Essays on agricultural development in Tanzania

This thesis is made of three self-contained essays on the agricultural sector of Tanzania, each of them focusing on an aspect of direct policy relevance. In the first essay, I study whether an inverse relationship exists between cultivated area and physical productivity (yield per acre) for a set of important annual crops. I define size as the area of a plot on which a crop is grown, thus introducing a more disaggregated level of analysis than the common plot or crop levels of analysis. I control for the existing hypotheses in the literature potentially explaining this inverse relationship and propose to control for two new hypotheses which are only testable at this level of analysis. In the second essay, I look at output marketing for a set of important crops. I stress the links between the market failure theoretical narrative and empirical applications, and argue this has resulted in less attention being paid to the reasons why farmers may enter -or not- the market for a particular crop. I estimate participation and supply equations for a set of important crops and show that the rationale for entry differs across crops. This calls for a more flexible conception of `the market'. The first two essays use the Tanzanian National Panel Surveys to conduct econometric analysis. The third essay is based on primary data collected in 2016 in order to carry analysis of the Bambara nut, an underutilised crop. Because underutilised crops hardly feature in national datasets, primary data is needed to understand their socio-economic dynamics. Focusing on the Mtwara region of Tanzania, I study the importance of Bambara for local livelihoods using a mixed-methods study based on both quantitative and qualitative data. This study contributes to the growing interest on underutilised crops and their importance in designing more sustainable agricultural strategies

Under-utilized crops and rural livelihoods: Bambara groundnut in Tanzania

Indigenous crops are often neglected in development research, largely because they are grown in particular localities and only account for modest shares of agricultural production at a national level. This article aims to rectify this neglect with respect to the Bambara groundnut using a mixed methods study of farmers in Mtwara, Tanzania. The interest is in determining the importance of the crop in local production patterns and livelihoods, as well as potential levers for improved utilisation. Using the Sustainable Rural Livelihoods framework, we show that the crop is popular and recognised for its agronomic and nutritional properties. It is grown as an additional (or marginal) rather than main crop, with most growers reporting meeting consumption and food security needs as their primary motivation. The absence of markets constitutes a strong barrier towards sales of Bambara, and many farmers report being deterred from growing it for that reason

Fonio and Bambara Groundnut value chains in Mali: issues, needs, and opportunities for their sustainable promotion

As the effects of climate change are severely straining West African agricultural systems, the adoption of more incisive interventions in support of sustainable development agendas for the region is highly critical and cannot be further delayed by governments. Neglected and underutilized species (NUS) are one important ally in pursuing resilience in both production and food systems because of their promising traits in terms of nutrition, adaptation to local agroecosystems, and economic potential for local populations. Focusing on fonio, a gluten-free traditional cereal, and Bambara groundnut, a protein-rich leguminous crop, we investigate issues in their production, commercialization, and consumption in southern Mali. The aim was to assess needs and opportunities for improving their value chains and increasing their use and societal benefits. Using a Rapid Market Appraisal method, we surveyed traders, producers, processors, and consumers of target crops in 2017 and 2018. Our findings indicate that while both crops are consumed and praised by local populations, critical bottlenecks inhibit their wider socioeconomic potential. Lack of access to inputs and equipment and presence of sand in the commercialized product are important issues for fonio, whereas the Bambara groundnut value chain suffers from poor processing facilities and lack of market promotion. Policy recommendations to tackle the identified bottlenecks are proposed

Essays on agricultural development in Tanzania

This thesis is made of three self-contained essays on the agricultural sector of Tanzania, each of them focusing on an aspect of direct policy relevance. In the first essay, I study whether an inverse relationship exists between cultivated area and physical productivity (yield per acre) for a set of important annual crops. I define size as the area of a plot on which a crop is grown, thus introducing a more disaggregated level of analysis than the common plot or crop levels of analysis. I control for the existing hypotheses in the literature potentially explaining this inverse relationship and propose to control for two new hypotheses which are only testable at this level of analysis. In the second essay, I look at output marketing for a set of important crops. I stress the links between the market failure theoretical narrative and empirical applications, and argue this has resulted in less attention being paid to the reasons why farmers may enter -or not- the market for a particular crop. I estimate participation and supply equations for a set of important crops and show that the rationale for entry differs across crops. This calls for a more flexible conception of `the market'. The first two essays use the Tanzanian National Panel Surveys to conduct econometric analysis. The third essay is based on primary data collected in 2016 in order to carry analysis of the Bambara nut, an underutilised crop. Because underutilised crops hardly feature in national datasets, primary data is needed to understand their socio-economic dynamics. Focusing on the Mtwara region of Tanzania, I study the importance of Bambara for local livelihoods using a mixed-methods study based on both quantitative and qualitative data. This study contributes to the growing interest on underutilised crops and their importance in designing more sustainable agricultural strategies

Brain MRI Findings in Severe COVID-19: A Retrospective Observational Study

International audienceBackgroundBrain MRI parenchymal signal abnormalities have been associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2).PurposeTo describe the neuroimaging findings (excluding ischemic infarcts) in patients with severe coronavirus disease 2019 (COVID-19) infection.Materials and MethodsThis was a retrospective study of patients evaluated from March 23, 2020, to April 27, 2020, at 16 hospitals. Inclusion criteria were (a) positive nasopharyngeal or lower respiratory tract reverse transcriptase polymerase chain reaction assays, (b) severe COVID-19 infection defined as a requirement for hospitalization and oxygen therapy, (c) neurologic manifestations, and (d) abnormal brain MRI findings. Exclusion criteria were patients with missing or noncontributory data regarding brain MRI or brain MRI showing ischemic infarcts, cerebral venous thrombosis, or chronic lesions unrelated to the current event. Categorical data were compared using the Fisher exact test. Quantitative data were compared using the Student t test or Wilcoxon test. P < .05 represented a significant difference.ResultsThirty men (81%) and seven women (19%) met the inclusion criteria, with a mean age of 61 years ± 12 (standard deviation) (age range, 8–78 years). The most common neurologic manifestations were alteration of consciousness (27 of 37, 73%), abnormal wakefulness when sedation was stopped (15 of 37, 41%), confusion (12 of 37, 32%), and agitation (seven of 37, 19%). The most frequent MRI findings were signal abnormalities located in the medial temporal lobe in 16 of 37 patients (43%; 95% confidence interval [CI]: 27%, 59%), nonconfluent multifocal white matter hyperintense lesions seen with fluid-attenuated inversion recovery and diffusion-weighted sequences with variable enhancement, with associated hemorrhagic lesions in 11 of 37 patients (30%; 95% CI: 15%, 45%), and extensive and isolated white matter microhemorrhages in nine of 37 patients (24%; 95% CI: 10%, 38%). A majority of patients (20 of 37, 54%) had intracerebral hemorrhagic lesions with a more severe clinical presentation and a higher admission rate in intensive care units (20 of 20 patients [100%] vs 12 of 17 patients without hemorrhage [71%], P = .01) and development of the acute respiratory distress syndrome (20 of 20 patients [100%] vs 11 of 17 patients [65%], P = .005). Only one patient had SARS-CoV-2 RNA in the cerebrospinal fluid.ConclusionPatients with severe coronavirus disease 2019 and without ischemic infarcts had a wide range of neurologic manifestations that were associated with abnormal brain MRI scans. Eight distinctive neuroradiologic patterns were described

Cerebral perfusion using ASL in patients with COVID-19 and neurological manifestations: A retrospective multicenter observational study

Background and purpose: Cerebral hypoperfusion has been reported in patients with COVID-19 and neurological manifestations in small cohorts. We aimed to systematically assess changes in cerebral perfusion in a cohort of 59 of these patients, with or without abnormalities on morphological MRI sequences.Methods: Patients with biologically-confirmed COVID-19 and neurological manifestations undergoing a brain MRI with technically adequate arterial spin labeling (ASL) perfusion were included in this retrospective multicenter study. ASL maps were jointly reviewed by two readers blinded to clinical data. They assessed abnormal perfusion in four regions of interest in each brain hemisphere: frontal lobe, parietal lobe, posterior temporal lobe, and temporal pole extended to the amygdalo-hippocampal complex.Results: Fifty-nine patients (44 men (75%), mean age 61.2 years) were included. Most patients had a severe COVID-19, 57 (97%) needed oxygen therapy and 43 (73%) were hospitalized in intensive care unit at the time of MRI. Morphological brain MRI was abnormal in 44 (75%) patients. ASL perfusion was abnormal in 53 (90%) patients, and particularly in all patients with normal morphological MRI. Hypoperfusion occurred in 48 (81%) patients, mostly in temporal poles (52 (44%)) and frontal lobes (40 (34%)). Hyperperfusion occurred in 9 (15%) patients and was closely associated with post-contrast FLAIR leptomeningeal enhancement (100% [66.4%-100%] of hyperperfusion with enhancement versus 28.6% [16.6%-43.2%] without, p=0.002). Studied clinical parameters (especially sedation) and other morphological MRI anomalies had no significant impact on perfusion anomalies.Conclusion: Brain ASL perfusion showed hypoperfusion in more than 80% of patients with severe COVID-19, with or without visible lesion on conventional MRI abnormalities

Cerebral perfusion using ASL in patients with COVID-19 and neurological manifestations: A retrospective multicenter observational study

Background and purpose: Cerebral hypoperfusion has been reported in patients with COVID-19 and neurological manifestations in small cohorts. We aimed to systematically assess changes in cerebral perfusion in a cohort of 59 of these patients, with or without abnormalities on morphological MRI sequences.Methods: Patients with biologically-confirmed COVID-19 and neurological manifestations undergoing a brain MRI with technically adequate arterial spin labeling (ASL) perfusion were included in this retrospective multicenter study. ASL maps were jointly reviewed by two readers blinded to clinical data. They assessed abnormal perfusion in four regions of interest in each brain hemisphere: frontal lobe, parietal lobe, posterior temporal lobe, and temporal pole extended to the amygdalo-hippocampal complex.Results: Fifty-nine patients (44 men (75%), mean age 61.2 years) were included. Most patients had a severe COVID-19, 57 (97%) needed oxygen therapy and 43 (73%) were hospitalized in intensive care unit at the time of MRI. Morphological brain MRI was abnormal in 44 (75%) patients. ASL perfusion was abnormal in 53 (90%) patients, and particularly in all patients with normal morphological MRI. Hypoperfusion occurred in 48 (81%) patients, mostly in temporal poles (52 (44%)) and frontal lobes (40 (34%)). Hyperperfusion occurred in 9 (15%) patients and was closely associated with post-contrast FLAIR leptomeningeal enhancement (100% [66.4%-100%] of hyperperfusion with enhancement versus 28.6% [16.6%-43.2%] without, p=0.002). Studied clinical parameters (especially sedation) and other morphological MRI anomalies had no significant impact on perfusion anomalies.Conclusion: Brain ASL perfusion showed hypoperfusion in more than 80% of patients with severe COVID-19, with or without visible lesion on conventional MRI abnormalities