Functional significance of low-intensity polyparasite helminth infections in anemia

Background. We wanted to quantify the impact that polyparasite infections, including multiple concurrent low-intensity infections, have on anemia. Methods. Three stool samples were collected and read in duplicate by the Kato-Katz method in a cross-sectional sample of 507 children from Leyte, The Philippines. The number of eggs per gram of stool was used to define 3 infection intensity categories-uninfected, low, and moderate/high (M+)-for 3 geohelminth species and Schistosomiasis japonicum. Four polyparasite infection profiles were defined in addition to a reference profile that consisted of either no infections or low-intensity infection with only 1 parasite. Logistic regression models were used to quantify the effect that polyparasitism has on anemia (hemoglobin level < 11 g/dL). Results. The odds of having anemia in children with low-intensity polyparasite infections were nearly 5-fold higher (P=.052) than those in children with the reference profile. The odds of having anemia in children infected with 3 or 4 parasite species at M+ intensity were 8-fold greater than those in children with the reference profile (P <.001). Conclusion. Low-intensity polyparasite infections were associated with increased odds of having anemia. In most parts of the developing world, concurrent infection with multiple parasite species is more common than single-species infections. This study suggests that concurrent low-intensity infections with multiple parasite species result in clinically significant morbidity.