in article , at
wrote on 5/16/04 11:15 PM:

look up black spot disease of fish, among other diseases carried by snails.
more
diseases are known in humans, a more intense area of scientific investigation.
Ingrid


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Solve the problem, dont waste energy finding who's to blame
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Unfortunately, I receive no money, gifts, discounts or other
compensation for all the damn work I do, nor for any of the
endorsements or recommendations I make.
Here's what I found at
http://www.biosci.ohio-state.edu/~pa.../uvulifer.html

"Several members of this genus cause "black spot" in fish --- the best known
species is Uvulifer ambloplitis.* The life cycles of most members of this
genus are similar.* The definitive host is most often a bird, and the
parasite's eggs are passed in the bird's feces.* The first intermediate host
is a snail, and the second intermediate host is a fish.* The fish is
infected when cercariae penetrate the skin.* The cercariae lose their tails
and transform into a stage called the "neascus larva" or "neascus
metacercaria."* The definitive host is infected when it eats an infected
second intermediate host.

These encysted metacercariae often turn black and are visible on the fish's
surface -- hence, "black spot" in fish.* Heavily infected fish are often
discarded by fishermen, although they pose no threat of infection to
humans."

So, the life cycle goes snails eat eggs from bird poop, snails pass the
parasite on to fish, and fish are eaten by birds completing the cycle.

Snails that are wild-caught, or raised in situations where they may get
access to bird poop (outdoor culture ponds, etc.) can pick up the parasites
and pass them on to fish, while snails that have no access to bird poop,
that have lived for generations inside various aquariums, can't pass on the
parasites.

Because I keep snails, I have done google-research (research lite) on a
number of different parasites that snails can carry and pass on to fish and
humans. What I have found over and over is that only snails that live
outdoors pick up these parasites. Snails cannot give these parasites to
each other, and the parasites I have researched do not get passed on in the
snails' eggs.

An uninfected snail can not pass on these parasites. So while it would be a
good idea to keep snails out of your outdoor ponds so as to interrupt the
potential parasite life cycle, in an aquarium the life cycle is already
interrupted, due to the lack of birds.

You always need to know your sources of plants and animals. It would make
sense to treat any new plant you got in a 10 mg/liter potassium permanganate
solution to kill any snails or snail eggs especially since you don't want
them. And if you got any snails that you wanted it would make sense to know
their source & history, and quarantine them for awhile like any other new
addition knowing that they could potentially be a source of problems. In
snails with a fast life cycle it makes sense to culture them separately and
only introduce the young to your aquarium.

That said, after more than 20 years of keeping many various species of
snails, aquarium cultured and wild caught, I have never seen any of these
parasites in my fish.
--
Chris