Growing concern over amphibian declines and deformities have caused enhanced interest in the effects of parasites and disease on amphibian populations. The Johnson Lab at the University of Colorado, Boulder, explores the effects of macroparasite infections on frogs, toads, and salamanders.  These include flatworms (trematodes), roundworms (nematodes), tapeworms (cestodes), spiny-headed worms (acanthocephalans), and various ectoparasites. We are particularly interested in the effects of Ribeiroia spp. infection on amphibians. Field surveys and  experiments have established that infection by the trematode Ribeiroia ondatrae causes severe limb malformations and increased mortality in a variety of amphibian species. These malformations are suspected to increase the likelihood infected frogs fall prey to predators, which can increase the parasite’s transmission when such predators are suitable definitive hosts (such as waterbirds). Whether malformations can contribute to amphibian declines, and why deformities in amphibians appear to be increasing, remain open questions.