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

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.

Factors Associated with Malaria Infection among Head Porters in Agbogbloshie Market in the Greater Accra Region of Ghana

Background

Head porters constitute the mobile population who are at an increasing risk of being infected with malaria. They move around the city to carry out their duties with no accommodation. Therefore, they sleep wherever they find themselves in the evening and do not benefit from most of the malaria intervention programs such as the use of long-lasting insecticide net. The inability to identify them because they are mobile means that they can continue to drive malaria transmission even if malaria in the general population is controlled.

Objectives

This study assessed the factors associated with malaria infection among head porters in the Agbogbloshie market in the Greater Accra Region of Ghana.

Method

A total of 218 head porters were recruited from the Agbogbloshie market, and blood samples were collected from participants to test for malaria parasite infection using Rapid Diagnostic Test (RDT) and microscopy and were interviewed using a closed-ended questionnaire. The data were analyzed using Stata version 15. Simple descriptive statistics, Pearson chi-square, and Multiple Logistic Regression were performed with significance set at <0.05.

Result

The study revealed 12% (CI 95% = 8.2‐16.9) and 9.6% (CI 95% = 6.3‐14.4) infection of malaria using RDT and microscopy, respectively. Plasmodium falciparum (21/218) was the main parasite detected in all positive blood samples. Age and marital status are significant factors associated with malaria infection among head porters. Age group 40 years and above had 89% (AOR 0.11 (CI 95% = 0.01‐0.98)) reduced odds of getting malaria compared to those below 20 years, while those who are single are 3.52 times more likely to be infected with malaria compared with those who are married (AOR (95%CI) = 3.52 (1.13‐10.92)).

Conclusion

This study concludes that the increasing age of head porters significantly decreased the probability of malaria infection, while head porters who are single have greater odds of being infected with malaria. Age and marital status are important factors to be considered for malaria intervention programs in head porters.

Lack of Consistent Malaria Incidence Hotspots in a Highland Kenyan Area During a 10-Year Period of Very Low and Unstable Transmission

The use of spatial data in malaria elimination strategies is important to understand whether targeted interventions against malaria can be used, particularly in areas with limited resources. We previously documented consistent areas of increased malaria incidence in the epidemic-prone area of Kipsamoite in highland Kenya from 2001 to 2004. In this area and a neighboring subcounty (Kapsisiywa), malaria incidence decreased substantially in 2005, going from peak incidence of 31.7 per 1,000 persons in June 2004 to peak incidence of 7.4 per 1,000 persons in May 2005. Subsequently, the use of indoor residual spraying and artemisinin combination therapy malaria treatment led to a possible interruption of malaria transmission for a 13-month period from 2007 to 2008, after which the incidence returned to very low levels until an epidemic in April-July 2013. In the present study, we used novel kernel density estimation methods to determine whether areas of increased malaria incidence were consistent in six periods of peak incidence from 2003 to 2013, and to assess patterns of incidence in the period before versus. after the period of possible interruption. Areas of highest incidence differed during peak malaria transmission periods over the years 2003-2013, and differed before and after the potential malaria interruption. In this epidemic-prone region with very low malaria transmission, consistent malaria "hotspots" identified in a time of higher transmission are no longer present. Ongoing assessment of spatial malaria epidemiology to identify and target current areas of elevated malaria risk may be important in campaigns to control or eliminate malaria in epidemic-prone areas.

Updates on malaria epidemiology and profile in Cabo Verde from 2010 to 2019: the goal of elimination

BACKGROUND

Located in West Africa, Cabo Verde is an archipelago consisting of nine inhabited islands. Malaria has been endemic since the settlement of the islands during the sixteenth century and is poised to achieve malaria elimination in January 2021. The aim of this research is to characterize the trends in malaria cases from 2010 to 2019 in Cabo Verde as the country transitions from endemic transmission to elimination and prevention of reintroduction phases.

METHODS

All confirmed malaria cases reported to the Ministry of Health between 2010 and 2019 were extracted from the passive malaria surveillance system. Individual-level data available included age, gender, municipality of residence, and the self-reported countries visited if travelled within the past 30 days, therby classified as imported. Trends in reported cases were visualized and multivariable logistic regression used to assess risk factors associated with a malaria case being imported and differences over time.

RESULTS

A total of 814 incident malaria cases were reported in the country between 2010 and 2019, the majority of which were Plasmodium falciparum. Overall, prior to 2017, when the epidemic occurred, 58.1% (95% CI 53.6-64.6) of infections were classified as imported, whereas during the post-epidemic period, 93.3% (95% CI 86.9-99.7) were imported. The last locally acquired case was reported in January 2018. Imported malaria cases were more likely to be 25-40 years old (AOR: 15.1, 95% CI 5.9-39.2) compared to those under 15 years of age and more likely during the post-epidemic period (AOR: 56.1; 95% CI 13.9-225.5) and most likely to be reported on Sao Vicente Island (AOR = 4256.9, 95% CI = 260-6.9e+4) compared to Boavista.

CONCLUSIONS

Cabo Verde has made substantial gains in reducing malaria burden in the country over the past decade and are poised to achieve elimination in 2021. However, the high mobility between the islands and continental Africa, where malaria is still highly endemic, means there is a constant risk of malaria reintroduction. Characterization of imported cases provides useful insight for programme and enables better evidence-based decision-making to ensure malaria elimination can be sustained.

Phosphorylation of Rhoptry Protein RhopH3 Is Critical for Host Cell Invasion by the Malaria Parasite

Host cell invasion by the malaria parasite is critical for establishing infection in human host and is dependent on discharge of key ligands from organelles like rhoptry and microneme, and these ligands interact with host RBC receptors. In the present study, we demonstrate that phosphorylation of a key rhoptry protein, RhopH3, is critical for host invasion. Phosphorylation regulates its localization to rhoptries and discharge from the parasite.

Merozoites formed after asexual division of the malaria parasite invade the host red blood cells (RBCs), which is critical for initiating malaria infection. The process of invasion involves specialized organelles like micronemes and rhoptries that discharge key proteins involved in interaction with host RBC receptors. RhopH complex comprises at least three proteins, which include RhopH3. RhopH3 is critical for the process of red blood cell (RBC) invasion as well as intraerythrocytic development of human malaria parasite Plasmodium falciparum. It is phosphorylated at serine 804 (S804) in the parasite; however, it is unclear if phosphorylation regulates its function. To address this, a CRISPR-CAS9-based approach was used to mutate S804 to alanine (A) in P. falciparum. Using this phosphomutant (R3_S804A) of RhopH3, we demonstrate that the phosphorylation of S804 is critical for host RBC invasion by the parasite but not for its intraerythrocytic development. Importantly, the phosphorylation of RhopH3 regulates its localization to the rhoptries and discharge from the parasite, which is critical for RBC invasion. We also identified P. falciparum CDPK1 (PfCDPK1) as a possible candidate kinase for RhopH3-S804 phosphorylation and found that it regulates RhopH3 secretion from the parasite. These findings provide novel insights into the role of phosphorylation in rhoptry release and invasion, which is poorly understood.

Transmission of West Nile and five other temperate mosquito-borne viruses peaks at temperatures between 23°C and 26°C

The temperature-dependence of many important mosquito-borne diseases has never been quantified. These relationships are critical for understanding current distributions and predicting future shifts from climate change. We used trait-based models to characterize temperature-dependent transmission of 10 vector-pathogen pairs of mosquitoes (Culex pipiens, Cx. quinquefascsiatus, Cx. tarsalis, and others) and viruses (West Nile, Eastern and Western Equine Encephalitis, St. Louis Encephalitis, Sindbis, and Rift Valley Fever viruses), most with substantial transmission in temperate regions. Transmission is optimized at intermediate temperatures (23-26°C) and often has wider thermal breadths (due to cooler lower thermal limits) compared to pathogens with predominately tropical distributions (in previous studies). The incidence of human West Nile virus cases across US counties responded unimodally to average summer temperature and peaked at 24°C, matching model-predicted optima (24-25°C). Climate warming will likely shift transmission of these diseases, increasing it in cooler locations while decreasing it in warmer locations.

Antimalarial effect of cell penetrating peptides derived from the junctional region of Plasmodium falciparum dihydrofolate reductase-thymidylate synthase

Dihydrofolate reductase-thymidylate synthase of Plasmodium falciparum (PfDHFR-TS) is an important target of antifolate antimalarial drugs. However, drug resistant parasites are widespread in malaria endemic regions. The unique bifunctional property of PfDHFR-TS could be exploited for the design of allosteric inhibitors that interfere with the active dimer conformation. In this study, peptides were derived from the junctional region (JR) of PfDHFR-TS amino acid sequence in the α_j1 helix (JR-helix) and the DHFR domain that is necessary for interaction with α_j1 helix (JR21). Five peptides were synthesized and tested for inhibition of PfDHFR-TS enzyme by Bacterial inhibition assay (BIA) based on the growth of an E. coli DHFR and TS knockout complemented with a recombinant plasmid expressing PfDHFR-TS enzyme. Significant inhibition was observed for JR21 and JR21 conjugated to cell-penetrating octa-arginine peptide (rR8-JR21) with 50 % inhibitory concentration (IC₅₀) of 3.87 and 1.53 μM, respectively. The JR-helix and rR8-JR-helix peptides were inactive. JR21 and rR8-JR21 peptides showed similar growth inhibitory effects on P. falciparum NF54 parasites cultured in vitro. Treatment with rR8-JR21 delayed parasite development, in which an accumulation of ring stage parasites was observed after 12 h of culture. Minimal red blood cell (RBC) hemolysis was observed at the highest dose of peptide tested. The most potent peptide rR8-JR21 not only compromised the development of the P. falciparum, but also inhibited the parasite growth and has low hemolytic effect on human RBCs.

In Vivo Antimalarial Activity of Crude Fruit Extract of Capsicum frutescens Var. Minima (Solanaceae) against Plasmodium berghei-Infected Mice

BACKGROUND

The alarming spread of parasite resistance to current antimalarial agents is threatening malaria controlling efforts. This, consequently, urged the scientific community to discover novel antimalarial drugs. Successful and most potent antimalarial drugs were obtained from medicinal plants. Capsicum frutescens is claimed to possess an antiplasmodial activity in Ethiopian and Ugandan folkloric medicine. However, there is a lack of pharmacological evidence for its antiplasmodial activity. This study, hence, was aimed at evaluating the in vivo antiplasmodial activity of C. frutescens in a mouse model.

METHODS

The dried fruits of the plant were extracted with 80% methanol using cold maceration. A 4-day suppressive test was employed to ascertain the claimed antiplasmodial effect of the plant. Following inoculation with P. berghei, mice in treatment groups were provided with three dose levels (100, 200, and 400 mg/kg) of the extract, while 2% Tween 80 and chloroquine served as the negative and positive controls, respectively. Weight, temperature, packed cell volume, parasitemia, and survival time were then monitored.

RESULTS

The acute oral toxicity study revealed that the crude extract caused no mortality and revealed no overt sign of toxicity. In the 4-day suppressive test, all dose levels of the extract were found to exhibit a significant (p < 0.05) inhibition of parasitemia compared to those of the negative control. Maximum parasite suppression (93.28%) was exerted by the highest dose (400 mg/kg/day) of extract. Also, the extract significantly (p < 0.05) prolonged survival time and prevented body weight loss and reduction in temperature and anemia compared to the vehicle-treated group.

CONCLUSION

This investigation found strong evidence that the fruit extract of C. frutescens is endowed with promising antiplasmodial activity. Hence, the plant could serve as a potential source of a newer antimalarial agent.

The host targeting effect of chloroquine in malaria

Due to the rapid onset and spread of the COVID-19 pandemic, the treatment of COVID-19 patients by hydroxychloroquine alone or in combination with other drugs has captured a great deal of attention and triggered considerable debate. Historically, the worldwide use of quinoline based-drugs has led to a spectacular reduction in death from malaria. Unfortunately, scientists have been forced to seek alternative drugs to treat malaria due to the emergence of chloroquine-resistant parasites in the 1960s. The repurposing of hydroxychloroquine against viral infections, various types of cancer and autoimmune diseases has been ongoing for more than 70 years, with no clear understanding of its mechanism of action (MOA). Here, we closely examine the MOA of this old but influential drug in and beyond malaria. Better insights into how chloroquine targets the host's cellular and immune responses may help to develop applications against to new pathogens and diseases, and perhaps even restore the clinical utility of chloroquine against malaria.

Tuberculosis: a timeless challenge for medicine

This overview shows how tuberculosis has represented and still represents a continuous challenge for Medicine. Starting from the dawn of medicine, when tuberculosis was called “phthisis” by Hippocrates, passing through the discovery of the tubercles and the creation of the word “tuberculosis”, following the application of the anatomo-clinical method, until the discovery of a microscopic enemy: Mycobacterium tuberculosis. The progressive discovery of the pathological basis of tuberculosis has allowed to devise important therapeutic strategies in Pre-Antibiotic and Post-Antibiotic Era. In particular, “antibiotic therapy” had to be the end of the challenge between man and tuberculosis. However it was only an illusion. Despite progress in care and prevention, tuberculosis remains one of the world’s leading causes of ill-health and the first cause of death from infectious disease. Nowadays, the drug resistance, individuals with immune deficiencies, the ageing and globalization are just some of the causes responsible for the increasing of the challenge between man and tuberculosis.

Effect of Impregnated Mosquito Bed Nets on the Prevalence of Malaria among Pregnant Women in Foumban Subdivision, West Region of Cameroon

Background

Malaria is one of the major public health problems in many tropical developing countries including Cameroon. Impregnated mosquito bed nets are one of the control measures put in place by the WHO and adopted by the Cameroon's Ministry of Public Health to fight against malaria in pregnancy. This study was a population-based cross-sectional study that investigated the level of adherence, respondent's knowledge, altitude, and practices toward malaria prevention and control.

Methods

To investigate this, a sample size of 410 pregnant women who were inhabitants of Foumban Subdivision was examined. Data on net ownership versus usage, pregnancy status, and socioeconomic background were collected using a questionnaire. Parasitological tests for malaria parasites were carried out using peripheral blood samples obtained from finger pricks of the pregnant women for the preparation of thick blood smear and RDTs.

Results

Two hundred and eighteen tested positive (53.4%) with the highest prevalence occurring during the first trimester (79.6%) and in primigravidae (68.8%). Participants believed that mosquito bed nets can protect them against malaria infection. The highest number (81.0%) of the women who had mosquito nets acquired them during antenatal visits. Among those who possessed nets, 42.7% adhered to sleeping under them and few (50%) experienced problems of sweating, discomfort, and heat. Also, the study revealed a high prevalence rate of 63.8% for those who did not use nets during pregnancy as compared to those who owned and used them.

Conclusion

The findings indicated that increased access to impregnated mosquito bed nets is required to lower the risk of malaria infection amongst pregnant women. The Cameroon government should improve health education to families within the locality and pursue an integrated approach to fight against mosquitoes during the rainy season.

Purification and production of Plasmodium falciparum zygotes from in vitro culture using magnetic column and Percoll density gradient

Background

Plasmodium falciparum zygotes develop in the mosquito midgut after an infectious blood meal containing mature male and female gametocytes. Studies of mosquito-produced P. falciparum zygotes to elucidate their biology and development have been hampered by high levels of contaminating mosquito proteins and macromolecules present in zygote preparations. Thus, no zygote-specific surface markers have been identified to date. Here, a methodology is developed to obtain large quantities of highly purified zygotes using in vitro culture, including purification methods that include magnetic column cell separation (MACS) followed by Percoll density gradient centrifugation. This straightforward and effective approach provides ample material for studies to enhance understanding of zygote biology and identify novel zygote surface marker candidates that can be tested as transmission blocking vaccine (TBV) candidates.

Methods

Plasmodium falciparum gametocyte cultures were established and maintained from asexual cultures. Gametocytes were matured for 14 days, then transferred into zygote media for 6 h at 27 ± 2 °C to promote gamete formation and fertilization. Zygotes were then purified using a combination of MACS column separation and Percoll density gradient centrifugation. Purity of the zygotes was determined through morphological studies: the parasite body and nuclear diameter were measured, and zygotes were further transformed into ookinetes. Immunofluorescence assays (IFA) were also performed using the ookinete surface marker, Pfs28.

Results

After stimulation, the culture consisted of transformed zygotes and a large number of uninfected red blood cells (RBCs), as well as infected RBCs with parasites at earlier developmental stages, including gametes, gametocytes, and asexual stages. The use of two MACS columns removed the vast majority of the RBCs and gametocytes. Subsequent use of two Percoll density gradients enabled isolation of a pure population of zygotes. These zygotes transformed into viable ookinetes that expressed Pfs28.

Conclusion

The combined approach of using two MACS columns and two Percoll density gradients yielded zygotes with very high purity (45-fold enrichment and a pure population of zygotes [approximately 100%]) that was devoid of contamination by other parasite stages and uninfected RBCs. These enriched zygotes, free from earlier parasites stages and mosquito-derived macromolecules, can be used to further elucidate the biology and developmental processes of Plasmodium.

Prevalence of and factors associated with malaria in children under five years of age in Malawi, using malaria indicator survey data

BACKGROUND

Malaria remains a public health problem in developing countries and Malawi is no different. Although there has been an improvement in reducing malaria in Malawi, it remains a problem, especially in children less than five years old. The primary objective of the study was to assess whether socio-economic, geographic and demographic factors are associated with malaria, using the generalized additive mixed model (GAMM).

DATA AND METHODOLOGY

The study used a 2017 dataset from the Malawi Malaria Indicator Survey (MMI) with a total number of 2724 children under five years old. The study also utilized the GAMM to analyze data. The outcome was that either the child had malaria or did not, as detected using the malaria Rapid Diagnostic Test (RDT) (Ayele et al., 2014a).

RESULTS

In this study, more than 37 % of the total number of children who were tested showed a positive malaria result. In addition, the results from this study using GAMM indicated that anaemia, mother's education level, wealth index, child's age, the altitude of the place of residence, region, place of residence, toilet facility and electricity were significantly associated with a positive malaria RDT.

CONCLUSION

The study revealed that socio-economic, geographical and demographic variables are the key factors in improving malaria vectors in children. Improving income levels and supporting the poorer rural community mostly from the Central Region would be a great achievement in reducing malaria vectors in Malawi. In addition, improving health care in rural areas, especially at higher altitudes, would contribute to controlling malaria and reducing anaemia.

The IL-33/ST2 Axis in Immune Responses Against Parasitic Disease: Potential Therapeutic Applications

Parasitic infections pose a wide and varying threat globally, impacting over 25% of the global population with many more at risk of infection. These infections are comprised of, but not limited to, toxoplasmosis, malaria, leishmaniasis and any one of a wide variety of helminthic infections. While a great deal is understood about the adaptive immune response to each of these parasites, there remains a need to further elucidate the early innate immune response. Interleukin-33 is being revealed as one of the earliest players in the cytokine milieu responding to parasitic invasion, and as such has been given the name "alarmin." A nuclear cytokine, interleukin-33 is housed primarily within epithelial and fibroblastic tissues and is released upon cellular damage or death. Evidence has shown that interleukin-33 seems to play a crucial role in priming the immune system toward a strong T helper type 2 immune response, necessary in the clearance of some parasites, while disease exacerbating in the context of others. With the possibility of being a double-edged sword, a great deal remains to be seen in how interleukin-33 and its receptor ST2 are involved in the immune response different parasites elicit, and how those parasites may manipulate or evade this host mechanism. In this review article we compile the current cutting-edge research into the interleukin-33 response to toxoplasmosis, malaria, leishmania, and helminthic infection. Furthermore, we provide insight into directions interleukin-33 research may take in the future, potential immunotherapeutic applications of interleukin-33 modulation and how a better clarity of early innate immune system responses involving interleukin-33/ST2 signaling may be applied in development of much needed treatment options against parasitic invaders.

GHS-POP Accuracy Assessment: Poland and Portugal Case Study

The Global Human Settlement Population Grid (GHS-POP) the latest released global gridded population dataset based on remotely sensed data and developed by the EU Joint Research Centre, depicts the distribution and density of the total population as the number of people per grid cell. This study aims to assess the GHS-POP data accuracy based on root mean square error (RMSE), mean absolute error (MAE), and mean absolute percentage error (MAPE) and the correlation coefficient. The study was conducted for Poland and Portugal, countries characterized by different population distribution as well as two spatial resolutions of 250 m and 1 km on the GHS-POP. The main findings show that as the size of administrative zones decreases (from NUTS (Nomenclature of Territorial Units for Statistics) to LAU (local administrative unit)) and the size of the GHS-POP increases, the difference between the population counts reported by the European Statistical Office and estimated by the GHS-POP algorithm becomes larger. At the national level, MAPE ranges from 1.8% to 4.5% for the 250 m and 1 km resolutions of GHS-POP data in Portugal and 1.5% to 1.6%, respectively in Poland. At the local level, however, the error rates range from 4.5% to 5.8% in Poland, for 250 m and 1 km, and 5.7% to 11.6% in Portugal, respectively. Moreover, the results show that for densely populated regions the GHS-POP underestimates the population number, while for thinly populated regions it overestimates. The conclusions of this study are expected to serve as a quality reference for potential users and producers of population density datasets.

Safety Considerations for Malaria Volunteer Infection Studies: A Mini-Review

Malaria clinical studies entailing the experimental infection of healthy volunteers with Plasmodium parasites by bites from infected mosquitos, injection of cryopreserved sporozoites, or injection of blood-stage parasites provide valuable information for vaccine and drug development. Success of these studies depends on maintaining safety. In this mini-review, we discuss the safety risks and associated mitigation strategies of these three types of experimental malaria infection. We aimed to inform researchers and regulators who are currently involved in or are planning to establish experimental malaria infection studies in endemic or non-endemic settings.

Plasmodium vivax Malaria Viewed through the Lens of an Eradicated European Strain

The protozoan Plasmodium vivax is responsible for 42% of all cases of malaria outside Africa. The parasite is currently largely restricted to tropical and subtropical latitudes in Asia, Oceania, and the Americas. Though, it was historically present in most of Europe before being finally eradicated during the second half of the 20th century. The lack of genomic information on the extinct European lineage has prevented a clear understanding of historical population structuring and past migrations of P. vivax. We used medical microscope slides prepared in 1944 from malaria-affected patients from the Ebro Delta in Spain, one of the last footholds of malaria in Europe, to generate a genome of a European P. vivax strain. Population genetics and phylogenetic analyses placed this strain basal to a cluster including samples from the Americas. This genome allowed us to calibrate a genomic mutation rate for P. vivax, and to estimate the mean age of the last common ancestor between European and American strains to the 15th century. This date points to an introduction of the parasite during the European colonization of the Americas. In addition, we found that some known variants for resistance to antimalarial drugs, including Chloroquine and Sulfadoxine, were already present in this European strain, predating their use. Our results shed light on the evolution of an important human pathogen and illustrate the value of antique medical collections as a resource for retrieving genomic information on pathogens from the past.

Antimalarial herbal remedies of Bukavu and Uvira areas in DR Congo: An ethnobotanical survey

ETHNOPHARMACOLOGICAL RELEVANCE

The main objective of the present study was to collect and gather information on herbal remedies traditionally used for the treatment of malaria in Bukavu and Uvira, two towns of the South Kivu province in DRC.

MATERIAL AND METHODS

Direct interview with field enquiries allowed collecting ethnobotanical data; for each plant, a specimen was harvested in the presence of the interviewed traditional healers (THs). The recorded information included vernacular names, morphological parts of plants, methods of preparation and administration of remedies, dosage and treatment duration. Plants were identified with the help of botanists in the herbaria of INERA/KIPOPO (DRC) and the Botanic Garden of Meise (Belgium), where voucher specimens have been deposited. The results were analysed and discussed in the context of previous published data.

RESULTS

Interviewees cited 45 plant species belonging to 41 genera and 21 families used for the treatment of malaria. These plants are used in the preparation of 52 recipes, including 25 multi-herbal recipes and 27 mono-herbal recipes. Apart of Artemisia annua L. (Asteraceae; % Citation frequency = 34%) and Carica papaya L. (Caricaceae; % Citation frequency = 34%), the study has highlighted that the most represented families are Asteraceae with 12 species (26%), followed by Fabaceae with 7 species (16%) and Rubiaceae with 4 species (9%). For a majority of plants, herbal medicines are prepared from the leaves in the form of decoction and administered by oral route.

CONCLUSION

Literature data indicate that part of cited species are already known (38%) and/or studied (30%) for antimalarial properties, which gives credit to the experience of Bukavu and Uvira interviewees and some level of confidence on collected information. The highly cited plants should be investigated in details for the isolation and identification of active ingredients, a contribution to the discovery of new possibly effective antimalarials.

The effect of urbanization and climate change on the mosquito population in the Pearl River Delta region of China

The rising incidence of mosquito-borne diseases is a global concern. Changes in regional climate, due to urbanization and global greenhouse gas concentrations, may affect the ecology of mosquitoes and mosquito-transmitted pathogens. The effects of changes in climate on mosquito population dynamics are complex but critical and urgent for implementing more effective public health policies. This study quantified the impact of urbanization and global climate change on the population of the mosquito species, Culex quinquefasciatus, in the Pearl River Delta region in southern China-an area that has undergone substantial urbanization and is expected to experience changes in climate. This study employed a mechanistic model to simulate mosquito population dynamics under various greenhouse gas emission and land-cover change scenarios based on climate data provided by a state-of-the-art regional climate model. Our results show a 12.6% decrease in the annual mosquito population in newly urbanized areas and a 5.9% increase in the annual mosquito population in existing urban areas. Furthermore, changing climate conditions are projected to cause a 15-17% reduction in the total annual mosquito population; however, the change will not be uniform throughout the year. Peak months exhibit a reduction in population, whereas non-peak months show a significant increase. These findings suggest mosquito control strategies may need to be adjusted to respond to the impacts of urbanization and climate change on mosquito population dynamics to maximize effectiveness. Region specific, quantitative analyses of environmental impacts on mosquito-borne disease ecology, like this study, are needed to provide policy makers with a scientific reference to guide the formation of effective transmission intervention strategies.

Antimalarial Activity of Aqueous and 80% Methanol Crude Seed Extracts and Solvent Fractions of Schinus molle Linnaeus (Anacardiaceae) in Plasmodium berghei-Infected Mice

BACKGROUND

Malaria is among the leading causes of mortality and morbidity. Moreover, the emergence of resistance to antimalarial drugs is a major problem in controlling the disease. This makes the development of novel antimalarial drugs a necessity. Medicinal plants are important sources in discovering antimalarial drugs. Schinus molle is claimed for its antimalarial effect in Ethiopian folkloric medicine and endowed with in vitro antiplasmodial activity. In the present study, the in vivo antimalarial activity of the plant was investigated.

METHODS

Acute toxicity was carried out using a standard procedure. To screen the in vivo antimalarial activity of the plant was investigated. S. molle against Plasmodium berghei (ANKA), a 4-day suppressive test was employed. The extracts and fractions were given to infected mice by oral gavage at 100, 200, and 400 mg/kg/day for four consecutive days. Parameters such as parasitemia were then evaluated.

RESULTS

Any sign of toxicity was not observed in the oral acute toxicity test. The crude extracts and solvent fractions exerted a significant (p < 0.05) inhibition of parasite load compared to the negative control. The highest inhibition (66.91%) was exhibited by the 400 mg/kg/day dose of 80% methanolic crude extract. Among the fractions, chloroform fraction demonstrated maximal chemosuppressive effect (55.60%). Moreover, crude extracts and solvent fractions prevented body weight loss, reduction in temperature, and anemia compared to the negative control. Except the aqueous fraction, the tested plant extracts were able to significantly prolong the survival time of infected mice.

CONCLUSION

The findings of the present study confirmed the safety and a promising in vivo antimalarial activity of S. molle, thus supporting the traditional claim and in vitro efficacy. In-depth investigations on the plant, however, are highly recommended.in vivo antimalarial activity of the plant was investigated. S. molle against in vitro antiplasmodial activity. In the present study, the.

Mapping Worldwide Environmental Suitability for Artemisia annua L

Artemisinin, which is isolated from the naturally occurring plant Artemisia annua L. (A. annua; Qinghao in traditional Chinese medicine), is considered to be the active ingredient in the most effective treatment for malaria. Current malaria eradication plans rely on an affordable and robust supply of artemisinin, resulting in the demand to expand the area of A. annua under cultivation. However, there is no reliable assessment of the potential land resources suitable for planting A. annua at the global scale. By explicitly incorporating the assembled contemporary occurrence records of A. annua with various spatial predictor variables, a species distribution modelling procedure was adopted to produce the first global environmental suitability map for A. annua with high geographic detail (5 × 5 km2). The estimated map reveals that the total amount of potential land resources suitable for planting A. annua is approximately 1496.56 million hectares, mainly distributed in Asia (516.50 million hectares), Europe (378.82 million hectares), North America (354.56 million hectares) and South America (172.01 million hectares). The relationships between the relevant variables and A. annua were explored, and these illustrated that the most noteworthy predictor variables were meteorological factors, followed by solar radiation factors, soil factors and topographical factors. The map provides a rigorous environmental niche baseline to support the reasonable expansion of the A. annua cultivation area.

Lizards and rabbits may increase Chagas infection risk in the Mediterranean-type ecosystem of South America

Studies of host-parasite relationships largely benefit from adopting a multifactorial approach, including the complexity of multi-host systems and habitat features in their analyses. Some host species concentrate most infection and contribute disproportionately to parasite and vector population maintenance, and habitat feature variation creates important heterogeneity in host composition, influencing infection risk and the fate of disease dynamics. Here, we examine how the availability of specific groups of hosts and habitat features relate to vector abundance and infection risk in 18 vector populations along the Mediterranean-type ecosystem of South America, where the kissing bug Mepraia spinolai is the main wild vector of the parasite Trypanosoma cruzi, the etiological agent of Chagas disease. For each population, data on vectors, vertebrate host availability, vegetation, precipitation, and temperature were collected and analyzed. Vector abundance was positively related to temperature, total vegetation, and European rabbit availability. Infection risk was positively related to temperature, bromeliad cover, and reptile availability; and negatively to the total domestic mammal availability. The invasive rabbit is suggested as a key species involved in the vector population maintenance. Interestingly, lizard species -a group completely neglected as a potential reservoir-, temperature, and bromeliads were relevant factors accounting for infection risk variation across populations.

Forest Goers and Multidrug-Resistant Malaria in Cambodia: An Ethnographic Study

Multidrug-resistant Plasmodium falciparum malaria on the Cambodia-Thailand border is associated with working in forested areas. Beyond broad recognition of "forest-going" as a risk factor for malaria, little is known about different forest-going populations in this region. In Oddar Meanchey Province in northwestern Cambodia, qualitative ethnographic research was conducted to gain an in-depth understanding of how different populations, mobility and livelihood patterns, and activities within the forest intersect with potentiate malaria risk and impact on the effectiveness of malaria control and elimination strategies. We found that most forest-going in this area is associated with obtaining precious woods, particularly Siamese rosewood. In the past, at-risk populations included large groups of temporary migrants. As timber supplies have declined, so have these large migrant groups. However, groups of local residents continue to go to the forest and are staying for longer. Most forest-goers had experienced multiple episodes of malaria and were well informed about malaria risk. However, economic realities mean that local residents continue to pursue forest-based livelihoods. Severe constraints of available vector control methods mean that forest-goers have limited capacity to prevent vector exposure. As forest-goers access the forest using many different entry and exit points, border screening and treatment interventions will not be feasible. Once in the forest, groups often converge in the same areas; therefore, interventions targeting the mosquito population may have a potential role. Ultimately, a multisectoral approach as well as innovative and flexible malaria control strategies will be required if malaria elimination efforts are to be successful.

Immunological Evaluation of Synthetic Glycosylphosphatidylinositol Glycoconjugates as Vaccine Candidates against Malaria

Glycosylphosphatidylinositols (GPIs) are complex glycolipids present on the surfaces of Plasmodium parasites that may act as toxins during the progression of malaria. GPIs can activate the immune system during infection and induce the formation of anti-GPI antibodies that neutralize their activity. Therefore, an antitoxic vaccine based on GPI glycoconjugates may prevent malaria pathogenesis. To evaluate the role of three key modifications on Plasmodium GPI glycan in the activity of these glycolipids, we synthesized and investigated six structurally distinct GPI fragments from Plasmodium falciparum. The synthetic glycans were conjugated to the CRM197 carrier protein and were tested for immunogenicity and efficacy as antimalarial vaccine candidates in an experimental cerebral malaria model using C57BL/6JRj mice. Protection may be dependent on both the antibody and the cellular immune response to GPIs, and the elicited immune response depends on the orientation of the glycan, the number of mannoses in the structure, and the presence of the phosphoethanolamine and inositol units. This study provides insights into the epitopes in GPIs and contributes to the development of GPI-based antitoxin vaccine candidates against cerebral malaria.

Antagonistic Pleiotropy in Human Disease

Between the 1930s and 1950s, scientists developed key principles of population genetics to try and explain the aging process. Almost a century later, these aging theories, including antagonistic pleiotropy and mutation accumulation, have been experimentally validated in animals. Although the theories have been much harder to test in humans despite research dating back to the 1970s, recent research is closing this evidence gap. Here we examine the strength of evidence for antagonistic pleiotropy in humans, one of the leading evolutionary explanations for the retention of genetic risk variation for non-communicable diseases. We discuss the analytical tools and types of data that are used to test for patterns of antagonistic pleiotropy and provide a primer of evolutionary theory on types of selection as a guide for understanding this mechanism and how it may manifest in other diseases. We find an abundance of non-experimental evidence for antagonistic pleiotropy in many diseases. In some cases, several studies have independently found corroborating evidence for this mechanism in the same or related sets of diseases including cancer and neurodegenerative diseases. Recent studies also suggest antagonistic pleiotropy may be involved in cardiovascular disease and diabetes. There are also compelling examples of disease risk variants that confer fitness benefits ranging from resistance to other diseases or survival in extreme environments. This provides increasingly strong support for the theory that antagonistic pleiotropic variants have enabled improved fitness but have been traded for higher burden of disease later in life. Future research in this field is required to better understand how this mechanism influences contemporary disease and possible consequences for their treatment.

Plant leaves for wrapping zongzi in China: an ethnobotanical study

BACKGROUND

Zongzi, a common Chinese rice-pudding and one of the most symbolic foods in traditional Chinese festivals, is integral to both Chinese traditional culture and daily meals. Traditionally, the leaves of different plant species have been used to wrap zongzi. The variety of zongzi leaves (ZLs) can contribute to the zongzi-based cultural diversity. Given the cultural and dietary significance of zongzi, the ethnobotanical surveys were carried out, aiming to investigate the diversity of plant species and associated traditional botanical knowledge of ZLs, which could attract particular attention for their further studies.

METHOD

Both literature studies and field surveys were conducted in the study. The field investigations were carried out from May 2006 to June 2018 throughout China. Ethnobotanical information about ZLs was obtained by direct observation, semi-structured interviews, and key informant interviews.

RESULTS

In total, ZLs from 57 plant species were identified and recorded, belonging to 38 genera and 18 families. Several folk legends have been formed to explain the origin of using plant leaves to pack zongzi. Over time, Chinese people have developed diverse traditional botanical knowledge surrounding ZLs, especially regarding the zongzi flavor, antiseptic functions, and medicinal values. Based on the literature review, some species of ZLs such as the leaves of Corchorus capsularis and Vernicia fordii may even pose a potential threat to human health. Presently, in some regions of China, the traditional ZLs, such as Cocos nucifera, Tilia tuan, and Zizania latifolia, are being substituted by commercialized ZLs such as Phragmites australis and Indocalamus tessellatus.

CONCLUSION

A variety of traditional ZLs have been discovered in China. Although diverse traditional knowledge exists in China surrounding the usage of ZLs, some species may have the potential of threatening human health. Therefore, further explorations are necessary to comprehensively evaluate traditional ZLs, the results of which could help to conserve the cultural diversity of zongzi, to guarantee food safety, and to encourage the uses of plant leaves in food, medicine, and environmental management, for our human health.

Antiplasmodial natural products: an update

Background

Malaria remains a significant public health challenge in regions of the world where it is endemic. An unprecedented decline in malaria incidences was recorded during the last decade due to the availability of effective control interventions, such as the deployment of artemisinin-based combination therapy and insecticide-treated nets. However, according to the World Health Organization, malaria is staging a comeback, in part due to the development of drug resistance. Therefore, there is an urgent need to discover new anti-malarial drugs. This article reviews the literature on natural products with antiplasmodial activity that was reported between 2010 and 2017.

Methods

Relevant literature was sourced by searching the major scientific databases, including Web of Science, ScienceDirect, Scopus, SciFinder, Pubmed, and Google Scholar, using appropriate keyword combinations.

Results and Discussion

A total of 1524 compounds from 397 relevant references, assayed against at least one strain of Plasmodium, were reported in the period under review. Out of these, 39% were described as new natural products, and 29% of the compounds had IC₅₀ ≤ 3.0 µM against at least one strain of Plasmodium. Several of these compounds have the potential to be developed into viable anti-malarial drugs. Also, some of these compounds could play a role in malaria eradication by targeting gametocytes. However, the research into natural products with potential for blocking the transmission of malaria is still in its infancy stage and needs to be vigorously pursued.

Protein Kinase A Is Essential for Invasion of Plasmodium falciparum into Human Erythrocytes

Understanding the mechanisms behind host cell invasion by Plasmodium falciparum remains a major hurdle to developing antimalarial therapeutics that target the asexual cycle and the symptomatic stage of malaria. Host cell entry is enabled by a multitude of precisely timed and tightly regulated receptor-ligand interactions. Cyclic nucleotide signaling has been implicated in regulating parasite invasion, and an important downstream effector of the cAMP-signaling pathway is protein kinase A (PKA), a cAMP-dependent protein kinase. There is increasing evidence that P. falciparum PKA (PfPKA) is responsible for phosphorylation of the cytoplasmic domain of P. falciparum apical membrane antigen 1 (PfAMA1) at Ser610, a cAMP-dependent event that is crucial for successful parasite invasion. In the present study, CRISPR-Cas9 and conditional gene deletion (dimerizable cre) technologies were implemented to generate a P. falciparum parasite line in which expression of the catalytic subunit of PfPKA (PfPKAc) is under conditional control, demonstrating highly efficient dimerizable Cre recombinase (DiCre)-mediated gene excision and complete knockdown of protein expression. Parasites lacking PfPKAc show severely reduced growth after one intraerythrocytic growth cycle and are deficient in host cell invasion, as highlighted by live-imaging experiments. Furthermore, PfPKAc-deficient parasites are unable to phosphorylate PfAMA1 at Ser610. This work not only identifies an essential role for PfPKAc in the P. falciparum asexual life cycle but also confirms that PfPKAc is the kinase responsible for phosphorylating PfAMA1 Ser610.IMPORTANCE Malaria continues to present a major global health burden, particularly in low-resource countries. Plasmodium falciparum, the parasite responsible for the most severe form of malaria, causes disease through rapid and repeated rounds of invasion and replication within red blood cells. Invasion into red blood cells is essential for P. falciparum survival, and the molecular events mediating this process have gained much attention as potential therapeutic targets. With no effective vaccine available, and with the emergence of resistance to antimalarials, there is an urgent need for the development of new therapeutics. Our research has used genetic techniques to provide evidence of an essential protein kinase involved in P. falciparum invasion. Our work adds to the current understanding of parasite signaling processes required for invasion, highlighting PKA as a potential drug target to inhibit invasion for the treatment of malaria.

A two-colour multiplexed lateral flow immunoassay system to differentially detect human malaria species on a single test line

BACKGROUND

Malaria continues to impose a tremendous burden in terms of global morbidity and mortality, yet even today, a large number of diagnoses are presumptive resulting in lack of or inappropriate treatment.

METHODS

In this work, a two-colour lateral flow immunoassay (LFA) system was developed to identify infections by Plasmodium spp. and differentiate Plasmodium falciparum infection from the other three human malaria species (Plasmodium vivax, Plasmodium ovale, Plasmodium malariae). To achieve this goal, red and blue colours were encoded to two markers on a single test line of strips, for simultaneous detection of PfHRP2 (red), a marker specific for P. falciparum infection, and pLDH (blue), a pan-specific marker for infections by all species of Plasmodium. The assay performance was first optimized and evaluated with recombinant malarial proteins spiked in washing buffer at various concentrations from 0 to 1000 ng mL-1. The colour profiles developed on the single test line were discriminated and quantified: colour types corresponded to malaria protein species; colour intensities represented protein concentration levels.

RESULTS

The limit of detection (the lowest concentrations of malaria antigens that can be distinguished from blank samples) and the limit of colour discrimination (the limit to differentiate pLDH from PfHRP2) were defined for the two-colour assay from the spiked buffer test, and the two limits were 31.2 ng mL-1 and 7.8 ng mL-1, respectively. To further validate the efficacy of the assay, 25 human whole blood frozen samples were tested and successfully validated against ELISA and microscopy results: 15 samples showed malaria negative; 5 samples showed P. falciparum positive; 5 samples showed P. falciparum negative, but contained other malaria species.

CONCLUSIONS

The assay provides a simple method to quickly identify and differentiate infection by different malarial parasites at the point-of-need and overcome the physical limitations of traditional LFAs, improving the multiplexing potential for simultaneous detection of various biomarkers.

A Systematic Review: Performance of Rapid Diagnostic Tests for the Detection of Plasmodium knowlesi, Plasmodium malariae, and Plasmodium ovale Monoinfections in Human Blood

Background

Despite the increased use and worldwide distribution of malaria rapid diagnostic tests (RDTs) that distinguish between Plasmodium falciparum and non-falciparum species, little is known about their performance detecting Plasmodium knowlesi (Pk), Plasmodium malariae (Pm), and Plasmodium ovale (Po). This review seeks to analyze the results of published studies evaluating the diagnostic accuracy of malaria RDTs in detecting Pk, Pm, and Po monoinfections.

Methods

MEDLINE, EMBASE, Web of Science, and CENTRAL databases were systematically searched to identify studies that reported the performance of RDTs in detecting Pk, Pm, and Po monoinfections.

Results

Among 40 studies included in the review, 3 reported on Pk, 8 on Pm, 5 on Po, 1 on Pk and Pm, and 23 on Pm and Po infections. In the meta-analysis, estimates of sensitivities of RDTs in detecting Pk infections ranged 2%-48%. Test performances for Pm and Po infections were less accurate and highly heterogeneous, mainly because of the small number of samples tested.

Conclusions

Limited data available suggest that malaria RDTs show suboptimal performance for detecting Pk, Pm, and Po infections. New improved RDTs and appropriately designed cross-sectional studies to demonstrate the usefulness of RDTs in the detection of neglected Plasmodium species are urgently needed.

Comparison of malaria incidence rates and socioeconomic-environmental factors between the states of Acre and Rondônia: a spatio-temporal modelling study

BACKGROUND

Plasmodium falciparum malaria is a threat to public health, but Plasmodium vivax malaria is most prevalent in Latin America, where the incidence rate has been increasing since 2016, particularly in Venezuela and Brazil. The Brazilian Amazon reported 193,000 cases in 2017, which were mostly confirmed as P. vivax (~ 90%). Herein, the relationships among malaria incidence rates and the proportion of accumulated deforestation were contrasted using data from the states of Acre and Rondônia in the south-western Brazilian Amazon. The main purpose is to test the hypothesis that the observed difference in incidence rates is associated with the proportion of accumulated deforestation.

METHODS

An ecological study using spatial and temporal models for mapping and modelling malaria risk was performed. The municipalities of Acre and Rondônia were the spatial units of analysis, whereas month and year were the temporal units. The number of reported malaria cases from 2009 until 2015 were used to calculate the incidence rate per 1000 people at risk. Accumulated deforestation was calculated using publicly available satellite images. Geographically weighted regression was applied to provide a local model of the spatial heterogeneity of incidence rates. Time-series dynamic regression was applied to test the correlation of incidence rates and accumulated deforestation, adjusted by climate and socioeconomic factors.

RESULTS

The malaria incidence rate declined in Rondônia but remained stable in Acre. There was a high and positive correlation between the decline in malaria and higher proportions of accumulated deforestation in Rondônia. Geographically weighted regression showed a complex relationship. As deforestation increased, malaria incidence also increased in Acre, while as deforestation increased, malaria incidence decreased in Rondônia. Time-series dynamic regression showed a positive association between malaria incidence and precipitation and accumulated deforestation, whereas the association was negative with the human development index in the westernmost areas of Acre.

CONCLUSION

Landscape modification caused by accumulated deforestation is an important driver of malaria incidence in the Brazilian Amazon. However, this relationship is not linearly correlated because it depends on the overall proportion of the land covered by forest. For regions that are partially degraded, forest cover becomes a less representative component in the landscape, causing the abovementioned non-linear relationship. In such a scenario, accumulated deforestation can lead to a decline in malaria incidence.

Precopulatory acoustic interactions of the New World malaria vector Anopheles albimanus (Diptera: Culicidae)

Background

Anopheles albimanus is a malaria vector in Central America, northern South America and the Caribbean. Although a public health threat, An. albimanus precopulatory mating behaviors are unknown. Acoustics play important roles in mosquito communication, where flight tones allow males to detect and attract potential mates. The importance of sound in precopulatory interactions has been demonstrated in Toxorhynchites brevipalpis, Aedes aegypti, Culex quinquefasciatus and Anopheles gambiae; convergence in a shared harmonic of the wing beat frequency (WBF) during courtship is thought to increase the chance of copulation. To our knowledge, An. albimanus precopulatory acoustic behaviors have not been described to date. Here, we characterized An. albimanus (i) male and female flight tones; (ii) male–female precopulatory acoustic interactions under tethered and free flight conditions; and (iii) male-male acoustic interactions during free flight.

Results

We found significant increases in the WBFs of both sexes in free flight compared to when tethered. We observed harmonic convergence between 79% of tethered couples. In free flight, we identified a female-specific behavior that predicts mate rejection during male mating attempts: females increase their WBFs significantly faster during mate rejection compared to a successful copulation. This behavior consistently occurred during mate rejection regardless of prior mating attempts (from the same or differing male). During group flight, males of An. albimanus displayed two distinct flying behaviors: random flight and a swarm-like, patterned flight, each associated with distinct acoustic characteristics. In the transition from random to patterned flight, males converged their WBFs and significantly decreased flight area, male-male proximity and the periodicity of their trajectories.

Conclusions

We show that tethering of An. albimanus results in major acoustic differences compared to free flight. We identify a female-specific behavior that predicts mate rejection during male mating attempts in this species and show that male groups in free flight display distinct flying patterns with unique audio and visual characteristics. This study shows that An. albimanus display acoustic features identified in other mosquito species, further suggesting that acoustic interactions provide worthwhile targets for mosquito intervention strategies. Our results provide compelling evidence for swarming in this species and suggests that acoustic signaling is important for this behavior.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3648-8) contains supplementary material, which is available to authorized users.

Mapping the global endemicity and clinical burden of Plasmodium vivax, 2000-17: a spatial and temporal modelling study

BACKGROUND

Plasmodium vivax exacts a significant toll on health worldwide, yet few efforts to date have quantified the extent and temporal trends of its global distribution. Given the challenges associated with the proper diagnosis and treatment of P vivax, national malaria programmes-particularly those pursuing malaria elimination strategies-require up to date assessments of P vivax endemicity and disease impact. This study presents the first global maps of P vivax clinical burden from 2000 to 2017.

METHODS

In this spatial and temporal modelling study, we adjusted routine malariometric surveillance data for known biases and used socioeconomic indicators to generate time series of the clinical burden of P vivax. These data informed Bayesian geospatial models, which produced fine-scale predictions of P vivax clinical incidence and infection prevalence over time. Within sub-Saharan Africa, where routine surveillance for P vivax is not standard practice, we combined predicted surfaces of Plasmodium falciparum with country-specific ratios of P vivax to P falciparum. These results were combined with surveillance-based outputs outside of Africa to generate global maps.

FINDINGS

We present the first high-resolution maps of P vivax burden. These results are combined with those for P falciparum (published separately) to form the malaria estimates for the Global Burden of Disease 2017 study. The burden of P vivax malaria decreased by 41·6%, from 24·5 million cases (95% uncertainty interval 22·5-27·0) in 2000 to 14·3 million cases (13·7-15·0) in 2017. The Americas had a reduction of 56·8% (47·6-67·0) in total cases since 2000, while South-East Asia recorded declines of 50·5% (50·3-50·6) and the Western Pacific regions recorded declines of 51·3% (48·0-55·4). Europe achieved zero P vivax cases during the study period. Nonetheless, rates of decline have stalled in the past five years for many countries, with particular increases noted in regions affected by political and economic instability.

INTERPRETATION

Our study highlights important spatial and temporal patterns in the clinical burden and prevalence of P vivax. Amid substantial progress worldwide, plateauing gains and areas of increased burden signal the potential for challenges that are greater than expected on the road to malaria elimination. These results support global monitoring systems and can inform the optimisation of diagnosis and treatment where P vivax has most impact.

FUNDING

Bill & Melinda Gates Foundation and the Wellcome Trust.

Genetic comparison of sickle cell anaemia cohorts from Brazil and the United States reveals high levels of divergence

Genetic analysis of admixed populations raises special concerns with regard to study design and data processing, particularly to avoid population stratification biases. The point mutation responsible for sickle cell anaemia codes for a variant hemoglobin, sickle hemoglobin or HbS, whose presence drives the pathophysiology of disease. Here we propose to explore ancestry and population structure in a genome-wide study with particular emphasis on chromosome 11 in two SCA admixed cohorts obtained from urban populations of Brazil (Pernambuco and São Paulo) and the United States (Pennsylvania). Ancestry inference showed different proportions of European, African and American backgrounds in the composition of our samples. Brazilians were more admixed, had a lower African background (43% vs. 78% on the genomic level and 44% vs. 76% on chromosome 11) and presented a signature of positive selection and Iberian introgression in the HbS region, driving a high differentiation of this locus between the two cohorts. The genetic structures of the SCA cohorts from Brazil and US differ considerably on the genome-wide, chromosome 11 and HbS mutation locus levels.

Characterization of Lipid Binding Properties of Plasmodium falciparum Acyl-Coenzyme A Binding Proteins and Their Competitive Inhibition by Mefloquine

Malaria remains a worldwide concern in terms of morbidity and mortality. Limited understanding of the Plasmodium proteome makes it challenging to control malaria. Understanding of the expression and functions of different Plasmodium proteins will help in knowing this organism's virulence properties, besides facilitating the drug development process. In this study, we characterize the lipid binding and biophysical properties of the putative Plasmodium falciparum acyl-CoA binding proteins (PfACBPs), which may have intriguing functions in different stages of P. falciparum life cycle. While the PfACBPs can bind to long-chain fatty acyl-CoAs with high affinity, their affinity for short-chain fatty acyl-CoAs is weak. Base-stacking, electrostatic, and hydrophobic interactions between the aromatic rings, charged groups or residues, and hydrophobic chains or residues are responsible for acyl-CoA binding to PfACBPs. PfACBPs can also bind to phospholipids. PfACBPs cannot bind to the fatty acids and unphosphorylated fatty acid esters. PfACBPs are globular-helical proteins that contain a conserved acyl-CoA binding region. They exist in folded or unfolded conformations without attaining any intermediate state. In a systematic high-throughput in silico screening, mefloquine is identified as a potential ligand of PfACBPs. Binding affinities of mefloquine are much higher than those of fatty acyl-CoAs for all PfACBPs. Mefloquine binds to the acyl-CoA binding pocket of PfACBPs, thereby engaging many of the critical residues. Thus, mefloquine acts as a competitive inhibitor against fatty acyl-CoA binding to PfACBPs, leading to the prevention of P. falciparum growth and proliferation. Taken together, our study characterizes the functions of annotated PfACBPs and highlights the mechanistic details of their inactivation by mefloquine.

Consanguinity and Inbreeding in Health and Disease in North African Populations

North Africa is defined as the geographical region separated from the rest of the continent by the Sahara and from Europe by the Mediterranean Sea. The main demographic features of North African populations are their familial structure and high rates of familial and geographic endogamy, which have a proven impact on health, particularly the occurrence of genetic diseases, with a greater effect on the frequency and spectrum of the rarest forms of autosomal recessive genetic diseases. More than 500 different genetic diseases have been reported in this region, most of which are autosomal recessive. During the last few decades, there has been great interest in the molecular investigation of large consanguineous North African families. The development of local capacities has brought a substantial improvement in the molecular characterization of these diseases, but the genetic bases of half of them remain unknown. Diseases of known molecular etiology are characterized by their genetic and mutational heterogeneity, although some founder mutations are encountered relatively frequently. Some founder mutations are specific to a single country or a specific ethnic or geographic group, and others are shared by all North African countries or worldwide. The impact of consanguinity on common multifactorial diseases is less evident.

Pesticides and pollinators: A socioecological synthesis

The relationship between pesticides and pollinators, while attracting no shortage of attention from scientists, regulators, and the public, has proven resistant to scientific synthesis and fractious in matters of policy and public opinion. This is in part because the issue has been approached in a compartmentalized and intradisciplinary way, such that evaluations of organismal pesticide effects remain largely disjoint from their upstream drivers and downstream consequences. Here, we present a socioecological framework designed to synthesize the pesticide-pollinator system and inform future scholarship and action. Our framework consists of three interlocking domains-pesticide use, pesticide exposure, and pesticide effects-each consisting of causally linked patterns, processes, and states. We elaborate each of these domains and their linkages, reviewing relevant literature and providing empirical case studies. We then propose guidelines for future pesticide-pollinator scholarship and action agenda aimed at strengthening knowledge in neglected domains and integrating knowledge across domains to provide decision support for stakeholders and policymakers. Specifically, we emphasize (1) stakeholder engagement, (2) mechanistic study of pesticide exposure, (3) understanding the propagation of pesticide effects across levels of organization, and (4) full-cost accounting of the externalities of pesticide use and regulation. Addressing these items will require transdisciplinary collaborations within and beyond the scientific community, including the expertise of farmers, agrochemical developers, and policymakers in an extended peer community.

Identification and characterization of Pv50, a novel Plasmodium vivax merozoite surface protein

Background

Plasmodium vivax contains approximately 5400 coding genes, more than 40% of which code for hypothetical proteins that have not been functionally characterized. In a previous preliminary screening using pooled serum samples, numerous hypothetical proteins were selected from among those that were highly transcribed in the schizont-stage of parasites, and highly antigenic P. vivax candidates including hypothetical proteins were identified. However, their immunological and functional activities in P. vivax remain unclear. From these candidates, we investigated a P. vivax 50-kDa protein (Pv50, PVX_087140) containing a highly conserved signal peptide that shows high transcription levels in blood-stage parasites.

Results

Recombinant Pv50 was expressed in a cell-free expression system and used for IgG prevalence analysis of patients with vivax malaria and healthy individuals. Immune responses were analyzed in immunized mice and mouse antibodies were used to detect the subcellular localization of the protein in blood-stage parasites by immunofluorescence assay. A protein array method was used to evaluate protein-protein interactions to predict protein functional activities during the invasion of parasites into erythrocytes. Recombinant Pv50 showed IgG prevalence in patient samples with a sensitivity of 42.9% and specificity of 93.8% compared to that in healthy individuals. The non-cytophilic antibodies IgG1 and IgG3 were the major components involved in the antibody response in Pv50-immunized mice. Pv50 localized on the surface of merozoites and a specific interaction between Pv50 and PvMSP1 was detected, suggesting that Pv50-PvMSP1 forms a heterodimeric complex in P. vivax.

Conclusions

Increased immune responses caused by native P. vivax parasites were detected, confirming its immunogenic effects. This study provides a method for detecting new malaria antigens, and Pv50 may be a vivax malaria vaccine candidate with PvMSP1.

Electronic supplementary material

The online version of this article (10.1186/s13071-019-3434-7) contains supplementary material, which is available to authorized users.

Hematological Profile and Gametocyte Carriage in Malaria Patients from Southern Pakistan

Background Malarial infection is a major cause of concern, both worldwide and in Pakistan. Gametocytes are the sexual forms of the parasite that are essential for transmission. They fuse inside the mosquito to develop sporozoites. Gametocytes of the plasmodium parasites, which cause the infection, differentiate into male and female gametocytes. These gametocytes constitute the sexual stage of the malaria parasite and are essential in transmission of the disease from human to vector Anopheles. Gametocytes are affected by factors such as host immunity, drug treatment, reticulocytemia, anemia, low levels of asexual parasitemia and stress to the parasite. The aim of this study was to observe the hematological parameters, age and gametocyte carriage in an area of seasonal malaria transmission. Methods The study was conducted at Aga Khan University Hospital (AKUH) Laboratory over the period of one year and 294 patients with uncomplicated malaria were recruited. Patients infected with Plasmodium falciparum (P. falciparum) or Plasmodium vivax (P. vivax) malaria and no co-morbidities were included in the study. Results Gametocytemia was highest during the period of July to November, with P. vivax, 267 (90.8%), predominating compared to P. falciparum, 27 (9.2%). P. vivax gametocytes were observed from May to October and P. falciparum gametocytes were observed from July to December. Low hemoglobin in females and low platelet levels were observed. The mean platelet count was significantly lower in cases of P. vivax having gametocytes compared to P. falciparum with gametocytes. Higher parasitic index was associated with lower platelet count. The most significantly altered parameters were hemoglobin, hematocrit, white blood cell (WBC), and platelet count. Hemoglobin and platelets were significantly lower during the malaria season in study participants, both male and female. Conclusion In conclusion, infection with P. falciparum and P. vivax modulates significant changes in hematological parameters in populations living in malaria endemic regions. In the malaria season males were more frequently affected by malaria with thrombocytopenia. Gametocyte carriage remains unaffected by seasonal changes thus ensuring parasite transmission during the dry season.

3,3'-Disubstituted 5,5'-Bi(1,2,4-triazine) Derivatives with Potent in Vitro and in Vivo Antimalarial Activity

A series of 3,3'-disubstituted 5,5'-bi(1,2,4-triazine) derivatives was synthesized and screened against the erythrocytic stage of Plasmodium falciparum 3D7 line. The most potent dimer, 6k, with an IC₅₀ (50% inhibitory concentration) of 0.008 μM, had high in vitro potency against P. falciparum lines resistant to chloroquine (W2, IC₅₀ = 0.0047 ± 0.0011 μM) and artemisinin (MRA1240, IC₅₀ = 0.0086 ± 0.0010 μM). Excellent ex vivo potency of 6k was shown against clinical field isolates of both P. falciparum (IC₅₀ = 0.022-0.034 μM) and Plasmodium vivax (IC₅₀ = 0.0093-0.031 μM) from the blood of outpatients with uncomplicated malaria. Despite 6k being cleared relatively rapidly in mice, it suppressed parasitemia in the Peters 4-day test, with a mean ED₅₀ value (50% effective dose) of 1.47 mg kg^-1 day^-1 following oral administration. The disubstituted triazine dimer 6k represents a new class of orally available antimalarial compounds of considerable interest for further development.

Variability in malaria cases and the association with rainfall and rivers water levels in Amazonas State, Brazil

Understanding the relations between rainfall and river water levels and malaria cases can provide important clues on modulation of the disease in the context of local climatic variability. In order to demonstrate how these relations can vary in the same endemic space, a coherence and wavelet phase analysis was performed between environmental and epidemiological variables from 2003 to 2010 for 8 municipalities (counties) in the state of Amazonas, Brazil (Barcelos, Borba, Canutama, Carauari, Coari, Eirunepé, Humaitá, and São Gabriel da Cachoeira). The results suggest significant coherences, mainly on the scale of annual variability, but scales of less than 1 year and of 2 years were also found. The analyses show that malaria cases display a peak at approximately 1 and a half months before or after peak rainfall and on average 1-4 months after peak river water levels in most of the municipalities studied. Each environmental variable displayed distinct local behavior in time and in space, suggesting that other local variables (e.g. topography) may control environmental conditions, favoring different patterns in each municipality. However, when the analyses were performed jointly it was possible to show a non-random order in these relations. Although environmental and climatic factors indicate a certain influence on malaria dynamics, surveillance, prevention, and control issues should not be overlooked, meaning that government public health interventions can mask possible relations with local hydrological and climatic conditions.

Repellency Assessment of Nepeta cataria Essential Oils and Isolated Nepetalactones on Aedes aegypti

There is an increased need for improved and affordable insect repellents to reduce transmission of rapidly spreading diseases with high mortality rates. Natural products are often used when DEET cannot be afforded or accessed and when consumers choose not to use a synthetic repellent. The essential oils from two newly bred Nepeta cataria (catnip) plants representing two different chemotypes and their respective isolated nepetalactone isomers were evaluated as mosquito repellents against Aedes aegypti mosquitoes that transmit the Zika and Dengue virus in a one choice landing rate inhibition assay. A dose response curve was generated for each treatment and a time course analysis of repellency was performed over 24 hours with a N. cataria essential oil sample. The results indicate that all essential oil samples and their respective purified nepetalactone isomers were able to achieve greater than 95% repellency. Between two and four hours, the ability to repel more than 95% of the mosquitoes diminished. At the lowest concentrations tested, the nepetalactones and crude essential oil samples were more effective than DEET at reducing the number of mosquito landings.

Earth Observation: Investigating Noncommunicable Diseases from Space

The United Nations has called on all nations to take immediate actions to fight noncommunicable diseases (NCDs), which have become an increasingly significant burden to public health systems around the world. NCDs tend to be more common in developed countries but are also becoming of growing concern in low- and middle-income countries. Earth observation (EO) technologies have been used in many infectious disease studies but have been less commonly employed in NCD studies. This review discusses the roles that EO data and technologies can play in NCD research, including ( a) integrating natural and built environment factors into NCD research, ( b) explaining individual-environment interactions, ( c) scaling up local studies and interventions, ( d) providing repeated measurements for longitudinal studies including cohorts, and ( e) advancing methodologies in NCD research. Such extensions hold great potential for overcoming the challenges of inaccurate and infrequent measurements of environmental exposure at the level of both the individual and the population, which is of great importance to NCD research, practice, and policy.

High malaria transmission sustained by Anopheles gambiae s.l. occurring both indoors and outdoors in the city of Yaoundé, Cameroon

Background: Malaria remains a major public health problem in Cameroon; however, despite reports on the adaptation of anopheline species to urban habitats, there is still not enough information on malaria transmission pattern in urban settings. In the frame of a larval control trial in the city of Yaoundé, we conducted baseline surveys to assess malaria transmission dynamics in this city. Methods: Adult mosquitoes were collected indoors and outdoors using CDC light traps and human landing catches from March 2017 to March 2018 in 30 districts of Yaoundé, Cameroon. Mosquitoes were sorted by genus and identified to the species level using PCR. The TaqMan method and ELISA were used to determine mosquito infection status to Plasmodium. Bioassays were conducted to assess female Anopheles gambiae susceptibility to insecticides. Results: A total of 218,991 mosquitoes were collected. The main malaria vectors were An. gambiae s.l. (n=6154) and An. funestus s.l. (n=229). Of the 1476 An. gambiae s.l. processed by PCR, 92.19% were An. coluzzii and 7.81% An. gambiae. An. funestus s.l. was composed of 93.01% (173/186) An. funestus and 4.84% (13/186) An. leesoni. The average biting rate of anopheline was significantly high outdoor than indoor (P=0.013). Seasonal variation in mosquito abundance and biting rate was recorded. The infection rate by Plasmodium falciparum was 2.13% (104/4893 mosquitoes processed). The annual entomological inoculation rate was found to vary from 0 to 92 infective bites/man/year (ib/m/y). Malaria transmission risk was high outdoor (66.65 ib/m/y) compared to indoor (31.14 ib/m/y). An. gambiae s.l. was found highly resistant to DDT, permethrin and deltamethrin. High prevalence of the West Africa kdr allele 1014F was recorded and this was not found to influence An. gambiae s.l. infection status.   Conclusion: The study suggests high malaria transmission occurring in the city of Yaoundé and call for immediate actions to improve control strategies.

Using Gene Drive Technologies to Control Vector-Borne Infectious Diseases

After years of success in reducing the global malaria burden, the World Health Organization (WHO) recently reported that progress has stalled. Over 90% of malaria deaths world-wide occurred in the WHO African Region. New tools are needed to regain momentum and further decrease the burden of malaria. Gene drive, an emerging technology that can enhance the inheritance of beneficial genes, offers potentially transformative solutions for overcoming these challenges. Gene drives may decrease disease transmission by interfering with the growth of the malaria parasite in the mosquito vector or reducing mosquito reproductive capacity. Like other emerging technologies, development of gene drive products faces technical and non-technical challenges and uncertainties. In 2018, to begin addressing such challenges, a multidisciplinary group of international experts published comprehensive recommendations for responsible testing and implementation of gene drive-modified mosquitoes to combat malaria in Sub-Saharan Africa. Considering requirements for containment, efficacy and safety testing, monitoring, stakeholder engagement and authorization, as well as policy and regulatory issues, the group concluded that gene drive products for malaria can be tested safely and ethically, but that this will require substantial coordination, planning, and capacity development. The group emphasized the importance of co-development and co-ownership of products by in-country scientists.

Inter-sectoral approaches for the prevention and control of malaria among the mobile and migrant populations: a scoping review

Background

Malaria cases among mobile and migrant populations (MMPs) represent a large and important reservoir for transmission, if undetected or untreated. The objectives of this review were to identify which intersectoral actions have been taken and how they are applied to interventions targeted at the MMPs and also to assess the effect of interventions targeted to these special groups of population.

Results

A total of 36 studies met the inclusion criteria for this review. Numerous stakeholders were identified as involved in the intersectoral actions to defeat malaria amongst MMPs. Almost all studies discussed the involvement of Ministry of Health/Public Health (MOH/MOPH). The most frequently assessed intervention among the studies that were included was the coverage and utilization of insecticide-treated nets as personal protective measures (40.5%), followed by the intervention of early diagnoses and treatment of malaria (33.3%), the surveillance and response activities (13.9%) and the behaviour change communication (8.3%). There is a dearth of information on how these stakeholders shared roles and responsibilities for implementation, and about the channels of communication between-and-within the partners and with the MOH/MOPH. Despite limited details in the studies, the intermediate outcomes showed some evidence that the intersectoral collaborations contributed to improvement in knowledge about malaria, initiation and promotion of bed nets utilization, increased access to diagnosis and treatment in a surveillance context and contributed towards a reduction in malaria transmission. Overall, a high proportion of the targeted MMPs was equipped with correct knowledge about malaria transmission (70%, 95% CI 57–83%). Interventions targeting the use of bed nets utilization were two times more likely to reduce malaria incidence amongst the targeted MMPs (summary OR 2.01, 95% CI 1.43–2.6) than the non-users. The various intersectoral actions were often more vertically organized and not fully integrated in a systemic way within a given country or sub-national administrative setting.

Conclusion

Findings suggest that interventions supported by the multiple stakeholders had a significant impact on the reduction of malaria transmission amongst the targeted MMPs. Well-designed studies from different countries are recommended to robustly assess the role of intersectoral interventions targeted to MMPs and their impact on the reduction of transmission.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2562-4) contains supplementary material, which is available to authorized users.

Plasmodium genomics: an approach for learning about and ending human malaria

Malaria causes high levels of morbidity and mortality in human beings worldwide. According to the World Health Organization (WHO), about half a million people die of this disease each year. Malaria is caused by six species of parasites belonging to the Plasmodium genus: P. falciparum, P. knowlesi, P. vivax, P. malariae, P. ovale curtisi, and P. ovale wallikeri. Currently, malaria is being kept under control with varying levels of elimination success in different countries. The development of new molecular tools as well as the use of next-generation sequencing (NGS) technologies and novel bioinformatic approaches has improved our knowledge of malarial epidemiology, diagnosis, treatment, vaccine development, and surveillance strategies. In this work, the genetics and genomics of human malarias have been analyzed. Since the first P. falciparum genome was sequenced in 2002, various population-level genetic and genomic surveys, together with transcriptomic and proteomic studies, have shown the importance of molecular approaches in supporting malaria elimination.