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Mầm bệnh Một người nước ngoài của Waters Hàu ở Mỹ trong đầu mùa hè năm 1960, tôi cam lần đầu tiên cho phòng thí nghiệm sinh học Oxford trên bờ Đông của Maryland. Như một phòng thí nghiệm nghiên cứu động vật có vỏ mới của Dịch vụ Thủy sản Quốc gia biển, nó đã được đối mặt trong năm của tôi Trước khi đến với tỉ lệ chết cao của hàu Rõ ràng do một căn bệnh không rõ nguồn gốc | 8 Biological Pollution Invasions by Alien Species An Alien Pathogen of Oysters in American Waters In early summer of 1960 1 came for the first time to the Oxford Biological Laboratory on Maryland s Eastern Shore. As a new shellfish research laboratory of the National Marine Fisheries Service it had been confronted in the year before my arrival with high mortalities of oysters due apparently to a disease of unknown origin. Oysters of the Middle Atlantic region had died in great numbers beginning in 1957 in Delaware Bay and in 1959 in Chesapeake Bay and production had declined precipitously. The laboratory s programs were being reoriented to develop information about the cause. During the 1960s and 1970s staff members worked full-time on the problem as did research scientists at several state and university laboratories in the Middle Atlantic area. The pathogen a protozoan named Haplosporidium nelsoni and its life cycle were described as were some controlling environmental factors especially salinity and temperature but the origin of the disease agent and its method of natural transmission remained a mystery for many years thereafter. Impact of the disease varied annually with periods of severe mortalities and intervals of decreased prevalence and less severe effects. Today the pathogen is still present and is still killing oysters. Research has continued but at reduced intensity except at the Haskin Laboratory of Rutgers University and at the Virginia Institute of Marine Science where major programs have continued to the present emphasizing attempts to develop disease-resistant stocks. Knowledge about the possible origin of H. nelsoni was finally achieved during the late 1990s Burreson Stokes Friedman 2000 using newly developed genetic techniques. Its genetic makeup was found to be almost completely comparable to that of a rare parasitic organismfound in Japanese oysters which had been grown on the Pacific coast of North America since early in the 20th century and .
