OBJECTIVES:Artemisinin-resistant Plasmodium falciparum has emerged in several East African countries neighbouring Madagascar. Despite the island's substantial malaria burden, recent data on artemisinin partial resistance are limited, raising concerns about the potential emergence of resistant parasites. This study provides an updated overview of the prevalence and diversity of P. falciparum Kelch13 (pfkelch13) polymorphisms in Madagascar. METHODS:During a nationally representative, cross-sectional survey conducted between January and May 2024, dried blood samples were collected from 4850 febrile patients at 65 health facilities. Pfkelch13 genotyping was performed using a targeted amplicon deep sequencing approach. RESULTS:Of the 1944 P. falciparum-positive samples, 963 (49.5%) pfkelch13 sequences were successfully obtained, and 885 (91.9%) corresponded to the 3D7 wild-type. Non-synonymous and synonymous mutations were detected in 1.8% (17/963) and 6.2% (60/963) of isolates, respectively, whereas one isolate (0.1%) carried double mutations. Of the 18 mutations identified, 5 had not been previously reported. The two most frequent polymorphisms in Madagascar were the synonymous mutations C469C (3.0%, 29/963) and P417P (2.8%, 27/963). None of the WHO-validated artemisinin partial resistance markers were detected. CONCLUSION:This study provides an updated baseline of pfkelch13 polymorphisms in Madagascar, with no evidence of artemisinin partial resistance emergence. Importantly, no parasites harbouring a validated artemisinin resistance marker were detected across the regions sampled, suggesting that resistant parasites have not yet become established. These findings provide a valuable baseline for future genomic surveillance efforts aimed at the early detection of mutations associated with artemisinin partial resistance.
Bats are reservoir hosts for numerous well-known zoonotic viruses, but their broader virus-hosting capacities remain understudied. Picornavirales are an order of enteric viruses that cause disease across a wide range of mammalian hosts, including Hepatitis A in humans and foot-and-mouth disease in ungulates. Host-switching and recombination drive the diversification of Picornavirales worldwide. Picornaviridae and Caliciviridae (families within Picornavirales) have been described in bats across mainland Africa, but surveillance for these viruses has been rare in the Southwest Indian Ocean Islands. Prior work in Madagascar has described numerous bat viruses, some with zoonotic potential, that demonstrate both high identity to and extreme divergence from viruses found in sister bat species in Africa. Using metagenomic Next Generation Sequencing of urine and fecal samples obtained from three species of endemic Malagasy fruit bats (Eidolon dupreanum, Pteropus rufus, and Rousettus madagascariensis), we identify and describe 13 full-length and 38 partial-length genomic sequences within the Picornaviridae and Caliciviridae families (36 picornavirus and 15 Sapovirus sequences). We find evidence that host-switching between Madagascar and mainland African bat picornaviruses and sapoviruses, followed by host-parasite co-speciation, likely shaped the diversification pattens of these novel sequences, with little evidence for cross-species transmission among Malagasy bat species in close contact.
This research aimed to investigate the prevalence and diversity of Bartonella in small mammals and their ectoparasites from the Central Highlands of Madagascar and to refine existing information on potential associated zoonotic diseases. A retrospective analysis was performed on mammals and their ectoparasites collected in the Fandriana and Ankazobe districts, including 253 spleen samples from seven small mammal species and 183 individual ectoparasites (132 fleas and 51 ticks). Genomic DNA was extracted and amplified by polymerase chain reaction (PCR) targeting the nuoG gene (346 bp). Sanger sequencing of the PCR products was performed to assess Bartonella diversity using phylogenetic analysis. In total, 60.1
Background West Nile virus (WNV) is an emerging disease transmitted from bird hosts to humans by Culex mosquitoes. Thousands of human cases of WNV infection are reported each year in the United States and Europe, and circulation has been confirmed in Africa and the Indian Ocean, including Madagascar. However, little is known about the current riskscape for people in Madagascar, and what determines its local distribution and human exposure across the population. The goal of this study was to assess WNV seroprevalence and identify associated socio-ecological risk factors in rural Madagascar. Methodology and principal findings A cross-sectional serological survey was conducted in Ifanadiana District in 2021, nested within a representative longitudinal cohort. We evaluated serological responses to WNV and to Dengue virus in 3,948 individuals using a multiplex bead assay. We estimated WNV seroprevalence using a Gaussian Mixture Model (GMM) and characterized environmental, socioeconomic, and demographic factors that could be associated with exposure to WNV using various data sources, including optical and Synthetic Aperture Radar (SAR) satellite images, climate variables, and household survey data. Overall seroprevalence was 43%, and populations living in geographically isolated areas and those engaged in agricultural activities were at higher risk, while proximity to dense forests and residential areas were protective against WNV exposure. Conclusions This study found high rates and local heterogeneity in WNV exposure in a rural district of Madagascar. In addition, environmental, climatic, and socio-demographic data were determinants of WNV transmission, providing a valuable tool for surveillance and decision-making in arbovirus prevention and control. Extending this approach to other orthoflaviviruses could improve understanding of local viral co-circulation and promote the development of more precise and context-specific prevention strategies. ### Competing Interest Statement The authors have declared no competing interest. ### Author Declarations I confirm all relevant ethical guidelines have been followed, and any necessary IRB and/or ethics committee approvals have been obtained. Yes The details of the IRB/oversight body that provided approval or exemption for the research described are given below: French and Malagasy questionnaires used in the IHOPE cohort, as well as data collection protocols, were standardized and validated for Madagascar during previous national surveys carried out by INSTAT. The study was approved by the Madagascar National Ethics Committee Comite d Ethique de la Recherche Biomedicale aupres du Ministere de la Sante CERBM and Harvard Medical School (Institutional Review Board IRB, N IRB160347). An amendment was obtained for changes in the 2021 surveys and collection of dried blood spot samples (CERBM N 024 MSANP/SG/AGMED/CNPV/CERBM; 26 February 2021). Use of these samples for the current study was authorized in 2023 (N 53 MSANP/SG/AMM/CERBM). All adults (≥ 15 years) provided oral informed consent for the in-person interview and written informed consent for biological sample collection. Parents or guardians provided written consent for biological sample collection from children < 15 years of age, and children 7-14 years provided written assent separately. I confirm that all necessary patient/participant consent has been obtained and the appropriate institutional forms have been archived, and that any patient/participant/sample identifiers included were not known to anyone (e.g., hospital staff, patients or participants themselves) outside the research group so cannot be used to identify individuals. Yes I understand that all clinical trials and any other prospective interventional studies must be registered with an ICMJE-approved registry, such as ClinicalTrials.gov. I confirm that any such study reported in the manuscript has been registered and the trial registration ID is provided (note: if posting a prospective study registered retrospectively, please provide a statement in the trial ID field explaining why the study was not registered in advance). Yes I have followed all appropriate research reporting guidelines, such as any relevant EQUATOR Network research reporting checklist(s) and other pertinent material, if applicable. Yes Data are available upon request to the address science{at}pivotworks.org. Analysis code is available on github (https://github.com/mauricianot/wnv.git). Agence Nationale de la Recherche, https://ror.org/00rbzpz17, Project ANR-19-CE36-000101 Agence française de développement, https://ror.org/04tqhj682, PREACTS program (AFRICAM project)
The Mandoto District in the central highlands of Madagascar experiences year-round transmission of Plasmodium vivax (P. vivax) and Plasmodium falciparum (P. falciparum). Monthly malaria case data from 27 health centers across Mandoto between 2019 and 2024 were analyzed alongside meteorological data to understand transmission dynamics and forecast potential influences of climate change using descriptive, cross-correlation, and seasonal autoregressive integrated moving average forecast models. Over a period of 6 years, 276,318 rapid diagnostic tests (RDTs) were performed, yielding a 39.6% positivity rate, totaling 109,428 malaria cases. After 2021, when multispecies RDTs became available, 71.5% of cases were attributed to P. falciparum, and 28.5% were attributed to P. vivax. Both species were co-endemic across all health centers, with the western region experiencing a higher transmission risk. Malaria cases peaked in January, with a second peak from April to June after the rainy season, and declined between July and September. Precipitation and temperature effectively revealed the seasonality of malaria dynamics, thereby improving model accuracy. Plasmodium falciparum exhibited stronger associations with precipitation and temperature variability. The present study highlights that combining time-series modeling with precipitation and temperature data can help predict malaria cases and support timely planning and resource allocation.
