Columnaris disease, caused by the bacterial pathogen Flavobacterium columnare, continues to be a major problem worldwide in both wild and cultured freshwater finfish. Despite the far-reaching negative impacts of columnaris disease, safe and efficacious preventatives and curatives for this disease remain limited. In this study, we evaluated the potential of
kaolin (Al2 Si2 05 (
OH)4 ), a type of
clay, for the prevention of columnaris disease. Channel catfish, Ictalurus punctatus (Rafinesque), fingerlings were experimentally challenged with Flavobacterium columnare in untreated water or with water containing
kaolin (1 g L(-1) ). Over the 7-day course of study,
kaolin treatment led to significantly (P < 0.001) improved survival (96%) as compared to untreated fish (78% survival). Histological examination of the gills revealed that
kaolin-treated fish had substantially less gill damage than untreated controls. Quantitative PCR analysis of gill tissue revealed that
kaolin significantly reduced F. columnare adhesion (measured at 1 h post-challenge) and colonization (24 h post-challenge). Incubation of
kaolin with F. columnare in vitro demonstrated that
kaolin reduced the number of F. columnare cells in culture supernatants, presumably through the formation of physical complexes through adsorption. In summary,
kaolin can improve survival, reduce gill pathologies and reduce bacterial attachment to key tissues associated with columnaris disease in channel catfish by binding to F. columnare.