On Neglected Tropical Diseases

Malaria, HIV/AIDS, and tuberculosis are often considered the most pressing disease-related threats to individuals in the developing world and the quest to eradicate them receives a large portion of government and private funding. However, a group of conditions known collectively as neglected tropical diseases (NTDs) have a more widespread and devastating effect on the lives of people in many regions of sub-Saharan Africa, Southeast Asia, and Latin America. These regions account for up to 90 percent of the disease burden for this group of 13 parasitic and bacterial conditions. Reports from the Global Network for Neglected Tropical Diseases indicate that these parasitic and bacterial infections affect over 1.4 billion people, most of whom survive on less than US$1.25 per day. While NTDs may not necessarily kill those infected, they can lead to malnutrition, anemia, a range of disabilities (most often blindness), stunted growth, and greater susceptibility to other illnesses.

Neglected Tropical Diseases

Clockwise from top left: An egg of the roundworm, which causes Ascariasis; a man with Lymphatic Filariasis being examined by a physician; the whipworm, which causes Trichuriasis; and a child receiving antibiotic treatment for Trachoma.

Individuals affected by NTDs live primarily in tropical and subtropical climates, and many experience more than one infection or parasite at a given time. According to the World Health Organization (WHO), the majority of individuals affected by NTDs live in remote and rural areas, urban slums, or areas experiencing conflict situations. Seventy percent of infections occur in low- or lower-middle income areas, and are frequently caused by unsafe water and poor housing and sanitation conditions. Further, NTDs contribute to a cycle of poverty in which children are likely to become infected due to their poor living conditions, and once infected they may experience delays in cognitive development inhibiting their ability to escape their impoverished conditions.

The seven most common NTDs are: Ascariasis, Hookworm, Lymphatic Filariasis, Onchocerciasis, Scistosomiasis, Trachoma, and Trichuriasis. These diseases, many of which are caused by parasitic intestinal worms known as helminthes, have the most devastating impact on those who contract them. For example, Ascariasis, resulting from roundworm infestation, affects 800 million people; and trichuriasis, resulting from whipworm, affects 600 million. Helminths rob children of nutrients and can lead to stunted growth, iron-deficiency anemia, and protein malnutrition. They are at an increased risk of contracting parasitic worms, as are the elderly and pregnant women. Over 40 million pregnant women are infected with hookworms, parasitic worms that attach to the small intestine and suck blood from their host, increasing vulnerability to malaria and additional blood loss during labor.

Based on Disability-Adjusted Life Years (DALYs), which refer to the years of healthy life lost to disability or premature death, NTDs are a greater health burden than tuberculosis or malaria, and approach the level of burden of HIV/AIDS. In addition, NTDs are the cause of approximately 534,000 deaths worldwide each year. Through programs to distribute medications, the WHO, pharmaceutical companies, government agencies, and international aid organizations hope to ensure fewer lives are lost. Coordinated efforts have allowed for the rapid deployment of inexpensive diagnostic tools, medications, and treatments, many of which can be administered by trained non-medical staff including teachers and community health workers. Medications are often distributed in “rapid-impact packages,” reducing costs and putting less strain on already weakened healthcare systems in the areas where NTDs are most prevalent. These packages also offer the opportunity to bundle life-saving drug treatments with other interventions such as antimalarial bed nets or nutritional supplements.

Through these and other similar efforts, it has been possible to reduce the occurrence of a number of conditions in many parts of the world. The number of cases of guinea worm disease, also known as dracunculiasis, has fallen from 3.5 million in the 1980s to just 4,619 in 2008, and the WHO has declared eradication in Nigeria and Uganda. Many other conditions are now found only in remote villages and are nearing total eradication through education programs, medication distribution, and improved sanitation.

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