Iron and infection in infancy--report on field studies in Papua New Guinea: II. Protocol and description of study cohort

Iron and infection: narrative review of a major iron supplementation study in Papua New Guinea undertaken by the Department of Tropical Paediatrics, Liverpool School of Tropical Medicine, 1979-1983, its aftermath and the continuing relevance of its results

In 1978, I returned from a 2-year government posting as provincial paediatrician to East and West Sepik provinces of Papua New Guinea (PNG), having already enrolled on the Diploma of Tropical Medicine and Hygiene (DTM&H) course at the Liverpool School of Tropical Medicine. I had been too late to enrol for the more relevant Diploma in Tropical Paediatrics course, but, whilst on the DTM&H course, made up for lost time by presenting myself to Professor Ralph Hendrickse in his office. I outlined my proposal for a double-blind, controlled, randomised trial of iron intervention with the aim of improving iron nutrition and decreasing susceptibility to and morbidity from infections in a cohort of infants in PNG. My reason for suggesting such a study was the high rate of anaemia in infants there and my perception from the literature of the time that the balance of studies favoured a beneficial effect of iron supplementation on infectious susceptibility, and that iron deficiency was associated with reversible abnormalities of immune function (although it had and has since been difficult to demonstrate the severity and relevance of these in observational in-vivo studies in humans).1,2 Ralph made an on-the-spot decision, immediately offering me the opportunity to join his department on 1 January 1979 on temporary funding while I applied for (and secured) a major grant from the Wellcome Trust for this work.

Iron and its relation to immunity and infectious disease

The continuing unresolved debate over the interaction of iron and infection indicates a need for quantitative review of clinical morbidity outcomes. Iron deficiency is associated with reversible abnormalities of immune function, but it is difficult to demonstrate the severity and relevance of these in observational studies. Iron treatment has been associated with acute exacerbations of infection, in particular, malaria. Oral iron has been associated with increased rates of clinical malaria (5 of 9 studies) and increased morbidity from other infectious disease (4 of 8 studies). In most instances, therapeutic doses of oral iron were used. No studies in malarial regions showed benefits. Knowledge of local prevalence of causes of anemia including iron deficiency, seasonal malarial endemicity, protective hemoglobinopathies and age-specific immunity is essential in planning interventions. A balance must be struck in dose of oral iron and the timing of intervention with respect to age and malaria transmission. Antimalarial intervention is important. No studies of oral iron supplementation clearly show deleterious effects in nonmalarious areas. Milk fortification reduced morbidity due to respiratory disease in two very early studies in nonmalarious regions, but this was not confirmed in three later fortification studies, and better morbidity rates could be achieved by breast-feeding alone. One study in a nonmalarious area of Indonesia showed reduced infectious outcome after oral iron supplementation of anemic schoolchildren. No systematic studies report oral iron supplementation and infectious morbidity in breast-fed infants in nonmalarious regions.

Fetal anaemia in malarious areas: its causes and significance

This analysis reviews published studies of cord haemoglobin values in developing countries and compares findings for populations that are either exposed or not exposed to malaria. The review indicates: first, that fetal anaemia is common in women with chronic moderate-to-severe iron deficiency anaemia; second, that a severe degree of fetal anaemia is reported in several areas where malaria in pregnancy is common. Different levels of fetal anaemia or polycythaemia arise in relation to the duration and severity of maternal anaemia during pregnancy, but in malarious areas the fetal anaemia appears to be out of proportion to the level of maternal anaemia. Haemoglobinopathies are likely to play a contributory role in causing fetal anaemia. The concept is advanced that malaria may contribute to fetal anaemia as a result of immune haemolysis of sensitized red cells. Sensitization could be from malaria antibodies and antigens which cross the placenta. Further evidence is required to prove this hypothesis. The importance of fetal anaemia is that it is likely to relate to the pattern and risk of developing anaemia in infancy.

The interaction of alpha thalassaemia with malaria

A controlled trial of iron dextran prophylaxis in infants 2 months old was carried out on the north coast of New Guinea, where malaria is holoendemic. These infants have a high carrier rate (80%) for alpha + thalassaemia. The neighbouring highland area has a low rate of both malaria and alpha + thalassaemia. The results of clinical and haematological examination of these infants at 6 and 12 months were analysed to determine the relationship between alpha thalassaemia and susceptibility to malaria. Infants were divided according to haemoglobin Bart's levels found at birth into 3 groups corresponding to probable genotypes. Homozygotes had higher slide malarial positivity and spleen rates at 6 and 12 month than the normal or heterozygote groups. Analysis of variance of haemoglobin levels showed that the anaemia associated with malaria was greatest in the normals and least in the homozygotes at 6 months. A possible protective mechanism of alpha thalassaemia is discussed.

Total dose iron infusion, malaria and pregnancy in Papua New Guinea

A study was made of 544 mothers and their 556 newborns in an area of endemic malaria, to analyse effects of total dose intravenous iron infusion (TDI) to mothers during pregnancy. 34% of these mothers received TDI before delivery. A range of haematological tests was carried out on newborns and mothers in addition to anthropometry. 84% of mothers had had ante-natal care and data were also collected retrospectively from ante-natal records. TDI was associated with more slide positive peri-natal malaria in primipara (odds ratio: 5.46) but not in multipara. When all relevant factors were considered TDI was not associated with an overall improvement in haemoglobin status from the first ante-natal level recorded to the post-natal check. Post-natal malaria was associated with lower ante-natal and post-natal haemoglobin levels. There was no evidence of any effect of TDI in pregnancy or of maternal malaria on foetal maturity or birth weight. Gestational age, maternal weight, parity and maternal post-natal haemoglobin were all significantly correlated with birth weight. TDI to the mother was associated with higher neo-natal serum ferritins and lower neo-natal haemoglobins. Maternal post-natal malaria was associated with significantly lower iron in serum in newborns. It is suggested that routine total dose iron infusion to anaemic pregnant mothers in malaria endemic areas may be contraindicated.

Iron supplementation increases prevalence and effects of malaria: report on clinical studies in Papua New Guinea

A placebo-controlled trial of intramuscular iron dextran prophylaxis for two-month-old infants was carried out on the north coast of Papua New Guinea where there is high transmission of malaria. The results indicate that the placebo group became relatively iron deficient whereas the iron dextran group had adequate iron stores and, in the absence of malaria, a higher mean haemoglobin. However in the iron dextran group there was a higher prevalence of malaria, as judged by parasite and spleen rates at 6- and 12-month follow-up; a lower haemoglobin associated with malaria when compared with the placebo group and a greater reticulocytosis in response to malaria infection. Within the placebo group it was noticed that the malaria rates were lower at follow-up in those infants who had had a low birth haemoglobin. In neither group was there apparent suppression of marrow activity in the presence of malaria. Malaria infection in both groups was associated with a significantly raised serum ferritin level and transferrin saturation. Over-all these data give evidence for a protective role of iron deficiency against malaria and would argue against the injudicious use of iron replacement in areas where malaria is endemic.

Effect of iron prophylaxis on morbidity due to infectious disease: report on clinical studies in Papua New Guinea

A controlled trial of iron prophylaxis (3 ml intramuscular iron dextran) to two-month-old infants was carried out on the north coast of Papua New Guinea where there is high transmission of malaria. The initial hypothesis was that iron deficiency increased susceptibility to infections and thus iron supplementation in a situation of actual or potential iron deficiency would diminish this susceptibility. Findings detailed elsewhere indicate that the placebo control group became relatively iron deficient and that the iron dextran group had adequate iron stores and a higher mean haemoglobin; however, prevalence of malaria recorded in the field was higher in the iron dextran group. Analysis of field and hospital infectious morbidity in the trial indicated a deleterious effect of iron dextran for all causes and for respiratory infections (the main single reason for admission). Total duration of stay in hospital was significantly increased in the iron dextran group. Analysis of other factors showed a deleterious effect of low weight for height at the start of the trial; a significant positive correlation between birth haemoglobin and hospital morbidity rates and a positive interaction between haemoglobin and iron dextran on hospital morbidity. A possible association between malarial experience and other infectious morbidity is discussed.