sampled in 203 houses. Of these, 633 (9.6%) were blood-fed mosquitoes comprising of 279 (44.1%) Anopheles arabiensis, 103 (16.3%) Anopheles gambiae 212 (33.5), Anopheles funestus, 2 (0.3%), Anopheles parensis and 37 (5.8%) were unidentified Anopheles spp. Blood meal hosts were successfully identified for 85.5% (n = 541) of the blood-fed mosquitoes, of which 436 (81.0%) were human blood meals, 28 (5.2%) were goats, 11 (2.0%) were dogs, 60 (11.1%) were mixed goat-human blood meals, 5 (0.9%) were dog–human, and 1 was a mixed dog-goat. Human blood index (fraction of blood meals that were humans) was significantly higher in Namanolo (0.96) than Ntaja (0.89). Even though human blood index was high, goats were over-selected than humans after accounting for relative abundance of both hosts. The number of infectious Anopheles bites per person-year was 44 in Namanolo and 22 in Ntaja.

Conclusion

Although LLINs with PBO PBO may have reduced human blood feeding, access to humans was extremely high despite high LLIN ownership and usage rates in both sites. This finding could explain persistently high rates of malaria infections in Malawi. However, this study had one village for each net type, thus the observed differences may have been a result of other factors present in each village.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-022-04089-7.

On multifactorial drivers for malaria rebound in Brazil: a spatio-temporal analysis

Background

Malaria incidence in Brazil reversed its decreasing trend when cases from recent years, as recent as 2015, exhibited an increase in the Brazilian Amazon basin, the area with the highest transmission of Plasmodium vivax and Plasmodium falciparum. In fact, an increase of more than 20% in the years 2016 and 2017 revealed possible vulnerabilities in the national malaria-control programme.

Methods

Factors potentially associated with this reversal, including migration, economic activities, and deforestation, were studied. Past incidences of malaria cases due to P. vivax and P. falciparum were analysed with a spatio-temporal Bayesian model using more than 5 million individual records of malaria cases from January of 2003 to December of 2018 in the Brazilian Amazon to establish the municipalities with unexpected increases in cases.

Results

Plasmodium vivax incidence surpassed the past trends in Amazonas (AM), Amapá (AP), Acre (AC), Pará (PA), Roraima (RR), and Rondônia (RO), implying a rebound of these states between 2015 and 2018. On the other hand, P. falciparum also surpassed the past trends in AM, AC, AP, and RR with less severity than P. vivax incidence. Outdoor activities, agricultural activities, accumulated deforestation, and travelling might explain the rebound in malaria cases in RR, AM, PA, and RO, mainly in P. vivax cases. These variables, however, did not explain the rebound of either P. vivax and P. falciparum cases in AC and AP states or P. falciparum cases in RR and RO states.

Conclusion

The Amazon basin has experienced an unexpected increase in malaria cases, mainly in P. vivax cases, in some regions of the states of Amazonas, Acre, Pará, Amapá, Roraima, and Rondônia from 2015 to 2018 and agricultural activities, outdoor activities, travelling activities, and accumulated deforestation appear linked to this rebound of cases in particular regions with different impact. This shows the multifactorial effects and the heterogeneity of the Amazon basin, boosting the necessity of focusing the malaria control programme on particular social, economic, and environmental conditions.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12936-021-04037-x.