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Elucidating Liver Fluke Transmission Dynamics: Synthesizing Lab, Field, and Modeling Methods

  • Author(s): Leon, Tomas
  • Advisor(s): Spear, Robert C
  • et al.
Abstract

Opisthorchiasis, infection with the Southeast Asian liver fluke Opisthorchis viverrini, and liver fluke-associated cholangiocarcinoma cause significant disease burden in Southeast Asia. Northeast Thailand is a particular region where this disease is a public health priority, infecting over 50% of the population in some villages and causing 5000 excess cancer cases per year. People acquire the parasite by eating raw or undercooked fish, a deeply embedded local cultural and culinary tradition. Health education is essential to preventing and controlling the disease, but the environment also plays a major role in enabling and catalyzing transmission between hosts. An emphasis on disease ecology and the environmental determinants of transmission is useful and necessary for public health understanding and for informing and designing future treatment and control interventions. This dissertation takes that approach, investigating each disease host and linkage for the role of the environment in influencing transmission.

Chapter 1 describes and contextualizes liver fluke transmission and why it matters, introducing Lawa Lake and the Lawa Project, which are the background for the context and data examined herein. Chapter 2 presents lab, field, and modeling results related to infection and ecology of the intermediate host Bithynia snails and cyprinid fish. Chapter 3 introduces and presents results from the single-village mathematical model simulating transmission in six village clusters around Lawa Lake. Chapter 4 discusses the role of reservoir hosts (cats and dogs) in the transmission cycle, adds them to the model framework, and simulates the impact of regular praziquantel treatment on long-term infection prevalence. Chapter 5 introduces the rainfall-runoff hydrology model, whose output is incorporated into a metapopulation disease transmission model to connect the six village clusters around Lawa Lake, and the impacts of connectivity and upstream villages are studied and discussed. Chapter 6 concludes with some comments on engineering and public health perspectives, limitations, progress, and future directions for liver fluke and neglected tropical disease control.

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