116 M. Bechir et al. Kruskal–Wallis tests for categorical and ordinal comparisons of small samples of mother’s milk and livestock milk. Logistic regression models related retinol deﬁciency (<0.7 lmol/L) as an outcome to explanatory variables of anaemia (binary categorisation in anaemic, Hb < 120 mg/L, and non- anaemic, Hb 120 mg/L), emaciation (binary categorisa- tion in emaciated, Z-score < -2, and non-emaciated, Z-score -2, for children and in emaciated, BMI < 18.5 kg/ m2, and non-emaciated, BMI 18.5 kg/m2, for women), multi-parasite infection (binary categorisation in multi- infection and non-multi-infection), age (categorisation in <12, 12–36 and >36 months for children and <25, 25–35 and >35 years for women), lifestyle (categorisation in no- mad, semi-nomad and settled) and sex (binary categorisa- tion in male and female for children). Ethical Consideration This study was approved by the Ministry of Heath of Chad (N 236/MSP/SE/SG/DGAS/2007) and by the ethical com- mittee of both cantons of Basel, Switzerland (Ref. Nr. EK: 362/07). In each study site, local health authorities were informed and involved in the study. Collective and indi- vidual consent was solicited from heads of camps and vil- lage areas and from all participating women. Vitamin A supplements and systemic mebendazole were administered by qualiﬁed health personnel. RESULTS Of the 288 collected samples, 260 (90.5%) were analysed and included. The remaining 28 were considered erroneous values and were excluded from statistical analysis. Blood Retinol Concentration Among Women and Children Table 1 lists blood retinol levels among women and chil- dren of different communities. Nomadic women and children had higher blood retinol concentrations when compared to semi-nomadic and sedentary communities. One in ﬁve semi-nomadic and sedentary women and one in twenty nomadic women were moderately retinol deﬁcient. A similar trend was observed in children, with higher levels of retinol deﬁciency in sedentary children (1 in 4). Figure 2 shows the frequency of blood retinol concentration among children. Table 1. Averages and Proportions of Blood Retinol Among Children and Women According to Lifestyle Retinol average Avg. (lmol/L) Women Nomads Semi-nomads Sedentary All Children Nomads Semi-nomads Sedentary All Boys Nomads Semi-nomads Sedentary All Girls Nomads Semi-nomads Sedentary All not applicable. n 54 34 14 102 71 59 28 158 45 34 14 93 26 25 14 65 2.8 2.1 1.1 2.5 2.8 2.1 0.7 2.1 2.8 2.5 0.4 2.5 2.8 1.8 0.7 2.1 95% CI 2.5–3.2 1.4–2.8 0.4–2.1 1.8–2.8 2.5–3.2 2.1–2.8 0.3–0.7 1.8–2.45 2.5–3.3 1.4–3.3 0.2–0.7 1.8–2.8 2.1–3.5 1.1–2.8 0.2–1.1 1.4–2.4 Retinol proportion %<0.7 lmol/L 5 29 22 17 1 17 28 14 0 10 27 14 2 17 27 15 95% CI 1–11 13–45 8–35 10–23 0.1–4 9–25 18–39 10–19 0.1–18 12–42 9–20 0.0–7 4–30 12–42 8–21 Figure 2. Frequency of blood retinol concentration among children. Retinol and b-Carotene in Milk Average retinol values in mother’s milk, the primary food for infants, were slightly higher compared to the blood levels in the same women (Table 2). Mother’s milk retinol content between sedentary and semi-nomadic women was