Endemic tropical sprue in Rhodesia

Understanding the role of the gut in undernutrition: what can technology tell us?

Gut function remains largely underinvestigated in undernutrition, despite its critical role in essential nutrient digestion, absorption and assimilation. In areas of high enteropathogen burden, alterations in gut barrier function and subsequent inflammatory effects are observable but remain poorly characterised. Environmental enteropathy (EE)-a condition that affects both gut morphology and function and is characterised by blunted villi, inflammation and increased permeability-is thought to play a role in impaired linear growth (stunting) and severe acute malnutrition. However, the lack of tools to quantitatively characterise gut functional capacity has hampered both our understanding of gut pathogenesis in undernutrition and evaluation of gut-targeted therapies to accelerate nutritional recovery. Here we survey the technology landscape for potential solutions to improve assessment of gut function, focussing on devices that could be deployed at point-of-care in low-income and middle-income countries (LMICs). We assess the potential for technological innovation to assess gut morphology, function, barrier integrity and immune response in undernutrition, and highlight the approaches that are currently most suitable for deployment and development. This article focuses on EE and undernutrition in LMICs, but many of these technologies may also become useful in monitoring of other gut pathologies.

Tropical sprue and subclinical enteropathy: a vision for the nineties

Aside from infectious intestinal diseases with known etiology, there is a group of gastrointestinal disorders mainly affecting the small intestine of individuals predominantly living in and less often visiting or returning from the Third World, usually the tropics, and ranging from asymptomatic structural and/or functional abnormalities of the gastrointestinal mucosa (subclinical enteropathy, SE) to a fully symptomatic condition highlighted by malabsorption of nutrients with associated nutritional deficiencies responsive to folate and broad spectrum antibiotic treatment (tropical sprue, TS). Mounting evidence supports an infectious cause in many instances. The exact nature of the infection, whether initiated and/or perpetuated by enterotoxigenic coliform bacteria, virus(es) or a combination of these, is not clear. Further studies, including those using molecular techniques, are needed in order to clarify various aspects of these widely prevalent disorders.

Vitamin B12 deficiency is the primary cause of megaloblastic anaemia in Zimbabwe

In a study of the pathogenesis and clinical features of megaloblastic anaemia in southern Africa, we evaluated 144 consecutive Zimbabwean patients with megaloblastic haemopoiesis. Vitamin B12 deficiency was diagnosed in 86.1% of patients and was usually due to pernicious anaemia; isolated folate deficiency accounted for only 5.5% of cases. Anaemia was present in 95.8% of patients; the haemoglobin (Hb) was < or = 6 g/dl in 63.9%. Neurological dysfunction was noted in 70.2% of vitamin B12-deficient patients and was most striking in those with Hb values > 6 g/dl. Serum levels of methylmalonic acid, homocysteine, or both, were increased in 98.5% of patients. Vitamin B12 deficiency is the primary cause of megaloblastic anaemia in Zimbabwe and, contrary to textbook statements, is often due to pernicious anaemia. Isolated folate deficiency is less common. As reported in industrialized countries 75 years ago, anaemia is almost always present and often severe. Neurological dysfunction due to vitamin B12 deficiency is most prominent in patients with mild to moderate anaemia.

Non-specific ileojejunitis in Arequipa, Peru

Non-specific ileojejunitis, characterised by mild to moderate structural changes in the intestinal mucosa and often associated with asymptomatic malabsorption, is known to occur in the tropics and in countries with hot climates. This acquired condition is probably related to environmental factors, and some consider it to be a subclinical form of tropical sprue. Changes in the intestinal mucosa typical of non-specific ileojejunitis were found in 10 indigenous Indians as well as 5 people of Latin stock living in the Southern Peruvian sierra, where tropical sprue has not as yet been demonstrated and which has a temperate climate.

Tropical enteropathy in Rhodesia

Tropical enteropathy, which may be related to tropical sprue, has been described in many developing countries including parts of Africa. The jejunal changes of enteropathy are seen in Rhodesians of all social and racial categories. Xylose excretion, however, is related to socioeconomic status, but not race. Upper socioeconomic Africans and Europeans excrete significantly more xylose than lower socioeconomic Africans. Vitamin B12 and fat absorption are normal, suggesting predominant involvement of the proximal small intestine. Tropical enteropathy in Rhodesia is similar to that seen in Nigeria but is associated with less malabsorption than is found in the Caribbean, the Indian subcontinent, and South East Asia. The possible aetiological factors are discussed. It is postulated that the lighter exposure of upper class Africans and Europeans to repeated gastrointestinal infections may accound for their superior xylose absorption compared with Africans of low socioeconomic circumstances. It is further suggested that the milder enteropathy seen in Africa may be explained by a lower prevalence of acute gastroenteritis than in experienced elsewhere in the tropics.