40 



FISHERY BULLETIN OF THE FISH AND WILDLIFE SERVICE 



As in the bkieback salmon, a search for para- 

 sites that could be responsible for the disease was 

 unsuccessful. Similarly bacteriological studies 

 failed to provide an explanation for it. To test 

 for a filtrable infectious agent, a suspension was 

 prepared by blending one group of moribund 

 kokanees with Ringer's solution; a second sus- 

 pension was prepared from a group of five fish 

 with scoliosis and five with lordosis by grinding 

 them in Ringer's solution with mortar and pestle. 

 Both suspensions were centrifuged. 



A portion of each suspension was passed through 

 a 7-pound-test Mandler filter that retained bac- 

 teria. Portions of both filtered and unfiltered ma- 

 terial were heated at 80° C. for 15 minutes. Each 

 of the four preparations was injected into a group 



of 20 2- to 3-inch healthy kokanee fingerlings. 

 Ten of each group wjere injected intramuscularly 

 with 0.1 milliliter and 10 intraperitoneally with 

 the same amount. 



Ninety-five percent of the fish injected with the 

 unfiltered and unheated material from both orig- 

 inal suspensions died within a week (table 4) 

 with evidence of inflammation and necrosis of the 

 muscle in the area of the injection or inflammation 

 throughout the body cavity and viscera. Cultures 

 from these fish indicated the presence of miscel- 

 laneous bacteria. Death was probably the result 

 of infection by bacterial contaminants, and not 

 related to the disease in the hatchery. No fish 

 died among those injected with the heated 

 material. 



Table 4. — jrortality of healthy kokanee fingerlings injected with f ructions of diseased kokanees 



Leavenworth station, 1951 



[IP— group injected intraperitoneally; IM— group injected intramuscularly; each group comprised 10 fish] 



1 One missing. 



Fifty percent of the fish that were injected with 

 the Mandler filtrate of the suspension of moribund 

 fish died in a period of 1 month. They developed 

 petechiae at the base of paired fins, on the isthmus, 

 or on the side of the body. The viscera were in- 

 flamed, and often the inoculation site showed in- 

 flammation with some necrosis in the muscle. 

 Cultures of kidney and muscle on agar yielded 

 colonies of a variety of bacteria on about half the 



plates, presumably contaminants or secondary in- 

 vaders. The other plates remained negative. 



Sixty percent of the fish died that were injected 

 with the Mandler filtrate of the suspension from 

 kokanees affected with scoliosis and lordosis. 

 They also showed areas of inflammation on the 

 body surface, at the base of the fins, on the isthmus, 

 <iii the viscera, fat, and especially on the intestine. 

 Bacteria were not always recovered from the kid- 



