other fish in which the disease has been found in nature are: 

 tench (Tinea tinea ), carp ( Qyprinus carpio ), catfish ( Silurus glanis, 

 Cambridge Natural History classification)^ pike ( Esox lucius), and 

 sculpins (Cottus spp. ) (Furunculosis Committee 1930). Plehn (1911) 

 has noted it in perch (Perca flavescens ). 



Recovery from the disease 



There is only one record of a definite recovery from furunculosis 

 without treatment. In a rainbow trout which Blake and Clark (1931) had 

 inoculated, a furunculous lesion was formed in a few days but soon 

 subsided. Some months later the fish was found to be free from 

 infection. 



Sources of Infection and Methods of Spread of Disease 



Spread of disease by water and food 



Emmerich and Weibel (1894-) and Plehn (1911) first shcrwed that 

 water would probably serve as a vehicle for the spread of furunculosis. 

 Home (1928) added three broth cultures to a sink of circulating water 

 containing twelve gobies, stopping circulation each time for 6 hours to 

 increase chances of infection. Five fish died between 15 and 26 days 

 after the last e:3qD0sure to infection. 



Blake and Clark (1931) succeeded in bringing about the spread 

 of disease by placing one infected trout in a tank with healthy fish. 

 Of six healthy contacts the first died in 14 days and the fifth in 120 

 days. The other survived. The Furunculosis Committee (1935) showed 

 that dead fish readily spread the infection, even at low temperatures. 



Blake and Clark (1931) also showed that the spread of infection 

 could be brought about when healthy fish were not in actual contact 

 with diseased specimens. In one experiment a tanlc was divided into tvro 

 compartments by a perforated double grid permitting free interchange of 

 water but keeping the fish separate. On one side were placed two 

 inoculated trout and on the other healthy fish. In less than a month 

 five of six previously healthy trout died of furunculosis. 



Clayton (1927) infected brown trout by giving them food 

 contaminated with B. salmonicida . 



Carriers 



Early in the study of furunculosis the occurrence of carriers of 

 B. salmonicida was evident. Ark?.-right (1912) cultured B. salmonicida 

 from apparently healthy fish which had been bred in captivity. He 

 suggested that these fish were in the incubation stage of the disease. 

 Plehn (1909) and Mulsow (1913) pointed out that B. salmonicida may be 



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