Publications by authors named "Tanjona Ramiadantsoa"

The emergence of SARS-CoV-2 into a highly susceptible global population was primarily driven by human mobility-induced introduction events. Especially in the early stages, understanding mobility was vital to mitigating the pandemic prior to widespread vaccine availability. We conducted a systematic review of studies published from January 1, 2020, to May 9, 2021, that used population-level human mobility data to understand SARS-CoV-2 transmission.

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Morphometric analyses of male genitalia are routinely used to distinguish genera and species in beetles, butterflies, and flies, but are rarely used in ants, where most morphometric analyses focus on the external morphology of the worker caste. In this work, we performed linear morphometric analysis of the male genitalia to distinguish and in Madagascar. For 80 specimens, we measured 10 morphometric characters, especially on the paramere, volsella, and penisvalvae.

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Cricket Frass Fertilizer (CFF) was tested for its efficiency and potential as a fertilizer on the growth of green beans (Phaseolus vulgaris L.) in central Madagascar from April 2020 to October 2020. We grew green beans experimentally for 93 days with seven different fertilizer treatments: NPK 200 kg/ha (0.

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Disturbances are ubiquitous in ecological systems, and species have evolved a range of strategies to resist or rebound following disturbance. Understanding how the presence and complementarity of regeneration traits will affect community responses to disturbance is increasingly urgent as disturbance regimes shift beyond their historical ranges of variability. We define "disturbance niche" as a species' fitness across a range of disturbance sizes and frequencies that can reflect the fundamental or realized niche, that is, whether the species occurs alone or with other species.

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Article Synopsis
  • The study explores how public health authorities can effectively implement targeted surveillance for disease control when resources are limited, using social network analysis.
  • By evaluating sociodemographic factors, such as age and marital status, as proxies for degree centrality, the researchers tested their effectiveness against known network data in low-resource settings.
  • Results showed that using these sociodemographic proxies can significantly reduce infection rates while decreasing the number of tests needed, indicating that they are a viable alternative when direct social network data is not accessible.
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  • Limited availability of COVID-19 vaccines in low and middle-income countries (LMICs) like Madagascar necessitates prioritization schemes for effective distribution, targeting health care workers and vulnerable populations initially.
  • The study utilized a mathematical model to simulate various vaccination strategies, focusing on geographical allocation and the impact of past infection rates.
  • Results showed that prioritizing vaccine distribution based on the elderly population size or overall regional population leads to a greater reduction in COVID-19 mortality compared to using reported cases and deaths as criteria for allocation.
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  • Quantifying travel is crucial for predicting disease spread in emerging epidemics like COVID-19, particularly in low- and middle-income countries (LMICs) where travel data is often limited.
  • Data from Madagascar's COVID-19 dashboard was used to compare real reported case timing against expectations from various connectivity models, revealing that mobile phone data and a gravity model based on distance provided the best predictions.
  • The study emphasizes the need for better data availability and collaboration among institutions, as the effectiveness of predictive models relies heavily on the quality of the data they use.
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For emerging epidemics such as the COVID-19 pandemic, quantifying travel is a key component of developing accurate predictive models of disease spread to inform public health planning. However, in many LMICs, traditional data sets on travel such as commuting surveys as well as non-traditional sources such as mobile phone data are lacking, or, where available, have only rarely been leveraged by the public health community. Evaluating the accuracy of available data to measure transmission-relevant travel may be further hampered by limited reporting of suspected and laboratory confirmed infections.

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A surprising feature of the SARS-CoV-2 pandemic to date is the low burdens reported in sub-Saharan Africa (SSA) countries relative to other global regions. Potential explanations (for example, warmer environments, younger populations) have yet to be framed within a comprehensive analysis. We synthesized factors hypothesized to drive the pace and burden of this pandemic in SSA during the period from 25 February to 20 December 2020, encompassing demographic, comorbidity, climatic, healthcare capacity, intervention efforts and human mobility dimensions.

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Objectives: Quantitative estimates of the impact of infectious disease outbreaks are required to develop measured policy responses. In many low- and middle-income countries, inadequate surveillance and incompleteness of death registration are important barriers.

Design: Here, we characterize how large an impact on mortality would have to be for being detectable using the uniquely detailed mortality notification data from the city of Antananarivo, Madagascar, with application to a recent measles outbreak.

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Pulsed fluxes of organisms across ecosystem boundaries can exert top-down and bottom-up effects in recipient food webs, through both direct effects on the subsidized trophic levels and indirect effects on other components of the system. While previous theoretical and empirical studies demonstrate the influence of allochthonous subsidies on bottom-up and top-down processes, understanding how these forces act in conjunction is still limited, particularly when an allochthonous resource can simultaneously subsidize multiple trophic levels. Using the Lake Mývatn region in Iceland as an example system of allochthony and its potential effects on multiple trophic levels, we analyzed a mathematical model to evaluate how pulsed subsidies of aquatic insects affect the dynamics of a soil-plant-arthropod food web.

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Article Synopsis
  • There is a notable discrepancy in the impact of the SARS-CoV-2 pandemic in sub-Saharan Africa (SSA) compared to other regions, with lower reported cases and fatalities.
  • Various factors like climate, demographics, and healthcare capacity are analyzed to understand this phenomenon, highlighting the important role of human mobility and connectivity in the spread of the virus.
  • The study suggests that despite a younger population, variations in comorbidities and healthcare access could lead to severe outcomes, emphasizing the need for urgent data to manage potential high-burden scenarios effectively.
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Multiple abrupt and sometimes near-synchronous declines in tree populations have been detected in the temperate forests of eastern North America and Europe during the Holocene. Traditional approaches to understanding these declines focus on searching for climatic or other broad-scale extrinsic drivers. These approaches include multi-proxy studies that match reconstructed changes in tree abundance to reconstructed changes in precipitation or temperature.

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Empirical studies have shown that, unlike species with specialized resource requirements, generalist species may benefit from habitat destruction. We use a family of models to probe the causes of the contrasting responses of these two types of species to habitat destruction. Our approach allows a number of mechanisms to be switched on and off, thereby making it possible to study their marginal and joint effects.

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Article Synopsis
  • * These changes are hard to identify because they can be caused by sudden shifts in factors like climate or resource use, gradual changes, or the interplay of multiple issues.
  • * It’s crucial to understand and diagnose these changes so that society can adapt effectively to the fast and complex environmental shifts we are facing.
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Background: Malaria is one of the primary health concerns in Madagascar. Based on the duration and intensity of transmission, Madagascar is divided into five epidemiological strata that range from low to mesoendemic transmission. In this study, the spatial and temporal dynamics of malaria within each epidemiological zone were studied.

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In biodiversity conservation, habitat corridors are assumed to increase landscape-level connectivity and to enhance the viability of otherwise isolated populations. While the role of corridors is supported by empirical evidence, studies have typically been conducted at small spatial scales. Here, we assess the quality and the functionality of a large 95-km long forest corridor connecting two large national parks (416 and 311 km2) in the southeastern escarpment of Madagascar.

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