An investigation into the relative resistance of Irish flat oysters Ostrea edulis L. to the parasite Bonamia ostreae (Pichot et al., 1980)

The parasite Bonamia ostreae has caused significant mortalities in the flat oyster Ostrea edulis. To date, methods of control and eradication have proved largely unsuccessful. Research is now concentrating on development of a population of oysters that has increased resistance to bonamiasis. This study evaluated the relative resistance of three Irish strains of flat oysters to this disease: two naive strains that had not previously been exposed to the parasite, and one that has been exposed to B. ostreae since the 1980s and has been selectively bred from survivors. In both field and laboratory trials, oysters from the selected strain showed lower prevalence of infection, intensity of infection and mortalities compared to the two naive strains. Development of a strain showing some resistance to B. ostreae would allow oysters to be grown to market size before significant mortalities occurred, and would also allow restocking of areas that have been decimated by the disease.