114 M. Bechir et al. vitamin A supplementation (Benn et al. 2009; Kraemer et al. 2008). The United Nations Children’s Fund (UNI- CEF) and the World Health Organization (WHO) inte- grated vitamin A supplementation into the expanded programme of immunization (EPI) in developing countries (United Nations Children’s Fund 1998), and the Pro- grammes against Blindness in Developing Countries regis- tered xerophthalmia as one of ﬁve targeted blindness diseases (Traore´ et al. 1998). Remote communities, such as Sahelian mobile pasto- ralists, have limited access to health services (Wyss et al. 2004; Zinsstag et al. 2005), and their micronutrient status is not well-documented in Chad. One of the few studies done in a Chadian mobile pastoralist population found that the primary source of dietary retinol was milk and 40% of women were deﬁcient (Zinsstag et al. 2002). In the study, blood samples were transported from Chad to Switzerland for high-performance liquid chromatography analysis. Both food consumption and community socio-cultural aspects determine vitamin A levels. Becquey and Martin- Prevel (2010) showed that higher intake of animal products was signiﬁcantly associated with a lower risk of micronu- trient deﬁciency. In Ethiopia, Demissie et al. (2009) found an association between VAD and age or household char- acteristics. Pasture provides the fodder for livestock throughout most of the world. In remote areas, the milk of cows, goats, sheep and camels is an important source of nutrition for the local people. Livestock milk also provides vitamin A, which is vital for human health. The essential precursors of vitamin A (including b-carotene) are synthesized by plants but not by animals or humans. In grassland areas, seasonal rainfall inﬂuences the annual growth of vegetation, including the level of b-carotene in fodder, which then determines retinol levels in livestock, milk and, ultimately, human vitamin A status. Earlier study demonstrated that human serum retinol depends signiﬁcantly on livestock milk retinol in nomadic pastoralists and supported con- sumption of goat and cow’s milk as an important source of vitamin A (Zinsstag et al. 2002). In this study, the aim was to extend these assessments to communities with different lifestyles, including nomadic and semi-nomadic pastoralists who depend nearly exclu- sively on their livestock for nutritional needs, to further document an ecological linkage between human blood retinol and food sources like livestock milk in the south- eastern Lake Chad area. In addition, a portable ﬂuoro- metric device for on-site retinol and b-carotene measurement was tested. This portable measurement method was developed in Germany using cow’s milk (Kawashima et al. 2009) and evaluated for human blood in the USA and Liberia (Craft 2001), where a correlation of portable ﬂuorescence and retinol concentration of 0.9987, in the range of 0.25–3.5 lmol/L, was reported. The objective of this study was to assess comparative blood and milk retinol level among women and children under ﬁve-year-old in nomadic, semi-nomadic (cattle rearing) and rural-settled communities, to determine the association of human blood and milk retinol with livestock milk consumption and to test the practical use of portable ﬂuorometry devices for human and animal samples in a remote area. MATERIALS AND METHODS A stratiﬁed cross-sectional study between mobile pastoralist and rural-settled women and children under ﬁve-year-old was done in October 2008, at the end of the rainy season, among Foulbe nomadic and Arabic semi-nomadic com- munities living near Lake Chad and sedentary communities of Baltram village in the same area. Sedentary communities were composed of Haoussa, Kanembou, Sara and Hadjarai ethnic groups originating from different regions of Chad. Their data were pooled to represent the sedentary popu- lation. Sampling The sample size was based on a prevalence of retinol deﬁ- ciency of 40% among nomadic children (Zinsstag et al. 2002) and 22% among sedentary children, assuming a conﬁdence level of 95%, a power of 90% and a minimum odds ratio of 2.2. Based on these assumptions 150 nomadic/semi-nomadic and 150 sedentary children and their mothers were selected. Random transects were used for the selection of nomadic camps in the study zone, as previously described (Weibel et al. 2008). Pastoral communities were composed of Foulbe pastoralists, who are nomadic throughout the year, and Arabic communities, who practice a semi-nomadic lifestyle with higher mobility during the dry season. Rural-settled women and children were selected in three areas using ran- dom numbers from a list of all village areas. The chief of each area and the health centre staff notiﬁed mothers of children under age ﬁve by megaphone. A mobile laboratory was established in the selected area (Fig. 1).