When a disease is suspected, it is important to correctly diagnose as soon as possible.
Suspicion of a disease can be revealed during routine health controls, through unusual fish behaviour or through high fish mortality.
National laws for aquaculture demand immediate health control when a disease is suspected. The cause must be determined as long as it is unclear that the mortality is not caused by disease. Authorized fish health personnel must perform this health control.
Diagnosis is based on multiple sampling of the fish and visual evaluation of the fish:
- Bacteriology – determination of fish pathogen bacteria causing disease
- Histology – histopathological determination of tissue changes
- PCR – determination of agents causing disease
- Microscopy and stereo magnifier – determination of parasites
- Visual methods / scoring to estimate extent of different conditions