DescriptionPerkinsus marinus is the protozoan endoparasite of the Eastern oyster (Crassostrea virginica) responsible for Dermo disease. While not harmful to humans, Dermo disease causes extensive oyster mortality, increasing annual natural mortality from 10 to 35% or more in Delaware Bay annually. The disease spreads through the water as parasites are shed from infected and moribund hosts. One prior study has indicated that scavengers may spread the parasite to new hosts, but little information exists as to how such trophic interactions affect host-parasite dynamics. From July 2010 to September 2011, uninfected, or specific-pathogen free (SPF) oyster hosts were exposed in the laboratory to four different species of scavengers feeding on infected or uninfected oyster tissue. In each experiment, the accumulation of P. marinus in oyster hosts was compared after 1-2 months as a measure of parasite transmission. Results indicated that scavengers, regardless of species, increase the rate of parasite transmission to new hosts when compared to passive shedding of parasites from infected tissue alone. These laboratory studies demonstrate that non-host organisms for the parasite have their own sets of interactions that can influence disease dynamics, and such interactions should be taken into consideration in future studies where transmission dynamics come into play.