Disentangling complex parasite interactions: Protection against cerebral malaria by one helminth species is jeopardized by co-infection with another

PLoS Negl Trop Dis. 2018 May 10;12(5):e0006483. doi: 10.1371/journal.pntd.0006483. eCollection 2018 May.


Multi-species interactions can often have non-intuitive consequences. However, the study of parasite interactions has rarely gone beyond the effects of pairwise combinations of species, and the outcomes of multi-parasite interactions are poorly understood. We investigated the effects of co-infection by four gastrointestinal helminth species on the development of cerebral malaria among Plasmodium falciparum-infected patients. We characterized associations among the helminth parasite infra-community, and then tested for independent (direct) and co-infection dependent (indirect) effects of helminths on cerebral malaria risk. We found that infection by Ascaris lumbricoides and Trichuris trichiura were both associated with direct reductions in cerebral malaria risk. However, the benefit of T. trichiura infection was halved in the presence of hookworm, revealing a strong indirect effect. Our study suggests that the outcome of interactions between two parasite species can be significantly modified by a third, emphasizing the critical role that parasite community interactions play in shaping infection outcomes.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adult
  • Animals
  • Ascariasis / parasitology*
  • Ascaris lumbricoides / physiology*
  • Coinfection / parasitology*
  • Female
  • Humans
  • Malaria, Cerebral / parasitology*
  • Male
  • Plasmodium falciparum / physiology*
  • Trichuriasis / parasitology*
  • Trichuris / physiology*
  • Young Adult

Grant support

This study is a contribution of the ANR JC project ‘STORY’, granted to BR and supporting JLA. MN, JFG and BR are supported by ‘an Investissement d’Avenir’ grant from the Agence Nationale de la Recherche (CEBA ANR-10-LABX-2501). VOE received support from a US Fulbright Scholar Award. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.