Pieter T. J. Johnson et al have a new paper in PNAS Aquatic eutrophication promotes pathogenic infection in amphibians.

That shows how nutrient runoff from agriculture increase algal growth, which in turn leads to increases in snail populations that host parastites.  These parasites can then infect and deformed  frogs. What is particularly important is eutrophication, which is expected to increase with increased agricultural production, could enhance the spread of other diseases that harm people as well as wildlife.  The authors write:

Our results have broad applicability to other multihost parasites and their hosts. Recent increases in a variety of human and wildlife multihost parasites have been linked to eutrophication, including cholera, salmonid whirling disease, West Nile virus, coral diseases, and malaria.

Trematode parasites similar to Ribeiroia that use snails as intermediate hosts also infect humans, ranging from the nuisance, but relatively innocuous, cercarial dermatitis to the pathogenic schistosomiasis, which is estimated to afflict 200 million people across Africa and Asia.  If the life cycles of Schistosoma spp. are similarly affected by eutrophication, forecasted increases in agricultural nutrient applications in developing countries where schistosomiasis is endemic could hinder or inhibit efforts to control this disease.

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