Mechanism of anemia in Schistosoma mansoni-infected school children in Western Kenya

Abstract

A better understanding of the mechanism of anemia associated with Schistosoma mansoni infection might provide useful information on how treatment programs are implemented to minimize schistosomiasis-associated morbidity and maximize treatment impact. We used a cross-sectional study with serum samples from 206 Kenyan school children to determine the mechanisms in S. mansoni-associated anemia. Serum ferritin and soluble transferrin receptor levels were measured by using an enzyme-linked immunosorbent assay. Results suggest that S. mansoni-infected persons are more likely (odds ratio = 3.68, 95% confidence interval = 1.33-10.1) to have levels of serum ferritin (> 100 ng/mL) that are associated with anemia of inflammation (AI) than S. mansoni-uninfected children. Our results suggest that AI is the most common form of anemia in S. mansoni infections. In contrast, the mechanism of anemia in S. mansoni-uninfected children was iron deficiency. Moreover, the prevalence of AI in the study participants demonstrated a significant trend with S. mansoni infection intensity (P < 0.001). Our results are consistent with those observed in S. japonicum-associated anemia.

Figure 1.

Distribution of ferritin levels in school children, western Kenya. The frequency of children with reduced ferritin levels were comparable between Schistosoma mansoni–infected (S⁺) and -uninfected (S⁻) children (1A). Although there was a difference between the frequency of children with increased ferritin levels, this difference was not significant (1B). When the frequency of reduced or elevated ferritin was analyzed for anemic children (1C and 1D), S. mansoni-infected children were 2.99 times more likely to have increased ferritin levels, consistent with anemia of inflammation, than uninfected children (95% confidence interval = 1.1–7.9) (1D).

Figure 2.

Soluble serum transferrin receptor (sTfR) levels in anemic (A+) and nonanemic (A−) children with (S+) or without (S−) schistosomiasis, western Kenya. The four groups differed significantly (P = 0.009, by Kruskal-Wallis test). sTfR was significantly increased in uninfected, anemic children compared with children who had no anemia or schistosomiasis (P < 0.01, by Dunn's post test).

Figure 3.

Ferritin levels by Schistosoma mansoni infection intensity in school children, western Kenya. Data represent means and upper 95% confidence intervals. Kruskal-Wallis analysis indicated a significant difference in the median ferritin values for the three eggs per gram (of feces) (EPG) categories (P = 0.004). Dunn's post test analysis indicated a significant difference between the uninfected and highly infected groups (P < 0.01) and between the low/medium intensity infection group and the high intensity group (P < 0.05).