Southern hemisphere mollusc diseases and an overview of associated risk assessment problems

In Australia and New Zealand, Bonamia sp. causes epizootics in flat oysters (Tiostrea chilensis, Ostrea angasi); Marteilia sydneyi and Mikrocytos roughleyi cause mortality in farmed rock oysters (Saccostrea commercialis); and Perkinsus olseni is pathogenic in abalone (Haliotis spp.). Marteilia lengehi, Marteilioides branchialis, other Marteilioides spp. and two species of Haplosporidium are regarded as potential pathogens. A review of the pathogens causing diseases listed in the Office International des Epizooties 'notifiable diseases' of molluscs shows major gaps in the information available. The life cycles and transmission of Haplosporidium nelsoni and Marteilia refringens are unknown, Bonamia spp. and Mikrocytos spp. cannot be diagnosed with certainty, monoclonal antibodies and molecular probes are not generally available, and little is known of survival parameters or treatment of the pathogens. The author concludes that stringent guidelines and protocols are needed to minimise the high risks involved in translocation of molluscs.