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Dr. Fiona Mactaggart is a multi-disciplinary technical advisor with more than 10 years of experience in monitoring, evaluation, research, and learning (MERL); infectious disease control; and public health. As a co-lead of Abt's MERL portfolio, she draws on complexity theory and scientific methods to help clients test what works, discover why it works, and provide timely evidence-based recommendations to inform important decisions about policy and practice. Mactaggart contributes to business development, programme delivery, and thought leadership. She works in five key areas: monitoring (e.g., design of digital tools and visualisation platforms) research (e.g., cross-sectional survey design), evaluation methodologies (e.g., contribution analysis), learning (e.g., portfolio level evidence-informed strategic decision making), and cross-cutting MERL capabilities (e.g., adaptive management and GEDSI). Mactaggart has worked extensively in the Pacific and Southeast Asia.

Brian Chirwa is an agricultural and environmental scientist with over three decades worth of experience working on projects funded by the World Bank, the U.S. President’s Malaria Initiative (PMI), the Environmental Council of Zambia, and the Southern African Development Community (SADC). He brings 18 years’ experience on PMI-funded projects focused on indoor residual spraying (IRS) and insecticide-treated nets (ITNs) and has provided technical leadership, assistance, and high-level management for country-wide Zambian IRS and ITN campaigns. Brian also has three decades' worth of experience designing environmental information systems (EIS) for public organizations.

In his career as a senior finance and operations executive, Rehberger most recently served as the Senior Vice President, Chief Financial Officer of Engility, a Virginia-based government contractor.  He held similar positions with TASC from 2010 until its merger with Engility in 2015.  Rehberger helped guide both companies as the government industry cycled through a severe downturn and recovery, counseling the Board of Directors regarding strategy, enterprise risk management, cyber security, and compensation.  He previously held executive positions with telecommunications firms XO Communications and MCI. In 2017, Virginia Business awarded Rehberger the Virginia CFO of the Year award for his outstanding commitment to financial stewardship and dedication to the success of Engility.

Lakshmi Shyam-Sunder is the former Vice President and World Bank Group Chief Risk Officer (2014-2024). Lakshmi was previously Chief Financial Officer at the Multilateral Investment Guarantee Agency (MIGA), and Director of Risk and Financial Policy at the International Finance Corporation both also part of the World Bank Group.

Katharine Witgert is a health policy researcher with 20 years of public health and health care policy experience. Witgert manages research and analysis of health system innovations, conducting program evaluations for federal clients, including design, implementation, and reporting of findings. She provides technical assistance to state officials, primarily in the areas of Medicaid reforms and building Medicaid agency partnerships with public health, behavioral health, and social services programs.

Mariandrea Chamorro has 20 years of experience managing international development programs. She has provided oversight for the high-quality and compliant execution of large flagship USAID programs while contributing to business development. Chamorro’s areas of expertise include prevention of vector-borne diseases, infectious diseases, maternal and child health, and health systems strengthening. Her clients have included the U.S. Agency for International Development (USAID), the Australian Department of Foreign Affairs and Trade (DFAT), and the UK’s Foreign Commonwealth & Development Office (FCDO). 

William Tuleu leads strategic growth initiatives across the company's U.S. foreign assistance and domestic portfolios.

Geoff Scahill has over 20 years of experience working in and managing international development programs. He has worked extensively within Papua New Guinea (PNG) and the Pacific – predominantly in Indonesia, Fiji, Samoa, and the Solomon Islands. He brings a long history as a health sector professional and has held roles as a health management advisor and health systems adviser in Pacific Island Countries. Geoff draws on his background in finance and economics to work with counterparts to increase efficiencies within the programs Abt Global delivers.

Dereje Dengela is an epidemiologist and entomologist with more than 25 years of experience in planning, implementation, monitoring, and evaluation of malaria control programs. He has extensive managerial experience, having supervised as many as 94 professionals. He has held senior positions with the government of Ethiopia, worked on projects for the U.S. Agency for International Development (USAID), and served as a national malaria program officer in Ethiopia. He supported the Ministry of Health of Ethiopia in mobilization of financial resources from donors, particularly the Global Fund. Dengela has authored or co-authored more than 30 publications in peer-reviewed journals.

Dr. Michael Plotzke is a senior health economist with expertise in the area of Medicare payment policy, the organization of healthcare providers and quality measurement. His work typically involves the analysis of large datasets such as Medicare claims, assessment and enrollment data. Dr. Plotzke serves as principal investigator for multiple projects with the Centers for Medicare & Medicaid Services.  On the “Home Health Prospective Payment System and Hospice: Analysis Support and Monitoring” project, Dr. Plotzke leads a team of researchers in analyzing trends in Medicare hospice and home health usage and constructing large-scale payment reform options for both benefits.  Dr. Plotzke also leads the “Evaluation of the Medicare Care Choices Model” project that evaluates a new payment model for end-of-life care that is being tested with 141 hospice providers.  This project involves analysis of existing administrative data and collection of new data through surveys of caregivers, surveys of hospice providers and in-depth case studies of hospice providers participating in the model.