Potential resistance of a number of populations of the oyster Ostrea edulis to the parasite Bonamia ostreae

The study investigated the susceptibility of a number of European populations of Ostrea edulis to the protistan parasite Bonamia ostreae. The study was carried out at oyster-growing regions in three European countries where Bonamia is endemic. The oyster populations screened during the trial were either: naïve populations, which had never previously been exposed to the parasite; populations of oysters, which had been exposed to the parasite for a number of years and where no management of the population to try to reduce infection had occurred; and an infected population, where selective breeding has taken place to try to reduce susceptibility to the parasite. Results of the study indicated that this latter population 'Rossmore' performed significantly better in some trials than the other populations in terms of prevalence and intensity of infection. Another population from Lake Grevelingen performed best in one trial when cumulative mortality rates were compared.