Abstract
Taenia solium (TS), responsible for porcine cysticercosis, human taeniasis and (neuro)cysticercosis, was included in the World Health Organization neglected tropical disease (NTD) roadmap published in 2012. Targets set in this roadmap have not been met, but T. solium has been included in the consultation process for the new 2030 goals proposed for priority NTDs. Taenia solium transmission dynamics models can contribute to this process. A recent review has compared existing T. solium transmission models, identifying their similarities and differences in structure, parameterization and modelled intervention approaches. While a formal model comparison to investigate the impact of interventions is yet to be conducted, the models agree on the importance of coverage for intervention effectiveness and on the fact that human- and pig-focused interventions can be optimally combined. One of these models, cystiSim, an individual-based, stochastic model has been used to assess field-applicable interventions, some currently under evaluation in on-going trials in Zambia. The EPICYST, population-based, deterministic model has highlighted, based on simulating a generic sub-Saharan Africa setting, the higher efficacy (measured as the percentage of human cysticercosis cases prevented) of biomedical interventions (human and pig treatment and pig vaccination) compared to improved husbandry, sanitation, and meat inspection. Important questions remain regarding which strategies and combinations thereof provide sustainable solutions for severely resource-constrained endemic settings. Defining realistic timeframes to achieve feasible targets, and establishing suitable measures of effectiveness for these targets that can be quantified with current monitoring and evaluation tools, are current major barriers to identifying validated strategies. Taenia solium transmission models can support setting achievable 2030 goals; however, the refinement of these models is first required. Incorporating socio-economic elements, improved understanding of underlying biological processes, and consideration of spatial dynamics are key knowledge gaps that need addressing to support model development.
Highlights
Taeniasis andcysticercosis are infections caused by the cestode Taenia solium (TS), involving a complex transmission cycle between the intermediate pig host and the definitive human host
When humans act as the accidental intermediate host, localization of larval-stage cysticerci in the central nervous system can result in neurocysticercosis (NCC), the main condition contributing to TS-associated morbidity and mortality, including epileptic seizures/epilepsy
Health education will be settingdependent given varying husbandry and sanitation practices, and it would be highly valuable to test its impact with the transmission dynamics models as and when data become available on the impact of health education on TS transmission
Summary
Taeniasis and (neuro)cysticercosis are infections caused by the cestode Taenia solium (TS), involving a complex transmission cycle between the intermediate pig host and the definitive ( accidental intermediate) human host. CystiSim has identified, within the context of an endemic district in Tanzania, that two-host interventions (human MDA plus pig vaccination and treatment), are optimal strategies to achieve elimination of transmission (EOT) if high coverage can be reached and sustained for prolonged periods. Simulating the impact on transmission of control programs using mathematical models can help to assess whether “intensified control” could firstly be achieved with transmission dynamics in humans and pigs as observable in the field (adjusted by diagnostic characteristics), and, secondly, what would be the prospects for local true elimination were this possible in a specific location. CystiSim simulated a schoolbased MDA for one of these districts, indicating that there was little impact on PCC prevalence and minimal impact on human taeniasis33 These results indicate that a TS intervention constrained to targeting SAC (within an integrated school-based NTD program) would have limited impact on TS transmission, and will require additional TS-specific interventions to be effective. Data availability Underlying data No data are associated with this article
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