A scoping review of burden of disease studies estimating disability-adjusted life years due to Taenia solium

Background: Taenia solium is the most significant global foodborne parasite and the leading cause of preventable human epilepsy in low and middle-income countries in the form of neurocysticercosis. Objectives: This scoping review aimed to examine the methodology of peer-reviewed studies that estimate the burden of T. solium using disability-adjusted life years. Eligibility criteria: Studies must have calculated disability-adjusted life years relating to T. solium. Charting methods: The review process was managed by a single reviewer using Rayyan. Published data relating to disease models, data sources, disability-adjusted life years, sensitivity, uncertainty, missing data, and key limitations were collected. Results: 15 studies were included for review, with seven global and eight national or sub-national estimates. Studies primarily employed attributional disease models that relied on measuring the occurrence of epilepsy before applying an attributable fraction to estimate the occurrence of neurocysticercosis-associated epilepsy. This method relies heavily on the extrapolation of observational studies across populations and time periods; however, it is currently required due to the difficulties in diagnosing neurocysticercosis. Studies discussed that a lack of data was a key limitation and their results likely underestimate the true burden of T. solium. Methods to calculate disability-adjusted life years varied across studies with differences in approaches to time discounting, age weighting, years of life lost, and years of life lived with disability. Such differences limit the ability to compare estimates between studies. Conclusions: This review illustrates the complexities associated with T. solium burden of disease studies and highlights the potential need for a burden of disease reporting framework. The burden of T. solium is likely underestimated due to the challenges in diagnosing neurocysticercosis and a lack of available data. Advancement in diagnostics, further observational studies, and new approaches to parameterising disease models are required if estimates are to improve. Author summary: Taenia solium is a parasitic worm of people and pigs. It is the most significant global foodborne parasite and causes neurocysticercosis, the leading cause of preventable human epilepsy in low and middle-income countries. Due to this significance, many people have attempted to estimate the burden of disease of T. solium. The disability-adjusted life year is the most common method for measuring burden of disease and combines the number of years of life lost with the number of years of life lived with disability due to an illness. This review found that many published studies probably underestimate the true burden of disease due to the challenges in diagnosing neurocysticercosis. If estimates are to become more accurate there must be further research into the epidemiology of T. solium and new approaches to disease modelling. Current estimates can be difficult to compare and a reporting framework for burden of disease studies may increase their utility by facilitating subsequent use and interpretation of different approaches.