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An exciting new project uses mathematical modelling techniques to assess the additional impact of the drug praziquantel (PZQ) on Taenia solium – or pork tapeworm in Uganda.
The project, a collaboration between Merck, Bayer and SCI Foundation, will also assess the impact of supplementary delivery of praziquantel, beyond its current use for treatment of schistosomiasis, specifically for T. solium control, towards the targets of the new WHO neglected tropical disease (NTD) 2021-2030 road map.
Praziquantel is currently delivered through Mass Drug Administration (MDA) campaigns for treatment of schistosomiasis, particularly to school-age children (SAC), as a low-cost approach to reducing the morbidity and transmission of these infections.
Robust evidence confirms the long-term positive impact of deworming programmes on affected communities. However, there is little evidence on the additional benefits of MDA on other parasitic worms such as T. solium, thus potentially underestimating the true impact.
The new project is anticipated to have wider implications for human health by helping to reduce the burden of disease associated with epilepsy and other neurological complications.
Children receiving anthelmintics through national deworming programmes, which are supported by the SCI Foundation (left-hand side). A simplified version of the Taenia solium life cycle, indicating the intervention point for preventive chemotherapy with anthelmintics such as praziquantel, through mass-drug administration to control taeniasis in humans (right-hand side). The graph inset on the right-hand side provides an illustrative example of the potential impact of repeated human MDA on taeniasis prevalence over several years.
Taenia solium and epilepsy
T. solium infection causes neurocysticercosis (NCC), the leading preventable cause of epilepsy in low- and middle- income countries. It is estimated that NCC may account for approximately one third of epilepsy cases in countries where T.solium is endemic.
The lifecycle of T. solium is complex, involving pigs, which act as the intermediate host (porcine cysticercosis) and humans, which can act as both the definitive host (human taeniasis) and as an accidental intermediate host (human neurocysticercosis).
The parasite thrives in areas of unsafe sanitation, where the environment is contaminated with T. solium eggs, allowing constant exposure of free-ranging pigs.
Beyond the human health burden associated with NCC, smallholder pig farmers face a substantial economic burden as pig cysticercosis reduces the value of pork in food-value chains and leads to infected carcasses being discarded.
Uganda has the highest pork consumption per capita in East Africa (3.4 kg per capita), with smallholder pig farming systems common across much of the country. Previous studies indicate a high prevalence of cysticercosis in Uganda among both humans and pigs.
A mathematical model, developed at Imperial College London will be used to determine the impact of the SCH control programme delivered to SAC on T. solium transmission in Uganda and to investigate the additional requirement of PZQ necessary to achieve T. solium intensified control in high prevalence (hyperendemic) settings.
Talking of the new collaboration, Dr Matt Dixon-Zegeye of SCI Foundation and the lead investigator said:
“This exciting collaboration will use mathematical modelling techniques to highlight the extent to which the Ugandan SCH programme has had an additional impact on transmission of T. solium. We will also get an idea of the progress we can make through solely targeting interventions in the human host, given that a One Health approach is likely needed to achieve the most stringent targets for T. solium such as elimination efforts in the short term”.
About this initiative, Dr Ulrich-Dietmar Madeja, Head of the Neglected Tropical Disease programme at Bayer AG, comments:
“We believe this alliance will be an opportunity to show how our praziquantel donations for the treatment of taeniasis can be used in synergy with existing NTD programmes to achieve the maximum benefit. We hope to use evidence generated from projects such as this one to break down silos between different control programmes”.
Dr Johannes Waltz, Head of the Schistosomiasis Elimination Program at Merck Group, said:
“Providing evidence through modelling studies to show the additional benefit of disease-specific NTD programmes on other NTDs such as this one will be critical to showing the wider impact of existing NTD programmes, including Merck’s praziquantel program for schistosomiasis. This will have important implications for cost-effectiveness as well”.