Environmental risk assessment of veterinary medicines used in Asian aquaculture

Summary

One of the major constraints for the development and expansion of the Asian aquaculture industry has been the proliferation of disease outbreaks. To overcome this issue, a wide range of veterinary medicines including antibiotics, parasiticides and medical disinfectants have been recently developed. Residual concentrations of veterinary medicines applied in aquaculture farms may enter the environment by waste-water discharges, posing a risk for the biodiversity of surrounding ecosystems.

The main objective of this thesis was to assess the current use of veterinary medicinal products in Asian aquaculture production and to investigate their environmental fate and toxicological risks for tropical and sub-tropical aquatic ecosystems. For this, extensive surveys were performed to assess chemical use practices in four Asian countries: China, Vietnam, Thailand and Bangladesh. Models were developed to assess chemical exposure and ecological risks, as well as to quantify antibiotic resistance development risks in aquaculture production systems and surrounding environments. Furthermore, the toxicological risks of aquaculture antibiotics for tropical aquatic ecosystems were evaluated by performing experiments at the molecular, individual and community level.

This thesis shows that intensive aquaculture production constitutes an important source of environmental contamination. Antiparasitic treatments generally pose the greatest ecological risks as compared to the other compound groups. Aquaculture antibiotics were found to pose minimal short-term risks for pelagic communities, but are relatively persistent in aquatic sediments, posing a risk for some microorganism groups and probably increasing the prevalence of antibiotic resistance. This thesis also provides recommendations to improve the regulatory control on chemical use, to reduce their environmental discharge, and to continue developing the knowledge and tools that underpin the environmental risk assessment of veterinary medicines applied in Asian aquaculture.