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Anemia is estimated to affect one-half of school-age children in developing countries. The school years are an opportune time to intervene, and interventions must be based on sound epidemiologic understanding of the problem in this age group. We report on the distribution of iron deficiency and anemia across age, sex, anthropometric indexes, and parasitic infections in a representative sample of 3595 schoolchildren from Pemba Island, Zanzibar. Iron status was assessed by hemoglobin, erythrocyte protoporphyrin (EP), and serum ferritin concentrations from a venous blood sample. Overall, 62.3% of children were anemic (hemoglobin < 110 g/L), and 82.7% of anemia was associated with iron deficiency. The overall prevalence of iron-deficient erythropoiesis (EP > 90 mumol/mol heme) was 48.5%, and the prevalence of exhausted iron stores (serum ferritin < 12 micrograms/L) was 41.3%. In bivariate analyses, iron status was slightly better in girls than in boys, and was better in children aged 7-11 y than in those older or younger. Hemoglobin but not EP or serum ferritin concentrations were lower in stunted children. Infection with malaria, Trichuris trichiura, Ascaris lumbricoides, and hookworms were all associated with worse iron status; the association with hookworms was strongest by far. In multivariate analyses, hookworm infection intensity was the strongest explanatory variable for hemoglobin, EP, and serum ferritin. Sex, malarial parasitemia, A. lumbricoides infection, and stunting were also retained in the multivariate model for hemoglobin. Twenty-five percent of all anemia, 35% of iron deficiency anemia, and 73% of severe anemia were attributable to hookworm infection; < 10% of anemia was attributable to A. lumbricoides, malaria infection, or stunting. We conclude that anthelminthic therapy is an essential component of anemia control in schoolchildren in whom hookworms are endemic, and should be complemented with school-based iron supplementation.

Objective To measure the effects of iron supplementation and anthelmintic treatment on iron status, anaemia, growth, morbidity, and development of children aged 6-59 months. Design Double blind, placebo controlled randomised factorial trial of iron supplementation and anthelmintic treatment. Setting Community in Pemba Island, Zanzibar. Participants 614 preschool children aged 6-59 months. Main outcome measures Development of language and motor skills assessed by parental interview before and after treatment in age appropriate subgroups. Results Before intervention, anaemia was prevalent and severe, and geohelminth infections were prevalent and light-Plasmodium falciparum infection was nearly universal. Iron supplementation significantly improved iron status, but not haemoglobin status. Iron supplementation improved language development by 0.8 (95% confidence interval 0.2 to 1.4) points on the 20 point scale. Iron supplementation also improved motor development, but this effect was modified by baseline haemoglobin concentrations (P = 0.015 for interaction term) and was apparent only in children with baseline haemoglobin concentrations < 90 g/l. In children with a baseline haemoglobin concentration of 68 g/l (one standard deviation below the mean value), iron treatment increased scores by 1.1 (0.1 to 2.1) points on the 18 point motor scale. Mebendazole significantly reduced the number and severity of infections caused by Ascaris lumbricoides and Trichuris trichiura, but not by hookworms. Mebendazole increased development scores by 0.4 ( − 0.3 to 1.1) points on the motor scale and 0.3 ( − 0.3 to 0.9) points on the language scale. Conclusions Iron supplementation improved motor and language development of preschool children in rural Africa. The effects of iron on motor development were limited to children with more severe anaemia (baseline haemoglobin concentration < 90 g/l). Mebendazole had a positive effect on motor and language development, but this was not statistically significant.

In Zanzibar and other tropical regions, iron deficiency, malaria and multiple helminth infections coexist. We addressed the following questions: 1) What are the predictors of low hemoglobin in Zanzibari preschool children? 2) Are indicators of iron status informative in this population? 3) Does malaria modify the relation of iron indicators to hemoglobin? We used multivariate regression to analyze cross-sectional data from a community-based sample of rural Zanzibari children who were not ill (n = 490; 4-71 mo of age) in whom we assessed hemoglobin, serum ferritin (SF), erythrocyte protoporphyrin (EP), serum transferrin receptor (TfR), recent fever, malaria parasitemia and helminth fecal egg counts. Of hemoglobin values, 80% were <100 g/L and 15.5% were <70 g/L. In children <18 mo of age, 40.2% of hemoglobin values were <70 g/L. Our primary findings were as follows: 1) In children <30 mo old, hemoglobin was associated with malaria but not hookworms, whereas in children >/=30 mo, hemoglobin was related to hookworms but not malaria. In the younger age group, male sex and recent fever also predicted lower hemoglobin. 2) The three iron indicators were informative in this population but did not reflect only iron status. Malaria elevated SF in younger children and TfR and EP in both age groups. Fever elevated SF in older children and EP in both age groups, but not TfR. 3) Malaria modified the relation of all three indicators to hemoglobin. The relation of SF to hemoglobin was weak overall, and absent in malaria-infected children. EP and TfR were strongly related to hemoglobin, but this relation was attenuated by malaria.

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The comparative efficacy of albendazole and mebendazole in the treatment of intestinal nematode infections were compared 3 weeks after treatment in a randomized trial among schoolchildren on Pemba Island, Tanzania. Egg counts were compared 3 weeks, 4 months and 6 months after treatment of 731 children seen on each occasion. Differences in the efficacies were apparent with some nematodes 21 d after treatment, but these were no longer apparent 4 months after treatment, and by 6 months intensities of infection were similar to pre-treatment levels. These findings suggest that treatment of schoolchildren every 4 months may be necessary in this highly endemic area in order to have an impact on the intensity of intestinal nematode infections sufficient to be likely to reduce morbidity.

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This paper describes the longitudinal changes in height and weight of children in school grades 1-3 on Pemba Island, Zanzibar, a poor rural population in which parasitic infections and anemia are highly prevalent. Heights and weights of children were measured at base line, and 6 and 12 mo later, and were compared with U.S. reference data. At base line, the prevalence of height-for-age Z-score < -2 rose from 14% in 7-y-old children to 83% in 13-y-old children. Prevalence of weight-for-age Z-score < -2 in children < 10 y was approximately 10% or less. Median 6-mo height increments for Pembian boys were around the 5th percentile at age 8 and around the 10th percentile from age 9 to 13 y. Height increments for girls improved from below the 25th percentile to above the median in this age range. Based on the longitudinal yearly gains observed, boys accumulate a height deficit of 11.9 cm and girls 8.5 cm, relative to the reference population. In multivariate analyses, a small part of the variability in growth increments was explained by ascariasis and anemia (for weight gain) and schistosomiasis (for height gain). A review of other growth data from rural African Bantu populations provides supporting evidence that stunting occurs in older as well as younger children. It has been controversial whether school-based health and nutrition interventions could induce catch-up growth in already stunted children. Our results suggest that appropriate interventions might actually prevent stunting in late childhood.