Etiology of anaemia in South -East Asia

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1.2 Etiology of anaemia in South -East Asia

Nutritional deficiencies, mainly of iron, caused by inadequate diet is the predominant cause of anaemia in the SEAR. 3 Infections, particularly parasitic diseases, including malaria and helminth infections that cause both extracorporeal iron loss and anemia of inflammation, decreasing bioavailability of iron to host tissues 9 10 Genetic disorders such as thalassemia traits in the population also contribute. 11 Figure 1.1 provides an overview of the determinants of anaemia at individual, intermediate and underlying levels. South Asian diets are mostly based on staples with little intake of animal foods, have low iron bio-availability and contain inhibitors of iron absorption, so that intake andor absorption of iron and other nutrients is inadequate for haemopoesis. 12 Iron responsive anaemias are estimated as 40-50 of anaemias in the Region. 3 However, effect sizes are heterogenous between countries, and even within regions of countries. Other nutrients that contribute include vitamins B 12 , and folate and deficiencies of other minerals including zinc and copper may also influence. 12 Severe protein-energy malnutrition also contribute to anaemia. 12 Intestinal infections causing diarrhoea, malabsorption and blood loss e.g. hookworm infection may, in addition to depleting body iron also exacerbate risk of other micronutrient deficiencies by reducing digestion and absorption and enhancing nutrient losses. 10 Another frequent cause of anaemia, globally, is the anaemia of chronic disease, triggered by inflammation. 11 In malaria, tuberculosis, HIV infection, and perhaps other common bacterial, viral and parasitic infections eg diarrhea, pneumonia, cutaneous infections, inflammation, mediated via hepcidin, suppresses haemoglobin synthesis and red blood cell RBC production. Poor water, sanitation and hygiene WASH may therefore play an important role in contributing to high anaemia rates through gastrointestinal infections, causing diarrhoea and loss of nutrients, as well as through systemic inflammation which prevents iron absorption and utilisation. 10 This latter mechanism has not yet been empirically established. WHO estimates that 50 of malnutrition is 11 associated with repeated diarrhoea or intestinal worm infections from unsafe water or poor sanitation or hygiene. 9 Children who are exposed to open defecation or without access to safe water have increased risk of intestinal infection and chronic gastrointestinal track inflammation environmental enteropathy, contributing to stunting and anaemia, and poor early childhood development. 10 Haemoglobinopathies are the most common genetic disorders in South-East Asia that contribute to anaemia. 11 The most prevalent are α and β-thalassaemias, and haemoglobin Hb E. The gene frequencies of α-thalassaemia are approximately 30-40 in Northern Thailand and Lao PDR. Hb Constance Spring a form of alpha thalassemia gene frequencies vary between 1 and 8. β-thalassaemias vary between 1 and 9. Hb E trait is most common in parts of South-East Asia, attaining a frequency of 50-60 at the junction of Thailand, Laos and Cambodia. Data from India show that thalassemia, G6PD deficiency and sickle cell disease are significant contributors amongst speicifc populations Sindhis in Gujarat and Maharashtra and in some regions North-Eastern states, tribal areas of Orissa and West Bengal. 13,14,15,16 These abnormal genes in different combinations lead to over 60 different thalassaemia syndromes, making South and East Asia the Regions with the most complex thalassaemia genotypes. In the Central Terai region of Nepal, some tribal populations have a significant incidence of sickle cell disease. a These genetic conditions do not preclude iron deficiency, which needs to be treated when present, except in thalassemia intermedia and major, which are relatively rare. Determinants of anaemia vary across countries, but the relative degree of influence of each remains largely unclear. Most likely anaemia is due to a combination of causes which coexist, with individual contributions varying in different settings. Since anaemia is the result of multiple factors, it is essential to obtain adequate information on the main causes of anaemia in a given population. a Shrestha A, Karki S. Analysis of sickle hemoglobin, Journal of Pathology of Nepal 2013 Vol. 3, 437 -40. 12 Figure 1.1 Determinants of anaemia Adapted from USAID. Conceptual Frameworks. Multisectoral Anemia Partners Meeting, hosted by the USAID Anemia Task Force held on 18 October 2013. Washington DC, USA. https:www.spring- nutrition.orgsitesdefaultfileseventsmultisectoral_anemia_meeting_diagrams . pdf Iron deficien cy Inadequate access or intake of nutrient- rich diets Inadequate maternal child care practices Poor supply or demand of curative preventive health services Excess blood loss High number inadequate spacing of births: Unsafe water, poor hygiene and sanitation Socio-cultural and economic conditions and policies, basic healthcare infrastructure, inequitable distribution of services, inadequate local evidence on etiology Other micro nutrien t deficien cies Malaria, helminths causing increased blood loss Inflammation due to multiple causes including malaria, helminths, chronic infections; tuberculosis, HIV, and caused by other toxins Genetic disorders; hemoglob inopathie

s, G6PD deficiency