Candidatus Xenohaliotis californiensis and Haplosporidium montforti associated with mortalities of abalone Haliotis tuberculata cultured in Europe

Haliotis tuberculata experimentally grown in Galicia (NW Spain) and originated from Ireland began to experience mortalities during the late spring of 2004. Diseased abalone presented dark foot pigmentation, loss of surface adherence and limited ability for right themselves after they were set on their backs. Histopathological analyses showed the presence of Candidatus Xenohaliotis californiensis, a bacterial pathogen from the family Rickettsiaceae, in the gastrointestinal epithelial cells of diseased abalone. To our knowledge, this is the first report of Candidatus Xenohaliotis californiensis in H. tuberculata cultured in Europe. The presence of several stages of development of a new protozoan parasite belonging to the phylum Haplosporidia, Haplosporidium montforti, described by us in a separate paper, was also detected in the connective tissue of gill, digestive gland and foot muscle. Complete mortality (100% of the stock) was reached during spring and summer. PCR analyses showed that these two pathogens were already present in juveniles from Ireland before their introduction in Galician waters. Juveniles imported from France were also infected with both pathogens. In adult abalone collected from natural beds of the surroundings of the aquaculture facilities, only the pathogen Candidatus Xenohaliotis californiensis was detected by PCR, but not by histology.