IMPROVING TILAPIA HEALTH AND INCREASING DISEASE PROTECTION WITHOUT THE USE OF VACCINES OR ANTIBIOTICS

David D. Kuhn*, Stephen A. Smith
 
 *Department of Food Science and Technology
 Virginia Polytechnic Institute and State University
 Blacksburg, VA 24061
 davekuhn@vt.edu

Tilapia is one of the most important food fish produced by the aquaculture industry because it can tolerate adverse water quality conditions and other stressors during production, and as a result occupies a very large segment of the global seafood market. The tilapia industry grew rapidly in the 1990's. With rapid growth and increased competition, tilapia producers intensified production to remain economically viable and to supply the growing market. Intensification has led to numerous disease outbreaks around the world. Diseases can be caused by bacteria, fungi, parasites and viruses. The most important pathogens of current concern include but are not limited to the following: Streptococcus spp., Flavobacterium columnare, Aeromonas hydrophila, Mycobacterium spp. and the new orthomyxo-like tilapia lake virus.

There are two major biosecurity techniques that should be employed in preventing disease at a tilapia farm. The first biosecurity methods is a plan that will minimize the introduction of the pathogen into the facility or pond. The second biosecurity methods is to minimize production stressors by providing fish with good water quality and nutrition. Unfortunately, commercial vaccines/bacterins have not been developed or are available for minimizing the risk of disease in tilapia. And the use of antibiotics to treat a disease comes with increased regulatory constraints and negative consumer acceptance.

Though the use of vaccines or antibiotics will continue to be an important strategy for disease intervention at finfish farms, many researchers, biotechnology firms, and feed manufacturers are investigating alternative methods for improving fish health and increasing disease resistance without the use of vaccines or antibiotics. Research and development efforts at Virginia Tech are currently underway to investigate some of these alternative strategies such as dietary micronutrients, probiotics, and antibodies. Specific micronutrients and strains of probiotics have been successfully used in tilapia to alter the physiology of the fish and to stimulate the innate immune system. In addition, studies are underway to evaluate the effects of an anti-interleukin-10 antibody on disease resistance to bacterial pathogens in tilapia. Challenge studies in the biosafety laboratory level-2 (BSL2) and other molecular tools are used to confirm improved health and increased disease resistance. These alternative methods will offer the tilapia industry options for minimizing economic loss due to pathogen-based biosecurity risks.