Evaluation of the ecotoxicity induced by veterinary pharmaceuticals and environmental samples in the aquatic vertebrate Danio rerio through a One Health approach

The aim of this thesis is to deepen the knowledge on the application of zebrafish, and in particular zebrafish embryos as a model for the detection of the effects induced by mixtures of chemical pollutants using sublethal endpoints. This work was structured on three different phases. To investigate the actual knowledge on the subject and to highlight possible gaps and future development, a scoping review was elaborated with a focus on the use of zebrafish for chemical-induced neurotoxicity identification with sublethal behavioural endpoints. Then zebrafish embryos were employed for the detection of acute toxicity on known substances (veterinary pharmaceuticals) and on environmental samples obtained from the Tiber River after extreme weather events that were cause of fish-kills in Rome. In both cases the FET test based on mortality was applied, but was also supported by sublethal endpoints, in line with the aim of this thesis. In the Tiber River work however, the aim was to investigate the possible causes of the fish-kill and to test the use of sublethal endpoints at detecting the effect of complex mixture such as those that can be found in a heavily impacted river. In the experimental activity on the known substances a new assay aimed at the detection of neurotoxicity, the CAT, was also applied, as well as others sublethal endpoints. In conclusion, as highlighted in our review the model Zebrafish is knowing growing popularity in the evaluation of the effects of chemical pollutants in mixtures, especially through the use of sublethal endpoints, such as behavioural alterations. Sublethal effects are also a valid tool, especially in early warning systems. Finally, the CAT is a simple and quick method in the assessment of neurotoxicity that could be a valuable addition in the regulatory guidelines for identify the risks linked to neurotoxicity in the ecosystem.