Browsing by Subject "sub-Saharan Africa"

Now showing 1 - 3 of 3
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    Economics of Scaling Agricultural Research Recommendations to Up-Scale Adoption and Impact
    (2019-06) Mkondiwa, Maxwell
    A fundamental challenge of agricultural development in sub-Saharan Africa (SSA) is that technologies which prove successful at a small scale, in limited locations, and with few farmers, often fail to scale to encompass the preponderance of poor farmers. This study focuses on the economics of deploying technologies and recommendations that are then scaled beyond their initial targeted groups. The dissertation is composed of three essays. In the first essay, we address the stylized fact that experimental crop responses are typically higher than observational crop responses obtained in farmers’ fields. This is arguably a canonical example of a failure to scale from experimental plots. To close these crop response gaps—necessary goal assuming general constant long-term trends in maize output/fertilizer price ratios—, we propose that fertilizer recommendations be based on a Bayesian combination of experimental and observational crop response estimates. We use Bayesian econometric methods to combine estimates from experimental and observational evidence. In the second essay, we build on the first to determine the likelihood that farmers will adopt new varietal technologies. We modify the differentiated product demand models used in the industrial organization literature to the economics of hybrid maize varietal adoption in Malawi. By focusing on the characteristics space of maize varieties, our approach can help in ex-ante evaluation of the scaling-up potential of new crop varieties. The final essay calibrates inter-district food flows in Malawi thereby providing statistics for improving the targeting of national and regional food policies and technology commercialization strategies. We develop a food sector model for Malawi and use it to analyze the impacts of varying transport costs on food traded among districts within the country.
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    Estimating the contribution of N. gonorrhoeae infection to pelvic inflammatory disease and tubal factor infertility in the United States and the Infertility Belt of Africa
    (2022-04) Faherty, Emily
    Gonorrhea is the second most common bacterial sexually transmitted infection (STI) globally. Persistent gonorrhea infection can cause pelvic inflammatory disease (PID), ectopic pregnancy (EP) and tubal factor infertility (TFI). Infertility disproportionately impacts women in high fertility countries, especially in the Infertility Belt of Africa from Gabon to Tanzania. To examine gonorrhea’s contribution to these reproductive tract outcomes, we 1) conducted a survey and medical record review at Dodoma Christian Medical Center (DCMC) in Dodoma, Tanzania, 2) analyzed U.S. administrative claims data, and 3) created a mathematical model of STI transmission and reproductive tract disease among U.S. women.First, we examined determinants of female infertility by interviewing and reviewing medical records of 168 women seeking infertility treatment at DCMC. Women with PID had 1.9 (95% CI: 1.3-2.9) times the prevalence of TFI compared to women with other infertility factors. Logistic barriers to treatment were most common, regardless of women’s geographic residence. Next, we analyzed the rates of PID, EP, and TFI after gonorrhea diagnosis using the IBM MarketScan national claims database from 2013-2018 and tested an interaction in rates over time. We found elevated rates of PID, EP and TFI among women with a prior gonorrhea diagnosis compared to women who had no prior gonorrhea diagnoses. These rate ratios were steady over time, indicating that higher reported STI rates reflect increased infection burden, not greater incidence resulting from increased testing. Finally, we created a mathematical model simulating the disease process to estimate the number of cases of PID and TFI due to gonorrhea or chlamydia. We estimated that 24% of PID episodes and 26% of undetected tubal damage occurred among women who were previously infected with gonorrhea. Findings from this dissertation are timely due to increasing rates of gonorrhea infection and may motivate and inform global STI prevention efforts.
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    Identifying Optimal Cervical Cancer Prevention Strategies for HIV-positive Women in Senegal, West Africa – Quantification of the Natural History of HPV Among HIV-positive Women and Markov Cohort Cost-Effectiveness Analyses
    (2015-05) Whitham, Hilary
    Objective. The interaction between human immunodeficiency virus (HIV) and human papillomavirus (HPV) results in an increased burden of cervical cancer among HIV-positive women. This research aims to shed light on the important topic of HIV/HPV co-infection with the goal of informing HPV disease prevention efforts. Specifically, using longitudinal data we estimated the natural history of HPV and cervical cancer among HIV-positive women to inform cost-effectiveness modeling aimed at identifying optimal targeted prevention approaches for this high-risk population. Methods. In total 1,277 women (45% positive for HIV-1 and/or HIV-2) were followed for an average of two years in Senegal, West Africa between 1994 and 2010. Cytology and HPV DNA testing were performed at approximately 4-month intervals. Competing risk modeling was used to estimate rates for transitioning between three clinical relevant natural history stages (Normal, HPV, and HSIL) for HIV-positive and HIV-negative women separately. Markov cohort modeling was used to simulate the impact of various cervical cancer screening strategies among HIV-positive women. Specifically, we compared the relative cost-effectiveness of six screening strategies (Hybrid Capture 2 HPV testing, rapid HPV testing, cytology, visual inspection with acetic acid (VIA), HPV testing followed by cytology triage, and HPV testing followed by VIA triage) and five screening frequencies using projected life expectancy and incremental cost-effectiveness ratios (ICER). Further, the potential cost-effectiveness of HPV vaccination at the time of HIV diagnosis was simulated under various theoretical effectiveness scenarios. One-way and probabilistic sensitivity analyses were conducted to explore the impact of uncertainty on results. Results. HIV-positive women had significantly higher rates of progression and lower rates of regression compared to HIV-negative women (i.e. adverse transitions). Among those with HIV infection with multiple HPV types, HPV-16/18, HIV-1, and CD4+ count <200 were associated with adverse transitions. Across a broad range of screening scenarios, VIA was identified as the most cost-effective and contextually feasible screening approach. Compared to no screening, annual VIA resulted in an average discounted increased life expectancy of 1.7 months and a 40% reduction in cervical cancer incidence with an ICER of I$1,500 per life year saved. High underlying HPV prevalence among HIV-positive women significantly reduced the cost-effectiveness of HPV testing. HPV vaccination was only cost-effective under optimal vaccine efficacy and/or costing scenarios. Specifically, with costs ≥I$31 vaccination became dominated when vaccine efficacy fell below approximately 70% and 40% for reducing transitions from Normal to HPV-16/18 and HPV-Other states, respectively. Conclusions. High rates of adverse transitions indicate that targeted screening for the growing population of HIV-positive women in Africa is needed. Based on World Health Organization criterion for cost-effectiveness, targeted VIA screening represents an important prevention opportunity among this high-risk population. With lower vaccine-induced titer levels reported among adult HIV-positive women and a potential corresponding reduction in vaccine efficacy, HPV vaccination costs must be reduced for primary prevention to be cost-effective in comparison to screening. Efforts to implement targeted screening, reduce vaccine costs, develop therapeutic vaccines, and evaluate upcoming HPV antiviral treatments should be made.