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A parasite is an organism that spends a significant portion of its life in or on the living tissue of a host organism and which causes harm to the host without immediately killing it. Parasites also commonly show highly specialized adaptations allowing them to exploit host resources.

The harm caused to a host by a parasite can take many forms, from direct pathology, including various specialized types of tissue damage, such as castration, to more subtle effects such as modification of host behaviour. Many cuckoos, for example, are brood parasites that use their unwitting hosts as lifetime "babysitters": cuckoo young are raised by adults of the host species, but adult cuckoos fend for themselves.

The biological interaction between host and parasite is considered by some to be a type of symbiosis. Classically, the distinction between parasites and other symbionts was methodological: parasites were symbionts that could not be kept alive outside the host, unlike bacteria, for example, which could be cultured in a laboratory.

Evolutionarily speaking, parasitism is an extremely successful mode of life. Depending on the definition used, as many as half of all animals have at least one parasitic phase in their life cycles, and it is also frequent in plants and fungi. Moreover, almost all free-living animals are host to one or more parasite taxa.

Contents 1 Examples 1.1 Endoparasites 1.2 Ectoparasites 2 See also 3 References

Examples

Endoparasites

(endo = within; parasites that live inside their hosts)

• Plants
  • Rafflesia
• Animals
  • Acanthocephala
  • Candiru (Vampire fish of Brazil)
  • Clonorchis sinensis (the Chinese liver fluke)
  • Cymothoa exigua
  • Dracunculiasis (Guinea Worm Disease)
  • Enterobius vermicularis
  • Strepsiptera
  • Strongyloides stercoralis
• Fungi (such as ringworm)
  • Gymnosporangium and other rusts
• Protists (Protozoa)
  • Plasmodium (malarias)
  • Kinetoplastid protists of the Trypanosoma and Leishmania genera (sleeping sickness, Chagas disease and leishmania)
  • Balantidium coli (the only ciliated protozoan to infect humans)
  • Giardia lamblia (the most common intestinal protozoan in the United States)
  • Entamoeba histolytica (causes Amebiasis, common in developing countries)

Ectoparasites

(ecto = outside; parasites that live on but not within their hosts, for example, attached to their skin)

• Plants
  • Cuscuta
  • Mistletoe
  • Toothwort
  • The wood rose, Dactylanthus taylorii
• Animals
  • Hirudinea (some leeches)
  • Phthiraptera (Lice)
  • Siphonaptera (Fleas)
  • Acarina (Ticks)
  • Tantulocarida

See also

• Intestinal parasite
• Saprophyte
• Malarial parasite
• Teratology
• Successful parasite vs. Parasitoid
• Macroparasite

References

• Centers for Disease Control and Prevention
  • Division of Parasitic Diseases
    • DPDx - Laboratory Identification of Parasites of Public Health Concern - Reference and Training as well as Diagnostic Assistance