Examination of the slides, performed decades later, revealed an epizootic of Haplosporidium
nelson in eastern oysters, Crassostrea virginica (Haskin and Ford, 1979; Allen Jr.
By 2006, this 54-yr record covered a number of unique periods, including the period of time after the onset of MSX, a disease caused by the protozoan Haplosporidium
nelsoni, circa 1957 (Haskin and Andrews, 1988; Ford, 1997) and the period after the onset of Dermo, a disease caused by the protozoan Perkinsus marinus, circa 1990 (Ford, 1996; Cook et al.
A third "Dark Age" began for the oyster industry in the late 1950's when a new disease, later named MSX aid caused by the Haplosporidium
nelsoni parasite, began to kill huge quantities of oysters in Delaware and Chesapeake Bays.
Infection and mortality patterns in strains of oysters Crassostrea virgininca selected for resistance to the parasite Haplosporidium
Unfortunately, for managing oyster populations, obstacles exist in meeting this objective because oyster populations do not appear to be inherently equilibrious, particularly those subjected to MSX, a disease caused by the protozoan Haplosporidium
nelsoni, or Dermo, a disease caused by the protozoan Perkinsus marinus.
2008), Denman Island disease of the European oyster (Ostrea edulis) (Gagne 2008), and two diseases, Haplosporidium
nelsoni (or multinucleated sphere unknown, or MSX) and Perkinsus marinus, in the eastern oyster (Crassostrea virginica) (Burreson et al.
ABSTRACT A selective breeding program for Crassostrea virginica was established in 1997 as part of an initiative in Virginia to address declining oyster harvests caused by the two oyster pathogens Haplosporidium
nelsoni (MSX) and Perkinsus marinus (Dermo).
KEY WORDS: eastern oyster, Crassostrea virginica, fecundity, Perkinsus marinus, Haplosporidium
Most predators are inactive during winter (Carriker 1955, Gunter 1979, Eggleston 1990), and oyster diseases such as Dermo (causative agent Perkinsus marinus) and MSX (causative agent Haplosporidium
nelsoni) are in remission during the winter months (Ragone Calvo & Burreson 1994, Powell et al.
nelsoni (MSX) on Delaware Bay seed oyster beds: a host parasite relationship along a salinity gradient.
In addition, artificial selection for 4 generations based on survival, growth, and disease susceptibility has produced a strain with dual resistance to the parasites Haplosporidium