Serum retinol concentrations and Schistosoma mansoni, intestinal helminths, and malarial parasitemia: a cross-sectional study in Kenyan preschool and primary school children.

Parasitic determinants of serum retinol concentrations were studied in 159 preschool (0.25-5.1 y) and 695 primary school (9.2-17 y) children in western Kenya. Mean serum retinol was 0.63 micromol/L in preschool and 0.94 micromol/L in primary school children; 62% and 24%, respectively, had serum retinol < 0.70 micromol/L. Serum retinol was lower in boys than in girls among both preschool (P = 0.04) and primary school children (P = 0.0001). Schistosoma mansoni, Ascaris lumbricoides, hookworm, and Trichuris trichiura egg output and malarial parasitemia were determined and their relation with serum retinol assessed. Among preschool children, sex, elevated serum concentrations of C-reactive protein, and malarial parasitemia were significant predictors of serum retinol. Among the 63 children from whom stool samples were available, none of the helminth infections were significant predictors of serum retinol. For primary school children, age, sex, and S. mansoni egg output were predictors of serum retinol. Malarial parasitemia among nonimmune preschool children may contribute to low serum retinol, whereas malarial parasitemia did not have any effects in semiimmune primary school children. In contrast, the inverse relation between S. mansoni and serum retinol found in primary school children could be due to an effect of infection on serum retinol or an increased susceptibility to infection among children with low serum retinol. Although parasitic infections may contribute to poor vitamin A status in children, they do not explain the age and sex differences.