Title: Studies with Morone experimentally infected with Flavobacterium columnare identify superior disease resistance in white bass Morone chrysops versus its hybrid Authors
Submitted to: Diseases of Aquatic Organisms
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 2, 2014
Publication Date: N/A
Interpretive Summary: Hybrid striped bass and white bass were tested in a series of experiments to see how sensitive they were to columnaris disease, a lethal disease of wild and farmed freshwater fish caused by the bacterium Flavobacterium columnare. In the first experiment, hybrid striped bass were exposed to either a low-, intermediate-, or high-dose of the bacteria, which showed an increase in fish mortality as bacterial dose increased. In the second experiment, using the intermediate-dose of bacteria, hybrid striped bass and white bass were both found to be susceptible to columnaris disease, with all the fish dying in both groups, but the hybrid striped bass died significantly faster than the white bass. In the third experiment, using the lowest dose of bacteria, all of the hybrid striped bass died while 33% of the white bass survived until the end of the experiment. Infected hybrid striped bass showed extensive gill damage after 24 hours as compared to healthy control fish. The gills of white bass challenged with the lowest dose of bacteria did not look normal, but showed less gill damage. The gill damage in hybrid striped bass could have contributed to the higher mortality we saw in the experiments as compared to white bass. To our knowledge, this is the first report in which columnaris disease susceptibility has been assessed in white bass, and adds to the small amount of information available on columnaris disease in hybrid striped bass. These results should assist fish farmers by allowing for better management of columnaris disease.
Technical Abstract: Hybrid striped bass (HSB) and white bass (WB) were evaluated for their susceptibility to Flavobacterium columnare, the causative agent of columnaris disease, in three fundamental studies. In the first experiment, we determined whether columnaris disease could be developed by experimental challenge in HSB. This challenge consisted of three levels of F. columnare (10-mL, 30-mL, 60-mL volumes) determined to be 2.25 x 10E7, 6.75 x 10E7 and 1.35 x 10E8 CFU/mL, respectively. Each treatment group exhibited significantly different survival rates (P<0.05): the 60-mL group had 0% survival, 30-mL group showed 3.3% survival, and the 10-mL group showed 13.3% survival. In Experiment 2, using the 30-mL dose, there was a 0% survival rate in both HSB and WB, with WB taking significantly longer to reach 100% mortality (P=0.009). In Experiment 3, using the 10-mL dose, no HSB survived while 33% of WB survived (P<0.0001). HSB treated with 10-mL showed extensive gill damage at 24h as compared to controls, while WB gills showed noticeably less gill damage, which could have contributed to the higher mortality observed in HSB. From these series of experiments it is clear that HSB are more sensitive to F. columnare, having lower survival and more extensive histological damage compared to WB following challenge. To our knowledge, this is the first report in which columnaris disease susceptibility has been assessed in WB, and adds to the paucity of information available on columnaris disease in HSB.