Recent Studies in the United States on Parasites and Pathogens of Marine Mollusks With Emphasis on Diseases of the American Oyster, Crassostrea virginica Gmelin
Morphological, systematic, faunal, and life cycle studies predominated research on marine parasites and pathogens in the United States before World War II. Much was primarily basic or academic in nature. Since then it has grown and diversified under pressure of efforts to: 1) Increase yields of invertebrate-based fisheries, in nature and under controlled conditions; and 2) understand, protect, and improve the resources, estuarine and marine environments, and human health and welfare. Over the last 30 yr pathobiological investigations of economically and ecologically Important marine Invertebrates have broadened into submicroscopical anatomy (TEM and SEM techniques), physiology, immunology, genetics, host-parasite ecology, interactions between environmental pollution and disease, and prophylaxis and treatment of their diseases. Importation of foreign oysters (and other shellfish species) and their transfer and transplantation between the coastal regions, provinces, and states of North America have resulted in growing disease problems and a corresponding interest in the parasitology and pathology of the mollusks involved. It has also spawned efforts to control introductions and transfers. Two major diseases have been found to interfere with production of native Atlantic oysters along the Gulf and or Atlantic coasts of the United States. These are the "Dermo" or "fungus" disease, caused by the apicomplexan protistan Perkinsus marinus (both coasts) and "MSX" or Delaware Bay disease, caused by the sporozoan Haplosporidium nelsoni (the Atlantic coast-prlncipally in Chesapeake and Delaware Bays). Knowledge of these important epizootic-producing diseases is reviewed and discussed, along with that of other parasites and pathogens of molluskan shellfish in North America, and an extensive References section of the results of recent research on molluskan parasites and diseases is presented.