Disease outbreaks are one of the major constricting factors for aquaculture’s expansion, and they yield losses of around $6 billion every year. Aquatic environments impose a constant risk of exposure to disease-causing pathogens and poor knowledge of the existence of microbial populations in aquatic farm systems often leads to frequent emergence of previously unknown diseases. Therefore, disease management and assessment of cultured fish is a major concern to commercial fish farmers. The ability to identify the presence/absence and amount of a pathogenic organism in fish or bivalves has major economic benefits, as it allows for early treatment protocols implementation. The molecular methodologies (commonly known as “omic tools”) have gained much importance as invaluable tools to assess the welfare and health of farmed organisms. These tools can be used to detect, identify and/or quantify pathogenic agents in a faster and more reliable way, complementing the classical biochemical methodologies and thus directly impacting the success of aquaculture production.
Taking this into account, in the last few years, S2AQUAcoLAB implemented and optimized pathogen detection and identification using molecular tools (e.g. PCR and qPCR). Sequence data available in public databases was used to design specific primers to detect marine organisms’ parasites, such as Amoebas sp, Amyloodinium occelatum, Microsporidium, Mixosporidium and Monogenean. Also, specific PCR reaction were developed to detect several bacteria species found in aquacultures in the Mediterranean, including Photobacterium damselae subsp. damseale and Phd. subsp. piscicida, Tenacibaculum maritimum, T. solae, and T. discolor, Chlamydia, Aeromonas salmonicida and A. hydrophila, Pseudomonas aeruginosa and P. anguilliseptica and several species of Vibrios (V. harveyi, V. anguillarum, V. pelagius, V. vulnificus, V. splendidus, V. algynolyticus, and V. fischeri), among others. For a fastest detection of several Vibrio species, multiplex PCRs were used in which a combination of primers allowed for the specific detection of five vibrio species at a time (one reaction = five analyses) in different samples (eg infected tissue or cultivated bacteria). We have also developed molecular protocols for the identification and quantification (qPCR) of Nodavirus (VNN) and Norovirus (NoV) in fish and bivalves, respectively.
Altogether, our results show that a faster and more reliable detection of different pathogens in aquaculture can be performed for several parasite, bacteria and virus species. Our results could help develop new preventive and treatment methods to control fish diseases, reducing economic losses for the aquaculture industry and improving fish health and welfare.
This study had the support of the projects WP9- Portuguese Blue Biobank under the Blue Economy Pact - Project Nº. C644915664-00000026 co-funded by PRR, The Portuguese Republic and the European Union, and SAUDE&AQUA II (MAR-021.1.3-FEAMPA-00018) project.