A Spatially Explicit Model of the Dynamics of Opisthorchis viverrini Spread

Opisthorchis viverrini is a water-based disease-causing parasite whose public health implications are relevant in Southeast Asia. Untreated or chronic infections often lead to severe hepatobiliary morbidity including cholangiocarcinoma, a lethal bile duct cancer. The liver fluke O. viverrini can be contracted by consumption of raw fish, after which it settles in the small biliary ducts. The life cycle involves, besides freshwater snails in which asexual reproduction takes place, freshwater cyprinid fish as intermediate hosts. Piscivorous mammals, including humans, dogs and cats, are definitive hosts. Here, we propose a spatially explicit model for the transmission dynamics in realistic freshwater environments. Our model generalises existing local-scale models by assimilating novel spreading mechanisms in space and time. Our study emphasises that spatial connectivity is key to shaping patterns of disease spread. Fish distribution and mobility through river corridors affect disease transmission routes. Our study provides baseline information on the role of connected freshwater bodies and their suitability for intermediate and final hosts. The distributions of fish catch and fish market supplies are also considered because they affect the spatiotemporal spread of opisthorchiasis. Adding a spatial component to transmission models fundamentally changes the description of epidemiological dynamics and the related scenarios of disease propagation through an improved description of the ecology of hosts, parasites and their transmission cycles. This work provides a more realistic description of the environment where infection cycles develop and spread than previous modelling attempts did, thus allowing a better characterisation of transmission routes and enabling a proper design of containment measures.