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Present Impacts Of Enteric Septicemia Of Catfish On The Channel Catfish Industry

 

 

Lester Khoo1, P. S. Gaunt1, B. A. Wagner2, and D. J. Wise3

 

1Mississippi State University, College of Veterinary Medicine, Thad Cochran National Warmwater Aquaculture Center, P.O. Box 197, Stoneville, MS 38776; 2Centers for Epidemiology and Animal Health, USDA:APHIS:VS Fort Collins, CO 80521, 3Mississippi Agriculture & Forestry Experiment Station, Thad Cochran National Warmwater Aquaculture Center, P.O. Box 197, Stoneville, MS 38776

 

 

The two major bacterial diseases that afflict channel catfish are Enteric Septicemia of Catfish (ESC) caused by Edwardsiella ictaluri and Columnaris, caused by Flavobacterium columnare.  Based on case submissions from the past 5 years, to the Fish Diagnostic Laboratory (FDL) at Stoneville, these are also the two most prevalent disease diagnoses.  Of these two diseases, Columnaris now appears to be more common although ESC is a close second.  This apparent difference may reflect the method of diagnosis used at the FDL since ESC is based on identification of isolated on bacterial cultures while the diagnosis of Columnaris is based not only on cultures (internal Columnaris) but also identification of characteristic bacteria on wet mount preparations of affected tissues (external Columnaris).  It is recognized that there are inherent biases when utilizing case submissions to the diagnostic laboratory to base conclusions on the impact of a disease on the industry.  However, the free service coupled with the relatively high case load (approximately 2000 cases/year) should help to ameliorate some of these biases.  In addition, there is also supporting evidence from the National Animal Health Monitoring System (NAHMS) survey, “Catfish 97” which was conducted by the United States Department of Agriculture’s Veterinary Services and the National Agriculture Statistics Service.  In this survey, which was based on the1996 season, a majority of the operations (70.2%) reported that ESC/Columnaris was the disease that caused the heaviest economic losses.  Although bacterial diseases continue to inflict severe economic losses, there are only 2 antibiotics available to the channel catfish industry, namely Romet® (a potentiated sulfonamide, and Terramycin®, (tetracycline).  Of these, Romet is licensed for the treatment of ESC.  Producers have also been utilizing management strategies such as pulling the fish off feed to control losses due to ESC.  In spite of the best efforts of researchers and producers, ESC continues to have large negative impacts on the channel catfish industry.




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