Grants and Contracts Details
Project Summary. Many amphibian declines have been attributed to emergent infectious diseases, but little is known about how diseases emerge. The goal of this proposed work is to identify factors that contribute to the emergence of amphibian diseases using amphibians and parasites endemic to Kentucky. The focal disease organisms are the parasitic digenetic trematodes Ribeiroia ondatrae and Echinostoma trivo/vis. They are transmitted from snails to amphibians and induce limb deformities and kidney damage, respectively, that have been associated with extensive amphibian mortality. The underlying hypothesis is that stressors can interact synergistically to increase trematode transmission and virulence (parasite-induced lethality). The specific objectives of this project are to determine how trematode disease properties and amphibian fitness are influenced by 1) the anthropogenic stressors - pesticides and pond drying (associated with global climate change), and 2) the natural stressors - competition and predation. To evaluate the effects of anthropogenic stressors (Exp. 1), we will expose mesocosms consisting of spring-breeding frog tadpoles (Rana pipiens, R sylvatica, Bufo americanus) and R ondatrae- and E. trivolvis-infected snails to two hydroperiods (dry-down or constant water level) crossed by eight ecologically-relevant pesticide treatments (water and solvent control, atrazine: 3, 30, 300 /lg/L, endosulfan: 2, 20, 200 /lg/L). To assess the influence of natural stressors (Exp. 2), two species of tadpoles, half infected with trematodes and half left un infected, will be reared under two densities in the presence and absence of caged predators. Half the un infected tadpoles will be exposed to trematode cercariae at the end of the experiment to assess the influence of treatments on trematode transmission. In both experiments, parasite transmission, pathogenicity (parasite-induced debilitation) and virulence and various snail and frog traits (such as growth, behavior, and survival) will be quantified.
|Effective start/end date||5/1/04 → 4/30/05|
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