Inactivation tests of the dinoflagellate Amyloodinium ocellatum parasite of marine fish

• Autor(a) principal: Sousa, Rui Manuel Couto de
• Data de Publicação: 2022
• Tipo de documento: Dissertação
• Idioma: eng
• Título da fonte: Repositório Científico de Acesso Aberto de Portugal (Repositórios Cientìficos)
• Texto Completo: http://hdl.handle.net/10400.1/18745
• topic: Aquaculture; Fish pathology; Earth ponds; Parasite prevention; Tomonts; Domínio/Área Científica::Ciências Naturais::Outras Ciências Naturais

The ectoparasite Amyloodinium ocellatum is the most common and important dinoflagellate affecting fish, causing severe morbidity and mortality in both brackish and marine warmwater aquaculture fishes worldwide. A. ocellatum has a triphasic life cycle, consisting of a free-living flagellate, the dinospore, a parasitic stage, the trophont, and a resting and reproductive cyst, the tomont. Tomonts of A. ocellatum can settle in the bottom of tanks and ponds and resist for long periods of time maintaining the ability to reinfest. Biosecurity in ponds is changeling, due to the size of the aquaculture farms and because they are normally located near natural water reservoirs, which limits the application of aggressive chemical treatments. Chemotherapy has shown efficacy in eliminating the dinospore but not the tomont, which is very resistant to treatments. This work focused on the development of in vitro inactivating tests for the cystic stage of the parasite. To propagate the parasite, an infection system with 6 European sea bass Dicentrarchus labrax was established with parasites collected during the season of higher prevalence in fish aquaculture production earthen ponds. Preservation tests of the tomont were also performed to reduce the need of keeping the infection system for long periods. Different chemicals and physical methods were tested for their capacity to inactivate the tomonts. Efficacy of the inactivation was evaluated through germination tests, dinospores concentration and motility.. This work showed that tomonts can be inactivated by several chemicals and physical methods, in particular by chemicals with a lesser impact on the environment, like peroxides. this work also presents the first documented results on the efficacy of UV-C irradiation on tomont inactivation. Overall, this study shows that A. ocellatum treatment and prevention can be achieved following more sustainable environmental strategies.