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Title: Survival of vaccinated, feed-trained largemouth bass fry (Micropterus salmoides floridanus) during natural exposure to Flavobacterium columnare

Author
item Bebak, Julie
item MATTHEWS, MICHAEL - FLORIDA BASS CONS. CTR.
item Shoemaker, Craig

Submitted to: Vaccine
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 5/11/2009
Publication Date: 7/9/2009
Citation: Bebak, J.A., Matthews, M., Shoemaker, C.A. 2009. Survival of vaccinated, feed-trained largemouth bass fry (Micropterus salmoides floridanus) during natural exposure to Flavobacterium columnare. Vaccine. 27:4297-4301.

Interpretive Summary: Flavobacterium spp. are a group of bacteria considered to be ubiquitous in the aquatic environment. Worldwide, all fish species are susceptible to infection with at least one member of this genus. One species in particular, Flavobacterium columnare, is an important pathogen of freshwater wild, farmed and ornamental fish. Largemouth bass, a very popular sportfish in the United States, are often reared in government hatchery programs, then stocked to supplement wild fish populations. After the eggs obtained from broodstock are hatched, fry are stocked into ponds to feed naturally. After this period eating live food the fry are more likely to accept commercial feed, so they are harvested from the ponds, stocked into tanks for “feed training”, and provided with manufactured feed until they are the size needed for stocking into lakes and ponds. Fry may be exposed to the bacteria while they are in the pond and/or after they are moved indoors, via the water supplied to the tanks. Consequently, outbreaks of columnaris disease are very likely to occur during and after this stressful feed training period. The objective of this study was to conduct a field trial testing the efficacy of the columnaris vaccine, AQUAVAC-COL to enhance the survival of vaccinated feed-trained largemouth bass fry naturally exposed to F. columnare. Results indicated that during every time interval, survival was significantly greater for vaccinated than for unvaccinated fish. In addition, vaccinated fish had a 43% lower risk of death during the field trial and mean death rate was almost twice as great for the unvaccinated as compared to the vaccinated fish. In this field trial, AQUAVAC COL provided feed-trained largemouth bass fry with significant protection from mortality during natural challenge with F. columnare.

Technical Abstract: Vaccinated, feed-trained largemouth bass fry (Micropterus salmoides floridanus) were cohabited with sham-vaccinated fish. Fish were exposed, under natural conditions, to Flavobacterium columnare, a ubiquitous bacterium associated with columnaris disease. During every time interval, the probability that a vaccinated fish would survive past time, t, was greater than for sham-vaccinated fish and survivor functions were significantly different (p-value<0.001). Overall, vaccinated fish had a 43% lower risk of death during the field trial. Mean incidence was almost twice as great for the sham-vaccinated (1.5%/d) as compared to the vaccinated fish (0.8%/d). Vaccination with AQUAVAC-COL (Intervet/Schering Plough Animal Health) significantly reduced the risk of death from columnaris disease in feed-trained largemouth bass fry.