(3) Maintain a moderately low temperature. 



(4) The Yiater supply should permit the mixing of warm and cold 

 water so that any desired temperature can be maintained. 



(5) Pools should be constructed with emergency outlets and inlets 

 so that each pool can function as an independent unit. 



(6) Pool construction should pennit easy cleansing and 

 sterilizing. 



In general immunization of trout against furunculosis is neither 

 particularly successful (Snieszko and Friddle 1949a) nor simple to 

 carry out (Duff 1942). Duff (1942) did obtain some fairly good results 

 but the work of Snieszko and Friddle (1949) would indicate that 

 consistency can not be expected from this procedure. 



The results of Duff (1942) showed that, in the case of the 

 addition of live virulent culture to water at approximately 19° C, 

 prolonged prior oral vaccination decreased the mortality owing to an 

 initial infection from 75 percent to 24 percent in yearling cutthroat 

 ( Salmo clarkii ) and 71 percent to 26 percent in tests in which yearling 

 and 2-year-old fish were included. It is therefore only possible to 

 conclude, on the basis of a total of 267 trout involved that only one 

 heavy infection produces a mortality of roughly 75 percent in normal 

 fish, compared with roughly 25 percent in vaccinated fish. 



Mien vaccinated fish were infected by intramuscular inoculation, 

 mortalities were higher than by the method of adding virulent cxolture 

 or infected fish to water (Duff 1942). The results of Snieszko and 

 Friddle (1949a) also indicated that oral immunization did not increase 

 immunity sufficiently to protect brook trout ( Salve linus f ontinalis ) 

 from bacteria introduced parenterally in quantities capable of producing 

 an acute infection. 



Duff (1942) found a marked increase, in the vaccinated groups, 

 in the number of fish shoiving specific agglutinins and a tendency in 

 this group toward higher agglutinin- titres. 



Embody and Hayford (1925) and the Furunculosis Committee (1930) 

 suggested the selective breeding of a resistant race to furunculosis. 

 Embody and Hayford (1925) found that in the course of three generations 

 of selective breeding there was an increase in the average resistance 

 of trout to bacterial diseases. This \ias indicated in the decrease 

 from 98 percent mortality, in the eyed stage to fingerlings, to 30.8 

 percent in the same age group three generations later. Selection was 

 made from survivors of various diseases after the diseases had run their 

 courses. Although comparatively little vrork has been done on this 

 aspect of control of furunculosis, the author feels that there is much 

 to be said for it, in the light of the work of Embody and Hayford 

 (1925). 



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