Indigenous emergence and spread of kelch13 C469Y artemisinin-resistant Plasmodium falciparum in Uganda.

Artemisinin-based combination therapies (ACTs) were introduced as the standard of care for uncomplicated malaria in Africa almost two decades ago. Recent studies in East Africa have reported a gradual increase in kelch13 (k13) mutant parasites associated with reduced artesunate efficacy. As part of the Community Access to Rectal Artesunate for Malaria project, we collected blood samples from 697 children with signs of severe malaria in northern Uganda between 2018 and 2020, before and after the introduction of rectal artesunate (RAS) in 2019. K13 polymorphisms were assessed, and parasite editing and phenotyping were performed to assess the impact of mutations on parasite resistance. Whole-genome sequencing was performed, and haplotype networks were constructed to determine the geographic origin of k13 mutations. Of the 697 children, 540 were positive for Plasmodium falciparum malaria by PCR and were treated with either RAS or injectable artesunate monotherapy followed in most cases by ACT. The most common k13 mutation was C469Y (6.7%), which was detected more frequently in samples collected after RAS introduction. Genome editing confirmed reduced in vitro susceptibility to artemisinin in C469Y-harboring parasites compared to wild-type controls (P < 0.001). The haplotypic network showed that flanking regions of the C469Y mutation shared the same African genetic background, suggesting a single and indigenous origin of the mutation. Our data provide evidence of selection for the artemisinin-resistant C469Y mutation. The realistic threat of multiresistant parasites emerging in Africa should encourage careful monitoring of the efficacy of artemisinin derivatives and strict adherence to ACT treatment regimens.

Intermittent preventive treatment for forest goers by forest malaria workers: an observational study on a key intervention for malaria elimination in Cambodia.

Background: Cambodia targets P. falciparum malaria elimination by 2023 and all human malaria species by 2025, aligning with WHO's Mekong Malaria Elimination program. The Intermittent Preventive Treatment for Forest Goers (IPTf) project aimed at forest-specific malaria elimination. The study aims to pinpoint the main factors driving malaria transmission in Cambodian forests and evaluate the initial implementation and effectiveness of IPTf in accelerating the elimination of malaria by treating and preventing infections among at-risk populations in these areas. Methods: From March 11, 2019, to January 30, 2021, a malaria intervention program took place in isolated forests in Northeast Cambodia. The first phase focused on observing forest goers (FGs) within the forests, documenting their malaria risk. In the second phase, a monthly artesunate-mefloquine IPTf was implemented by trained forest malaria workers who were former FGs conducting interviews, blood collection, and IPTf administration. Findings: Throughout the two-year period, 2198 FGs were involved in 3579 interviews, with 284 in both the observation and intervention phases. Following IPTf implementation, PCR-confirmed malaria prevalence significantly decreased from 2.9% to 0.5% for P. falciparum and from 21.0% to 4.7% for P. vivax. Among the 284 participants tracked through both phases, malaria prevalence fell from 2.5% to 0.3% for P. falciparum and from 22.5% to 3.7% for P. vivax. The intervention phase demonstrated a rapid decline in P. falciparum prevalence among mobile and previously inaccessible populations, while also revealing a higher P. falciparum infection risk associated with activities inaccurately labelled as farming, underscoring the need for customized interventions. Interpretation: The successful implementation of IPTf in Cambodia's remote forests has markedly decreased malaria prevalence among high-risk groups. Cambodia's National Malaria Program has acknowledged this strategy as essential for malaria elimination intervention, endorsing forest-specific approaches to meet the 2025 goal of eradicating all human malaria species in Cambodia. Funding: The study received funding from the French 5% Initiative (Initiative Canal 2-17SANIN205).

Comparing malaria risk exposure in rural Cambodia population using GPS tracking and questionnaires.

BACKGROUND: The Great Mekong Subregion has attained a major decline in malaria cases and fatalities over the last years, but residual transmission hotspots remain, supposedly fueled by forest workers and migrant populations. This study aimed to: (i) characterize the fine-scale mobility of forest-goers and understand links between their daily movement patterns and malaria transmission, using parasites detection via real time polymerase chain reaction (RT PCR) and the individual exposure to Anopheles bites by quantification of anti-Anopheles saliva antibodies via enzyme-linked immunosorbent assay; (ii) assess the concordance of questionnaires and Global Positioning System (GPS) data loggers for measuring mobility. METHODS: Two 28 day follow-ups during dry and rainy seasons, including a GPS tracking, questionnaires and health examinations, were performed on male forest goers representing the population at highest risk of infection. Their time spent in different land use categories and demographic data were analyzed in order to understand the risk factors driving malaria in the study area. RESULTS: Malaria risk varied with village forest cover and at a resolution of only a few kilometers: participants from villages outside the forest had the highest malaria prevalence compared to participants from forest fringe's villages. The time spent in a specific environment did not modulate the risk of malaria, in particular the time spent in forest was not associated with a higher probability to detect malaria among forest-goers. The levels of antibody response to Anopheles salivary peptide among participants were significantly higher during the rainy season, in accordance with Anopheles mosquito density variation, but was not affected by sociodemographic and mobility factors. The agreement between GPS and self-reported data was only 61.9% in reporting each kind of visited environment. CONCLUSIONS: In a context of residual malaria transmission which was mainly depicted by P. vivax asymptomatic infections, the implementation of questionnaires, GPS data-loggers and quantification of anti-saliva Anopheles antibodies on the high-risk group were not powerful enough to detect malaria risk factors associated with different mobility behaviours or time spent in various environments. The joint implementation of GPS trackers and questionnaires allowed to highlight the limitations of both methodologies and the benefits of using them together. New detection and follow-up strategies are still called for.

Using serological diagnostics to characterize remaining high-incidence pockets of malaria in forest-fringe Cambodia.

BACKGROUND: Over the last decades, the number of malaria cases has drastically reduced in Cambodia. As the overall prevalence of malaria in Cambodia declines, residual malaria transmission becomes increasingly fragmented over smaller remote regions. The aim of this study was to get an insight into the burden and epidemiological parameters of Plasmodium infections on the forest-fringe of Cambodia. METHODS: 950 participants were recruited in the province of Mondulkiri in Cambodia and followed up from 2018 to 2020. Whole-blood samples were processed for Plasmodium spp. identification by PCR as well as for a serological immunoassay. A risk factor analysis was conducted for Plasmodium vivax PCR-detected infections throughout the study, and for P. vivax seropositivity at baseline. To evaluate the predictive effect of seropositivity at baseline on subsequent PCR-positivity, an analysis of P. vivax infection-free survival time stratified by serological status at baseline was performed. RESULTS: Living inside the forest significantly increased the odds of P. vivax PCR-positivity by a factor of 18.3 (95% C.I. 7.7-43.5). Being a male adult was also a significant predictor of PCR-positivity. Similar risk profiles were identified for P. vivax seropositivity. The survival analysis showed that serological status at baseline significantly correlated with subsequent infection. Serology is most informative outside of the forest, where 94.0% (95% C.I. 90.7-97.4%) of seronegative individuals survived infection-free, compared to 32.4% (95% C.I.: 22.6-46.6%) of seropositive individuals. CONCLUSION: This study justifies the need for serological diagnostic assays to target interventions in this region, particularly in demographic groups where a lot of risk heterogeneity persists, such as outside of the forest.

In Vitro Antimalarial Activity of Trichothecenes against Liver and Blood Stages of Plasmodium Species.

Trichothecenes (TCNs) are a large group of tricyclic sesquiterpenoid mycotoxins that have intriguing structural features and remarkable biological activities. Herein, we focused on three TCNs (anguidine, verrucarin A, and verrucarol) and their ability to target both the blood and liver stages of Plasmodium species, the parasite responsible for malaria. Anguidine and verrucarin A were found to be highly effective against the blood and liver stages of malaria, while verrucarol had no effect at the highest concentration tested. However, these compounds were also found to be cytotoxic and, thus, not selective, making them unsuitable for drug development. Nonetheless, they could be useful as chemical probes for protein synthesis inhibitors due to their direct impact on parasite synthesis processes.