Les résultats acquis en matière de pathologie des huîtres concernaient jusqu'à une date récente quelques maladies bactériennes et surtout de nombreuses parasitoses. Pour certaines épizooties graves, comme la maladie de l'huître américaine de Malpèque au Canada, les causes n'ont jamais été déterminées et pour d'autres, comme la mortalité massive de l'huître portugaise en France, les premiers résultats d'ordre étiologique n'ont été obtenus que tardivement avec la mise en évidence d'une infection virale. L'étude ultra-structurale de Marteilia refringens, parasite de l'huître plate, la mise en évidence d'une virose associées à la maladie des branchies de l'huître portugaise, puis la découverte récente de nouveaux germes pathogènes tels que mycoplasmes et rickettsies et l'isolement de virus sur cultures cellulaires chez plusieurs espèces d'huîtres devaient confirmer l'évolution des recherches dans ce domaine.

Until recently, the study of the pathology of oysters concerned some bacterial and a large number of parsitic diseases. Among the latter, diseases caused by fungi such as Labyrinthomyxa marina or by sporozoa such as Minchinia nelsoni in the American oyster have had very important econimic repercussions in the affected areas. The causes of some severe epizooties, such as the "Malpecue Bay disease" in Canada, have never been determined; in other cases, including the mass mortality of the Portuguese oyster in Fance, several years of investigations have been required before the first results of an etiologic nature were obtained. The use of electron microscopy has permitted great strides in the pathology of oysters. Thus, virus diseases have been found to be associated with the diseases of the Portuguse oyster, with gill disease and with the mass mortality of 1970. New and important data have also been obtained with regard to the structure and development of Marteilia refringens a parasite of the flat oyster which has been recognized as belonging to the haplosporidan species. Recently, Mycoplasma-like and Rickettsia-like organisms have been detected in several oyster species and oyster viruses have been isolated on cell cultures. Such results confirm the evolution of research in this field.