Abstract
Background:
Formaldehyde (FA) and oxytetracycline (OTC) arechemicals commonly used in aquaculture to prevent or to treat fish’s diseases due to protozoa, parasites and bacteria.
Aim:
The goal of the present study is to assess liver injury and oxidative stress induced by exposure of sea bass (Dicentrarchuslabrax L) to therapeutic doses of FA (200 mL.m-3) and OTC (40 g.m-3) under same conditions being applied in intensive aquaculture systems in Tunisia.
Methods:
Liver histopathological survey was achieved after 5 and 10 days of exposure to FA, OTC separately or mixed. In parallel, liver catalase activity and malondialdehyde (MDA) were measured to assess oxidative stress.
Results:
Results showed that treatment with FA and OTC used alone or in combinations induced liver damage as measured by sinusoid dilatation, intensive vacuolisation, blood congestion, and focal necrosis. Significant elevation in catalyse activity and MDA levels were also observed in liver homogenates by the treatment (p≤005).
Conclusion:
Combined treatment induced higher effects suggesting the critical hazards associated to FA and OTC when released to the environment.

Key words: Liver histopathology, Oxidative damage, Sea bass, Formaldehyde, Oxytetracycline