Etude des recentes epizooties de l'huitre plate Ostrea Edulis Linne et de leur impact sur l'ostreiculture bretonne

The study concerns two previously unseen Protozoa, Marteilia refringens and Bonamia ostreae, responsible for epizootics in the flat oyster, Ostrea edulis L. The epizootiological aspect, the impact of diseases on Breton oyster farming and the research for appropriate prophylaxes is addressed. The morphology, the ultrastructure and certain phases of the growth cycle are described for the two parasites, as well as their cyto- and histopathogenic effects. The epizootiology explains the evolution of the diseases in space and time, their conditions for propagating, the sensitivity of the parasites and the receptivity of various test hosts. A summary analysis of Breton oyster farming before and during the epizootic is done. It makes it possible to judge the impact of these diseases on the Breton oyster-farming economy and the changes to farming that they caused. A discussion is begun on research and the conditions for applying plans for prophylaxes adapted to the marine environment. The first results are given.