Submitted to: Journal of Fish Diseases
Publication Type: Peer reviewed journal
Publication Acceptance Date: 11/5/2003
Publication Date: 8/30/2003
Citation: BADER, J.A., NUSBAUM, K.E., SHOEMAKER, C.A. COMPARATIVE CHALLENGE MODEL OF FLAVOBACTERIUM COLUMNARE USING SCARIFIED ANDUNSCARIFIED CHANNEL CATFISH, ICTALURUS PUNCTATUS (RAFINESQUE). JOURNAL OF FISH DISEASES. 2003. Interpretive Summary: Flavobacterium columnare is the causative agent of columnaris disease. This disease is a cause of great economic losses in cultured catfish in the United States and in a number of other cultured fish species world-wide. Annual losses attributed to columnaris disease are estimated at $50-60 million to the catfish industry. Presently, there are no vaccines to prevent columnaris disease in catfish, therefore disease is prevented through good management practices. Prior to vaccine development a standardized method needs to be developed to artificially infect catfish with the disease. This manuscript describes the use of a molecular-biology technique called the Polymerase Chain Reaction (PCR) to evaluate how early the pathogen accumulates in catfish following artificial infection. It also evaluates the practice of abrating the catfish prior to artificial infection, which is supposed to mimics fish handing practices. The pathogen ncould be detected in various tissues as early as 5 min after artificial infection at 29+/-2deg C. The earliest detection of pathogen was made in mucus, skin and gill tissues, occurring at 5 min after infection. Liver and kidney tissues required as little as 60 minutes prior to detection. Detection times for F. columnare in blood varied between 11.6 and 60 minutes. Scarification or abrasion had little or no effect on the timing of early entry of pathogen at 29+/-2deg C, which calls into question the efficacy of the F. columnare infection model for channel catfish. However, survival data at 29+/-2deg C showed that scarification does significantly influence effectiveness of infection.
Technical Abstract: The early entry of the fish pathogen Flavobacterium columnare and enhancement by scarification was studied in channel catfish, Ictalurus punctatus (Rafinesque), using the polymerase chain reaction (PCR) and a species specific primer set for a bacterial 16-S rRNA gene product. Evaluations were conducted following a typical abrasion bacterial bath immersion challenge with F. columnare. The newly developed Fvp2-Fvp3 primer set was useful in detecting the early entry of F. columnare. The pathogen could be detected in various tissues as early as 5 min after immersion challenge at 29+/-2 deg C. The earliest detection of the pathogen was made in mucus, skin, and gill tissues, occurring at 5 min post challenge. Liver and kidney tissues required as little as 60 min prior to detection. Detection times for F. columnare in blood varied between 11.6 and 60 min. Scarification or abrasion, a practice which has been historically used prior to bacterial challenge, had little or no effect on the timing of early entry of pathogen at 29+/-2 deg C, which calls into question the efficacy of the F. columnare challenge model for channel catfish. However, survival data following abrasion challenge with F. columnare at 29+/-2 deg C showed that scarification does significantly affect the survival of the fish.