Diseases of fish, caused by biological agents (bacteria, fungi, virus or
parasites), are better known in farmed or ornamental fish, since the access to the
affected fish coming from the natural environment is less probable. In fact, the fish that
are infected by a specific pathogenic agent, natural inhabitants of the marine, estuarine
or freshwater ecosystems, are rapidly eliminated from its biotopes by other predatory
animals, due to its higher vulnerability and susceptibility to the social interactions.
Diffusion of pathogenic bacteria, fungi, virus or parasites in the aquatic environments is
more efficient than in the terrestrial ones. Diagnosis and therapeutics of fish disease
have specific difficulties and the application of preventive measures is a very complex
issue. Some of those diseases have the same epidemiological problems of the infectious
diseases of the terrestrial animals: High spread of diffusion, very significant economic
losses, restrictions to fish travel or commerce and some (few) have zoonotic impacts.
Keywords: Diagnosis of fish disease, Disease of fish, Health status of fish farms,
Icthyopathology, International sanitary certification.
