The goal of this project was to investigate the cause of oyster oedema disease (OOD) in Australian pearl oysters so that diagnostic tests and management practices for the disease can be developed. OOD has been associated with mortalities in some pearl oyster farming areas. However, the cause of these mortalities has remained unknown, hampering efforts to study the disease and develop effective control strategies. The project described in this report was conducted by researchers from Macquarie University, Fisheries Western Australia and the New Zealand Ministry for Primary Industries (Manatū Ahu Matua), working in collaboration with the Australian Pearl Producers Association and the Australian pearling industry. We compared OOD-affected oysters with healthy control oysters to identify any genetic material in the OOD-affected oysters that might come from an infectious agent such as a virus, bacteria or parasite. Our logic was, if OOD is caused by an infectious agent, genetic material (cDNA nucleotide sequences) from that infectious agent should be far more abundant in OOD-affected oysters than in healthy controls. That genetic material would act as a fingerprint for the disease and may provide information about its cause. We found clear differences between the nucleotide sequences present in oysters affected by OOD when compared to healthy controls. A number of nucleotide sequences were strongly associated with OOD and the abundance of some of these sequences was correlated with increasing mortality. None of these nucleotide sequences were closely related to any known infectious agents. However, the strong relationship between these sequences, OOD and mortality means that they may be very useful predictors of mortality. Their lack of resemblance to known infectious agents leaves open the possibility that OOD is not an infectious disease and may have some other cause.
Priscila Goncalves, David Raftos, David Jones, Kelli Anderson, Brian Jones & Michael Snow, 1st February 2017, FRDC Project No 2013/002, Year Fisheries Research and Development Corporation