Effects Of Perkinsus marinus Infection In The Eastern Oyster, Crassostrea virginica: I. Susceptibility Of Native And Msx-Resistant Stocks

A selective breeding program was implemented to attempt to decrease the disease susceptibility of the eastern oyster, Crassostrea virginica, to Perkinsus marinus. Six oyster strains were spawned and the progeny exposed to Haplosporidium nelsoni (MSX) and P. marinus in the lower Chesapeake Bay. Three strains, a Delaware Bay MSX-resistant strain, a Delaware Bay native strain, and a Mobjack Bay native strain (lower Chesapeake Bay) were exposed for three years (1988-90); three other strains, a separate Delaware Bay MSX-resistant strain, a lower James River native strain (lower Chesapeake Bay) and a susceptible control strain, were exposed for two years (1989-90). During the study period, P. marinus abundance was high and increased each year; H. nelson/ abundance was low and decreased each year. Both strains of MSX-resistant oysters developed by Rutgers University were highly susceptible to P. marinus. Cumulative mortality at the end of the study was 99% for both strains and growth virtually stopped after acquisition of P. marinus. Mean shell height did not reach market size in either MSX-resistant strain. All native strains (Delaware Bay, Mobjack Bay and James River) had about 80% cumulative mortality, mainly from P. marinus, but the Mobjack Bay strain also experienced moderate mortality from H. nelson/. However, these strains continued growing and survivors reached market size during the study period. The MSX-resistant strains offer little immediate benefit in a selective breeding program for the Chesapeake Bay oyster industry because of their high susceptibility to P. marinus and poor growth; however, they may be valuable, especially in crosses with native strains, during periods of H. nelson/ resurgence and P. marinus decline. The three native strains performed better than the resistant strains and will be utilized, both as direct lines and as intraspecific hybrids, in a continuing selective breeding program to decrease the disease susceptibility of C. virgin/ca stocks

Use of immunoassays in haplosporidan life cycle studies

The development of mitigating measures for the major oyster diseases has been hindered by our poor understanding of the life cycles of the pathogens. Evidence from epidemiological studies and transmission experiments suggests that an intermediate host is present in the life cycle of Haplosporidium species. Immunoassay is a valuable tool for identifying parasite antigen in an intermediate host, and, because of the potential for stage-specific antigens, assays incorporating polyclonal antibodies may be more effective than assays incorporating monoclonal antibodies. Rabbit antibody against purified spores of Haplosporidium costale recognized spores in paraffin sections of oyster tissue , but the antibody did not recognize plasmodia of H. costale.https://scholarworks.wm.edu/vimsbooks/1121/thumbnail.jp

Emerging areas of research reported during the CDC National Conference on Pfiesteria: From biology to public health

Since its identification in 1996, the marine dinoflagellate Pfiesteria piscicida Steidinger & Burkholder has been the focus of intense scientific inquiry in disciplines ranging from estuarine ecology to epidemiology and from molecular biology to public health. Despite these research efforts, the extent of human exposure and the degree of human illness directly associated with Pfiesteria is still in the process of being defined. Unfortunately, during this same time Pfiesteria has also stimulated media coverage that in some instances jumped ahead of the science to conclude that Pfiesteria presents a widespread threat to human health. Political and economic forces also came into play when the tourism and seafood industries were adversely impacted by rumors of toxin-laden water in estuaries along the east coast of the United States. Amid this climate of evolving science and public concern, Pfiesteria has emerged as a highly controversial public health issue. In October 2000 Centers for Disease Control and Prevention sponsored the National Conference on Pfiesteria: From Biology to Public Health to bring together Pfiesteria researchers from many disparate disciplines. The goal of this meeting was to describe the state of the science and identify directions for future research. In preparation for the conference an expert peer-review panel was commissioned to review the existing literature and identify research gaps; the summary of their review is published in this monograph. During the meeting primary Pfiesteria researchers presented previously unpublished results. The majority of those presentations are included as peer-reviewed articles in this monograph. The discussion portion of the conference focused upon researcher-identified research gaps. This article details the discussion segments of the conference and makes reference to the presentations as it describes emerging areas of Pfiesteria research

Status of the Major Oyster Diseases in Virginia 2004 A Summary of the Annual Monitoring Program

2004 was the second very wet year in a row. While rainfall and streamflows were normal in winter and early spring, and just slightly above average during the summer, the fall of 2004 was nearly as wet as the year before. Salinities were again depressed throughout the lower Bay. Water temperatures were below normal during the winter, but typical otherwise. Low salinities and, in the winter, temperatures brought continued abatement in the oyster diseases caused by Perkinsus marinus (Dermo) and Haplosporidium nelsoni (MSX). Among quarterly James River Survey sites, maximum annual P. marinus prevalences were the lowest they had been since before 1992. In summer and fall, when P. marinus is normally most prevalent, it was found in a maximum of 68% of oysters at Wreck Shoal and in no more than 20% of the oysters anywhere else. Advanced infections were rare, and limited to Wreck Shoal. H. nelsoni was found in a single oyster, at Wreck Shoal in July