Author
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Brazil, Brian |
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Welch, Timothy - Tim |
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Submitted to: International Aquaculture Meeting
Publication Type: Abstract Only Publication Acceptance Date: 3/1/2004 Publication Date: 7/1/2004 Citation: Brazil, B.L., Welch, T.J. 2004. Development of a novel strategy for clearing fish pathogens from recirculating aquaculture systems using bacteriophage. International Aquaculture Meeting. P. 41. Interpretive Summary: Technical Abstract: Biosecurity is more easily managed in environmentally controlled recirculating aquaculture systems (RAS) facilities. However, pathogenic organisms still invade systems and result in significant losses. Current RAS disinfection strategies include delivering medicated feeds to culture animals, increasing freshwater replacement rates, and/or applying chemical therapeutants to the water. Antibiotics are relatively non-specific agents that often disturb the normal beneficial flora along with intended pathogen populations. Aggressive water treatments such as ozone (O3), hydrogen peroxide (H2O2) and UV-irradiation are most effective at destroying pelagic organisms; however, pathogenic organisms are more likely to be found associated with suspended particulates or with other microbes in biofilms forming throughout the RAS pipe network, tank walls and biofilter. As result, it is virtually impossible to eradicate the targeted disease causing organism from a RAS without depopulating the culture system and disinfecting all components including the biofilter. Developing disinfection strategies should be effective at eradicating specific pathogens from the fish and/or culture system without disrupting normal bacteria flora. A promising biological control agent with just such high specificity is bacteriophage or phage. Phages are bacteria-specific viral agents whose activity can be used as an aggressive, yet highly specific agent for disinfecting recirculating systems. Researchers at the NCCCWA have successfully isolated, cultured, and purified a bacteriophage which is specific for the fish pathogen Yersinia ruckeri. Work has begun to test the potential use of this phage activity to clear Y. ruckeri from mature biofilters in a lab-scale RAS. Biofilters will be inoculated with a strain of Y. ruckeri that has been genetically modified to express the green fluorescent protein. Inoculated biofilters will then be treated with phage to determine the half-life and disinfection efficiency of the phage as well as to monitor nitrification performance of the biofilter. Given the specificity of the phage, nitrification performance is not expected to change nor should there be any negative impacts to rainbow trout being cultured in the system. The results presented here are expected to provide an initial indication of the efficacy of this strategy. |
