Schistosomiasis japonica, anemia, and iron status in children, adolescents, and young adults in Leyte, Philippines

Abstract

Observational and interventional evidence supports a relation between human schistosomiasis and anemia; however, the exact causal mechanisms remain unclear. Eggs translocating across the intestinal or bladder wall may result in extracorporeal blood loss with subsequent iron deficiency. Alternatively, anemia may result from cytokine-mediated dyserythropoiesis, as seen in anemia of inflammation. By evaluating the cross-sectional relation between the intensity of Schistosoma japonicum infection, hemoglobin concentration, and iron status in 7-30-y-old persons from S. japonicum-endemic rice-farming villages in the province of Leyte, Philippines, we assessed the relative contribution of iron deficiency and anemia of inflammation to schistosomiasis-associated anemia. We enrolled 627 S. japonicum-infected and 111 S. japonicum-uninfected persons. We obtained stool samples to quantify S. japonicum infection and venous blood samples for hemograms and measures of iron status and inflammation. Intensity of S. japonicum infection was independently associated with hemoglobin (beta = -0.24; 95% CI: -0.31, -0.17). Persons with high-intensity infection had a greater risk of iron deficiency anemia (adjusted prevalence odds ratio: 6.6; 95% CI: 2.9, 14.7), but there was no evidence of this relation in low-intensity infections. In contrast, anemia without iron deficiency was prevalent across all intensities (adjusted prevalence odds ratio: 3.8; 95% CI: 1.5, 9.5). Storage iron deficiency is a major contributor to anemia in high-intensity S. japonicum infection. A high prevalence of anemia without iron deficiency, exclusion of other mechanisms of anemia, and the evidence of low bioavailable iron suggest that anemia of inflammation contributes to S. japonicum-associated anemia at all infection intensities.