Aquatic Animal Health Subprogram: Bonamiasis in farmed Native Oysters (Ostrea angasi)
Bonamia ostreae and Bonamia exitiosa are significant pathogens of oysters that cause high mortality rates and substantial economic losses to the oyster farming industry globally. As such, both pathogens are listed by the OIE (the World Organisation for Animal Health). In Australia, infection by a Bonamia sp. was responsible for the devastation of experimental aquaculture of the Native Oyster Ostrea angasi and adjacent wild beds in Victoria in the early 1990s. Indeed, surveys have found Bonamia sp. in Native Oysters in Tasmania, WA, and NSW and recent monitoring of apparently healthy stock on Victorian aquaculture sites has determined that prevalence of this Bonamia sp. is high and once again is causing clinical disease. While the pathogen was identified as Bonamia sp. its relationship to the OIE-listed species, B. ostreae and B. exitiosa, is unclear. It is important to determine the identification of the Australian Bonamia to species level, to establish whether or not it is the presumed exotic species B. ostreae, B. exitiosa, or a different species endemic to Australia. Identification of the Australian species will clarify Australia’s international obligations as a member country to the OIE, with respect to reporting and international trade. Moreover, the conditions that trigger clinical disease are unknown. Identification of the risk factors associated with the onset of disease in infected oysters is needed to implement control strategies to minimise the impact on production and industry value. This information is essential for the development of improved biosecurity and farming practices that mitigate against disease caused by Bonamia and provide industry and regulators with management and control strategies.
1. Obtain nucleic acid sequence and compare with other, described Bonamia sp. and determine their taxonomic relationship and ensure that available diagnostic tools are suitable.
2. Improve understanding of Bonamiasis infestations in Native Oysters including the determination, under controlled conditions, of the stressors that induce clinical disease in sub - clinically infected oysters.
3. Develop a biosecurity plan and farm management practices to manage the risk of infestation and the mitigation of clinical infection with Bonamia sp.