MYCOBACTERIA IN ADULT SALMONID FISHES 

 RETURNING TO STATE HATCHERIES IN WASHINGTON 



By 



Brian J . Earp 



With Addendum by R . L . Westgard 



Washington State Department of Fisheries 



ABSTRACT 



A survey for tuberculosis in salmon returning to hatcheries 

 of the State of Washington Department of Fisheries situated in the 

 Columbia River Basin was conducted. Chinook salmon ( Oncorhynchus 

 tshawytscha) and silver salmon ( Oncorhynchus kisutch) were examined 

 for the presence of acid-fast bacteria. Tissues were examined by the standard 

 bacteriological smear technique and by a method designed to concentrate 

 the bacteria dispersed throughout the liver tissue. 



The Columbia River Disease Task Force 

 was formed in joint recognition that fish diseases 

 are a major factor influencing the successful 

 maintenance and rehabilitation of salmon and 

 steelhead populations in the Columbia River Bas- 

 in and that this area of study had been neglected 

 in the past. The Department of Fisheries, with 

 other fisheries agencies and universities of the 

 States of Washington, and Oregon, and the U.S. 

 Fish and Wildlife Service agreed in the neces- 

 sity for increased emphasis on the problems of 

 fish disease toward the end that their solution 

 would guide management practices and substan- 

 tially reduce losses from disease in salmon and 

 steelhead populations. Greatest emphasis was 

 given to determining the incidence of infections 

 by acid-fast bacteria in the various runs and 

 species of salmon and steelhead trout. 



This report deals specifically with the 

 survey of the incidence of acid-fast infections 

 in salmon in the designated areas and with the 

 results of that survey. 



METHODS 



The studies conducted during the fiscal 

 year 1958 entailed the collection of whole livers 

 from adult migrant salmon at hatcheries of the 

 State of Washington Department of Fisheries 

 situated in the Columbia River watershed, dur- 

 ing the 1957 spawning season. These included 

 Toutle, Elokomin, Kalama, Lewis River and 

 Klickitat hatcheries . Liver samples were also 



taken from adult salmon at the Samish hatchery. 

 This hatchery is located on the Samish River in 

 northwest Washington and is representative of 

 Washington State hatcheries lying outside the 

 Columbia River watershed. Individual livers 

 were preserved by freezing in plastic sacks and 

 transported to the Department of Fisheries 

 laboratory. 



The liver samples were processed and 

 examined by two different methods employed 

 simultaneously on each sample; one by the 

 standard bacterial smear method and the other 

 by a concentration technique developed in our 

 laboratory. In the standard smear method a 

 small piece of liver tissue was smeared on a 

 glass slide. In the concentration method, the 

 entire liver was emulsified and the acid-fast 

 bacteria concentrated by centrifugation and the 

 resultant centrifugate smeared on a slide . The 

 techniques of concentration of the acid-fast bac- 

 teria are dealt with in detail in the addendum to 

 this report. In both methods the preparations 

 were stained by the Ziehl-Neelsen method and 

 examined microscopically for the presence of 

 acid-fast bacteria. Slides were rated numer- 

 ically depending upon the numbers of acid-fast 

 bacilli present as follows: 



No. 1 1-20 bacilli in entire preparation 



No. 2 Over 20 bacilli in entire preparation 



No. 3 1-25 bacilli per field 



No. 4 2 5-100 bacilli per field 



No. 5 Over 100 bacilli per field 



10 



