Scuticociliate (Philasterides dicentrarchi) infection cluster in a multispecies marine aquarium system

Scuticociliatosis, caused by ciliated protozoa of the subclass Scuticociliatia, has been associated with high mortalities in marine fish. Environmental factors such as an increase in water temperature can enhance this disease. The aim of the present report is to describe the occurrence of a cluster of cases of scuticociliatosis in a multispecies marine cold-water system in a public aquarium. Philasterides dicentrarchi was identified by PCR in formalin-fixed tissues of some of the fish showing meningitis or meningoencephalitis, dermatitis and myositis with intralesional protozoa. An increase in water temperature of approximately 2°C was identified as a potential contributing factor for this cluster of infections. Higher temperature may have enhanced the propagation or pathogenicity of scuticociliates or increased host susceptibility of some species of fish, especially wolf-eel Anarrhichthys ocellatus and spotted ratfish Hydrolagus colliei. This report also highlights the complexity of dealing with mixed species systems housing fish from different natural ecozones.