Also called auxillary host or transport host. A species in which a parasite may survive longer than it would outside any host, but which is not necessary to the parasite's life cycle, and in which no significant development occurs. This usually means that a paratenic host supplies nourishment to the parasite, but does not enable it to multiply or develop to a different stage. In some cases, the parasite gets the opportunity to reenter its normal life cycle from the paratenic host, but most of the time it's a dead end.

For example, humans can act as paratenic hosts to dog roundworm by ingesting eggs (which contain already fully-developed larvae) contained in infested dogs' feces. The larvae can hatch, survive and migrate in the human body, but do not develop further, although they do cause toxocariasis. If a thusly infected human were eaten by suitable regular host animals, the larvae could complete their life cycle there.

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