Kinetics of glucose-6-phosphate dehydrogenase (G6PD) activity during Plasmodium vivax infection: implications for early radical malaria treatment.

BACKGROUND: Plasmodium vivax relapses due to dormant liver hypnozoites can be prevented with primaquine. However, the dose must be adjusted in individuals with glucose-6-phosphate-dehydrogenase (G6PD) deficiency. In French Guiana, assessment of G6PD activity is typically delayed until day (D)14 to avoid the risk if misclassification. This study assessed the kinetics of G6PD activity throughout P. vivax infection to inform the timing of treatment. METHODS: For this retrospective monocentric study, data on G6PD activity between D1 and D28 after treatment initiation with chloroquine or artemisinin-based combination therapy were collected for patients followed at Cayenne Hospital, French Guiana, between January 2018 and December 2020. Patients were divided into three groups based on the number of available G6PD activity assessments: (i) at least two measurements during the P. vivax malaria infection; (ii) two measurements: one during the current infection and one previously; (iii) only one measurement during the malaria infection. RESULTS: In total, 210 patients were included (80, 20 and 110 in groups 1, 2 and 3, respectively). Data from group 1 showed that G6PD activity remained stable in each patient over time (D1, D3, D7, D14, D21, D28). None of the patients with normal G6PD activity during the initial phase (D1-D3) of the malaria episode (n = 44) was categorized as G6PD-deficient at D14. Patients with G6PD activity < 80% at D1 or D3 showed normal activity at D14. Sex and reticulocyte count were statistically associated with G6PD activity variation. In the whole sample (n = 210), no patient had severe G6PD deficiency (< 10%) and only three between 10 and 30%, giving a G6PD deficiency prevalence of 1.4%. Among the 100 patients from group 1 and 2, 30 patients (26.5%) were lost to follow-up before primaquine initiation. CONCLUSIONS: In patients treated for P. vivax infection, G6PD activity did not vary over time. Therefore, G6PD activity on D1 instead of D14 could be used for primaquine dose-adjustment. This could allow earlier radical treatment with primaquine, that could have a public health impact by decreasing early recurrences and patients lost to follow-up before primaquine initiation. This hypothesis needs to be confirmed in larger prospective studies.

Cooperation for malaria control and elimination in the Guiana Shield.

The Guiana Shield, a small region of South America, is currently one of the main hotspots of malaria transmission on the continent. This Amazonian area is characterised by remarkable socioeconomic, cultural, health, and political heterogeneity and a high degree of regional and cross-border population mobility, which has contributed to the increase of malaria in the region in the past few years. In this context, regional cooperation to control malaria represents both a challenge and an indispensable initiative. This Viewpoint advocates for the creation of a regional cooperative mechanism for the elimination of malaria in the Guiana Shield. This strategy would help address operational and political obstacles to successful technical cooperation in the region and could contribute to reversing the regional upsurge in malaria incidence through creating a functional international control and elimination partnership.

Understanding the impact of mobility on Plasmodium spp. carriage in an Amazon cross-border area with low transmission rate.

Despite the large reduction in malaria incidence in the last decade, the last kilometre to elimination is often the hardest, especially in international border areas. This study investigated the impact of mobility on Plasmodium spp. carriage in people living in a cross-border area in Amazonia with a low malaria transmission rate. We implemented a longitudinal ancillary study in the French Guiana town of St. Georges de l'Oyapock, which is located on the border with Brazil. It was based on data from two transversal surveys performed in October 2017 and October 2018. Data were collected on peri-domestic mobility for food-producing activities, and longer-distance mobility in high-risk areas. Participants were screened for Plasmodium spp. carriage using PCR tests, and treated if positive. Vector density around a participant's home was estimated using a previously published model based on remote sensing and meteorological data. The association between Plasmodium spp. carriage and mobility was analysed using a generalized additive mixed model. A total of 1,192 inhabitants, aged between 0 and 92 years old, were included. Median age was 18 years in 2017 (IQR [8;35]). Plasmodium spp. prevalence in the study population was 7% in 2017 (n = 89) and 3% in 2018 (n = 35). Plasmodium spp. carriage was independently associated with i) travel to the adjoining Oiapoque Indigenous Territories in Brazil (OR = 1.76, p = 0.023), ii) the estimated vector density around a participant's home (High versus Low risk OR = 4.11, p<0.001), iii) slash-and-burn farming (OR = 1.96, p = 0.013), and iv) age (p = 0.032). Specific surveillance systems and interventions which take into account different types of mobility are needed in cross-border areas to achieve and maintain malaria elimination (e.g., reactive case detection and treatment in the places visited).

Temporal and spatial dynamics of Plasmodium falciparum clonal lineages in Guyana.

Plasmodium parasites, the causal agents of malaria, are eukaryotic organisms that obligately undergo sexual recombination within mosquitoes. However, in low transmission settings where most mosquitoes become infected with only a single parasite clone, parasites recombine with themselves, and the clonal lineage is propagated rather than broken up by outcrossing. We investigated whether stochastic/neutral factors drive the persistence and abundance of Plasmodium falciparum clonal lineages in Guyana, a country with relatively low malaria transmission, but the only setting in the Americas in which an important artemisinin resistance mutation (pfk13 C580Y) has been observed. To investigate whether this clonality was potentially associated with the persistence and spatial spread of the mutation, we performed whole genome sequencing on 1,727 Plasmodium falciparum samples collected from infected patients across a five-year period (2016-2021). We characterized the relatedness between each pair of monoclonal infections (n=1,409) through estimation of identity by descent (IBD) and also typed each sample for known or candidate drug resistance mutations. A total of 160 clones (mean IBD ≥ 0.90) were circulating in Guyana during the study period, comprising 13 highly related clusters (mean IBD ≥ 0.40). In the five-year study period, we observed a decrease in frequency of a mutation associated with artemisinin partner drug (piperaquine) resistance (pfcrt C350R) and limited co-occurence of pfcrt C350R with duplications of plasmepsin 2/3, an epistatic interaction associated with piperaquine resistance. We additionally report polymorphisms exhibiting evidence of selection for drug resistance or other phenotypes and reported a novel pfk13 mutation (G718S) as well as 61 nonsynonymous substitutions that increased markedly in frequency. However, P. falciparum clonal dynamics in Guyana appear to be largely driven by stochastic factors, in contrast to other geographic regions. The use of multiple artemisinin combination therapies in Guyana may have contributed to the disappearance of the pfk13 C580Y mutation.

Impact of piperaquine resistance in Plasmodium falciparum on malaria treatment effectiveness in The Guianas: a descriptive epidemiological study.

BACKGROUND: Plasmodium falciparum is an apicomplexan parasite responsible for lethal cases of malaria. According to WHO recommendations, P falciparum cases are treated with artemisinin-based combination therapy including dihydroartemisinin-piperaquine. However, the emergence of resistant parasites against dihydroartemisinin-piperaquine was reported in southeast Asia in 2008 and, a few years later, suspected in South America. METHODS: To characterise resistance emergence, a treatment efficacy study was performed on the reported patients infected with P falciparum and treated with dihydroartemisinin-piperaquine in French Guiana (n=6, 2016-18). Contemporary isolates collected in French Guiana were genotyped for P falciparum chloroquine resistance transporter (pfCRT; n=845) and pfpm2 and pfpm3 copy number (n=231), phenotyped using the in vitro piperaquine survival assay (n=86), and analysed through genomic studies (n=50). Additional samples from five Amazonian countries and one outside the region were genotyped (n=1440). FINDINGS: In field isolates, 40 (47%) of 86 (95% CI 35·9-57·1) were resistant to piperaquine in vitro; these phenotypes were more associated with pfCRTC350R (ie, Cys350Arg) and pfpm2 and pfpm3 amplifications (Dunn test, p<0·001). Those markers were also associated with dihydroartemisinin-piperaquine treatment failure (n=3 [50%] of 6). A high prevalence of piperaquine resistance markers was observed in Suriname in 19 (83%) of 35 isolates and in Guyana in 579 (73%) of 791 isolates. The pfCRTC350R mutation emerged before pfpm2 and pfpm3 amplification in a temporal sequence different from southeast Asia, and in the absence of artemisinin partial resistance, suggesting a geographically distinctive epistatic relationship between these genetic markers. INTERPRETATION: The high prevalence of piperaquine resistance markers in parasite populations of the Guianas, and the risk of associated therapeutic failures calls for caution on dihydroartemisinin-piperaquine use in the region. Furthermore, greater attention should be given to potential differences in genotype to phenotype mapping across genetically distinct parasite populations from different continents. FUNDING: Pan American Health Organization and WHO, French Ministry for Research, European Commission, Santé publique France, Agence Nationale de la Recherche, Fundação de Amparo à Pesquisa do Estado do Amazonas, Ministry of Health of Brazil, Oswaldo Cruz Foundation, and National Institutes of Health. TRANSLATIONS: For the French and Portuguese translations of the abstract see Supplementary Materials section.

Determination of different social groups' level of knowledge about malaria in a multicultural Amazonian cross-border context.

BACKGROUND: A steady decline in the number of cases of malaria was observed in the 2000s in French Guiana. This enabled regional health policies to shift their public health goal from control to elimination. To include inhabitants in this strategy, the main objective of this study was to describe knowledge about malaria, and related attitudes and practices in persons living in the French Guiana border. METHODS: We conducted a survey in people over 15 years old living in the twelve neighbourhoods of Saint-Georges de l'Oyapock with the highest malaria incidence. It comprised a 147-item questionnaire which collected data on socio-demographic characteristics and included a Knowledge Attitude and Practices survey on malaria. Knowledge-related data were studied using exploratory statistical methods to derive summary variables. A binary variable assessing level of knowledge was proposed and then assessed using exploratory approaches. RESULTS: The mean age of the 844 participants was 37.2 years [15.8], the male/female sex ratio was 0.8. In terms of nationality, 485 (57.5%) participants were Brazilian and 352 (41.7%) French. One third (305, 36.1%) spoke Brazilian Portuguese as their native language, 295 (34.9%) the Amerindian language Palikur, 36 (4.3%) French. The symptoms of malaria and prevention means were poorly known by 213 (25.2%) and 378 (44.8%) respondents, respectively. A quarter (206, 24.4%) did not know that malaria can be fatal. Overall, 251 people (29.7%) had an overall poor level of knowledge about malaria. Being under 25 years old, living in a native Amerindian neighbourhood, having an Amerindian mother tongue language, having risk behaviours related to gold mining were significantly associated with a poor level of knowledge. CONCLUSIONS: This study is the first to describe the poor level of knowledge about malaria in populations living in the malaria endemic border area along the Oyapock river in French Guiana. Results will allow to reinforce, to diversify and to culturally adapt prevention messages and health promotion to increase their effectiveness with a view to quickly reaching the goal of malaria elimination through empowerment.

Molecular detection of human Plasmodium species using a multiplex real time PCR.

Molecular detection methods have revealed higher sensitivity and specificity than conventional microscopy or rapid diagnostic tests for malaria diagnosis. In this study, we implemented, evaluated and validated according to the ISO 15,189 requirements, a multiplex real-time PCR assay to detect and identify the five human malaria parasites. DNA samples were extracted from whole blood or dried blood spots drawn from patients. Based on the External Quality Assessment (whole blood), this method shows 100% sensitivity and specificity. This PCR detected P. vivax up to 0.25 p/µl, P. falciparum and P. knowlesi up to 0.5 p/µl, P. ovale up to 1 p/µl and P. malariae up to 5 p/µl of blood. From blood spots (extraction from four punches), it detected P. vivax at 5 p/µl, P. falciparum, P. ovale and P. knowlesi at 20 p/µl and P. malariae at 125 p/µl. In conclusion, this quantitative PCR shows excellent performance, is easy to use and DNA saver. It is especially useful to actively screen large population groups and identify the five human malaria parasites in a context of low malaria transmission.

Emerging infectious diseases and new pandemics: dancing with a ghost! Lessons in inter- and transdisciplinary research in French Guiana, South America.

In light of current international public health challenges, calls for inter- and transdisciplinary research are increasing, particularly in response to complex and intersecting issues. Although widely used under the One Health flag, it is still unclear how inter- and transdisciplinary science should be applied to infectious disease research, public health, and the different stakeholders. Here, we present and discuss our common scientific and biomedical experience in French Guiana, South America to conduct and enrich research in vector-borne and zoonotic infectious diseases, with the aim to translate findings to public health and political stakeholders. We highlight the successful progressive dissolution of disciplinary boundaries that go beyond One Health positive-driven assumptions and argue that specific local conditions, as well as strong support from research and medical institutions, have facilitated an emulsion toward inter- and transdisciplinary science. This argument is intended to improve responses to public health concerns in French Guiana and other countries and regions of the world.

Declines in prevalence alter the optimal level of sexual investment for the malaria parasite Plasmodium falciparum.

Successful infectious disease interventions can result in large reductions in parasite prevalence. Such demographic change has fitness implications for individual parasites and may shift the parasite's optimal life history strategy. Here, we explore whether declining infection rates can alter Plasmodium falciparum's investment in sexual versus asexual growth. Using a multiscale mathematical model, we demonstrate how the proportion of polyclonal infections, which decreases as parasite prevalence declines, affects the optimal sexual development strategy: Within-host competition in multiclone infections favors a greater investment in asexual growth whereas single-clone infections benefit from higher conversion to sexual forms. At the same time, drug treatment also imposes selection pressure on sexual development by shortening infection length and reducing within-host competition. We assess these models using 148 P. falciparum parasite genomes sampled in French Guiana over an 18-y period of intensive intervention (1998 to 2015). During this time frame, multiple public health measures, including the introduction of new drugs and expanded rapid diagnostic testing, were implemented, reducing P. falciparum malaria cases by an order of magnitude. Consistent with this prevalence decline, we see an increase in the relatedness among parasites, but no single clonal background grew to dominate the population. Analyzing individual allele frequency trajectories, we identify genes that likely experienced selective sweeps. Supporting our model predictions, genes showing the strongest signatures of selection include transcription factors involved in the development of P. falciparum's sexual gametocyte form. These results highlight how public health interventions impose wide-ranging selection pressures that affect basic parasite life history traits.

Novel Chronic Anaplasmosis in Splenectomized Patient, Amazon Rainforest.

We report a case of unusual human anaplasmosis in the Amazon rainforest of French Guiana. Molecular typing demonstrated that the pathogen is a novel Anaplasma species, distinct to all known species, and more genetically related to recently described Anaplasma spp. causing infections in rainforest wild fauna of Brazil.

Assessment of electronic surveillance and knowledge, attitudes, and practice (KAP) survey toward imported malaria surveillance system acceptance in France.

Objective: An electronic surveillance system was released to monitor morbidity and mortality incidence of imported malaria cases, investigate autochthonous cases, and assess chemosensitivity of Plasmodium isolates among travelers to and from endemic areas. The aim of this study is to evaluate the use of an electronic surveillance system for imported malaria in France. Materials and Methods: Three main indicators were used to assess the online malaria web-based surveillance system: (1) the quality of the surveillance system; (2) the capacity of the online system to early warning in case of particular events of public health; (3) the knowledge, attitude, and practice of online electronic system by practitioners of malaria network in France. Results: Overall, the median time onset a case is reported to the system decrease by 99%, ranging from 227 days (144-309) to 2 days (1-6) in 2006 and 2020, respectively. Conclusion: The online malaria surveillance system in France has demonstrated its effectiveness and can therefore be extended to carry out numerous investigations linked to research on malaria.

Kelch13 mutations in Plasmodium falciparum and risk of spreading in Amazon basin countries.

BACKGROUND: The first potential focus for artemisinin resistance in South America was recently confirmed with the presence of the C580Y mutation in the Plasmodium falciparum kelch 13 gene (pfk13) in Guyana. OBJECTIVES: This study aimed to strengthen pfk13 monitoring in the Amazon basin countries, to compile the available data and to evaluate the risk of spreading of mutations. METHODS: Sanger sequencing was done on 862 samples collected between 1998 and 2019, and a global map of pfk13 genotypes available for this region was constructed. Then, the risk of spreading of mutations based on P. falciparum case importation between 2015 and 2018 within countries of the Amazon basin was evaluated. RESULTS: No additional pfk13 C580Y foci were identified. Few mutations (0.5%, 95% CI = 0.3%-0.8%) in the propeller domain were observed in the general parasite population of this region despite a high proportion of K189T mutations (49.1%, 95% CI = 46.2%-52.0%) in the non-propeller domain. Case information revealed two patterns of intense human migration: Venezuela, Guyana and the Roraima State in Brazil; and French Guiana, Suriname and the Amapá State in Brazil. CONCLUSIONS: There are few pfk13 mutant foci, but a high risk of dispersion in the Amazon basin, mainly from the Guiana Shield, proportionate to mining activities. Therefore, access to prompt diagnosis and treatment, and continuous molecular monitoring is essential in these geographical areas.

Ecology, evolution, and epidemiology of zoonotic and vector-borne infectious diseases in French Guiana: Transdisciplinarity does matter to tackle new emerging threats.

French Guiana is a European ultraperipheric region located on the northern Atlantic coast of South America. It constitutes an important forested region for biological conservation in the Neotropics. Although very sparsely populated, with its inhabitants mainly concentrated on the Atlantic coastal strip and along the two main rivers, it is marked by the presence and development of old and new epidemic disease outbreaks, both research and health priorities. In this review paper, we synthetize 15 years of multidisciplinary and integrative research at the interface between wildlife, ecosystem modification, human activities and sociodemographic development, and human health. This study reveals a complex epidemiological landscape marked by important transitional changes, facilitated by increased interconnections between wildlife, land-use change and human occupation and activity, human and trade transportation, demography with substantial immigration, and identified vector and parasite pharmacological resistance. Among other French Guianese characteristics, we demonstrate herein the existence of more complex multi-host disease life cycles than previously described for several disease systems in Central and South America, which clearly indicates that today the greater promiscuity between wildlife and humans due to demographic and economic pressures may offer novel settings for microbes and their hosts to circulate and spread. French Guiana is a microcosm that crystallizes all the current global environmental, demographic and socioeconomic change conditions, which may favor the development of ancient and future infectious diseases.

Spatio-Temporal Dynamics of Plasmodium falciparum and Plasmodium vivax in French Guiana: 2005-2019.

Aims: This study examines the dynamics of malaria as influenced by meteorological factors in French Guiana from 2005 to 2019. It explores spatial hotspots of malaria transmission and aims to determine the factors associated with variation of hotspots with time. Methods: Data for individual malaria cases came from the surveillance system of the Delocalized Centers for Prevention and Care (CDPS) (n = 17) from 2005-2019. Meteorological data was acquired from the NASA Goddard Earth Sciences Data and Information Services Center (GES DISC) database. The Box-Jenkins autoregressive integrated moving average (ARIMA) model tested stationarity of the time series, and the impact of meteorological indices (issued from principal component analysis-PCA) on malaria incidence was determined with a general additive model. Hotspot characterization was performed using spatial scan statistics. Results: The current sample includes 7050 eligible Plasmodium vivax (n = 4111) and Plasmodium falciparum (n = 2939) cases from health centers across French Guiana. The first and second PCA-derived meteorological components (maximum/minimum temperature/minimum humidity and maximum humidity, respectively) were significantly negatively correlated with total malaria incidence with a lag of one week and 10 days, respectively. Overall malaria incidence decreased across the time series until 2017 when incidence began to trend upwards. Hotspot characterization revealed a few health centers that exhibited spatial stability across the entire time series: Saint Georges de l'Oyapock and Antecume Pata for P. falciparum, and Saint Georges de l'Oyapock, Antecume Pata, Régina and Camopi for P. vivax. Conclusions: This study highlighted changing malaria incidence in French Guiana and the influences of meteorological factors on transmission. Many health centers showed spatial stability in transmission, albeit not temporal. Knowledge of the areas of high transmission as well as how and why transmission has changed over time can inform strategies to reduce the transmission of malaria in French Guiana. Hotspots should be further investigated to understand other influences on local transmission, which will help to facilitate elimination.

Self-diagnosis and self-treatment of malaria in hard-to-reach and mobile populations of the Amazon: results of Malakit, an international multicentric intervention research project.

Background: Illegal gold miners are currently key hosts for malaria in French Guiana (FG), with a risk of emergence of resistance linked to improper use of artemisinin-based combination therapy (ACT). The remoteness of the mines and regulatory issues hinder their access to health care. Methods: A quasi-experimental researched project (Malakit) implemented in FG borders with Brazil and Suriname aimed at determining the effectiveness of distributed kits for self-diagnosis and self-treatment to illegal gold miners, after training, at strategic border staging areas. Evaluation relied on questionnaires at inclusion and follow-up visits, and pre/post intervention surveys. The primary outcome was the proportion of persons reporting a use of certified ACT after a positive malaria diagnosis. The secondary outcomes assessed antimalarial adherence, kit use and impact on malaria epidemiology. Findings: The proportion of patients reporting a use of certified ACT after a positive diagnosis increased after the intervention (OR 1.8, 95%CI [1.1-3.0]). From April 2018 to March 2020, 3,733 persons participated in the intervention. The kit was used correctly by 71.7% [65.8-77.7] of the 223 persons reporting having used a malakit during the follow-up visits. No serious adverse events related to the misuse of malakit have been reported. The intervention appears to have accelerated the decline in malaria incidence in the region by 42.9%. Interpretation: This innovative international project showed that people with low education can correctly self-manage their malaria symptoms. This strategy could be integrated in the malaria control programs of the countries involved and considered in other regions with residual malaria in remote areas. Funding: This project was funded by the European Union, the Global Fund, Brazil MoH, Cayenne Hospital and FG Health Regional Agency. Editor's note: This translation in French was submitted by the authors and we reproduce it as supplied. It has not been peer reviewed. Our editorial processes have only been applied to the original abstract in English, which should serve as reference for this manuscript. The Lancet Group takes a neutral position with respect to territorial claims in published maps and institutional affiliations. Contexte: Les chercheurs d'or illégaux sont actuellement un réservoir clé du paludisme en Guyane, avec un risque d'émergence de résistance lié à une mauvaise utilisation des combinaisons thérapeutiques à base d'artémisinine (ACT). L'isolement de ces sites miniers clandestins et des contraintes règlementaires entravent leur accès aux soins. Méthodes: Un projet de recherche opérationnelle quasi-expérimental (Malakit) a été mis en œuvre aux frontières de la Guyane avec le Brésil et le Suriname. Il visait à déterminer l'efficacité de la distribution de kits d'autodiagnostic et d'autotraitement à des orpailleurs illégaux, après une formation adaptée, dans des zones stratégiques transfrontalières. L'évaluation s'est appuyée sur des questionnaires lors des visites d'inclusion et de suivi, et sur des enquêtes pré/post intervention. L'indicateur principal était la proportion de personnes déclarant avoir utilisé une ACT certifiée après un diagnostic positif de paludisme. Les indicateurs secondaires reposaient sur l'adhérence aux traitements antipaludiques, l'utilisation des kits et l'impact sur l'épidémiologie du paludisme. Résultats: La proportion de patients déclarant une utilisation d'ACT certifiée après un diagnostic positif a augmenté après l'intervention (OR 1,8, 95%CI [1,1-3,0]). D'avril 2018 à mars 2020, 3 733 personnes ont participé à l'intervention. Le kit a été utilisé correctement par 71,7% [65,8-77,7] des 223 personnes revues en visites de suivi ayant déclaré avoir utilisé un malakit. Aucun événement indésirable grave lié à une mauvaise utilisation du malakit n'a été signalé. L'intervention semble avoir accéléré la diminution de l'incidence du paludisme dans la région de 42,9%. Interprétation: Ce projet international innovant a montré que les personnes ayant un faible niveau d'éducation peuvent se prendre en charge par eux-mêmes pour des symptômes de paludisme. Cette stratégie pourrait être intégrée dans les programmes de lutte contre le paludisme des pays impliqués et envisagée dans d'autres régions où du paludisme résiduel persiste dans des zones isolées. Financement: Ce projet a été financé par l'Union Européenne, le Fonds Mondial, le Ministère de la santé du Brésil, le Centre Hospitalier de Cayenne et l'Agence Régionale de Santé de Guyane.

Contributing to Elimination of Cross-Border Malaria Through a Standardized Solution for Case Surveillance, Data Sharing, and Data Interpretation: Development of a Cross-Border Monitoring System.

BACKGROUND: Cross-border malaria is a significant obstacle to achieving malaria control and elimination worldwide. OBJECTIVE: This study aimed to build a cross-border surveillance system that can make comparable and qualified data available to all parties involved in malaria control between French Guiana and Brazil. METHODS: Data reconciliation rules based on expert knowledge were defined and applied to the heterogeneous data provided by the existing malaria surveillance systems of both countries. Visualization dashboards were designed to facilitate progressive data exploration, analysis, and interpretation. Dedicated advanced open source and robust software solutions were chosen to facilitate solution sharing and reuse. RESULTS: A database gathering the harmonized data on cross-border malaria epidemiology is updated monthly with new individual malaria cases from both countries. Online dashboards permit a progressive and user-friendly visualization of raw data and epidemiological indicators, in the form of time series, maps, and data quality indexes. The monitoring system was shown to be able to identify changes in time series that are related to control actions, as well as differentiated changes according to space and to population subgroups. CONCLUSIONS: This cross-border monitoring tool could help produce new scientific evidence on cross-border malaria dynamics, implementing cross-border cooperation for malaria control and elimination, and can be quickly adapted to other cross-border contexts.

Local emergence in Amazonia of Plasmodium falciparum k13 C580Y mutants associated with in vitro artemisinin resistance.

Antimalarial drug resistance has historically arisen through convergent de novo mutations in Plasmodium falciparum parasite populations in Southeast Asia and South America. For the past decade in Southeast Asia, artemisinins, the core component of first-line antimalarial therapies, have experienced delayed parasite clearance associated with several pfk13 mutations, primarily C580Y. We report that mutant pfk13 has emerged independently in Guyana, with genome analysis indicating an evolutionary origin distinct from Southeast Asia. Pfk13 C580Y parasites were observed in 1.6% (14/854) of samples collected in Guyana in 2016-2017. Introducing pfk13 C580Y or R539T mutations by gene editing into local parasites conferred high levels of in vitro artemisinin resistance. In vitro growth competition assays revealed a fitness cost associated with these pfk13 variants, potentially explaining why these resistance alleles have not increased in frequency more quickly in South America. These data place local malaria control efforts at risk in the Guiana Shield.

All recommended treatments against malaria include a drug called artemisinin or some of its derivatives. However, there are concerns that Plasmodium falciparum, the parasite that causes most cases of malaria, will eventually develop widespread resistance to the drug. A strain of P. falciparum partially resistant to artemisinin was seen in Cambodia in 2008, and it has since spread across Southeast Asia. The resistance appears to be frequently linked to a mutation known as pfk13 C580Y. Southeast Asia and Amazonia are considered to be hotspots for antimalarial drug resistance, and the pfk13 C580Y mutation was detected in the South American country of Guyana in 2010. To examine whether the mutation was still circulating in this part of the world, Mathieu et al. collected and analyzed 854 samples across Guyana between 2016 and 2017. Overall, 1.6% of the samples had the pfk13 C580Y mutation, but this number was as high as 8.8% in one region. Further analyses revealed that the mutation in Guyana had not spread from Southeast Asia, but that it had occurred in Amazonia independently. To better understand the impact of the pfk13 C580Y mutation, Mathieu et al. introduced this genetic change into non-resistant parasites from a country neighbouring Guyana. As expected, the mutation made P. falciparum highly resistant to artemisinin, but it also slowed the growth rate of the parasite. This disadvantage may explain why the mutation has not spread more rapidly through Guyana in recent years. Artemisinin and its derivatives are always associated with other antimalarial drugs to slow the development of resistance; there are concerns that reduced susceptibility to artemisinin leads to the parasites becoming resistant to the partner drugs. Further research is needed to evaluate how the pfk13 C580Y mutation affects the parasite's response to the typical combination of drugs that are given to patients.

Resurgence risk for malaria, and the characterization of a recent outbreak in an Amazonian border area between French Guiana and Brazil.

BACKGROUND: In 2017, inhabitants along the border between French Guiana and Brazil were affected by a malaria outbreak primarily due to Plasmodium vivax (Pv). While malaria cases have steadily declined between 2005 and 2016 in this Amazonian region, a resurgence was observed in 2017. METHODS: Two investigations were performed according to different spatial scales and information details: (1) a local study on the French Guiana border, which enabled a thorough investigation of malaria cases treated at a local village health center and the entomological circumstances in the most affected neighborhood, and (2) a regional and cross-border study, which enabled exploration of the regional spatiotemporal epidemic dynamic. Number and location of malaria cases were estimated using French and Brazilian surveillance systems. RESULTS: On the French Guianese side of the border in Saint-Georges de l'Oyapock, the attack rate was 5.5% (n = 4000), reaching 51.4% (n = 175) in one Indigenous neighborhood. Entomological findings suggest a peak of Anopheles darlingi density in August and September. Two female An. darlingi (n = 1104, 0.18%) were found to be Pv-positive during this peak. During the same period, aggregated data from passive surveillance conducted by Brazilian and French Guianese border health centers identified 1566 cases of Pv infection. Temporal distribution during the 2007-2018 period displayed seasonal patterns with a peak in November 2017. Four clusters were identified among epidemic profiles of cross-border area localities. All localities of the first two clusters were Brazilian. The localization of the first cluster suggests an onset of the outbreak in an Indigenous reservation, subsequently expanding to French Indigenous neighborhoods and non-Native communities. CONCLUSIONS: The current findings demonstrate a potential increase in malaria cases in an area with otherwise declining numbers. This is a transborder region where human mobility and remote populations challenge malaria control programs. This investigation illustrates the importance of international border surveillance and collaboration for malaria control, particularly in Indigenous villages and mobile populations.

Human Plasmodium vivax diversity, population structure and evolutionary origin.

More than 200 million malaria clinical cases are reported each year due to Plasmodium vivax, the most widespread Plasmodium species in the world. This species has been neglected and understudied for a long time, due to its lower mortality in comparison with Plasmodium falciparum. A renewed interest has emerged in the past decade with the discovery of antimalarial drug resistance and of severe and even fatal human cases. Nonetheless, today there are still significant gaps in our understanding of the population genetics and evolutionary history of P. vivax, particularly because of a lack of genetic data from Africa. To address these gaps, we genotyped 14 microsatellite loci in 834 samples obtained from 28 locations in 20 countries from around the world. We discuss the worldwide population genetic structure and diversity and the evolutionary origin of P. vivax in the world and its introduction into the Americas. This study demonstrates the importance of conducting genome-wide analyses of P. vivax in order to unravel its complex evolutionary history.