The global distribution and population at risk of malaria: past, present, and future

Global population datasets overestimate flood exposure in Sweden

Accurate population data is crucial for assessing exposure in disaster risk assessments. In recent years, there has been a significant increase in the development of spatially gridded population datasets. Despite these datasets often using similar input data to derive population figures, notable differences arise when comparing them with direct ground-level observations. This study evaluates the precision and accuracy of flood exposure assessments using both known and generated gridded population datasets in Sweden. Specifically focusing on WorldPop and GHSPop, we compare these datasets against official national statistics at a 100 m grid cell resolution to assess their reliability in flood exposure analyses. Our objectives include quantifying the reliability of these datasets and examining the impact of data aggregation on estimated flood exposure across different administrative levels. The analysis reveals significant discrepancies in flood exposure estimates, underscoring the challenges associated with relying on generated gridded population data for precise flood risk assessments. Our findings emphasize the importance of careful dataset selection and highlight the potential for overestimation in flood risk analysis. This emphasises the critical need for validations against ground population data to ensure accurate flood risk management strategies.

Active spread of β-thalassemia beyond the thalassemia belt: A study on a Russian population

β-Thalassemia is a disease traditionally associated with thalassemia belt countries. Nonetheless, as global migration intensifies, β-thalassemia-causing variants spread far from their origin. We investigated this process to detect some patterns underlying its course. We analyzed β-thalassemia-causing variants and the origin of 676 unrelated participants in Moscow, the largest city of Russia, far away from the thalassemia belt. Our analyses revealed that modern Russia has one of the broadest spectra of thalassemia-causing variants: 46 different variants, including two novel β0 variants. Only a small proportion of the reported pathogenic variants likely originated in the resident subpopulation. Almost half of the variants that supposedly had emerged outside the Russian borders have already been assimilated by (were found in) the resident subpopulation. The primary modern source of immigration transferring thalassemia to a nonthalassemic part of Russia is the Caucasus region. We also found traces of ancient migration flows from non-Caucasus countries. Our data indicate that β-thalassemia-causing variants are actively spilling over into resident populations of countries outside thalassemia belt regions. Therefore, viewing thalassemia as a disease exclusive to specific ethnic groups creates a mind trap that can complicate the diagnosis.

Range dynamics of Anopheles mosquitoes in Africa suggest a significant increase in the malaria transmission risk

Despite a more than 100-year effort to combat malaria, it remains one of the most malignant infectious diseases globally, especially in Africa. Malaria is transmitted by several Anopheles mosquitoes. However, until now few studies have investigated future range dynamics of major An. mosquitoes in Africa through a unified scheme. Through a unified scheme, we developed 21 species distribution models to predict the range dynamics of 21 major An. species in Africa under future scenarios and also examined their overall range dynamic patterns mainly through suitability overlap index and range overlap index. Although future range dynamics varied substantially among the 21 An. species, we predicted large future range expansions for all 21 An. species, and increases in suitability overlap index were detected in more than 90% of the African continent for all future scenarios. Additionally, we predicted high range overlap index in West Africa, East Africa, South Sudan, Angola, and the Democratic Republic of the Congo under future scenarios. Although the relative impacts of land use, topography and climate variables on the range dynamics depended on species and spatial scale, climate played the strongest roles in the range dynamics of most species. Africa might face an increasing risk of malaria transmissions in the future, and better strategies are required to address this problem. Mitigating climate change and human disturbance of natural ecosystems might be essential to reduce the proliferation of An. species and the risk of malaria transmissions in Africa in the future. Our strategies against their impacts should be species-specific.

Ronald Ross: Pioneer of Malaria Research and Nobel Laureate

Sir Ronald Ross, a British medical doctor and researcher, is renowned for his pioneering work in malaria research. His discovery of the malaria parasite's lifecycle within mosquitoes revolutionized the understanding and control of malaria, transitioning the field from the miasma theory to vector-based strategies. This literature review aims to explore the comprehensive contributions of Ronald Ross to malaria research and their enduring impact on public health.

Detection through the use of RT-MqPCR of asymptomatic reservoirs of malaria in samples of patients from the indigenous Comarca of Guna Yala, Panama: Essential method to achieve the elimination of malaria

BACKGROUND

Plasmodium vivax is the main causative agent of malaria in Panama. However, the prevalence of asymptomatic infections in the different endemic regions remains unknown. Understanding the epidemiological behavior of asymptomatic infections is essential for the elimination of malaria. This study aimed to determine the prevalence of asymptomatic malarial infections in one of the main endemic regions of Panama using multiplex real-time reverse transcription RT-MqPCR.

METHODS

A cross-sectional study was conducted in three communities in the Guna Yala Comarca. A total of 551 thick blood smears and their respective samples on filter paper were collected from volunteers of different ages and sexes from June 20 to 25, 2016. Infections by the Plasmodium spp. were diagnosed using microscopy and RT-MqPCR. All statistical analyses were performed using the R software.

RESULTS

The average prevalence of asymptomatic infections by P. vivax in the three communities detected by RT-MqPCR was 9.3%, with Ukupa having the highest prevalence (13.4%), followed by Aidirgandi (11.1%) and Irgandi (3.3%). A total of 74 samples were diagnosed as asymptomatic infections using RT-MqPCR. Light microscopy (LM) detected that 17.6% (13/74) of the asymptomatic samples and 82.4% (61/74) were diagnosed as false negatives. A 100% correlation was observed between samples diagnosed using LM and RT-MqPCR. A total of 52.7% (39/74) of the asymptomatic patients were female and 85.1% (63/74) were registered between the ages of 1 and 21 years. Factors associated with asymptomatic infection were community (aOR = 0.38 (95% CI 0.17-0.83), p < 0.001) and age aOR = 0.98 (95% CI 0.97-1.00), p < 0.05); F = 5.38; p < 0.05).

CONCLUSIONS

This study provides novel evidence of the considerable prevalence of asymptomatic P. vivax infections in the endemic region of Kuna Yala, representing a new challenge that requires immediate attention from the National Malaria Program. The results of this study provide essential information for the health authorities responsible for developing new policies. Furthermore, it will allow program administrators to reorient and design effective malaria control strategies that consider asymptomatic infections as a fundamental part of malaria control and move towards fulfilling their commitment to eliminate it.

Pathogen prospecting of museums: Reconstructing malaria epidemiology

Malaria is a disease of global significance. Ongoing changes to the earth's climate, antimalarial resistance, insecticide resistance, and socioeconomic decline test the resilience of malaria prevention programs. Museum insect specimens present an untapped resource for studying vector-borne pathogens, spurring the question: Do historical mosquito collections contain Plasmodium DNA, and, if so, can museum specimens be used to reconstruct the historical epidemiology of malaria? In this Perspective, we explore molecular techniques practical to pathogen prospecting, which, more broadly, we define as the science of screening entomological museum specimens for human, animal, or plant pathogens. Historical DNA and pathogen prospecting provide a means of describing the coevolution of human, vector, and parasite, informing the development of insecticides, diagnostics, therapeutics, and vaccines.

A History of Malaria and Conflict

It is supposed that in all armed conflicts until World War II more humans died of infectious diseases than of the actual violence. Especially malaria left a crucial imprint on wars throughout history. The disease aggravates wartime conditions, is thus responsible for significant morbidity and mortality in conflict zones, and is at the same time more commonly found in these areas. Malaria has halted many military campaigns in the past, with prominent examples ranging from antiquity through the medieval period and into the modern era. The parasitosis still continues to play an important role in the outcome of warfare and follow-up events today and is of special public health importance in areas of the Global South, where most of its endemicity and some of the most brutal conflicts of our time are located. Vice versa, wars and ensuing population movements increase malaria transmission and morbidity as well as impede control efforts. Awareness of this and the development of strategies to overcome both malaria and wars will massively improve the well-being of the population affected.

Modeling resource allocation strategies for insecticide-treated bed nets to achieve malaria eradication

Large reductions in the global malaria burden have been achieved, but plateauing funding poses a challenge for progressing towards the ultimate goal of malaria eradication. Using previously published mathematical models of Plasmodium falciparum and Plasmodium vivax transmission incorporating insecticide-treated nets (ITNs) as an illustrative intervention, we sought to identify the global funding allocation that maximized impact under defined objectives and across a range of global funding budgets. The optimal strategy for case reduction mirrored an allocation framework that prioritizes funding for high-transmission settings, resulting in total case reductions of 76% and 66% at intermediate budget levels, respectively. Allocation strategies that had the greatest impact on case reductions were associated with lesser near-term impacts on the global population at risk. The optimal funding distribution prioritized high ITN coverage in high-transmission settings endemic for P. falciparum only, while maintaining lower levels in low-transmission settings. However, at high budgets, 62% of funding was targeted to low-transmission settings co-endemic for P. falciparum and P. vivax. These results support current global strategies to prioritize funding to high-burden P. falciparum-endemic settings in sub-Saharan Africa to minimize clinical malaria burden and progress towards elimination, but highlight a trade-off with 'shrinking the map' through a focus on near-elimination settings and addressing the burden of P. vivax.

Malaria diagnosis using a combined system of a simple and fast extraction method with a lyophilised Dual-LAMP assay in a non-endemic setting

Malaria is a parasitic disease distributed in tropical areas but with a high number of imported cases in non-endemic countries. The most specific and sensitive malaria diagnostic methods are PCR and LAMP. However, both require specific equipment, extraction procedures and a cold chain. This study aims to solve some limitations of LAMP method with the optimization and validation of six LAMP assays, genus and species-specific, using an easy and fast extraction method, the incorporation of a reaction control assay, two ways (Dual) of result reading and reagent lyophilization. The Dual-LAMP assays were validated against the Nested-Multiplex Malaria PCR. A conventional column and saline extraction methods, and the use of lyophilized reaction tubes were also assessed. A new reaction control Dual-LAMP-RC assay was designed. Dual-LAMP-Pspp assay showed no cross-reactivity with other parasites, repeatability and reproducibility of 100%, a significant correlation between parasite concentration and time to amplification and a LoD of 1.22 parasites/µl and 5.82 parasites/µl using column and saline extraction methods, respectively. Sensitivity and specificity of the six Dual-LAMP assays reach values of 100% or close to this, being lower for the Dual-LAMP-Pm. The Dual-LAMP-RC assay worked as expected. Lyophilized Dual-LAMP results were concordant with the reference method. Dual-LAMP malaria assays with the addition of a new reaction control LAMP assay and the use of a fast and easy saline extraction method, provided low limit of detection, no cross-reactivity, and good sensitivity and specificity. Furthermore, the reagent lyophilization and the dual result reading allow their use in most settings.

Delayed Plasmodium falciparum Malaria in Pregnant Patient with Sickle Cell Trait 11 Years after Exposure, Oregon, USA

Delayed Plasmodium falciparum malaria in immigrants from disease-endemic countries is rare. Such cases pose a challenge for public health because mosquitoborne transmission must be rigorously investigated. We report a case of delayed P. falciparum malaria in a pregnant woman with sickle cell trait 11 years after immigration to the United States.

How plastic are upper thermal limits? A comparative study in tsetse (family: Glossinidae) and wider Diptera

Critical thermal maximum (CTmax) describes the upper thermal tolerance of an animal where biological functions start to fail. A period of acclimation can enhance CTmax through plasticity, potentially buffering animals from extreme temperatures caused by climate change. Basal and acclimated CTmax vary within and between species and may be explained by traits related to thermal physiology, such as body size and sex. Differences in CTmax have not been established among species of tsetse fly (Glossina spp.), vectors of animal and human African trypanosomiasis. Here, we investigated basal CTmax and its plasticity for five tsetse species following adult acclimation at constant 25 or 30 °C for five days. We then set our findings in context using a meta-analysis on 33 species of Diptera. We find that, of the five tsetse species considered, only Glossina palpalis gambiensis and Glossina brevipalpis exhibited plasticity of CTmax, with an increase of 0.12 °C and 0.10 °C per 1 °C acclimation respectively. Within some species, higher basal CTmax values were associated with larger body size and being female, while variation in plasticity (i.e., response to the acclimation temperature) could not be explained by sex or size. Our broader meta-analysis across Diptera revealed overall CTmax plasticity of 0.06 °C per 1 °C acclimation, versus a similar 0.05 °C mean increase in tsetse. In contrast, there was greater CTmax plasticity in males compared to females in Diptera. Our study highlights that CTmax and its plasticity varies even among closely related species. Broader patterns across groups are not always reflected at a finer resolution; we thus emphasise the need for detailed experimental studies across a wide range of insect species to capture their capacity to cope with rapidly warming temperatures.

Induction of Artesunate Resistance in Plasmodium falciparum 3D7 Strain Using Intermittent Exposure Method and Comparing P.fk13 Sequence between Susceptible and Resistant Strains

Background

Resistance to artemisinin has threatened major achievements in malaria control, more investigations is needed about resistant strains and related genes. We aimed to induce resistance to artesunate in the Plasmodium falciparum 3D7 strain using intermittent exposure method and comparing P.fk13 gene sequence between susceptible and resistance strains.

Methods

P. falciparum 3D7 strain was cultured according to Trager & Jensen method with some modifications. Serial concentrations between 10-2 mol/l, to 10-7mol/l were prepared, then P. falciparum 3D7 was exposed to each of the dilution to determine IC50 and lethal dose. Sensitivity reduction process was started from the concentration of 10-7mol/l and ended at 10-2mol/l. Exposed parasites were collected after at least 27 days after cultivation in each drug concentration. DNA extraction, PCR and sequencing process were performed to investigate any possible mutations in the P.fk13 gene sequence.

Results

Effectiveness of 10-2mol/l concentration of artemisinin was found as a lethal dose. IC50 value was equal to 5×10-4 mol/l. The resistant strain was provided in the lab, sequenced and registered in the gene bank as P.f Art -2, (accession number MH796123. 1). Alignment of this registered sample showed no mutation in P.f kelch13 gene in comparison with standard strain submitted in the GenBank.

Conclusion

Resistance to artesunate in malaria parasite may occur but with no mutation in the P.f kelch13 gene. Therefore, whole genome sequencing should be applied to determine mutations in resistant strains.

A Systematic Review on the Viruses of Anopheles Mosquitoes: The Potential Importance for Public Health

Anopheles mosquitoes are the vectors of Plasmodium, the etiological agent of malaria. In addition, Anopheles funestus and Anopheles gambiae are the main vectors of the O'nyong-nyong virus. However, research on the viruses carried by Anopheles is scarce; thus, the possible transmission of viruses by Anopheles is still unexplored. This systematic review was carried out to identify studies that report viruses in natural populations of Anopheles or virus infection and transmission in laboratory-reared mosquitoes. The databases reviewed were EBSCO-Host, Google Scholar, Science Direct, Scopus and PubMed. After the identification and screening of candidate articles, a total of 203 original studies were included that reported on a variety of viruses detected in Anopheles natural populations. In total, 161 viruses in 54 species from 41 countries worldwide were registered. In laboratory studies, 28 viruses in 15 Anopheles species were evaluated for mosquito viral transmission capacity or viral infection. The viruses reported in Anopheles encompassed 25 viral families and included arboviruses, probable arboviruses and Insect-Specific Viruses (ISVs). Insights after performing this review include the need for (1) a better understanding of Anopheles-viral interactions, (2) characterizing the Anopheles virome-considering the public health importance of the viruses potentially transmitted by Anopheles and the significance of finding viruses with biological control activity-and (3) performing virological surveillance in natural populations of Anopheles, especially in the current context of environmental modifications that may potentiate the expansion of the Anopheles species distribution.

Inflammatory profiles in febrile children with moderate and severe malnutrition presenting at-hospital in Uganda are associated with increased mortality

BACKGROUND

Children in Africa carry a disproportionate burden of malnutrition and infectious disease. Together, malnutrition and infection are major contributors to global child mortality; however, their collective impact on immune activation are not well described.

METHODS

This was a secondary analysis of a prospective cohort study of children hospitalized with acute febrile illness at a single centre in Uganda. We investigated the association between malnutrition (determined using the mid-upper arm circumference, MUAC), immune activation (as measured by inflammatory markers IL-6, IL-8, CXCL10, CHI3L1, sTNFR1, Cystatin C, granzyme B, and sTREM-1), and mortality.

FINDINGS

Of the 1850 children eligible for this secondary analysis, 71 (3.8%) and 145 (11.7%) presented with severe acute malnutrition (SAM, MUAC <115 mm) and moderate malnutrition (MUAC 115 to < 125 mm), respectively. SAM was associated with increased concentrations of CHI3L1, sTNFR1, Cystatin C, and sTREM-1, and decreased concentrations of CXCL10 and granzyme B, even after controlling for age, sex, and disease severity at presentation. There were 77 deaths (4.2%). SAM was associated with a 9.2-fold (95% CI 4.8-46), 17-fold (95% CI 3.9-74), and 13-fold (95% CI 3.5-52) increased odds of death in children with pneumonia, malaria, and diarrheal illness, respectively. Mediation analysis implicated sTREM-1 and CHI3L1 in the effect of SAM on mortality, suggesting that enhanced activation of these inflammatory pathways is associated with the increased mortality in undernourished children with pneumonia and malaria.

INTERPRETATION

Collectively, these data highlight systemic inflammation as a common pathway associated with malnutrition and infection that could be targeted to mitigate the burden of acute febrile illness in LMICs.

FUNDING

This work was supported in part by the Canadian Institutes of Health Research, and by kind donations from The Tesari Foundation and Kim Kertland. The funders had no role in design, analysis, or reporting of these studies.

Infectivity of symptomatic Plasmodium vivax cases to different generations of wild-caught and laboratory-adapted Anopheles arabiensis using a membrane feeding assay, Ethiopia

When measuring human to mosquito transmission of Plasmodium spp., laboratory-adapted (colony) mosquitoes can be utilized. To connect transmission studies to the local epidemiology, it can be important to comprehend the relationship between infectivity in laboratory-adapted (colony) and wild-caught (wild) mosquitoes of the same species. Microscopically confirmed Plasmodium vivax cases were recruited from health facilities in Arba Minch town, and a nested polymerase chain reaction (nPCR) was used for subsequent confirmation. We performed paired membrane-feeding assays using colony An. arabiensis and three generations of wild origin An. arabiensis. Anopheles arabiensis aged 3-6 days were fed after being starved for 8-14 h. Microscopically, the oocyst development was evaluated at day 7 after feeding. Circumsporozoite proteins (CSPs) assay was carried out by enzyme-linked immunosorbent assay (ELISA). In 19 paired feeding experiments, the feeding efficiency was more than doubled in colony (median: 62.5%; interquartile range, IQR: 35-78%) than in wild mosquitoes (median: 28.5%; IQR: 17.5-40%; P < 0.001). Among the 19 P. vivax gametocyte-positive blood samples, 63.2% (n = 12) were infective to wild An. arabiensis and 73.7% (n = 14) were infective to colony An. arabiensis. The median infection rate was twice as high (26%) in the colony than in the wild (13%) An. arabiensis, although the difference was marginally insignificant (P = 0.06). Although the observed difference was not statistically significant (P = 0.19), the median number of oocysts per midgut was more than twice as high (17.8/midgut) in colony than in wild (7.2/midgut) An. arabiensis. The median feeding efficiency was 26.5% (IQR: 18-37%) in F1, 29.3% (IQR: 28-40%) in F2 and 31.2% (IQR: 30-37%) in F3 generations of wild An. arabiensis. Also, no significant difference was observed in oocyst infection rate and load between generations of wild An. arabiensis. CSP rate of P. vivax was 3.1% (3/97; 95% CI: 0.6-8.8%) in wild and 3.6% (3/84; 95% CI: 0.7-10.1%) in colony An. arabiensis. The results of the present study revealed that oocyst infection and load/midgut, and CSP rate were roughly comparable, indicating that colony mosquitoes can be employed for infectivity studies, while larger sample sizes may be necessary in future studies.

Mapping current and future thermal limits to suitability for malaria transmission by the invasive mosquito Anopheles stephensi

BACKGROUND

Anopheles stephensi is a malaria-transmitting mosquito that has recently expanded from its primary range in Asia and the Middle East, to locations in Africa. This species is a competent vector of both Plasmodium falciparum and Plasmodium vivax malaria. Perhaps most alarming, the characteristics of An. stephensi, such as container breeding and anthropophily, make it particularly adept at exploiting built environments in areas with no prior history of malaria risk.

METHODS

In this paper, global maps of thermal transmission suitability and people at risk (PAR) for malaria transmission by An. stephensi were created, under current and future climate. Temperature-dependent transmission suitability thresholds derived from recently published species-specific thermal curves were used to threshold gridded, monthly mean temperatures under current and future climatic conditions. These temperature driven transmission models were coupled with gridded population data for 2020 and 2050, under climate-matched scenarios for future outcomes, to compare with baseline predictions for 2020 populations.

RESULTS

Using the Global Burden of Disease regions approach revealed that heterogenous regional increases and decreases in risk did not mask the overall pattern of massive increases of PAR for malaria transmission suitability with An. stephensi presence. General patterns of poleward expansion for thermal suitability were seen for both P. falciparum and P. vivax transmission potential.

CONCLUSIONS

Understanding the potential suitability for An. stephensi transmission in a changing climate provides a key tool for planning, given an ongoing invasion and expansion of the vector. Anticipating the potential impact of onward expansion to transmission suitable areas, and the size of population at risk under future climate scenarios, and where they occur, can serve as a large-scale call for attention, planning, and monitoring.

Malaria hotspots and climate change trends in the hyper-endemic malaria settings of Mizoram along the India-Bangladesh borders

India has made tremendous progress in reducing malaria mortality and morbidity in the last decade. Mizoram State in North-East India is one of the few malaria-endemic regions where malaria transmission has continued to remain high. As Mizoram shares international borders with Bangladesh and Myanmar, malaria control in this region is critical for malaria elimination efforts in all the three countries. For identifying hotspots for targeted intervention, malaria data from 385 public health sub-centers across Mizoram were analyzed in the Geographic Information System. Almost all the sub-centers reporting high Annual Parasite Index (> 10) are located in Mizoram's districts that border Bangladesh. Getis-Ord G_i* statistic shows most of the sub-centers located along the Bangladesh border in the Lawngtlai and Lunglei districts to be the malaria hotspots. The hotspots also extended into the Mamit and Siaha districts, especially along the borders of Lawngtlai and Lunglei. Analysis of terrain, climatic, and land use/land cover datasets obtained from the Global Modelling and Assimilation Office and satellite images show Mizoram's western part (Lawngtlai, Lunglei, and Mamit districts) to experience similar topographic and climatic conditions as the bordering Rangamati district in the Chittagong division of Bangladesh. Climatic trends in this region from 1981 to 2021, estimated by the Mann-Kendall test and Sen's slope estimates, show an increasing trend in minimum temperature, relative humidity, rainfall, and the associated shift of climatic pattern (temperate to tropical monsoon) could facilitate malaria transmission. The quasi-Poisson regression model estimates a strong association (p < 0.001) between total malaria cases, temperature range, and elevation. The Kruskal-Wallis H test shows a statistically significant association between malaria cases and forest classes (p < 0.001). A regional coordination and strategic plan are required to eliminate malaria from this hyper-endemic malaria region of North-East India.

Behavioral interactions of bed bugs with long-lasting pyrethroid-treated bed nets: challenges for vector control

BACKGROUND

Widespread vector control has been essential in reducing the global incidence and prevalence of malaria, despite now stalled progress. Long-lasting insecticide-treated nets (LLINs) have historically been, and remain, one of the most commonly used vector control tools in the campaign against malaria. LLINs are effective only with proper use, adherence, retention and community adoption, which historically have relied on the successful control of secondary pests, including bed bugs. The emergence of pyrethroid-resistant bed bugs in malaria-endemic communities and failure to control infestations have been suggested to interfere with the effective use of LLINs. Therefore, the behavioral interactions of bed bugs with commonly used bed nets should be better understood.

METHODS

To investigate the interactions between bed bugs (Cimex lectularius L.) and LLINs, insecticide-susceptible and pyrethroid-resistant bed bugs were challenged to pass through two commonly used LLINs in two behavioral assays, namely host (blood meal)-seeking and aggregation-seeking assays. The proportions blood-fed and aggregated bed bugs, aggregation time and mortality were quantified and analyzed in different bed bug life stages.

RESULTS

Overall, both the insecticide-susceptible bed bugs and highly resistant bed bugs showed a varying ability to pass through LLINs based on treatment status and net design. Deltamethrin-treated nets significantly impeded both feeding and aggregation by the susceptible bed bugs. While none of the tested LLINs significantly impeded feeding (passage of unfed bed bugs through the nets) of the pyrethroid-resistant bed bugs, the untreated bed net, which has small mesh holes, impeded passage of fed bed bugs. Mortality was only seen in the susceptible bed bugs, with significantly higher mortality on deltamethrin-treated nets (63.5 ± 10.7%) than on permethrin-treated nets (2.0 ± 0.9%).

CONCLUSIONS

Commonly used new LLINs failed to prevent the passage of susceptible and pyrethroid-resistant bed bugs in host- and aggregation-seeking bioassays. The overall low and variable mortality observed in susceptible bed bugs during both assays highlighted the potential of LLINs to impose strong selection pressure for the evolution of pyrethroid resistance. Already, the failure to control bed bug infestations has been implicated as a contributing factor to the abandonment or misuse of LLINs. For the first time to our knowledge, we have shown the potential of LLINs in selecting for resistant secondary pest populations and so their potential role in stalling malaria control programs should be further investigated. The emergence of pyrethroid-resistant bed bugs in malaria-endemic communities may interfere with the effective use of pyrethroid-impregnated bed nets. We assessed the interactions of two bed bug strains with commonly used bed nets using two behavioral assays, namely host (blood meal)-seeking by unfed bed bugs and aggregation-seeking by freshly fed bed bugs. These assays assessed the passage of bed bugs through various bed nets in response to host cues and aggregation stimuli, respectively. Conditioned paper is a section of file folder paper that has been exposed to bed bugs and has been impregnated with feces and aggregation pheromone; it is attractive to aggregation-seeking fed bed bugs. An unconditioned ramp is a similar section of file folder paper that allows bed bugs to traverse the bed net and gain access to a blood-meal source.

Emerging quinoline- and quinolone-based antibiotics in the light of epidemics

Pandemics are large-scale outbreaks of infectious disease that can greatly increase morbidity and mortality all the globe. Since past 1990 till twentieth century, these infectious diseases have been major threat all over the globe associated with poor hygiene and sanitation. In light of these epidemics, researches have gained enormous rise in the developing the potential therapeutic treatment. Thus, revolutionized antibiotics have led to the near eradication of such ailments. Around 50 million prescription of antibiotics written in US per year according to center for disease control and prevention (CDC) report. There is a wide range of antibiotics available which differ in their usage and their mechanism of action. Among these quinoline and quinolone class of antibiotics get attention as they show tremendous potential in fighting the epidemics. Quinoline and quinolone comprise of two rings along with substitutions at different positions which is synthetically obtained by structural modifications of quinine. Quinoline and quinolone antibiotics exhibit extensive activities approved by FDA in the treatment of the several ailments such as gastrointestinal infections, urinary tract infections, prostate inflammation, malaria, gonorrhea, skin infection, colorectal cancer, respiratory tract infections. These are active against both gram-negative and gram-positive bacteria. This basic core of quinoline and quinolone is vital due to its capability of targeting the pathogen causing disease and beneficial in treating the infectious disease. They inhibit the synthesis of nucleic acid of bacteria which results in the rupture of bacterial chromosome due to the interruption of enzymes such as DNA gyrase and topoisomerase IV. There are various quinoline and quinolone compounds that are synthetically derived by applying different synthesis approaches which show a wide range of pharmacological activities in several diseases. The most commonly used are fluoro, chloro, and hydroxychloro derivatives of quinoline and quinolone. These compounds are helpful in the treatment of numerous epidemics as a chief and combination therapy. These quinoline and quinolone pharmacophore fascinate the interest of researchers as they inhibit the entry of virus in host cell and cease its replication by blocking the host receptor glycosylation and proteolytic processing. They act as immune modulator by inhibiting autophagy and reduction of both lysosomal activity and production of cytokine. Therefore, quinoline and quinolone derivatives attain significance in area of research and treatment of various life-threatening epidemics such as SARS, Zika virus, Ebola virus, dengue, and COVID-19 (currently). In this chapter, the research and advancements of quinoline- and quinolone-based antibiotics in epidemic management are briefly discussed.

The malaria transmission in Anhui province China

Plasmodium vivax and Plasmodium falciparum cases have opposite trends in Anhui China in the past decade. Long term and seasonal trends in the transmission rate of P. falciparum in Africa has been well studied, however that of P. vivax transmitted by Anopheles sinensis in China has not been investigated. There is a lot of work on the relationship between P. vivax cases and climatic factors in China, with sometimes contradicting results. However, how climatic factors affect transmission rate of P. vivax in China is unknown. We used Anhui province as an example to analyze the recent transmission dynamics where two types of malaria have been reported with differing etiologies. We examined breakpoints of the P. vivax and P. falciparum malaria long term dynamics in the recent decade. For locally transmitted P. vivax malaria, we analyzed the transmission rate and its seasonality using the combined human and mosquitos SIR-SI model with time-varied mosquito biting rate. We identified the effects of meteorological factors on the seasonality in transmission rate using a GAM model. For the imported P. falciparum malaria, we analyzed the potential reason for the observed increase in cases. The breakpoints of P. vivax and P. falciparum dynamics happened in a same year, 2010. The seasonality in the transmission rate of P. vivax malaria was high (42.4%) and was linearly associated with temperature and nonlinearly with rainfall. The abrupt increase in imported P. falciparum cases after the breakpoint was significantly related to the increased annual Chinese investment in Africa. Under the conditions of the existing vectors of malaria, long-term trends in climatic factors, and increasing trend in migration to/from endemic areas and imported malaria cases, we should be cautious of the possibility of the reestablishment of malaria in regions where it has been eliminated or the establishment of other vector-borne diseases.

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

Background

In Ethiopia, malaria is a major concern to the health, and socio-economic development of the country because of its occurrence at the peak agricultural activities. Factors such as environmental, human host, parasite, and vector determine malaria transmission. Therefore, the present study was conducted to determine the prevalence and associated factors of malaria among febrile patients who visited selected health centres.

Methods

Institutional-based cross-sectional study was conducted between October 2020 to July 2021 in eight selected health centres located in Lake Tana and its surrounding areas. A simple random sampling technique was used to select febrile patients. Thick and thin blood films were prepared and processed according to the WHO guidelines. Socio-demographic and malaria risk factors were collected from study participants who could read and write using a self-administered questionnaire, whereas face-to-face interview was used to collect information from those participants who could not write and read. The strength of association between risk factors and malaria was assessed using univariate and multivariate logistic regression models.

Results

Of the total (531) febrile patients, 75.3% were malaria negative and 24.7% (overall prevalence) were malaria confirmed cases. Most of the infections were caused by Plasmodium falciparum (72.5%) followed by Plasmodium vivax (23.7%) and mixed-species (3.8%). The highest prevalence was recorded in Kidist Hana (51.5%) followed by Robit (34.8%), Gorgora (30.3%), and Wusha Tiris (25%) health centres. In terms of months, the highest prevalence (37.5%) was detected in October whereas the lowest (14%) was in March. Logistic regression analysis revealed that gender (p = 0.023), educational level (p = 0.025), study month (p = 0.036), presence of eave in the house (p = 0.002) and wall openings (p = 0.041), not using bed nets (p = 0.001), sleeping in the same house with cattle (p = 0.031) and the distance between mosquito-breeding site and living house (p = 0.020) were explanatory risk factors significantly associated with malaria among studied participants.

Conclusions

In this study, we confirmed that the occurrence of malaria prevalence was high and continued against the Ethiopian malaria elimination plan of 2021–2025. Therefore, to meet the goals of this plan, the current prevention and control efforts should be stepped up even better in the coming years.

An Ethical Overview of the CRISPR-Based Elimination of Anopheles gambiae to Combat Malaria

Approximately a quarter of a billion people around the world suffer from malaria each year. Most cases are located in sub-Saharan Africa where Anopheles gambiae mosquitoes are the principal vectors of this public health problem. With the use of CRISPR-based gene drives, the population of mosquitoes can be modified, eventually causing their extinction. First, we discuss the moral status of the organism and argue that using genetically modified mosquitoes to combat malaria should not be abandoned based on some moral value of A. gambiae. Secondly, we argue that environmental impact studies should be performed to obtain an accurate account of the possible effects of a potential eradication of the organism. However, the risks from the purposeful extinction of A. gambiae should not overtake the benefits of eradicating malaria and risk assessments should be used to determine acceptable risks. Thirdly, we argue that the eventual release of the genetically modified mosquitoes will depend on transparency, community involvement, and cooperation between different nations.

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.

Promising Larvicidal Efficacy of Solid Lipid Nanoparticles Containing Mentha longifolia L., Mentha pulegium L., and Zataria multiflora Boiss. Essential Oils Against the Main Malaria Vector, Anopheles stephensi Liston

PURPOSE

An attempt was made in the current study to develop a natural mosquito larvicide using nanotechnology.

METHODS

Solid lipid nanoparticles (SLNs) containing three essential oils were first prepared using the high-pressure homogenizer. Larvicidal effects of essential oils and the SLNs against Anopheles stephensi were then compared.

RESULTS

The size of SLN containing Mentha longifolia, Mentha pulegium, Zataria multiflora essential oil was obtained as 105 ± 7, 210 ± 4, and 137 ± 8 nm. Their zeta potentials were - 7.8, - 4.7, and - 9.7 mV. Besides, their efficacy with LC₅₀ values of 24.79, 5.11, and 9.19 µg/mL was significantly more potent than that of their un-formulated essential oils with LC₅₀ values of 36.2, 27.55, and 33.33 µg/mL.

CONCLUSION

SLNs containing M. pulegium with the best efficacy (P < 0.05) could be considered as potent larvicides against other important species of mosquitoes and field trials.

THE IN-VITRO STUDY OF NOVEL PHOSPHOLIPID MICELLES LOADED WITH AMPHOTERICIN B ON PLASMODIUM FALCIPARUM PROTOZOAN

Malaria is one of the most challenging parasitic infectious diseases in tropical and subtropical regions all over the world. The increasing drug resistance of plasmodium falciparum even makes the treatment procedure of malaria challenging and more problematic. Therefore, it is essential to develop new antimalarial drugs for effective treatments. In this study, the encapsulated amphotericin B (Constantinides et al.) in DSPC/DSPE-PEG2000 micelles was investigated as an antimalarial drug against P. falciparum 3D7 strain. The mean particle size, morphological and microstructural properties of drug-free and drug-loaded micelles prepared with amphotericin B were determined through DLS, FESEM, and TEM analysis. The synthesized phospholipid micelles containing AmB drug with a mean diameter of 115nm and a polydispersity index of 0.331. The TEM and SEM studies indicate the uniform and homogeneous morphology of the micelles. Drug encapsulation efficiency is 88.3%. The slow release of the micellar system shows the maximum drug release of 75.67% within 24h. This in vitro study was conducted on P. falciparum 3D7 to investigate the interactions between AmB micelles and P. falciparum parasites using different drug ratios. According to the findings, the IC₅₀ of free AmB is 4.834µg/mL, while the nano-diameter AmB has a significantly lower IC₅₀ of 2.394µg/mL. The results of this study suggest that the drug-loaded phospholipid micelles have significantly higher bioactivity and greater plasmodial properties compared to the direct application of AmB against P. falciparum. Moreover, according to the results of this study, the encapsulated AmB drugs are promising nanostructures for malaria treatment. Therefore the nanoencapsulation AmB showed promising application for malaria treatment.

Is it time for Africa to adopt primaquine in the era of malaria control and elimination?

Primaquine is a gametocytocidal drug known to significantly reduce malaria transmission. However, primaquine induces a dose-dependent acute hemolytic anemia (AHA) in individuals with glucose-6-phosphate dehydrogenase (G6PD) deficiency that has led to a limited use of the drug especially in Africa where the condition is common. The World Health Organization (WHO) now recommends a single low dose (SLD) of primaquine (0.25 mg/kg) as P. falciparum gametocytocidal without the need for prior screening of G6PD status. Adoption and implementation of SLD primaquine in Africa may probably reduce malaria transmission, a pre-requisite for malaria elimination. This review therefore, focused on the safety of primaquine for control of malaria in Africa. The literature search was performed using online database Google Scholar, PubMed, HINARI, and Science Direct. Search terms used were “malaria”, “primaquine”, “safety”, “G6PD deficiency”, “large scale” or “mass administration”. Clinical trials in many African countries have shown SLD primaquine to be safe especially in a milder African G6PD A- variant. Likewise, large-scale primaquine administrations outside Africa involving hundreds of thousands to tenths of millions of participants and with severe variants of G6PD deficiency have also shown primaquine to be safe and well-tolerated. Fourteen deaths associated with primaquine have been reported globally over the past 6 decades, but none occurred following the administration of SLD primaquine. Available evidence shows that the WHO-recommended SLD primaquine dose added to effective schizonticides is safe and well-tolerated even in individuals with G6PD deficiency, and therefore, it can be safely used in the African population with the mildest G6PD A- variant.

Sub-Saharan Africa contributes about 95% of global malaria cases and related deaths.

Despite safety concerns adoption of SLD primaquine is needed to further reduce malaria transmission, an essential prerequisite for the elimination of the infection in Africa.

Large scale administrations of primaquine for control and elimination of malaria have been implemented in other parts of the world where there are severe variants of G6PD deficiency, but only around 1% of the population had mild adverse effects.

African G6PD A- is a milder variant of deficiency, and the hemolysis that occurs following a single 0.25 mg/kg primaquine administration in this group is usually mild and self-limiting.

With proper planning and preparation for the management of adverse effects, administration of SLD primaquine plus effective schizonticides, in a form of mass drug administration or seasonal malaria chemoprevention can be used in Africa to reduce malaria transmission.

Research and development of traditional medicines in low- and middle-income countries: A case study of artemisinin discovery in China

Though traditional medicines have been developed through practice for thousands of years, limited research has discussed the research and development (R&D) pattern of traditional medicines. China's discovery of artemisinin accumulated valuable experiences to explore traditional medicine under low-resource settings. With limited R&D resources, China mobilized all domestic research units at different levels and departments to develop artemisinin collaboratively. The discovery of artemisinin not only based on valuable experiential wisdom of traditional medicine, but also relied on excellent synergy among all units. In this study, we reviewed the story of how artemisinin was discovered in China, summarized key factors for new drug development from traditional medicines under limited resources, and raised suggestions to utilize traditional medicines in low- and middle-income countries. This case suggested that the vitality of traditional medicine could be extended by promoting new drug development based on modern methods and collaboration.

Prevalence and characteristics of malaria co-infection among individuals with visceral leishmaniasis in Africa and Asia: a systematic review and meta-analysis

Background

Malaria and visceral leishmaniasis (VL) co-infection can occur due to the overlapping geographical distributions of these diseases; however, only limited data of this co-infection have been reported and reviewed. This study aimed to explore the pooled prevalence and characteristics of this co-infection using a systematic review approach.

Methods

The PubMed, Web of Science and Scopus databases were searched for relevant studies. The quality of these studies was assessed in accordance with strengthening the reporting of observational studies in epidemiology (STROBE) guidelines. The numbers of individuals co-infected with Plasmodium and VL and the total numbers of individuals with VL were used to estimate the pooled prevalence using random-effects models. Differences in age, sex and the presence of anemia and malnutrition on admission were compared between co-infected individuals and individuals with VL using a random-effects model; the results are presented as odds ratios (ORs) and 95% confidence intervals (CIs). Heterogeneity among the included studies was assessed and quantified using Cochrane Q and I² statistics.

Results

Of the 3075 studies identified, 12 met the eligibility criteria and were included in this systematic review. The pooled prevalence of Plasmodium infection among the 6453 individuals with VL was 13%, with substantial heterogeneity of the data (95% CI 7–18%, I² 97.9%). Subgroup analysis demonstrated that the highest prevalence of co-infection occurred in African countries, whereas the lowest prevalence occurred in Asian countries. Patients aged < 5 years had higher odds of having co-infection than having VL (co-infection, n = 202; VL, n = 410) (OR 1.66, 95% CI 1.37–2.01, I² 0%; P < 0.0001), whereas patients aged 20–29 years had lower odds of having co-infection than having VL (co-infection, n = 170; VL, n = 699) (OR 0.75, 95% CI 0.60–0.93, I² 18%; P = 0.01). Male patients had equivalent odds of having co-infection and having VL (co-infection, n = 525; VL, n = 2232) (OR 0.92, 95% CI 0.078–1.08, I² 0%; P = 0.29). Patients with co-infection had lower odds of having anemia at admission than those with VL (co-infection, n = 902; VL, n = 2939) (OR 0.64, 95% CI 0.44–0.93, I² 0%; P = 0.02). No difference in malnutrition at admission was found in the meta-analysis.

Conclusions

The prevalence of malaria co-infection among individuals with VL was heterogeneous and ranged from 7 to 18%, depending on geographical area. Age and anemia at admission were associated with co-infection status. Further longitudinal studies are needed to determine if co-infection with malaria has an impact on the severity of VL.

Graphical abstract

Supplementary Information

The online version contains supplementary material available at 10.1186/s13071-021-05045-1.

In Vivo Antimalarial Activity of Leaf Extracts and a Major Compound Isolated from Ranunculus multifidus Forsk

The leaves of Ranunculus multifidus Forsk. are traditionally used for the treatment of malaria in several African countries. In the present study, 80% methanol (RM-M) and hydrodistilled (RM-H) extracts of fresh leaves from R. multifidus and its major constituent anemonin were tested for their in vivo antimalarial activity against Plasmodium berghei in mice. Anemonin was also tested for its in vitro antimycobacterial activity against Mycobacterium smegmatis and M. abscessus in a microbroth dilution assay, and bacterial growth was analyzed by OD measurement. The isolation of anemonin from RM-H was carried out using preparative thin layer chromatography (PTLC). The chemical structures of anemonin and its hydrolysis product were elucidated using spectroscopic methods (HR–MS; 1D and 2D-NMR). Results of the study revealed that both RM-M and RM-H were active against P. berghei in mice, although the latter demonstrated superior activity (p < 0.001), as compared to the former. At a dose of 35.00 mg/kg/day, RM-H demonstrated a chemosuppression value of 70% in a 4-day suppressive test. In a 4-day suppressive, Rane’s and prophylactic antimalarial tests, anemonin showed median effective doses (ED₅₀s) of 2.17, 2.78 and 2.70 μM, respectively. However, anemonin did not inhibit the growth of M. smegmatis and M. abscessus.

Transmitted Light as Attractant with Mechanical Traps for Collecting Nocturnal Mosquitoes in Urban Bangkok, Thailand

Mosquito surveillance is the cornerstone for determining abundance, species diversity, pathogen infection rates, and temporal and spatial distribution of different life stages in an area. Various methods are available for assessing adult mosquito populations, including mechanical trap devices using different forms of attractant cues (chemical and visual) to lure mosquitoes to the trap. So-called "light traps" use various electromagnetic wavelengths to produce a variety of visible spectral colors to attract adult mosquitoes. However, this type of trapping technology has not been widely used in Thailand. This study compared the efficacy of 4 light-emitting diodes (LEDs) (blue, green, yellow, and red) and 2 fluorescent (ultraviolet [UV] and white) lights for collecting mosquitoes in urban Bangkok. Using a Latin square experimental design, 6 light traps equipped with different lights were rotated between 6 trap site locations within the Kasetsart University (KU) campus. Each location received 6 replicate collections (6 consecutive trap-nights represented 1 replicate) over 36 collection nights for a total of 216 trap-nights. Traps were operated simultaneously (1800 to 0600 h), with captured mosquitoes removed at 3-h intervals. In total, 2,387 mosquitoes consisting of 11 species across 5 genera (Aedes, Anopheles, Armigeres, Culex, and Mansonia) were captured. Collectively, Culex species represented the predominant group sampled (2,252; 94.4%). The UV light source captured 1,544 (64.7%) of the total mosquitoes collected, followed by white 389 (16.3%), with the 4 LED sources collecting between 6.8% (blue) and 1.9% (yellow). Traps equipped with UV light were clearly the most effective for capturing nocturnally active mosquito species on the KU campus.

Ecological plasticity to ions concentration determines genetic response and dominance of Anopheles coluzzii larvae in urban coastal habitats of Central Africa

In Central Africa, the malaria vector Anopheles coluzzii is predominant in urban and coastal habitats. However, little is known about the environmental factors that may be involved in this process. Here, we performed an analysis of 28 physicochemical characteristics of 59 breeding sites across 5 urban and rural sites in coastal areas of Central Africa. We then modelled the relative frequency of An. coluzzii larvae to these physicochemical parameters in order to investigate environmental patterns. Then, we assessed the expression variation of 10 candidate genes in An. coluzzii, previously incriminated with insecticide resistance and osmoregulation in urban settings. Our results confirmed the ecological plasticity of An. coluzzii larvae to breed in a large range of aquatic conditions and its predominance in breeding sites rich in ions. Gene expression patterns were comparable between urban and rural habitats, suggesting a broad response to ions concentrations of whatever origin. Altogether, An. coluzzii exhibits a plastic response to occupy both coastal and urban habitats. This entails important consequences for malaria control in the context of the rapid urban expansion in Africa in the coming years.

In vitro antiplasmodial activity, cytotoxicity, and gas chromatography - flame ionization detector metabolites fingerprint of extracts and fractions from Tetrorchidium didymostemon

Background

Tetrorchidium didymostemon is used as an antimalarial remedy in southern Nigeria.

Objective(s)

This study was aimed at providing scientific validation for the use of T. didymostemon in the treatment of malaria in Nigeria.

Materials and methods

Plasmodium falciparum 3D7 (Pf3D7) strain was cultured and maintained in fresh O⁺ human erythrocytes. Standard methods were used to evaluate in vitro antiplasmodial activity, cytotoxic effect on Vero cell line, phytochemical screening, and antioxidant capacity. Gas Chromatography – Flame Ionization Detector (GC-FID) metabolite fingerprinting of the most potent fraction was carried out.

Results

The methanol leaf extract had higher antiplasmodial activity (IC₅₀Pf3D7 = 25 ± 0.21 μg/mL) in comparison with the stem bark extract (SBE) (IC₅₀Pf3D7 = 50 ± 0.94 μg/mL). The n-hexane fraction of the leaf extract had the best antiplasmodial activity (IC₅₀Pf3D7 = 3.92 ± 0.46 μg/mL) and selectivity index. This was followed by the dichloromethane (IC₅₀Pf3D7 = 12.5 ± 1.32 μg/mL), ethyl acetate (IC₅₀Pf3D7 = 35.0 ± 4.80 μg/mL), and hydromethanol fraction which was inactive (IC₅₀Pf3D7 > 100 μg/mL). All extracts and fractions were not toxic on Vero cell line (CC₅₀ > 1000 μg/mL). The n-hexane and dichloromethane fractions had the highest amount of phytochemicals. GC-FID analysis revealed high amounts of kaempferol, α-pinene, camphor, humulene, azulene, and β-caryophyllene in the n-hexane fraction.

Conclusion

The results of our study validate the traditional use of T. didymostemon in the treatment of malaria in southern Nigeria. They also suggest that the phytoconstituent(s) responsible for the antiplasmodial activity of this plant may be more extractable in non-polar solvents.

Associations of Single Nucleotide Polymorphisms in IL-18 Gene with Plasmodium falciparum-Associated Malaria

Introduction

Interleukin-18 (IL-18) is a pro-inflammatory cytokine, reported to be involved in the initial immune responses against malaria. Genetic variations in the host are an important factor that influences the etiology of malaria at several disease levels. Polymorphisms within the IL-18 gene are associated with susceptibility and clinical outcome of several diseases.

Methods

We genotyped single nucleotide polymorphisms (SNPs) in IL-18 of patients infected with Plasmodium falciparum with varying extent of parasitemia and different age groups.

Results

SNPs rs5744292 (OR = 70.446; 95% CI = 4.318-1149.323; p<0.0001) and rs544354 (OR = 1.498; 95% CI = 1.088-2.063; p=0.013) were found to be significantly associated with parasitemia in P. falciparum-infected patients when compared with healthy control subjects. SNP rs5744292 (OR = 7.597; 95% CI=1.028-56.156; p=0.019) was associated with increased parasite density in infected patients. SNPs rs544354 (OR 0.407; 95% CI=0.204-0.812; p = 0.009) and rs360714 (OR of 0.256; 95% CI=0.119-0.554; p = 0.001) were significantly associated with parasite density in an age-dependent manner, with the risk alleles present more frequently among the younger (1-9 years) patients. Several haplotypes were found to have a significant association with parasitemia. In-vitro expression analysis using luciferase reporter assay showed that SNPs rs1946518 and rs187238 in the IL-18 gene promoter region and rs360728 and rs5744292 in the 3'-untranslated region of the IL-18 gene were associated with enhanced transcriptional activity.

Conclusion

Our results suggest that polymorphisms within the IL-18 gene are associated with the susceptibility to P. falciparum infection and related parasitemia among groups with different parasite density and across various age groups.

resistancebank.org, an open-access repository for surveys of antimicrobial resistance in animals

Antimicrobial resistance (AMR) is a growing threat to the health of humans and animals that requires global actions. In high-income countries, surveillance systems helped inform policies to curb AMR in animals. In low- and middle-income countries (LMICs), demand for meat is rising, and developing policies against AMR is urgent. However, surveillance of AMR is at best nascent, and the current evidence base to inform policymakers is geographically heterogeneous. We present resistancebank.org, an online platform that centralizes information on AMR in animals from 1,285 surveys from LMICs. Surveys were conducted between 2000 and 2019 and include 22,403 resistance rates for pathogens isolated from chickens, cattle, sheep, and pigs. The platform is built as a shiny application that provides access to individual surveys, country-level reports, and maps of AMR at 10 × 10 kilometers resolution. The platform is accessed via any internet browser and enables users to upload surveys to strengthen a global database. resistancebank.org aims to be a focal point for sharing AMR data in LMICs and to help international funders prioritize their actions.

Ivermectin treatment in humans for reducing malaria transmission

BACKGROUND

Malaria is transmitted through the bite of Plasmodium-infected adult female Anopheles mosquitoes. Ivermectin, an anti-parasitic drug, acts by killing mosquitoes that are exposed to the drug while feeding on the blood of people (known as blood feeds) who have ingested the drug. This effect on mosquitoes has been demonstrated by individual randomized trials. This effect has generated interest in using ivermectin as a tool for malaria control.

OBJECTIVES

To assess the effect of community administration of ivermectin on malaria transmission.

SEARCH METHODS

We searched the Cochrane Infectious Diseases Group (CIDG) Specialized Register, CENTRAL, MEDLINE, Embase, LILACS, Science Citation index - expanded, the World Health Organization (WHO) International Clinical Trials Registry Platform, ClinicalTrials.gov, and the National Institutes of Health (NIH) RePORTER database to 14 January 2021. We checked the reference lists of included studies for other potentially relevant studies, and contacted researchers working in the field for unpublished and ongoing trials.

SELECTION CRITERIA

We included cluster-randomized controlled trials (cRCTs) that compared ivermectin, as single or multiple doses, with a control treatment or placebo given to populations living in malaria-endemic areas, in the context of mass drug administration. Primary outcomes were prevalence of malaria parasite infection and incidence of clinical malaria in the community.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data on the number of events and the number of participants in each trial arm at the time of assessment. For rate data, we noted the total time at risk in each trial arm. To assess risk of bias, we used Cochrane's RoB 2 tool for cRCTs. We documented the method of data analysis, any adjustments for clustering or other covariates, and recorded the estimate of the intra-cluster correlation (ICC) coefficient. We re-analysed the trial data provided by the trial authors to adjust for cluster effects. We used a Poisson mixed-effect model with small sample size correction, and a cluster-level analysis using the linear weighted model to adequately adjust for clustering.  MAIN RESULTS: We included one cRCT and identified six ongoing trials.  The included cRCT examined the incidence of malaria in eight villages in Burkina Faso, randomized to two arms. Both trial arms received a single dose of ivermectin 150 µg/kg to 200 µg/kg, together with a dose of albendazole. The villages in the intervention arm received an additional five doses of ivermectin, once every three weeks. Children were enrolled into an active cohort, in which they were repeatedly screened for malaria infection.  The primary outcome was the cumulative incidence of uncomplicated malaria in a cohort of children aged five years and younger, over the 18-week study. We judged the study to be at high risk of bias, as the analysis did not account for clustering or correlation between participants in the same village. The study did not demonstrate an effect of Ivermectin on the cumulative incidence of uncomplicated malaria in the cohort of children over the 18-week study (risk ratio 0.86, 95% confidence interval (CI) 0.62 to 1.17; P = 0.2607; very low-certainty evidence).

AUTHORS' CONCLUSIONS

We are uncertain whether community administration of ivermectin has an effect on malaria transmission, based on one trial published to date.

Identification of 3,3'-O-dimethylellagic acid and apigenin as the main antiplasmodial constituents of Endodesmia calophylloides Benth and Hymenostegia afzelii (Oliver.) Harms

Background

Endodesmia calophylloides and Hymenostegia afzelii belong to the Guttiferae and Caesalpiniaceae plant families with known uses in African ethno-medicine to treat malaria and several other diseases. This study aimed at identifying antiplasmodial natural products from selected crude extracts from H. afzelii and E. calophylloides and to assess their cytotoxicity.

Methods

The extracts from H. afzelii and E. calophylloides were subjected to bioassay-guided fractionation to identify antiplasmodial compounds. The hydroethanol and methanol stem bark crude extracts, fractions and isolated compounds were assessed for antiplasmodial activity against the chloroquine-sensitive 3D7 and multi-drug resistant Dd2 strains of Plasmodium falciparum using the SYBR green I fluorescence-based microdilution assay. Cytotoxicity of active extracts, fractions and compounds was determined on African green monkey normal kidney Vero and murine macrophage Raw 264.7 cell lines using the Resazurin-based viability assay.

Results

The hydroethanolic extract of H. afzelii stem bark (Hasb^HE) and the methanolic extract of E. calophylloides stem bark (Ecsb^M) exhibited the highest potency against both Pf3D7 (EC₅₀ values of 3.32 ± 0.15 μg/mL and 7.40 ± 0.19 μg/mL, respectively) and PfDd2 (EC₅₀ of 3.08 ± 0.21 μg/mL and 7.48 ± 0.07 μg/mL, respectively) strains. Both extracts showed high selectivity toward Plasmodium parasites (SI > 13). The biological activity-guided fractionation led to the identification of five compounds (Compounds 1–5) from Hasb^HE and one compound (Compound 6) from Ecsb^M. Of these, Compound 1 corresponding to apigenin (EC₅₀Pf3D7, of 19.01 ± 0.72 μM and EC₅₀PfDd2 of 16.39 ± 0.52 μM), and Compound 6 corresponding to 3,3′-O-dimethylellagic acid (EC₅₀Pf3D7 of 4.27 ± 0.05 μM and EC₅₀PfDd2 of 1.36 ± 0.47 μM) displayed the highest antiplasmodial activities. Interestingly, both compounds exhibited negligible cytotoxicity against both Vero and Raw 264.7 cell lines with selectivity indices greater than 9.

Conclusions

This study led to the identification of two potent antiplasmodial natural compounds, 3,3′-O-dimethylellagic acid and apigenin that could serve as starting points for further antimalarial drug discovery.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12906-021-03352-9.

A cross-country comparison of malaria policy as a premise for contextualized appropriation of foreign aid in global health

Background

Foreign aid continues to play an essential role in health sector development in low-resource countries, particularly in terms of providing a vital portion of their health expenditures. However, the relationship between foreign aid allocation and malaria policy formulation and/or implementation among state aid recipients remains unknown.

Methods

Publicly available data were collected with the country as observational unit to set up the conceptual framework. The quality and strength of relationships between socioeconomic, environmental and institutional parameters were estimated by Pearson and polychoric correlations. A correlation matrix was explored by factor analysis.

Results

The first policy index captured policy variation related to malaria burden and development assistance. Funding per capita from all international agencies was correlated with malaria burden, whereas governmental funding for national malaria programmes per capita was not. The second policy index captured variation beyond malaria endemicity and country size. Variation was found to be related to international country risk instruments and funding from the United States Agency for International Development President’s Malaria Initiative.

Conclusions

Not all agencies involved in malaria policy allocate assistance in alignment with the gross domestic product and malaria burden. While the country size does not negatively impact malaria burden, it does account for greater development assistance per capita from selected international agencies. Novel policy indexes describe complex relationships between malaria policy, international foreign aid and socioeconomic parameters. Small countries have distinct environmental and sociopolitical properties.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12961-021-00700-6.

Natural Products That Changed Society

Until the end of the 19th century all drugs were natural products or minerals. During the 19th century chemists succeeded in isolating pure natural products such as quinine, morphine, codeine and other compounds with beneficial effects. Pure compounds enabled accurate dosing to achieve serum levels within the pharmacological window and reproducible clinical effects. During the 20th and the 21st century synthetic compounds became the major source of drugs. In spite of the impressive results achieved within the art of synthetic chemistry, natural products or modified natural products still constitute almost half of drugs used for treatment of cancer and diseases like malaria, onchocerciasis and lymphatic filariasis caused by parasites. A turning point in the fight against the devastating burden of malaria was obtained in the 17th century by the discovery that bark from trees belonging to the genus Cinchona could be used for treatment with varying success. However isolation and use of the active principle, quinine, in 1820, afforded a breakthrough in the treatment. In the 20th century the synthetic drug chloroquine severely reduced the burden of malaria. However, resistance made this drug obsolete. Subsequently artemisinin isolated from traditional Chinese medicine turned out to be an efficient antimalarial drug overcoming the problem of chloroquine resistance for a while. The use of synthetic analogues such as chloroquine or semisynthetic drugs such as artemether or artesunate further improved the possibilities for healing malaria. Onchocerciasis (river blindness) made life in large parts of Africa and South America miserable. The discovery of the healing effects of the macrocyclic lactone ivermectin enabled control and partly elimination of the disease by annual mass distribution of the drug. Also in the case of ivermectin improved semisynthetic derivatives have found their way into the clinic. Ivermectin also is an efficient drug for treatment of lymphatic filariasis. The serendipitous discovery of the ability of the spindle toxins to control the growth of fast proliferating cancer cells armed physicians with a new efficient tool for treatment of some cancer diseases. These possibilities have been elaborated through preparation of semisynthetic analogues. Today vincristine and vinblastine and semisynthetic analogues are powerful weapons against cancer diseases.

Comparing malaria early detection methods in a declining transmission setting in northwestern Ethiopia

Background

Despite remarkable progress in the reduction of malaria incidence, this disease remains a public health threat to a significant portion of the world’s population. Surveillance, combined with early detection algorithms, can be an effective intervention strategy to inform timely public health responses to potential outbreaks. Our main objective was to compare the potential for detecting malaria outbreaks by selected event detection methods.

Methods

We used historical surveillance data with weekly counts of confirmed Plasmodium falciparum (including mixed) cases from the Amhara region of Ethiopia, where there was a resurgence of malaria in 2019 following several years of declining cases. We evaluated three methods for early detection of the 2019 malaria events: 1) the Centers for Disease Prevention and Control (CDC) Early Aberration Reporting System (EARS), 2) methods based on weekly statistical thresholds, including the WHO and Cullen methods, and 3) the Farrington methods.

Results

All of the methods evaluated performed better than a naïve random alarm generator. We also found distinct trade-offs between the percent of events detected and the percent of true positive alarms. CDC EARS and weekly statistical threshold methods had high event sensitivities (80–100% CDC; 57–100% weekly statistical) and low to moderate alarm specificities (25–40% CDC; 16–61% weekly statistical). Farrington variants had a wide range of scores (20–100% sensitivities; 16–100% specificities) and could achieve various balances between sensitivity and specificity.

Conclusions

Of the methods tested, we found that the Farrington improved method was most effective at maximizing both the percent of events detected and true positive alarms for our dataset (> 70% sensitivity and > 70% specificity). This method uses statistical models to establish thresholds while controlling for seasonality and multi-year trends, and we suggest that it and other model-based approaches should be considered more broadly for malaria early detection.

Supplementary Information

The online version contains supplementary material available at 10.1186/s12889-021-10850-5.

The influence of vector-borne disease on human history: socio-ecological mechanisms

Vector-borne diseases (VBDs) are embedded within complex socio-ecological systems. While research has traditionally focused on the direct effects of VBDs on human morbidity and mortality, it is increasingly clear that their impacts are much more pervasive. VBDs are dynamically linked to feedbacks between environmental conditions, vector ecology, disease burden, and societal responses that drive transmission. As a result, VBDs have had profound influence on human history. Mechanisms include: (1) killing or debilitating large numbers of people, with demographic and population-level impacts; (2) differentially affecting populations based on prior history of disease exposure, immunity, and resistance; (3) being weaponised to promote or justify hierarchies of power, colonialism, racism, classism and sexism; (4) catalysing changes in ideas, institutions, infrastructure, technologies and social practices in efforts to control disease outbreaks; and (5) changing human relationships with the land and environment. We use historical and archaeological evidence interpreted through an ecological lens to illustrate how VBDs have shaped society and culture, focusing on case studies from four pertinent VBDs: plague, malaria, yellow fever and trypanosomiasis. By comparing across diseases, time periods and geographies, we highlight the enormous scope and variety of mechanisms by which VBDs have influenced human history.

Fifty years after the eradication of Malaria in Italy. The long pathway toward this great goal and the current health risks of imported malaria

Fifty years ago, Italy was declared a malaria-free country by the World Health Organization (WHO). In remembering this important anniversary, the authors of this paper describe the long journey that led to this goal. In the century following the unification of Italy, malaria was one of the main public health problems. At the end of the 19th century, malaria cases amounted to 2 million, with 15,000-20,000 deaths per year. This manuscript examines the state of public and social health in Italy from the end of the 19th century to the beginning of the 20th century, with particular regard to the government's measures for the prevention, prophylaxis and treatment of malaria. The authors describe the main findings of Italian malariologists during the period under review, from the identification of Plasmodium as a malaria pathogen and the recognition of the Anopheles mosquito as its vector. They also make some considerations regarding the current situation and the importation of malaria by travelers and migrants from countries where the disease is still endemic.

Prevalence of Malaria among Adults in Ethiopia: A Systematic Review and Meta-Analysis

Background

Malaria is one of the leading causes of mortality and morbidity in tropical and subtropical regions. The bulk of the global malaria burden is in sub-Saharan African countries, including Ethiopia. Malaria adversely affects the health of the peoples as well as the economic development of many developing countries including Ethiopia.

Methods

This review article was reported according to PRISMA guidelines. Related published articles were searched from online public databases, such as PubMed, Google Scholar, and ScienceDirect. The search approach used to retrieve related articles were "prevalence," "malaria," "adults," and "Ethiopia." The quality of articles was assessed using Joana Brigg's Institute (JBI) critical appraisal checklist. The meta-analysis was computed using STATA version 14. The pooled prevalence estimates with 95% confidence interval were analyzed using a random-effect model, and the possible source of heterogeneity across studies was indicated through subgroup analysis, inverse of variance (I ²), and time series analysis. The presence of publication bias was evaluated using funnel plots and Egger's regression test.

Results

Out of 144 studies collected, only eight full-text articles were screened and included in the final quantitative meta-analysis. The pooled prevalence of malaria among adults in Ethiopia was 13.61%. Subgroup analysis based on types of malaria cases showed that the prevalence of malaria among symptomatic and asymptomatic adults was 15.34% and 11.99%, respectively. Similarly, regional subgroup analysis showed that the highest malaria prevalence was recorded in Southern Nations, Nationalities, and Peoples' Region (SNNPR) (16.17%) followed by Oromia Regional State (13.11%) and Amhara Regional State (12.41%). Discussion and Conclusion. The current systematic review and meta-analysis showed that the pooled prevalence of malaria among adults was found to be greater than the general population and nearly equal to pregnant women. Therefore, the current prevention and control measures, which are related to both vectors and parasites, should be strengthened.

Country size bias in global health: cross-country comparison of malaria policy and foreign aid

Background

Foreign aid has been shown to be favourably biased towards small countries. This study investigated whether country size bias also occurs in national malaria policy and development assistance from international agencies.

Methods

Data from publicly available sources were collected with countries as observational units. The exploratory data analysis was based on the conceptual framework with socio-economic, environmental and institutional parameters. The strength of relationships was estimated by the Pearson and polychoric correlation coefficients. The correlation matrix was explored by factor analysis.

Results

Malaria burden is strongly correlated with GDP per capita, total health expenditure per capita, HDI; moderately with latitude, weakly with elevation, urban population share, per capita funding from the Global Fund, PMI USAID, UK government and UNICEF. Small country status is strongly correlated with population size, land area, island status; moderately with development assistance received per capita, weakly with funding per capita from Global Fund, government NMP and PMI USAID. Policy score 1, a variable derived from our factor analysis and related to malaria endemicity, is significantly strongly correlated with the malaria burden, moderately with HDI, GDP per capita, total health expenditure per capita, PMI USAID funding; weakly with island status, urban population share, latitude, coastal population share, total government expenditure and trade openness, Global Fund funding, World Bank funding, UK government funding, and UNICEF funding per capita. Policy score 2, which captures variation not related to malaria endemicity, is significantly weakly related to the ICRG index, PMI USAID funding per capita and small country status.

Conclusions

The results suggest that malaria burden and economic development are bidirectionally related. Economic development can contribute to a reduction in the malaria burden. Country size does not negatively impact malaria burden, but it does account for greater development assistance per capita from selected international agencies. National malaria policy is associated with parameters related to public governance and is modified in small countries. Small country bias is present in the distribution of socio-economic resources and the allocation of foreign aid. Small countries are characterized by distinct environmental and socio-political properties.

Supplementary information

Supplementary information accompanies this paper at 10.1186/s41256-020-00176-x.

Modeling Relapsing Malaria: Emerging Technologies to Study Parasite-Host Interactions in the Liver

Recent studies of liver stage malaria parasite-host interactions have provided exciting new insights on the cross-talk between parasite and its mammalian (predominantly rodent) host. We review the latest state of the art and and zoom in on new technologies that will provide the tools necessary to investigate host-parasite interactions of relapsing parasites. Interactions between hypnozoites and hepatocytes are particularly interesting because the parasite can remain in a quiescent state for prolonged periods of time and triggers for reactivation have not been irrefutably identified. If we learn more about the cross-talk between hypnozoite and host we may be able to identify factors that encourage waking up these dormant parasite reservoirs and help to achieve the total eradication of malaria.

The elusive parasite: comparing macroscopic, immunological, and genomic approaches to identifying malaria in human skeletal remains from Sayala, Egypt (third to sixth centuries AD)

Although malaria is one of the oldest and most widely distributed diseases affecting humans, identifying and characterizing its presence in ancient human remains continue to challenge researchers. We attempted to establish a reliable approach to detecting malaria in human skeletons using multiple avenues of analysis: macroscopic observations, rapid diagnostic tests, and shotgun-capture sequencing techniques, to identify pathological changes, Plasmodium antigens, and Plasmodium DNA, respectively. Bone and tooth samples from ten individuals who displayed skeletal lesions associated with anaemia, from a site in southern Egypt (third to sixth centuries AD), were selected. Plasmodium antigens were detected in five of the ten bone samples, and traces of Plasmodium aDNA were detected in six of the twenty bone and tooth samples. There was relatively good synchronicity between the biomolecular findings, despite not being able to authenticate the results. This study highlights the complexity and limitations in the conclusive identification of the Plasmodium parasite in ancient human skeletons. Limitations regarding antigen and aDNA preservation and the importance of sample selection are at the forefront of the search for malaria in the past. We confirm that, currently, palaeopathological changes such as cribra orbitalia are not enough to be certain of the presence of malaria. While biomolecular methods are likely the best chance for conclusive identification, we were unable to obtain results which correspond to the current authentication criteria of biomolecules. This study represents an important contribution in the refinement of biomolecular techniques used; also, it raises new insight regarding the consistency of combining several approaches in the identification of malaria in past populations.

SUPPLEMENTARY INFORMATION

The online version contains supplementary material available at 10.1007/s12520-021-01350-z.

Biosensing based on field-effect transistors (FET): Recent progress and challenges

The use of field-Effect-Transistor (FET) type biosensing arrangements has been highlighted by researchers in the field of early biomarker detection and drug screening. Their non-metalized gate dielectrics that are exposed to an electrolyte solution cover the semiconductor material and actively transduce the biological changes on the surface. The efficiency of these novel devices in detecting different biomolecular analytes in a real-time, highly precise, specific, and label-free manner has been validated by numerous research studies. Considerable progress has been attained in designing FET devices, especially for biomedical diagnosis and cell-based assays in the past few decades. The exceptional electronic properties, compactness, and scalability of these novel tools are very desirable for designing rapid, label-free, and mass detection of biomolecules. With the incorporation of nanotechnology, the performance of biosensors based on FET boosts significantly, particularly, employment of nanomaterials such as graphene, metal nanoparticles, single and multi-walled carbon nanotubes, nanorods, and nanowires. Besides, their commercial availability, and high-quality production on a large-scale, turn them to be one of the most preferred sensing and screening platforms. This review presents the basic structural setup and working principle of different types of FET devices. We also focused on the latest progression regarding the use of FET biosensors for the recognition of viruses such as, recently emerged COVID-19, Influenza, Hepatitis B Virus, protein biomarkers, nucleic acids, bacteria, cells, and various ions. Additionally, an outline of the development of FET sensors for investigations related to drug development and the cellular investigation is also presented. Some technical strategies for enhancing the sensitivity and selectivity of detection in these devices are addressed as well. However, there are still certain challenges which are remained unaddressed concerning the performance and clinical use of transistor-based point-of-care (POC) instruments; accordingly, expectations about their future improvement for biosensing and cellular studies are argued at the end of this review.