Marine nocardiosis is a long-term and problematic bacterial infection of warm-water fish. It eventually presents itself as an underlying debilitating factor in many types of fish. Affected fish often have other concurrent or secondary infections. Nocardiosis begins as a "silent infection", developing undetected for months in fry or juvenile fish. The duration of the infection is a long-term (chronic) phenomenon. Nocardia bacteria multiply slowly within fish tissues before any visual symptoms arise, and certainly before lethargy and death rates increase. The typical outcomes within affected fish populations are: poorly performing yearling and pre-harvest fish, elevated feed conversion rates, and emaciation and rising mortality rates near the end of the summer.
Disease reprinted courtesy of OIE Diagnostic Manual for Aquatic Animal Diseases
, OIE (World Organisation for Animal Health), Paris, France.