Rescuing the bottom billion through control of neglected tropical diseases.

People in the bottom billion are the poorest in the world; they are often subsistence farmers, who essentially live on no money and are stuck in a poverty trap of disease, confl ict, and no education. One of the most potent reinforcements of the poverty trap is the neglected tropical diseases (panel 1). Almost everyone in the bottom billion has at least one of these diseases. Several diseases coexist in 56 of 58 countries that are home to the people in the bottom billion. Here we outline low-cost opportunities to control the neglected tropical diseases through preventive chemotherapy, and propose fi nancial innovations to provide poor individuals with essential drugs. 13 parasitic (helminthic and protozoan) and bacterial tropical infections, and dengue are the highest-burden neglected tropical diseases; another 20 include fungal, viral, and ectoparasitic infections (panel 2). Seven diseases are noteworthy because of their high prevalence and amenability to control. These are the soil-transmitted helminth infections (hookworm, ascariasis, and trichuriasis); lymphatic fi lariasis; schistosomiasis; and dis eases that cause blindness—trachoma and onchocerciasis (river blindness; table 1). About 600–800 million people, mostly children, have the soil-transmitted helminth infections. Of these, hookworm infection, which causes childhood and maternal anaemia, results in the greatest disability, and is the highest-burden neglected tropical disease. Among 200 million people with schistosomiasis, adolescents and young adults (15–25 years) have the highest infection intensities, as measured by numbers of eggs in stool or urine, and the most severe adverse eff ects—anaemia, wasting, and pain. Another 120 million people have lymphatic fi lariasis; most are adults and have lymphoedema, hydrocele, and disfi guring elephantiasis. Trachoma and onchocerciasis arise in about 84 million and 37 million people, respectively. In addition to these seven diseases, the vector-borne arboviral and protozoan diseases, including dengue, leishmaniasis, Chagas disease, and human African trypanosomiasis, can result in high mortality in some disadvantaged areas. The seven main diseases often cluster in the same rural geographic regions (fi gure 1), where commonly one person is concurrently infected with several of the seven neglected tropical diseases. Infections can last for decades and cause severe disability and disfi gurement, with profound economic, social, and political consequences. The core group of 13 neglected tropical diseases results in roughly 57 million disability-adjusted life years lost, which are greater than those for malaria and tuberculosis. More than 90% of this disease burden results from the seven major diseases. Three features of these diseases have brought them to international attention: they lead to poverty; low-cost and highly cost-eff ective control approaches might eliminate some of the diseases and create universal access to essential medicines; and control of these diseases would have simultaneous and sustainable eff ects on poverty reduction. The economic eff ects of disease control have been shown around the world since the early 20th cen tury. Investment in disease control could rescue the people in the bottom billion through its eff ect on four key elements of the poverty trap: health (especially maternal and child), agriculture, education, and infrastructure. Several major neglected tropical diseases adversely aff ect a family’s economic potential through their debilitating eff ect on the health of children. The soil-transmitted helminth infections and schistosomiasis impair children’s growth, development, and physical fi tness. Hookworm infection and schistosomiasis also reduce child survival by causing severe anaemia during pregnancy, which leads to low birthweight and increased infant and maternal mortality. In Africa, anaemia caused by hookworm infection can exacerbate the clinical course of falciparum malaria, especially in children and women. For diseases, such as leishmaniasis, the treatment can easily cost a family’s income for the year and lead to sale of assets (eg, land and livestock). Because they arise mainly in rural areas where families depend on subsistence agriculture, the neglected tropical diseases impair agricultural productivity. Lancet 2009; 373: 1570–75