Evaluation of the therapeutic effect of potassium permanganate at early stages of an experimental acute infection of Flavobacterium columnare in channel catfish,Ictalurus punctatus (Rafinesque)

The efficacy of potassium permanganate (KMnO₄) against the early stages of an experimental acute infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus, was evaluated. Fish were experimentally challenged by waterborne exposure for 2 h to F. columnare after cutaneous abrasion, and treated with KMnO₄ at 2.0 mg L^?1 above the KMnO₄ demand at 0, 1, 2 or 4 h postchallenge for 24 h. Challenged non‐treated fish acted as a positive control and non‐challenged non‐treated fish acted as a negative control. Fish challenged and treated with KMnO₄ at 0, 1, 2 or 4 h postchallenge had mortalities of 26%, 63%, 64% and 83% respectively. The mortality of challenged fish treated with KMnO₄ at 0 h postchallenge (26%) was significantly less than the positive control (77%). The mortalities of challenged fish treated at 1, 2 or 4 h postchallenge were not significantly different from the positive control fish. The results suggest that KMnO₄ has a clear therapeutic value in early stages of columnaris infection but limited therapeutic value once the infection has progressed.