Experimental transmission of Myxidium leei in gilt head sea bream Sparus aurata

Myxidium leei was experimentally transmitted to juvenile gilt head sea bream Sparus aurata. The parasite was conveyed to specific-pathogen-free fish which were cohabiting with diseased brood stock or exposed to water effluent from a tank of diseased fish. In both cases, the hindgut of approximately one third of the test fish were infected after 9 weeks. No parasite stages were found in the blood, spleen, kidney, liver or gills of any of the infected fish. Sloughed off gut mucosa fragments infected with M. leei shed by diseased brood stock were identified as significant in the transmission of the disease. While it seems likely that the gut mucosa is the primary tissue invaded by the infective stage, future work on M. leei will focus on the identification of this infective stage and mode of host entry.