Institut Pasteur de Madagascar

Mining activities can significantly alter surface and groundwater systems. Therefore, sustainable water resources management has become a central requirement and strategic necessity for responsible mining. This requires tools capable of characterizing water sources, flow paths, and contaminant dynamics to support informed and responsible decision-making. Stable and radioactive isotopes are powerful tracers of the origin, age, movement, and transport of water and its constituents, as well as indicators of the water-rock interactions affecting groundwater and surface water quality. This paper reviews publications from 2022 to 2024 that discuss advancements in isotopic techniques and their applications, with the goal to promote the adoption of integrated isotopic and geochemical methods in mining-related assessments. The review is organized into three sections: 1) the understanding of hydro(geo)logical circuits: water sources and circulation, mixing processes, hydro(geo)logical alteration, river-groundwater interactions and groundwater age; 2) the assessment of mining-related contamination processes: contamination by S or by N compounds, discrimination between mining and other contamination sources, the use of minor and trace element isotopes, the salinity issues, and the identification of gas production and exchange; and 3) the application of isotope approaches for monitoring the impact of mining and assessing remediation measures, whether natural or engineered. Finally, the intrinsic strengths and weaknesses, as well as the external opportunities and limitations to the application of isotopic approaches are discussed. The review summarizes the commonly encountered sources and processes in mining settings and provides graphical outputs to assist with interpreting new experimental data, highlighting environmental isotopes as “sustainable investigation tools”. • Isotopic approaches in mining-related settings are assessed with a SWOT analysis • Graphical outputs to assist with interpreting new experimental data are provided • Environmental isotopes represent fully-fledged “sustainable investigation tools”

ABSTRACT The status of most fish stocks in Madagascar remains poorly documented. Given their importance for food security and livelihoods, it is necessary to define management measures with reliable data. This study applied a length‐based Bayesian biomass (LBB) estimation method for analysing the fisheries' representative length‐frequency data of seven most commonly caught coral reef fish species in the southwest of Madagascar. Using Froese's indicators, the use of as a stock status indicator, allows a consistent comparison among species in multi‐gear, multi‐species fisheries and provides a practical basis for management advice in data‐limited contexts. The stock status was determined based on median estimates for the period 2018–2023, which provide an assessment of the overall status. Estimates for 2023 were used to describe the most recent status of the stocks. The outputs of this study provide a guide for fisheries managers, coastal communities and authorities to formulate effective management strategies for the sustainability of the marine fisheries in Madagascar. A key recommendation from the study is the need for fisheries managers to improve fisheries data and to periodically monitor biological indicators to assess the status of small‐scale fisheries stocks.

Seaweed farming offers a sustainable solution to malnutrition and economic challenges in southwestern Madagascar. This study assessed the seasonal performance of 12 edible seaweed species and optimized cultivation parameters for Gracilaria corticata and Gracilaria salicornia using long-line aquaculture. Environmental factors, including temperature, light intensity, salinity, and current speed, were monitored across warm and cool seasons. G. corticata, G. salicornia, and Hormophysa cuneiformis exhibited the highest retention rates (>50 %) and growth performance, with G. corticata demonstrating significant superior growth in both seasons. Smaller cuttings (0–50 g) achieved higher retention and specific growth rates, particularly in the first 30 days. Growth was significantly influenced by light intensity (4209.35 ± 3274.72 lux in the warm season; 3107.77 ± 3194.22 lux in the cool season) and temperature (30.20 ± 1.26 °C in the warm season; 24.83 ± 0.35 °C in the cool season), with optimal conditions occurring in the warm season. These findings highlight the potential of G. corticata and G. salicornia for sustainable aquaculture, contributing to species diversification and food security. Optimizing environmental conditions and cutting sizes is crucial for maximizing seaweed productivity in Madagascar.

BackgroundMalaria, whose parasites are transmitted by Anopheles mosquitoes, remains a major public health burden in Madagascar despite the control measures led by the National Malaria Control Program. Understanding the population dynamics of Anopheles mosquitoes is therefore essential to optimize malaria surveillance and control. This study aimed to develop a model incorporating environmental, climatic and agricultural determinants of Anopheles abundance to predict their spatiotemporal distribution.MethodsWe developed a model of spatiotemporal dynamics for four Anopheles species, vectors of malaria parasite in Madagascar: Anopheles arabiensis, Anopheles coustani, Anopheles funestus and Anopheles gambiae. This model was based on the life cycle of Anopheles and accounted for both the aquatic and aerial phases of their development. It used a system of differential equations to estimate the number of Anopheles mosquitoes at each stage of development. The Ocelet language, dedicated to the modeling of spatial dynamics, was used to produce simulations based on climate and environmental data. The model explicitly integrates the agricultural calendar to adjust the environmental carrying capacity of larval habitats. Model outputs were validated with entomological data collected in Vohimasy (Farafangana districts, 2014–2017).Results24 simulation outputs, from three Anopheles species and eight sites, were obtained and the validation revealed a significant correlation between field observations and model predictions: the correlation coefficients obtained ranged from 0.70 to 0.76. The predicted abundance of host-seeking Anopheles varied seasonally influenced by precipitation, temperature and environmental carrying capacity. The model exhibited robustness across sites with diverse climates and accurately reproduced interannual dynamics. The integration of the agricultural calendar significantly reduced the overestimation of the density of host-seeking adult females.ConclusionThe developed Anopheles dynamics model provides a valuable tool for predicting mosquito abundance and distribution over time and space. It correctly predicted the abundance at villages with contrasting climates and reproduced interannual dynamics well. A distinctive aspect of this work lies in the explicit integration of seasonal agricultural practices into the estimation of larval habitat availability. This allows for a more accurate and transferable modeling of Anopheles population dynamics.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12942-025-00424-8.

BackgroundBurkholderia pseudomallei (Bp), the causative agent of melioidosis, poses a significant health risk in endemic regions. This study aimed to characterize six previously identified Bp antigens for exposure monitoring in potential endemic setting of Madagascar and to assess potential exposure and reactivity across Madagascar to inform diagnostic strategies and understand regional exposure patterns.MethodsSix highly reactive Bp antigens, CPS I, LPS types A and B, HCP1, AhpC, and GroEL, were characterized using the protein BLAST (BLASTp) algorithm against the NCBI non-redundant protein database to evaluate conservation and specificity. Serological reactivity was analyzed in 5,736 serum samples from six regions of Madagascar using Luminex bead-based multiplex assays. Principal Component Analysis was conducted to identify co-reactivity patterns. Environmental sampling in Mahajanga assessed the presence of Bp DNA in soil and water samples via real-time PCR.ResultsAntigen conservation varied, with HCP1 and CPS I demonstrating the highest specificity, suggesting their potential for targeted serological detection. Seroprevalence and co-seroprevalence were highest in the Mahajanga region, particularly for HCP1 and CPS I (p < 0.0001). PCA revealed distinct antigen-specific immune response profiles. Environmental sampling confirmed the presence of Bp DNA in a water sample from Mahajanga, indicating local bacterial presence in the environment.ConclusionsThese findings suggest human exposure to Bp occurs in multiple regions in Madagascar. HCP1 and CPS I emerged as promising targets for diagnostic applications, and environmental detection of Bp underscores the need for targeted public health interventions in higher-risk regions like Mahajanga.

Introduction: In Madagascar, coverage of the optimal dose (three doses or more) of Intermittent Preventive Treatment with Sulfadoxine-Pyrimethamine during pregnancy (IPTp-SP) remains low, reaching only 31% in 2021. This study aimed to investigate the factors influencing this low coverage in a particularly affected community. Methods: This was a cross-sectional study using a mixed-methods approach, conducted among mothers with a child under 12 months and healthcare personnel in Farafangana from November 19, 2024, to January 10, 2025. A descriptive analysis, a bivariate and multivariate logistic regression, were conducted. The odds ratio with a 95% confidence interval was used as the measure of association. Qualitative data analysis was conducted manually based on predefined themes and sub-themes. Results: The coverage of the optimal dose of IPTp-SP was 28.9%. Factors significantly associated with the non-receipt of the optimal dose included women under 25 years of age (adjusted odds ratios (AOR) [95% confidence intervals (CI)] = 0.47 [0.26 – 0.83]), being multigravida (AOR [95% CI] = 1.66 [1.08 – 3.14]), multiparity (AOR [95% CI] = 1.62 [1.13 – 3.18]), poor knowledge of the recommended dose (AOR [95% CI] = 6.82 [3.21 – 14.49]), late initiation of intake (AOR [95% CI] = 2.28 [1.41 – 3.67]), and SP-related side effects (AOR [95% CI] = 1.58 [1.02 – 2.46]). The qualitative approach corroborated these findings and identified the influence of women’s social surroundings. Conclusion: Factors related to women, sociocultural aspects, and the health system influence the low coverage of the optimal IPTp-SP dose in Farafangana. An implementation approach addressing all these factors would be essential to improve coverage.

BackgroundMadagascar is a country with a high tuberculosis (TB) burden, and the incidence of the disease has remained unchanged since 2013. TB detection largely relies on passive strategies, with little attention given to TB infections (TBIs), which are silent reservoirs that fuel future active TB cases.MethodThis qualitative study investigated how Malagasy communities perceive TB and an innovative approach for TBI screening and care. This approach was developed through the APRECIT operational research project in partnership with the National Tuberculosis Control Program (NTP). Semi-structured in-depth interviews were conducted between March and May 2023 with a sample of stakeholders and health workers (26 HWs) at the national, regional and community levels and focus groups with household contacts (46 HHCs) of TB patients.ResultsThe fight against TB remains challenging in Madagascar. Community knowledge of TB is limited, and the disease is perceived as shameful. Individuals with TB and their families face stigmatization within their own family and the community. At the provider level, HWs reported challenges in promptly detecting and treating TB people with TB due to structural constraints within the health system and barriers at the household (HH) level. The introduction of home-based screening for TBI was perceived as a way to interrupt disease progression and help reduce stigma. For HWs, this strategy helps to limit TB transmission. However, HWs expressed concerns about giving treatment to asymptomatic people and the replicability of the strategy at the national level.ConclusionImproving communication about TB and implementing a home-based screening strategy for HHCs to identify individuals at high risk of TB progression have the potential to improve TB control in Madagascar.Supplementary InformationThe online version contains supplementary material available at 10.1186/s12889-025-24333-4.

Protected areas can play a crucial role in enhancing agricultural sustainability by supporting ecosystem services that mitigate key challenges faced by rural farming communities. In Madagascar, subsistence agriculture is a major driver of deforestation and biodiversity loss, worsened by pest-related agricultural and harvest losses. Insectivorous bats are widely known natural enemies of agricultural pests, but the role of protected areas in safeguarding this service in surrounding rural landscapes is unclear. This study investigates the benefits provided by insectivorous bats roosting within protected areas of northern Madagascar, focusing on their potential to suppress agricultural pests and disease vectors. We used molecular techniques to analyse the diet of bats based on faecal samples from several species and locations. We found that most bat species consumed arthropod pests affecting rice and other crops, as well as several vectors of pathogens that cause diseases in humans and animals, such as mosquito vectors of Plasmodium sp. Given their mobility and home ranges, we suggest that certain bat species roosting in protected areas have the dispersal capacity to forage in nearby agricultural landscapes, contributing to pest suppression and disease risk reduction. Hence, protecting bat roosts within and around protected areas may offer a cost-effective means to enhance agricultural productivity and public health. These findings underscore the need to integrate ecosystem services into conservation and land-use management strategies, fostering sustainability and rural welfare in Madagascar. • Malagasy bats consume agricultural pests and vectors of livestock and human diseases. • Certain bat species roosting in protected areas can forage in nearby rural areas. • Protected areas may enhance bat-mediated pest suppression beyond their limits. • Managing ecosystem services links conservation with agricultural productivity and welfare.

Expanding transportation infrastructure has facilitated the introduction and proliferation of invasive small mammals, particularly now cosmopolitan rodents like Rattus spp. and Mus musculus, within urban socio-ecosystems where they may severely impact local biodiversity, economy and public health. However, fine-scale dynamics of such biological invasions are still poorly documented, especially in African cities where such biological invasions are still ongoing. We took advantage of a long-term monitoring program of terrestrial small mammal communities of Niamey, the capital city of Niger, to compare rodent and shrew faunas at the same sampling points ten years apart, namely in 2009-2013 and in 2020-2023. We show that Rattus rattus has been expanding significantly in almost all trapping areas across the city, while Mastomys natalensis relative abundance has decreased. This clear trend of native-to-invasive rodent species turnover was particularly marked within the core city, but some notable exceptions exist in peripheral as well as traditionally built zones where the native species still remains dominant. These patterns are discussed, with special attention given to possible human socio-economic and health implications.

ObjectivePlague (Yersinia pestis infection) is a flea-borne zoonotic disease mainly affecting African countries, with most human cases reported from Madagascar and the Democratic Republic of Congo. Although curable, plague can be fatal without prompt treatment, highlighting the importance of reliable diagnostics. Current tests include bacteriological culture, PCR, and anti-F1 ELISA, however the anti-F1 serology has limitations due to the existence of F1-negative virulent strains. To address this, we developed a serological test detecting IgG antibodies against LcrV or V antigen, the main virulence factor of Y. pestis and further evaluated the developed test on clinical samples.ResultsV antigen was produced from the culture of V-pGEX-6P-2 clones and purified as GST-LcrV, which was functional for ELISA plate coating. The developed anti-V ELISA showed 60% sensitivity and 93.3% specificity when tested on confirmed plague patients’ serum samples from Madagascar. However, evaluation on convalescent sera collected from Day 1 to Month 3 post-infection revealed inconsistent anti-V antibody production. This suggests the anti-V ELISA is best used as a complementary test for plague diagnosis and during outbreak investigations. In addition, this study provides valuable insight into the humoral response diversity following Y. pestis infection, representing crucial information for plague vaccine development.