Bonamia exitiosa: the cause of bonamiasis in native oysters Ostrea angasi in Australia in 2015.

Bonamiasis, caused by haplosporidian parasites Bonamia spp., is an infectious disease prevalent in 'flat' oysters internationally. Bonamia was first detected in Australian native oysters Ostrea angasi in Victorian waters in the early 1990s and caused mass mortalities in this pilot industry. The species identity of Bonamia at that time was unclear and no attempts were made to unequivocally resolve it. Interest in O. angasi culture was renewed in 2010 alongside a small-scale bonamiasis surveillance programme, given previous experience with the parasite. Basic data on culture methods, epidemiology and pathology are presented from 2011 until the epizootic that destroyed most of the stock at the major aquaculture site in 2015. At that time, a comprehensive phylogenetic analysis of the relationship between the cause of this epizootic and other Bonamia spp. internationally demonstrated >98% homology to B. exitiosa. Moreover, the report on Perkinsus olseni is the first in O. angasi. The presumed incidental finding of the more recently identified P. beihaiensis is the first for any mollusc species in Australia.