An unlikely partnership: Parasites, concomitant immunity and host defence

Sam P. Brown, Bryan T. Grenfell

Research output: Contribution to journalArticlepeer-review

76 Scopus citations


Concomitant immunity (CI) against macroparasites describes a state of effective anti-larval immunity coupled with persistent adult infection. Experimental studies indicate that immunologically concealed adult worms might promote anti-larval immunity via the release of cross-reactive antigens, thus creating a barrier against continual infection and restricting burden size within the host. CI offers an important potential benefit to established worms by preventing overcrowding within the host. Thus, CI may be interpreted as akin to vaccination; relatively long-lived adult worms 'vaccinate' their host with larval surface antigens and so benefit from reduced conspecific competition. The shared responsibility for host vaccination among adult worms leads to a problem of collective action. Here, we build on earlier analytical findings about the evolutionary forces that shape cooperation among parasites in order to produce a stochastic simulation model of macroparasite social evolution. First, we theoretically investigate a parasite adaptation hypothesis of CI and demonstrate its plausibility under defined conditions, despite the possibility of evolutionary 'cheats'. Then we derive a set of predictions for testing the hypothesis that CI is partly a host-manipulative parasite adaptation. Evidence in support of this model would present an unusual case of adaptive population regulation.

Original languageEnglish (US)
Pages (from-to)2543-2549
Number of pages7
JournalProceedings of the Royal Society B: Biological Sciences
Issue number1485
StatePublished - Dec 22 2001
Externally publishedYes

All Science Journal Classification (ASJC) codes

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


  • Cooperation
  • Density-dependent fecundity
  • Group behaviour
  • Host manipulation
  • Schistosomiasis


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