CARACTERIZACIÓN EN DISTINTAS ETAPAS DE LA VIDA

3.2.1 Study countries

Cambodia and Lao PDR are two adjacent countries of Southeast Asia. They respectively counted 15.1 and 6.8 million inhabitants in 2013 and 2015. They have a tropical monsoon climate with the rainy season occurring between May and October. Both countries have experienced strong economic development in the past decades and moved up to the

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World Bank group of “lower middle income countries”, although at the very bottom of this

category. Their Human Development Index (HDI), a summary measure of a long and healthy life, access to knowledge, and a decent standard of living, were 138/188 and 143/188 for Lao PDR and Cambodia, respectively, in 2015 (UNDP, 2016b, UNDP, 2016a).

Cambodia’s landscape is dominated by a large central plain run through by two major

rivers: the Mekong River which crosses the country from North to South and the Tonle Sap River which flows from a large inland lake situated in the Northwest, the Tonle Sap, down to Phnom Penh. This large plain is surrounded by low-range mountains, particularly in the South and South West, which coast line opens onto the Gulf of Thailand. About 20% of land area is used for agriculture and rice fields occupy 75% of the cultivated areas (FAO, 2014). Rice fields are found across the entire country in the lowlands, and occupy most of the land surface in the alluvial plains of the Tonle Sap along a Northwest-Southeast axis and the Mekong in the South. In 2000, 49% of the country surface was occupied by forests, but 1.44 million hectares of forests were lost by 2014, with Cambodia losing its forests at one of the fastest rates in the world (Global-Forest-Watch, 2016, NASA-Earth-Observatory, 2017, Open- Development-Cambodia, 2016).

Cambodia underwent several decades of political instability which started in the mid- seventies with the Khmer rouge genocide which exterminated at least 1.7 million people and specifically targeted educated citizens, i.e. doctors, teachers, engineers … namely, any literate people. In the early nineties Cambodia had to re-build a completely destroyed infrastructure and re-develop everything, including its educational and health systems. In the past decades, the country experienced a marked economic development mostly driven by the garment sector, construction and services. In 2015, Cambodia had a gross national income per capita (GNI) of 1,070 US$, with agriculture -mostly rice growing- mainly consisting in subsistence farming, being the fourth important economic sector in the country. Despite significant

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progress, including in reaching the 1st Millennium Development Goal (MDG) to halve poverty in 2009, 17.7% of the population was still under the poverty line, with 90% of the poor living in rural areas, and almost half of the population actually remained on the edge of the poverty line (WorldBank, 2017a, WorldBank, 2017b). Cambodia also accomplished important achievements in matters of health, with malaria and HIV/AIDS being under control and the MDG child and maternal mortality targets met. However, a major challenge is child malnutrition, which is rampant particularly in rural areas, despite excellent progress made since the nineties. In 2014, a third (32.4%) and 9.6% of under-5 children were stunted or underweight respectively (International-Food-Policy-Research-Institute, 2016). Access to sage water and sanitation remains a major challenge in rural areas, where as much as 79.3% of the population lived in 2015. In contrast to the urban population, of which 88% and 100% had access to improved sanitation and water, respectively, those proportions were only 31% (improved sanitation) and 69% (improved water) for the rural population in 2015. (WHO/UNICEF-Joint-Monitoring-Programme-(JMP)-for-Water-Supply-and-Sanitation, 2015).Those poor water and sanitation conditions result in open defecation, which, combined to the humid tropical climate, creates most favourable conditions for the development and subsistence of protozoa and helminths in the environment.

Regarding helminth control, Cambodia is an exemplary country, and was the first to reach the WHO target of 75% coverage of school-based deworming (primary schools) in 2004. Cambodia has also eliminated lymphatic filariasis as a public health problem in 2016, a target that has been so far met by only eight countries worldwide (WHO, 2016a, Montresor et al., 2008, Sinuon et al., 2005). However, STH, which remain highly prevalent, are still an important public health problem in the country (Khieu et al., 2014b, Khieu et al., 2014c, Moore et al., 2015, Yong et al., 2014, Kuong et al., 2016).

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Lao PDR is a landlocked country mostly bordered by Thailand in the West and Vietnam in the East, and by China and Cambodia in the North, and the South, respectively. Up to 70% of its surface is occupied by mountains, highlands and plateaux. Its western border is run along or through by the Mekong river. The country economic growth is mostly due to its natural resources (water, mineral compounds, and forests) as well as services and construction. Regarding Millennium Development Goals, Lao PDR halved poverty by 2013, reduced maternal mortality by 75% by 2015, and achieved the MDG target for water and sanitation in 2015, with 76% and 71% of the population having access to improved water and sanitation, respectively (UNDP, 2015).

However the poverty rate was still high in 2012, with almost half of the population (46.9%) living under the 3.10 US$ poverty line and as many as 16.7% living below the extreme poverty line of 1.90 US$ (WorldBank). Helminths are endemic in the entire country, where the liver fluke Opisthorchis viverrini and STH are particularly highly prevalent (Sayasone et al., 2009, Sayasone et al., 2014, Sayasone et al., 2007, Chai et al., 2005, Phongluxa et al., 2013).

3.2.2 Study sites

The S. stercoralis national survey was conducted on all 25 provinces of Cambodia. Other studies conducted in Cambodia took place in the Preah Vihear province. The hookworm study from Lao PDR, was conducted in Champasack province.

a. Preah Vihear Province, Cambodia

Preah Vihear is a rural province of North Cambodia sharing its North border with the Champasack province, Lao PDR. There is no major river going through Preah Vihear province which is mostly flat and occupied by savannahs and shrub lands, but also rice fields, and forests. However the province has lost about 10% of its tree cover between 2001 and

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2014 (Genta, 1989). In 2013, Preah Vihear province hosted 235,370 people, 87.6 % of whom lived in rural areas with most of the urban population living in the province capital, Tbaeng Meanchey (National Institute of Statistics, 2013b, United-Nations-Population-Fund, 2014). Preah Vihear is one of the poorest provinces of Cambodia (Asian-Development-Bank, 2014). With a poverty incidence of 62.2% in 2014, it even has been ranked at the most poor province by the Multidimensional Poverty Index (MPI), a multidimensional poverty measure integrating education, health and living standard dimensions. As a comparison, the poverty incidence of whole Cambodia as assessed by the MPI would be 33.0% (OPHDI, 2016).

b. Champasack province, Lao PDR

Champasack province has a surface of 15,415 km2 and hosted a population of 603,370 according to the 2005 national census (Census 2005, Lao Statistics Bureau, Vientiane; http://www.nsc.gov.la). It is run through from North to South by the Mekong River. The landscape is dominated by the river floodplains and mostly occupied by rice fields and flatlands. Farther from the floodplain and east of the Mekong River, the topography gets hillier and is covered in forests, while the North East third is mountainous and culminates at 1,617 m above sea level. Helminths including STH, Opisthorchis viverrini and Schistosoma

mekongi are endemic in the province (Muth et al., 2010, Sayasone et al., 2011, Sayasone et

al., 2014, Sayasone et al., 2009, Forrer et al., 2012).