cestode lifespan

Mark Siddall mes at zoo.toronto.edu
Mon Jan 8 10:18:25 EST 1996


In article <4ckl5i$esc at ra.isisnet.com> ah166 at ccn.cs.dal.ca (Sa'ad Al-Omari) writes:
>
>
>--
>What is the maximum lifespan for a cestode?


I have a suspiscion that this is like asking "What's the maximum
life-span for a mammal?"  That is to say - _which_ cestode species?
For short-lived hosts I'd suggest that the life-span of the host may well 
be the maximum life-span of the worm.  For longer-lived hosts...
Also, are you referring to the adult tapeworm only or the larval 
stages?  Or both together?  Echinococcus species larval stages (hydatids)
can be very long-lived (so long as the host doesn't die). One could imagine
a young child being infected with eggs from the feces of a dog carrying 
E. granulosus.  This very healthy child has a very good immune system which
permits only slow growth of the hydatid.  The child grows up to the 
ripe old age of say 80 (with a bowling-ball sized hydatid cyst) and 
collapses from exhaustion one day in the woods.  Then a hungry wolf
comes along and has dinner and the larval worms become adult
E. granulosus in the intestines of the wolf.  Let's say it's just a pup
wolf too with an expected life-span of say 15 years.  Assuming 
senescence is not a factor in cestodes (doesn't seem to be) this worm
could live a grand total of 95 years, limited only by the life-span of
its intermediate and definitive hosts.

So you see it is a very complex question you have asked.
I would recommend that you have a look at some good intro parasitology
texts to get a feel for the complexity of life-cycles and life-history
stages in cestodes.

Cheers,
Mark
-- 
Mark E. Siddall                "I don't mind a parasite...
mes at vims.edu                    I object to a cut-rate one" 
Virginia Inst. Marine Sci.                     - Rick
Gloucester Point, VA, 23062



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