Transmission stage investment of malaria parasites in response to in-host competition

Andrew R. Wargo, Jacobus C. De Roode, Silvie Huijben, Damien R. Drew, Andrew F. Read

Research output: Contribution to journalArticlepeer-review

62 Scopus citations


Conspecific competition occurs in a multitude of organisms, particularly in parasites, where several clones are commonly sharing limited resources inside their host. In theory, increased or decreased transmission investment might maximize parasite fitness in the face of competition, but, to our knowledge, this has not been tested experimentally. We developed and used a clone-specific, stage-specific, quantitative PCR protocol to quantify Plasmodium chabaudi replication and transmission stage densities in mixed-clone infections. We co-infected mice from two strains with an avirulent and virulent parasite clone and found competitive suppression of in-host (blood-stage) parasite densities and generally corresponding reductions in transmission stage production, with the virulent clone obtaining overall competitive superiority. In response to competitive suppression, there was little evidence of any alteration in transmission stage investment, apart from a small reduction by one of the two clones in one of the two host strains. This alteration did not result in a competitive advantage, although it might have reduced the disadvantage. This study supports much of the current literature, which predicts that conspecific in-host competition will result in a competitive advantage and positive selection for virulent clones and thus the evolution of higher virulence.

Original languageEnglish (US)
Pages (from-to)2629-2638
Number of pages10
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1625
StatePublished - Oct 22 2007
Externally publishedYes


  • Gametocyte
  • Life history
  • Phenotypic plasticity
  • Quantitative RT-PCR
  • Transmission
  • Virulence

ASJC Scopus subject areas

  • General Immunology and Microbiology
  • General Biochemistry, Genetics and Molecular Biology
  • General Environmental Science
  • General Agricultural and Biological Sciences


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