infection has been found. There is no evidence of smolts carrying the 

 infection from infected waters on their migration to the sea. Large 

 numbers of smolts from a river in Great Britain in which the disease had 

 been exceedingly prevalent were examined with completely negative results. 



If the disease did occur among salmon in the sea, it would be 

 difficult to explain wl:^ fish of one river should be infected and not 

 those of another, since salmon which finally enter different rivers are 

 undoubtedly closely associated on approaching the coast. On the basis 

 of a sea origin, the partial distribution of the disease among different 

 rivers in Great Britain would be inexplicable, especially when an 

 infected and uninfected river may be close to one another (Furunculosis 

 Committee 1935). For instance, furunculosis T;as found present in the 

 Forss, but not in the Halladale or Thurso.; rivers which enter the sea a 

 few miles on either side of the Forss. Furunculosis was present in the 

 Bonn, but nonexistent in the Ayr only a mile away. Were the disease 

 generally present in the sea, such selective distribution in rivers 

 would be highly unlikely. 



In addition, were the infection introduced from the sea, one 

 would expect to find the disease invariably showing at or near the mouth 

 of each river, whereas in certain rivers in Great Britain furunculosis 

 was first seen many miles from salt water (Furunculosis Committee 1935). 

 Again, furunculosis has appeared in trout streams in which migratory- 

 fish, except eels, do not reach and in trout fsirms from which even eels 

 are rigidly excluded. 



The disease can be transmitted through a marine channel through 

 sea trout. In Great Britain they ai^e often in the habit of migrating 

 during autumn from estuarj^ to estuary. These wandering trout may 

 conceivably visit an infected area and should an epizootic be in progress 

 at that time, then one or more of these temporary visitors might also 

 become infected and carry the bacterium with it to another estuary at 

 no great distance. Of such transmission there is no direct evidence, 

 although it might conceivably account for one or two outbreaks the 

 origin of vrhich is obscure (Furunculosis Committee 1935 )• 



It has been shown ty large-scale experiments (Furunculosis 

 Committee 1930, 1933, 1935) how rapidly grilse and adult sea trout 

 contract the disease and die from it when placed in water with infected 

 broim trout. The infection often falls chiefly on salmon and trout in 

 Great Britain which have left the sea only a short time previously. 

 The Furunculosis Committee (1930) takes the stand that such fish on 

 entering a river in which the disease exists become rapidly infected, 

 due to environmental changes. They support the suggestion that salmon 

 entering a river may contract the disease in L, days to 2 weeks' time, 

 become weakened, pass down the river to the estuary or even into the sea, 

 reascend as far as the estuary, and die. Thus, fish passing into an 

 infected river might well succumb to the disease while still carrying sea 

 lice, but the committee feels that the occurrence of the infection in 



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