White bass Morone chrysops is less susceptible than its hybrid to experimental infection with Flavobacterium columnare

Abstract

Hybrid striped bass (HSB) and white bass (WB) were evaluated for their susceptibility to Flavobacterium columnare, the causative agent of columnaris disease, in 3 fundamental studies. In the first experiment, we determined whether columnaris disease could be developed by experimental challenge in HSB. This challenge consisted of 3 levels of F. columnare (10, 30, and 60 ml volumes) determined to be 2.25 × 107, 6.75 × 107, and 1.35 × 108 CFU ml-1, respectively. Each treatment group exhibited significantly different survival rates: 0, 3.3, and 13.3% in the 60, 30, and 10 ml groups, respectively. In Expt 2, using the 30 ml dose, both HSB and WBhad a 0% survival rate, with WB taking significantly longer to reach 100% mortality. In Expt 3, using the 10 ml dose, no HSB survived, whereas 33% of WB survived (p < 0.0001). Compared to controls, HSB treated with 10 ml showed extensive gill damage at 24 h, which could have contributed to the higher mortality observed in HSB; in contrast, WB gills showed noticeably less damage. 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. © Inter-Research 2014.