Persistent holoendemic malaria conditions have led to the emergence of host genes that offer different effects against malaria and anaemia, but awareness of the risks or benefits they provide in large-scale iron intervention studies among infants and young children is poorly understood.
In our study, the basic characteristics of the participants among the groups were homogeneous and these values were in line with studies of Zlotkin et al. (73). A prevalence of G6PD deficiency of 11.2% was observed and this was comparable to Carter et al. (16), studies in Burkina Faso (9.4%), Kenya (11.4, 13.5%) (16), and Ghana (13.4%) (16) and George et al. (29), a study in Nigeria (14.6%). However, the observed G6PDD prevalence rates from our study are higher when compared to that of Carter et al. (16), a study in Mali (5.6% and 8.7%) and Tanzania (7.6%) (16), including Ghana (5.3%, 6.0%) (12, 16). These variations in the prevalence rates suggest that the genes, although rare, are highly polymorphic (almost 500 variants) and clinically relevant variants may be ignored during G6PD genotyping in holoendemic malaria zones (11, 42).
The G6PDD prevalence among male children (8.5%) was higher compared to females (2.7%) among the study participants but similar (p = 0.668). Similarly, Carter et al. (16), reported 8.9% deficiency among males and 4.5% among females in a similar geopolitical setting in Ghana (16). This may explain why the recessive X- linked gene is consistent with G6PDD and more prevalent in males (46), with variable prevalence rates from one geopolitical zone to another among different ethnic communities (62). The prevalence of haemoglobin trait (HbAS and HbSC) was 17.5% and sickle cell disease (SCD) (HbSS) was 0.5% and these findings were similar to studies in three countries (Nigeria, India and the Democratic Republic of Congo) that populate half of the world’s SCD individuals including other reports from Ghana and Mali (5, 32, 39, 58). Blood group O children (41.4%) dominated, followed by A (29.6%), B (23.3%) and lastly, AB (5.7%). The results from our present study agreed with findings from Uganda (7), Cameroon (9), Brazil (17) and Ghana (49). The G6PD genotypes did not influence the anaemic status at the end of the MNP intervention even though G6PD deficient RBCs are known to be more vulnerable to oxidative stress which prevents malaria parasitization and eventually reduces anaemia (3). Our observation also showed that G6PD alleles were not associated with anaemia in iron or non-iron containing MNP participants, and these results were similar to reports from countries such as Tanzania (25), Ghana (53) and Nigerian (11).
The iron group HbAS and non-iron group HbAC children were less protected against anaemia at the end of the MNP intervention. However, studies have shown that the presence of HbS alleles enhances the removal of parasitized sickle trait red blood cells (RBCs) via the spleen and reduces cytoadhesion of parasitized erythrocytes resulting in increased anaemic status among affected haemoglobin genotypes (24). In agreement with our study, Kreuels et al. (39), demonstrated that HbC alleles reduce cytoadhesion of parasitized erythrocytes leading to less protection against anaemia (39). While poorly understood, the reasons for our observation with regards to defending against anaemia for non-iron HbAC can be due to reduced parasitization of malaria or other immune mechanisms (39). However, our study shows that haemoglobin genotypes were not associated with anaemia in MNP children with or without iron. These findings were consistent with the results of the iron supplementation cohort observational study among anaemic Gambian children (30) and Patel et al. (54), a study in India. By contrast, Kreuels and his colleagues in a cohort study stated that Ghanaian children with HbAS alleles were protected from anaemia (39). Albiti and Nsiah (2014) also shown Yemeni children with HbAS alleles were vulnerable to mild anaemia (10.0-10.9 g / dL) but resistant to moderate and severe anaemia (4).
The O blood group has anti-A and B antibodies with no terminal saccharide moiety, making its RBCs more haemolysis-stable than the non-O blood group (23). However, in our trial, the ABO blood group did not show any defence against anaemia and this finding corroborates with other studies among Nigerian pregnant women (48) and Indians (40). Blood group O susceptibility to anaemia may be attributable to the pathogenesis of malaria, gender or other unknown causes. Nevertheless, our study failed to establish the link between the ABO blood group among children with iron or non-iron-containing MNP and anaemia, as postulated in other findings in India (34) and the case-control analysis in Pakistan (13).
This study was performed during the rainy season (March to September) and malaria parasitaemia was high in both groups. Though, malaria parasitaemia was higher in the non-iron group compared to the iron group, there were similarities between the groups. However, there was a higher risk of malaria for children with G6PD A-A- in both groups. These findings were inconsistent with investigations by Ouattara et al (2014) who reported the existence of a protective association for the G6PD A- variant against uncomplicated malaria in Burkina Faso (51) and a study by Sirugo et al. (63), that established heterozygote G6PD A- variant females have immunity against malaria among Gambians (63). However, our findings are consistent with that of Carter and his colleagues, who found G6PD status had no association with malaria in six African countries (14). Moreover, a multi-centre trial involving Kenyan, Gabonese and Ghanaian severe malaria children, aged between 6 and 120 months also reported no association between G6PD variants and malaria (47). The reason for this could be that G6PD does not play any vital antioxidative role under the influence of MNP intervention.
Moreover, our study found the iron group with HbAS and HbAC were less protected against malaria because the administration of iron increased haemolysis of AS red blood cells by promoting auto-oxidation of haemoglobin S (ferroptosis), generation of free oxygen radicals (due to failure of the glutathione-dependent antioxidant defences) which damage the red cell membrane, and further damage it by the deposition of ferritin-like and haemosiderin-like iron on the red cell surface and eventually excessive loss of erythrocytes. Our study was consistent with similar research among pregnant Gambian women with HbAS who had lower anaemic status when offered iron supplements (44). However, these findings were in contrast with the concept that heterozygote sickle haemoglobin traits have an advantage in protecting against malaria (4, 33, 39, 66, 67). Similarly, these selective sickle malaria-infected RBCs enhance its removal via the spleen, timely phagocytosis, decreases RBC invasion, reduce parasitization in the venous micro-vessels due to oxygen stress, and reduce erythrocyte rosetting and cytoadherence (39, 69). These series of mechanisms enhance the acquired and innate immunity to offer protection against malaria.
Furthermore, blood group A and O participants were less protected against malaria in the Fe group. The possible reason to account for this could be that malaria parasites easily mimic antigens A with the erythrocytes of blood group A forming bigger and stronger rosettes which selectively allow merozoites to prefer A antigen receptors for RBCs invasion. Therefore, the presence of iron act as a nutrient for the parasites, thereby, increasing parasitization, and rapid expression of surface cell membrane proteins to enhance rosette formation and cytoadherence in endothelia of the microvessels. In addition, iron elevated macrophage-facilitated phagocytes of malaria parasitized RBCs of blood group O which increased their susceptibility to malaria.