An Ecological Approach to Understanding Host-Pathogen-Environment Interactions: the Case of Brown Ring Disease in Clams

International audienceBrown Ring Disease (BRD) is used as a case study to describe an ecological approach to understanding host-pathogen interactions. BRD is caused by a bacterial microparasite, Vibrio tapetis, which elicits the inhibition of the calcification process. Epidemiological studies of BRD are facilitated by the use of characteristic clinic signs on the inner surface of the valves. The phenology and dynamics of BRD are then described by coupling epidemiological, ecological and physiological data. Spatial distribution of BRD prevalence in natural clam populations and V. tapetis load in the sediment allows the investigation of the transmission mode of this pathogen. Experimental testing of different transmission modes has demonstrated the predominant role of feces and pseudofeces in V. tapetis transmission and diffusion processes. Some other hosts can harbor V. tapetis, including reservoir species such as cockles but also vertebrate predators such as fishes, and cross-species transmission could potentially play a major role in dispersion of the pathogen during its life cycle. Environmental factors such as temperature, salinity and nutrients strongly modulate the coevolution between Vibrio and bivalve