The U.S. Fish and Wildlife Service (USFWS) initiated a National Wild Fish Health Survey in 1997 in order to meet the congressional mandate of establishing and maintaining a National Fish Disease Database. The purpose of this national survey is to "determine the distribution of certain pathogens in fish in the wild". The development of this extensive survey has been dependent upon establishing partnerships between federal and state agencies that manage wild fish population throughout the country.
TWRA was contacted in 1997 by the Warm Springs Regional Fisheries Center as a potential cooperator in the program. After reviewing the objectives of the investigation and the procedures involved in collecting samples, the decision was made to begin testing Tennessee's wild trout populations that are subject to stockings of hatchery-reared fish. The program was of particular interest in light of the heightened awareness among user groups of whirling disease outbreaks in western trout populations and the presence of the pathogen in streams in northeastern states.
Rainbow (N=14-25 individuals) and brown trout (N=3-11 individuals) samples were collected from eight streams during October 1999 and sent via overnight express to the USFWS Warm Springs Fish Health Center in Georgia. A sample of rainbow trout from Left Prong Hampton Creek was submitted in March 1999. These fish were evaluated for eight different pathogens: Infectious Pancreatic Necrosis Virus (IPN), Infectious Hematopoietic Necrosis Virus (IHN), Viral Hemorrhagic Septicemia Virus (VHS), Oncorhynchus masou Virus (OMV), Renibacterium salmoninarum (RS), Aeromonas salmonicida (AS), Yersinia ruckeri (YR), and Myxobolis cerebralis (whirling disease, WD). All nine populations sampled in 1999 tested positive for Renibacterium salmoninarum (RS), but no clinical signs of disease were present. Results of the 1998 screening for RS (reported as incomplete in Habera et al. 1999) were also positive for all eight populations sampled that year (the same ones sampled in October 1999), but those fish were also asymptomatic. Whirling disease tests for samples collected in 1999 and 1998 are now complete and all results were negative. No other pathogens were detected in the 1999 samples.
Tennessee Wildlife Resources Agency