William H Wildgoose MRCVS
Pet fish vet
Dermocystidium
This uncommon parasitic organism causes skin diseases in a few species of pet fish. The lesions vary in appearance but are mainly small swellings that enlarge slowly and burst, exposing white thread-like tubules packed with microscopic spores. In koi, the disease occurs mainly in spring, and the swellings grow to about 1cm in size in a few weeks. There is no effective treatment and once burst, the lesions usually heal on their own. Occasionally, they may need to be removed surgically. Click here for a case report.
This lesion on the tail of a koi is starting to burst and expose the thread-like tubules
This swelling on the front (pectoral) fin has burst, exposing the tubules, which are visible under water
Early skin lesions in cardinal tetras are small and often look like a clear blister or are pale and opaque as seen between the eyes of this tetra
This lesion on the tail of a koi is starting to burst and expose the thread-like tubules