Mixed mycobacterial infection in an adult koi carp Cyprinus carpio L.

The koi (Cyprinus carpio var. koi) is a freshwater ornamental carp reared by hobbyists and professionals all over the world. From an adult koi specimen delivered for post-mortem investigations at the Fish Diseases Laboratory of the IZS in NW Italy, we got the opportunity to document a severe case of mycobacteriosis in this fish variety. Necropsy showed the presence of variably sized granulomas that occurred in number of hundreds, agglomerating the hepatopancreas, ovaries and the whole intestinal mass. Mycobacterium chelonae and Mycobacterium abscessus infections were detected from gross lesions by cultural, molecular (PCRRFLP), and histopathological investigations. Some considerations on the presence of this disease in the koi carp are discussed.