White Syndrome in Acropora muricata: Non-specific bacterial infection and ciliate histophagy

Selective antibiotic treatment of White Syndrome (WS)-affected corals (Acropora muricata) from Fiji was used to identify 3 potential bacterial pathogens of the disease. Interestingly, the suite of bacterial associates of the disease was different to that recently identified using identical primer sets for WS on the GBR and in the Solomon Islands. In addition to the three bacterial pathogenic candidates and as previously shown for WS and more recently for White Band Disease (WBD) in the Caribbean, all samples of the disease were specifically associated with the histophagous ciliate Philaster lucinda. From the pattern of disease progression and histopathology in relation to the selective elimination of microbial groups, we conclude that these ‘white’ diseases are a result of a non-specific bacterial infection and a ‘secondary’ infection by the P. lucinda ciliate. Although we have not observed the initiation of infection, a non-specific, multi-species bacterial infection appears to be a co...