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Obligate parasite

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noun, plural: obligate parasites

A parasite that entirely depends upon a host for its nourishment, reproduction, habitat, and survival


[[Parasitism[[ is a symbiotic relationship between organisms wherein the parasitic organism derives benefits from the relationship at the expense of the host. The parasitic organism, also referred to as the parasite, may depend either partially or entirely from its host to complete its life cycle. The parasite that is dependent entirely to its host is called an obligate parasite whereas the parasite that does not rely entirely on a host is referred to as a facultative parasite.

In an obligate parasitism, it is essential that the parasite is able to preserve the health of its host since its growth and reproductive needs depend on the latter. However, the exception is when the death of the host involves the transmission of the parasite to another host.1 Nonetheless, most obligate parasites need their host in order to survive and to be kept away from its host could mean the death of such parasite. Rickettsia and Chlamydia are examples of obligate parasites that require eukaryotic host cells to survive.2


  • obligatory parasite
  • holoparasite


See also:

1 Combes, C. (1997) Fitness of Parasites: Pathology and Selection International Journal for Parasitology 27(1): 1-10.
2 bacteria. (2015). In Encyclopædia Britannica. Retrieved from