The Synergistic Effect of Concomitant Schistosomiasis, Hookworm, and Trichuris Infections on Children's Anemia Burden

Amara E. Ezeamama^1,2*, Stephen T. McGarvey¹, Luz P. Acosta³, Sally Zierler⁴, Daria L. Manalo³, Hai-Wei Wu⁵, Jonathan D. Kurtis^6,7, Vincent Mor⁴, Remigio M. Olveda³, Jennifer F. Friedman^6,8

1 Department of Community Health and International Health Institute, Brown University Providence, Rhode Island, United States of America2 Health Effects Institute, Boston, Massachusetts, United States of America3 Department of Immunology, Research Institute of Tropical Medicine, Manila, The Philippines4 Department of Community Health, Brown University, Providence, Rhode Island, United States of America5 Department of Pathogenic Biology, Nanjing Medical University, Nanjing, Jiangsu, China6 Center for International Health Research, Rhode Island Hospital, Providence, Rhode Island, United States of America7 Department of Pathology and Laboratory Medicine, Brown University Medical School, Providence, Rhode Island, United States of America8 Department of Pediatrics, Brown University, Providence, Rhode Island, United States of America

Abstract

Objective

To estimate the degree of synergism between helminth species in their combined effects on anemia.

Methods

Quantitative egg counts using the Kato–Katz method were determined for Ascaris lumbricoides, hookworm, Trichuris trichiura, and Schistosoma japonicum in 507 school-age children from helminth-endemic villages in The Philippines. Infection intensity was defined in three categories: uninfected, low, or moderate/high (M+). Anemia was defined as hemoglobin <11>

Results

M+ co-infection of hookworm and S. japonicum (OR = 13.2, 95% CI: 3.82–45.5) and of hookworm and T. trichiura (OR = 5.34, 95% CI: 1.76–16.2) were associated with higher odds of anemia relative to children without respective M+ co-infections. For co-infections of hookworm and S. japonicum and of T. trichiura and hookworm, the estimated indices of synergy were 2.9 (95% CI: 1.1–4.6) and 1.4 (95% CI: 0.9–2.0), respectively.

Conclusion

Co-infections of hookworm and either S. japonicum or T. trichiura were associated with higher levels of anemia than would be expected if the effects of these species had only independent effects on anemia. This suggests that integrated anti-helminthic treatment programs with simultaneous deworming for S. japonicum and some geohelminths could yield a greater than additive benefit for reducing anemia in helminth-endemic regions.

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