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Paratenic host?

Charles T. Faulkner ctfaulkn at utkux.utcc.utk.edu
Wed Nov 13 13:41:41 EST 1996

On 12 Nov 1996, Omar O. Barriga wrote:

[stuff deleted]

> I still believe that the
> paratenic host is 
> only an accident in the life of the parasite that happens to be convenient.
> And because it is 
> convenient it persists in nature.
	Shoop's paper on amphiparatenesis and prenatal and perinatal
transmission is helpful for placing the concept of paratenic host in an
evolutionary perspective.  I doubt that paratenic host-parasite
relationships would persist in nature if they were mearly convenient and
selective advantages were not passed on to reproducing progeny. This
should be especially true in environments hostile to free living stages. 
The work on lactogenic transmission of Uncinaria lucasi by Drs. Lyons and
Olson is one good example. In other cases, extreme dependence on the
paratenic way of life has resulted in the elimination of freeliving and/or
environmental stages (e.g. Trichinella spiralis). Toxascaris leonina and
Capillaria hepatica are additional examples of species that depend on
paratenic hosts for maintainance and transmission in the definitive host
population, especially in zoological collections where sanitation measures
are often rigorously applied. The maintainance of the cat and
dog Isoporeans in their respective host populations may also be encouraged 
by use of paratenic hosts.  

	Here's another thread for consideration......how does the
paratenic host concept relate to virulence and Ewald's "sit an wait "
host contact strategy?

*      Charles T. Faulkner       *   Get your facts first and then you
*  Univ of Tennessee, Knoxville  *   can distort them as much as you please.
*     (ctfaulkner at utk.edu)       *                Mark Twain

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