Ectoparasite defence in humans: relationships to pathogen avoidance and clinical implications

Currently, disgust is regarded as the main adaptation for defence against pathogens and parasites in humans. Disgust's motivational and behavioural features, including withdrawal, nausea, appetite suppression and the urge to vomit, defend effectively against ingesting or touching sources of pathogens. However, ectoparasites do not attack their hosts via ingestion, but rather actively attach themselves to the body surface. Accordingly, by itself, disgust offers limited defence against ectoparasites. We propose that, like non-human animals, humans have a distinct ectoparasite defence system that includes cutaneous sensory mechanisms, itch-generation mechanisms and grooming behaviours. The existence of adaptations for ectoparasite defence is supported by abundant evidence from non-human animals, as well as more recent evidence concerning human responses to ectoparasite cues. Several clinical disorders may be dysfunctions of the ectoparasite defence system, including some that are pathologies of grooming, such as skin picking and trichotillomania, and others, such as delusory parasitosis and trypophobia, which are pathologies of ectoparasite detection. We conclude that future research should explore both distinctions between, and overlap across, ectoparasite defence systems and pathogen avoidance systems, as doing so will not only illuminate proximate motivational systems, including disgust, but may also reveal important clinical and social consequences. This article is part of the Theo Murphy meeting issue ‘Evolution of pathogen and parasite avoidance behaviours'.

• Publication year

  2018

• Venue

  Philosophical Transactions of the Royal Society B: Biological Sciences

• Publication date

  2018-06-04

• Fields of study

  Biology, Medicine

• Identifiers
  DOI 10.1098/rstb.2017.0207PMID 29866920PMCID PMC6000138
• External record

  Open on Semantic Scholar

• Source metadata

  Semantic Scholar, PubMed

• No claims are published for this paper.

• No concepts are published for this paper.

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