Earp et^al_. (1953) reported successful 

 transmission to fingerling blueback salmon 

 ( Oncorhynchus nerka) by two or more feedings 

 of infected tissues, but the disease also occur- 

 red among control fish. Wood and Wallis (1955) 

 fed infected viscera to fingerling chinook sal- 

 mon (O. tshawytscha ) for 41 to 52 days and 

 transmitted the disease in all trials. Kidney 

 disease occurred among control fish in one of 

 the trials, but in two others nearly 100 percent 

 transmission was effected, and control lots 

 were not found to have the disease during a 

 reasonable period of observation. As an aside, 

 Rucker et^aL (1953) stated, "Also, we have not 

 transmitted kidney disease by contact or feed- 

 ing experiments." Snieszko and Griffin (1955) 

 did not find kidney disease experimentally tranb- 

 mitted to eastern brook trout by 3 weeks of 

 contact with infected fish followed by a single 

 feeding of infected tissues. The differences 

 which were observed may be due to the fact that 

 different species of fish and different strains of 

 the bacterium were used. 



Because the method of feeding and con- 

 tact did not transmit kidney disease to brook 

 trout, the severe and highly artificial method of 

 parenteral injection was used to provide fish for 

 experimental chemotherapy . 



Materials and Methods 



Hatchery-raised eastern brook trout, 

 averaging 42 grams at the start, were used for 

 this experiment. They were fed a modified 

 Cortland No. 6 diet (Tunison et al_. 1939) at the 

 rate recommended by Deuel et al. (1952) except 

 on weekends when, for convenience, the quantity 

 was halved. Water temperature was 12.5° C. 

 Fish were graded for uniformity and were dis- 

 tributed in aliquots of 5 for a total of 25 fish foi 

 each trough. Two troughs of fish were used for 

 each method of attempted transmission with each 

 of the two strains of the bacterium . 



The western strain of the bacterium was 

 a laboratory culture which had been isolated 

 from Chinook salmon by Dr . E.J. Ordal and was 

 labeled by him Butte Falls No. 110. The eastern 

 strain of the bacterium was obtained from east- 

 em brook trout at the U.S. Fish -Cultural sta- 

 tion at Berlin, N. H. It was propagated by Dr. 



S. F. SnieszKo in susceptible fish at Leetown, 

 W. Va., for several years and was isolated on 

 a culture medium for the first time shortly be- 

 fore this experiment was initiated. 



Ordal and Earp's cysteine blood agar 

 (Ordal and Earp, 1956) was used as the culture 

 medium for much of the work, but we have found 

 that commercial Mueller Hinton medium (Difca)!' 

 supplemented with 0.1 percent 1 -cysteine hydro- 

 chloride worked equally well, and some cultures 

 were cultivated on it. 



Control fish and experimental fish were 

 maintained under identical conditions except that 

 the control fish were not exposed to the bacterium . 

 Half of the experimental fish were inoculated with 

 the eastern strain of the bacterium; the remain- 

 ing fish were inoculated with the western strain 

 of the bacterium . 



Five methods of attempted transmission 

 were used. (1) The bacterium was added to the 

 food of one group of fish . A moderately heavy 

 growth from a 1- to 2-week-old slant culture was 

 added to each 2 days' ration. (2) A second group 

 also received the bacterium, but in addition their 

 food included 5 percent glass shards which would 

 pass through a 5-mm. screen but be retained by 

 a 1.27-mm. screen. They were intended to scarif5 

 the gastro-intestinal tract and thus facilitate bac- 

 terial penetration. (3) Other troughs of fish 

 received the specific bacterium plus 1 percent 

 Difco No . 3 bile salts . Among the higher verte- 

 brates, bile salts inhibit gastric HCl secretion 

 and increase intestinal permeability. This, it 

 was postulated, would favor survival of and penetra 

 tion by the bacterium . (4) Rough bricks were 

 placed in the troughs of another group and were re- 

 arranged each day . Water levels were lowered 

 once each day, and the bacterium was added to 

 these troughs at the low level. Fish were allowed 

 to struggle half exposed to the air for 5 minutes 

 after which the troughs were refilled. This treat- 

 ment was intended to produce nose and abdominal 

 abrasions like those often encountered among fish 

 in concrete structures. (5) The last group of 

 fish was manually abraded with 100 -grit water- 

 proof garnet abrasive paper for a similar reason. 



1/ Mueller Hinton medium from other sources 

 gave significantly less growth. 



