Control of Schistosomiasis and Soil-Transmitted Helminthiasis in Sub-Saharan Africa: Challenges and Prospects
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Schistosomiasis and soil-transmitted helminthiasis (STH) are the most common types of parasitic infections in the world. These diseases have major health and socio-economic repercussions, and constitute an important public health problem in developing countries. Human schistosomiasis is caused by six species of schistosomes, i.e. Schistosoma haematobium, Schistosoma mansoni, Schistosoma japonicum, Schistosoma mekongi, Schistosoma intercalatum and Schistosoma guineensis; and is endemic in 78 countries, where 779 million people are at risk of infection. S. haematobium is responsible for urogenital schistosomiasis, and the other species cause intestinal schistosomiasis. It is estimated that 207 million people are infected (WHO, 2002; STH, also known as intestinal worm infection, is caused by four main species of worms commonly known as roundworms (Ascaris lumbricoides), whipworms (Trichuris trichiura) and hookworms (Ancylostoma duodenale and Necator americanus). It is estimated that STH affects more than 2 billion people worldwide, and the greatest numbers of infections occur in sub-Saharan Africa, the Americas, China and east Asia (WHO, 2006; These diseases affect the poorest of the poor and infections are particularly abundant among people living in rural or deprived urban settings with low socio-economic status, lack of clean water and poor sanitation The morbidity caused by these worms is commonly associated with heavy infection intensities. Compared with any other age group, school-aged children and pre-school children are the most vulnerable group and they harbor the greatest numbers of intestinal worms. As a result, they experience growth stunting and diminished physical fitness as well as impaired memory and cognition These adverse health consequences combine to impair childhood educational performance and reduce school attendance Studies have demonstrated that children may acquire helminth infections early in life Despite the existence of tools in the 1970s and 1980s, control was sustained for a prolonged period only in few countries and almost no progress was made in sub-Saharan African www.intechopen.com Current Topics in Tropical Medicine 360 countries, the most affected part of the world. In the 1990s, interest in the control of these diseases in Africa waned. Therefore, as with other neglected tropical diseases (NTDs), schistosomiasis and STH control has been overshadowed by other health priorities. The highest priority of the international health community was given to the 'big three', i.e. HIV/AIDS, tuberculosis and malaria, with less attention to other infections related to poverty (Molyneux et al., 2005). Recent years have witnessed an increased interest in the control of NTDs, and today there exists a global momentum for the control of these diseases. The control of NTDs has become a priority on the agenda of many governments, donors and international agencies. The World Health Organization (WHO) has played a major role in this prospect. Indeed, under the aegis of WHO, all member states of WHO (over 200 countries) have endorsed in May 2001 the World Health Assembly resolution WHA 54.19, with as a major objective the regular treatment of at least 75% of all school-aged children at risk of morbidity by 2010. The renewed impetus for schistosomiasis and STH control has generated a greater political commitment, as well as an unprecedented opportunity for cost-effective action (Molyneux et al., 2005). This momentum has encouraged many countries to establish national action plans and programmes to control schistosomiasis, STHs and other NTDs Within the past decade, significant progress has been made on large scale treatments through integrated control of schistosomiasis, STH and other NTDs, thanks to a number of international organizations, donor foundations, bilateral institutions and non-governmental organizations that responded to the 2001 WHO's call for action Today, treatment is cost-effective and the 'preventive chemotherapy' is currently the strategy of choice (WHO, 2006). With a support from the American (USAID) and British (DFID) governments, as well as the Bill and Melinda Gates Foundation, the pharmaceutical industry, and many not-for profit organizations, millions of children are regularly treated for schistosomiasis, STH and other NTDs. However, the control of these diseases is a long-term undertaking which involves several challenges. This paper highlights the progress made and also focuses on some main challenges that are reviewed and discussed.