Schistosomiasis and soil-transmitted helminthiases (STHs) are caused by parasitic worms and affect more than one billion people globally. These diseases cause chronic health and development problems including, abdominal pain, anaemia, malnutrition and stunted growth in children as well as rarer and more serious complications.
The latest estimate from the Lancet Global Burden of Disease summaries (2019 data) is that the approximately 3.61 million disability-adjusted life-years (DALYs) associated with schistosomiasis and the STHs ascariasis, trichuriasis, and hookworm account for over 50% of all DALYs associated with the preventive chemotherapy-controlled neglected tropical diseases.
There is a need to better understand optimal dosing in different population subgroups, the influence of co-infections, and the medicine side effect profiles in different demographic groups. Trials of new treatments, repurposed medicines, or new drug combinations need to be undertaken and analysed in the context of current standard treatments. It is also important to understand how different diagnostic methods impact parasitological measurements which are the basis for measuring infection, monitoring drug efficacy and evaluating mass drug administration, especially as newer molecular methods emerge.
The strategy recommended by the World Health Organization (WHO) to treat and control these diseases is regular mass distribution of praziquantel (for schistosomiasis) and albendazole or mebendazole (for ascariasis, trichuriasis, and hookworm) to affected communities. Approximately 600 million people at risk for schistosomiasis or STHs were treated in 2019 as part of the unprecedented scale-up of drug distribution towards the WHO’s 2020 control and elimination targets The WHO NTD roadmap for 2021-2030 targets schistosomiasis and STHs for elimination as a public health problem.
The ongoing effectiveness of this vast control effort could be threatened by changes in parasite ecology, natural immunity, and the selection of parasites with resistance or reduced susceptibility to the current medicines.
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