Dear Andrew et al;-
    Wonderful responce, Andy. You do good thinking. I was not asking about
marine transmited deseases in the human sense, but more in the snail-to-snail
sense. What I was really thinking of was the waves of Janthina that sometimes
wind up on almost any shore. And those shores might be homes of terrestrial
snail populations. Mangroves not only come down to the water but in it. And
snails live in Mangroves. So, in that case, desease bacteria doesn't even have
to climb the beach sands.
    Andy, you were the only one to reply to the question. Guess I'll have to
make it simpler in the future.
        Q-Man

Andrew Rindsberg wrote:

> Dear Art et al.,
>
> You asked, "Is there any mechanism that prevents marine creatures from
> transmitting diseases?"
>
> Well, yes and no. This is another of these very large topics, and I just
> know a bit here and there from courses in geochemistry and years of reading
> Discover magazine, but you are welcome to them:
>
> Some of the ions that occur naturally in seawater (e.g., iodate ion) are
> toxic to many bacteria. So pure seawater is not only relatively free of
> bacteria, but may even kill some of the bacteria on the surface of your
> skin. And sewage discharged into seawater is not as dangerous as sewage put
> into rivers, because kinds of the bacteria are quickly killed. Also,
> bacteria are generally concentrated along surfaces, such as the outer
> surfaces of sand grains, clay particles, and living organisms. They may be
> present in great abundance there.
>
> Most bacteria, from any environment including the marine realm, are not
> dangerous to human beings. They wouldn't know what to do with your flesh if
> you offered it to them, Art, since they are very simple and have very
> particular preferences. Most soil bacteria will not even grow properly in
> agar-agar, the biologists' preferred medium. Also, your body can
> successfully fight off most microbes without trying hard. Otherwise people
> would be dying of all kinds of weird diseases all the time, since microbes
> are everywhere.
>
> The diseases that tend to be transmitted most readily are those that affect
> related species. Diseases of sheep may be quite dangerous to goats, not as
> dangerous to horses, even less dangerous to birds, and not at all dangerous
> to snails. Shared diseases and parasites form some of the best evidence for
> shared ancestry. Complications arise in cases where diseases mutate and hop
> from species to species (for instance, there is good evidence that humans
> acquire new strains of influenza from domestic ducks and chickens). Life
> also gets interesting in cases where the normal life cycle of parasites
> includes stages that live in different animals, such as freshwater snails
> and mammals. Nature is full of special cases, but let's stick to the big
> picture for now.
>
> It's currently thought that humans have been acquiring some new and very
> dangerous diseases from other mammals. We didn't have a lot of contact with
> them before, but now there are more people living in the rain forests, and
> they hunt for "bush meat" and also for specimens for labs and zoos. HIV
> seems to be derived from primates. Mad cow disease apparently originated in
> sheep. We don't know what animal harbors Ebola virus in nature. People in
> medical circles are getting increasingly uneasy about using medical products
> derived from people and other animals for this reason. That millionth
> transfusion or transplant could have some nasty surprises in it!
>
> Anyway. Compare this with handling marine snails and clams. Although
> handling living mollusks certainly means contacting their parasites and
> bacteria and viruses too, the risk of disease is very low. Most microbes and
> parasites living in mollusks would not be able to invade a human body and
> thrive there. Some might cause problems from sheer toxicity, e.g., red tide.
> The risk is somewhat greater from handling marine fish (especially from
> eating raw fish), but fish are not very closely related to us and even that
> risk is low. The risk from domestic animals -- and in some cases from land
> and freshwater snails -- is much higher for us than from marine creatures.
>
> Andrew K. Rindsberg
> Geological Survey of Alabama