title: Evaluation of diquat against an acute experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus (Rafinesque).
abstract: A trial was performed to evaluate the efficacy of diquat (6,7-dihydrodipyrido[1,2-a:2',1'-c]pyrazinediium dibromide) against an acute experimental infection of Flavobacterium columnare in channel catfish, Ictalurus punctatus. Diquat is an Environmental Protection Agency-approved herbicide and has the potential to be legally and practically used against columnaris. Channel catfish were challenged, by cutaneous abrasion, and waterborne exposure to F. columnare and treated once at 22-h post-challenge with 2.5, 5.0, 10.0 and 15 mg L(-1) of diquat active ingredient for 6 h. At the conclusion of the trial, 21-day post-challenge, diquat at 5.0, 10.0 and 15 mg L(-1) significantly (P < 0.05) reduced the mortality of infected fish from 95% in the challenged non-treated fish to 68%, 59% and 49%, respectively. In vitro, the minimum inhibitory concentration (MIC) of 23 isolates of F. columnare was assayed. The majority of the isolates had an MIC value of 5 microg mL(-1) (15 of the 23 isolates). Infected fish exhibited acute clinical signs similar to a natural infection. The skin had severe ulcerative necrotizing dermatitis and the muscles had severe necrotizing myositis. The gills had severe multifocal necrotizing branchitis. The results demonstrate that diquat would reduce mortalities caused by an acute columnaris infection.
authors.affiliation: Harry K. Dupree-Stuttgart National Aquaculture Research Center Agricultural Research Service, United States Department of Agriculture, Stuttgart, AR, USA. ahmed.darwish@ars.usda.gov
authors.forename: A M
authors.initials: AM
authors.lastname: Darwish
authors.forename: A J
authors.initials: AJ
authors.lastname: Mitchell
mesh_terms: D000818:Animals; D000900:Anti-Bacterial Agents / Q000494:pharmacology / Q000627:therapeutic use*; D004178:Diquat / Q000494:pharmacology / Q000627:therapeutic use*; D005393:Fish Diseases / Q000188:drug therapy* / Q000382:microbiology / Q000401:mortality / Q000473:pathology; D045826:Flavobacteriaceae Infections / Q000188:drug therapy* / Q000401:mortality / Q000473:pathology; D005417:Flavobacterium / Q000187:drug effects / Q000502:physiology*; D007059:Ictaluridae / Q000502:physiology*; D011897:Random Allocation; D016019:Survival Analysis
chemical_list: D000900:Anti-Bacterial Agents; D004178:Diquat