28th ANNUAL EASTERN FISH HEALTH WORKSHOP April 21-25, 2003 Prospective Evaluation Of Four Handling Models Of Columnaris Induction Kenneth E. Nusbaum1, Joel A. Bader2, Sarah A. Miller3, John M. Grizzle4, and Craig A. Shoemaker2. 1Department of Pathobiology, College of Veterinary Medicine, Auburn University, AL 36849; 2USDA ARS Aquatic Animal Health Research Unit, Auburn, AL 36830;  3Merck-Merial Research Fellow, College of Veterinary Medicine, 4Department of Fisheries and Allied Aquacultures, Auburn University, AL 36849 Columnaris disease caused by Flavobacterium columnare is a re-emergent agent of channel catfish (Ictalurus punctatus) and most farmed fishes.  Two broad approaches have been taken to model columnaris infection:  the handling-injury approach and the “spontaneous disease” approach.  Earlier work indicated that agent entry and distribution in the host were not temporally altered by the presence of an abrasion.  To examine the potential of disruption of the skin, four published methods were compared:  abrasion with a cotton swab, chemical scald, thermal injury, and cold brand.  Only abrasion and thermal injury caused injury that persisted for more than 24 hours as determined by histopathology.  To test the relationship of injury and infection, catfish were abraded or branded and housed in 15 liter flow through tanks at 25-27oC.  Fish were treated 4,3,2, or 1 days and 4 or 0 hours before challenge with 10 /ml of virulent F columnare.  An additional group abraded at 0 hours was treated with an aloe vera based artificial slime product.  Fish were examined daily for 7 days.  In those groups, which had lesions over 24 hours, the death rate was sharply reduced, in many groups to 0.  In those fish abraded at 0 hours before challenge, all fish died within 24-36 hours post challenge.  In those fish treated with artificial slime, death was delayed at least 24 hours beyond abraded groups.  Based on these observations, clinical columnaris disease in handled catfish must be related to entry of the pathogen through a break in the epithelium shortly after creation of the lesion.  Artificial slime coats may be of use in netted fish to reduce or prevent columnaris in harvested fish. Return to 28th Annual Eastern Fish Health Workshop Return to Leetown Science Center Home Page