> As for mollusks, it appears that the human institution of slavery drove the
> introduction of schistosomiasis from Africa to South America. A bit of a
> stretch of Doug's  definition, but certainly affecting both Homo sapiens
> populations and Biomphalaria spp. (Gastropoda: Eupulmonata: Planorbidae)
> that had never experienced the infection <
> http://www.plosntds.org/article/info%3Adoi%2F10.1371%2Fjournal.pntd.0000071

Additional human actions relating to scistosomiasis include the
introduction of Old World monkeys (alternate schistosome hosts) to
certain Caribbean islands, creating warmer habitats (whether generally
through global warming or localized warm water such as nuclear power
plants cooling systems) that enable Biomphalaria to expand its range,
creating impoundments (such as the Three Gorges dam) that produce
habitats more conducive to schistosome hosts and less conducive to
some of their competitors, and overfishing mollusk-eating fish that
would normally control the schistosome host.  Ironically, one example
of that relates to malaria control efforts.  People in parts of Africa
have taken the netting distributed for mosquito protection and used
them for fishing.  This is a much finer net than the average make it
yourself by hand from natural fiber net, and rather more suited for
thoroughy depleting the local fish population down through much
smaller species and individuals.

A minimally mollusk-related example comes from birdfeeders.  Some bird
diseases are linked to feeders-not cleaning the feeders allows
pathogens to accumulate (particularly given that the inceased bird
concentration likely ties to increased fecal concentration); drawing
more birds together facilitates disease transmission; providing
handouts enables sick birds to survive longer and keep spreading
germs.

West Nile affects humans, but much more severely impacts a number of
wild animals.  These have indirect mollusk tie-ins, since birds are
important predators of mollusks.

General disruption of food chains affects pathogens as well.
Increasing incidence of tick-borne illness in North America reflects
deer overpopulation due to human-caused lack of predators; deer
overpopulation produces overgrazong and harm to habitats, which will
impact the land snails.

Apparent examples of pathogens affecting freshwater mussels have been
observed, but I don't know that they have been adequately
characterized.

Parasites wiped out at least one of the captive breeding populations
of partulid snails.

--
Dr. David Campbell
Visiting Professor
Department of Natural Sciences
Gardner-Webb University
Boiling Springs NC 28017

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