Moving from control to elimination of schistosomiasis in sub-Saharan Africa: time to change and adapt strategies

Schistosomiasis is a waterborne infection and is one of the most common parasitic diseases in the world, and is of public health global importance [1]. This disease has major health and socio-economic repercussions, and constitutes an important public health problem in developing countries as well as a significant hazard for visitors and travellers who visit disease endemic regions. Human schistosomiasis is caused by six species of schistosomes, i.e. Schistosoma haematobium, S. mansoni, S. japonicum, S. mekongi, S. intercalatum and S. guineensis; and is endemic in 78 countries [1, 2]. Of these six species, S. haematobium is responsible for urogenital schistosomiasis and has significant interactions with HIV and also HPV [3], whilst other species each cause intestinal or rectal schistosomiasis. It is estimated that 779 million people are at risk of infection, and about 250 million people are currently infected [2, 4]. The Global Burden of Disease study of 2010 attributed some 3.31 million disability-adjusted life years (DALYs) and 11 700 death per year to schistosomiasis, a mortality figure which has been challenged as a gross underestimate [5].

Schistosomiasis affects the poorest of the poor and infections are particularly abundant among people living in rural or deprived urban or peri-urban settings [6]. These populations typically have low socio-economic status with limited access to clean water and with inadequate sanitation provision [7, 8]. The morbidity caused by schistosomes is commonly associated with moderate-to-heavy egg-infection intensities and is progressive; as compared with any other age group, school-aged children and pre-school children are the most vulnerable groups to developing overt disease [9, 10]. These groups typically harbour the largest numbers of adult worms, with copious tissue entrapped eggs causing systematic and organ-specific inflammation, concomitantly when the consequences of this infection causes greatest physiological and developmental insult [2]. Studies have demonstrated that children can acquire schistosome infections within the first few months of life [11, 12], causing early life initial organ damage and altered development, mediated by fibrotic lesions around tissue-trapped eggs, manifesting overtly in adolescence and early adulthood [9, 13].

 

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Prof. Louis Albert Tchuem Tchuente