In the known parasite-paratenic host relationships that have been studied, the parasitic stages can persist for long periods of time in the paratenic host. Parasites may be transmitted between intermediate and paratenic hosts, and likewise transmission may occur between multiple paratenic hosts. Paratenesis is one way that parasite transmission stages can greatly extend their lifespans in an ecosystem. Paratenic hosts are not physiologically required by a parasite, but ecologically they may be very important for the regular completion of the parasite's life cycle . Parasites that use intermediate and paratenic hosts have indirect life cycles .
Parasites succeed, biologically-speaking, by surviving and reproducing.
In a complex ecosystem, some of these randomly-distributed parasite transmission stages may take paths that will not lead to success. Many transmission stages succumb to unsuitable environmental extremes of temperature, humidity, exposure to sunlight, etc . Parasites may enter aberrant hosts , in whom conditions are not adequate for survival, further development, or sexual maturity. Aberrant hosts are a dead-end for both the individual parasite and the parasite species. Almost every occurrence of a parasite in an aberrant host results in the failure of aberrant parasites to either survive or to produce viable transmission stages.