Wolf (1936) found that cottonseed meal had a bad effect on the 

 resistance of trout to furunculosiso He concluded that pure meat, and 

 a diet consisting of one part meat, one part dry skim milk, one part 

 fish meal, and one part salmon-egg meal were the diets most effective 

 in producing disease resistance » 



Course of infection set up by diseased fish 

 with healthy contacts 



After a colony of fish was brought into contact with the 

 infection, the peak of disease occurred within four to nine days 

 (Furunculosis Committee 1933, 1935). They found that the most 

 susceptible individuals contracted the disease at this time and then 

 died after varying inteinrals, as long as the temperature remained 

 favorable, and a certain portion of fish served for a while as 

 incubatory carriers. 



DIAGNOSIS 



While in some cases a presumptive diagnosis of the disease might 

 be made by observation of external appearances of dead or diseased fish, 

 other conditions msy be confused with furunculosis (see below), expecially 

 by persons who have no technical knowledge of the disease. Furthermore, 

 it has been clearly shown how a fatal infection may occur without 

 characteristic external lesions, and how apparently healthy fish may 

 carry the organism. An accurate diagnosis can only be made by isolation 

 and bacteriological examination of the specific organism. Identification 

 by morphological, cultural, and biochemical reactions can be relied 

 upon, and pathogenicity tests supply confirmatory evidence. The 

 complement fixation test is also excellent for confirmation but is not 

 necessary. According to the Furunculosis Committee (1930), 2-year-old 

 brown trout ( Salmo trutta ) are the ideal test animal, but frogs may be 

 more conveniently utilized under ordinary laboratory conditions. 



Technique of Bacteriological Examination 

 (Furunculosis Committee 1930) 



Precautions are taken in obtaining specimens for microscopic 

 examination or artificial cultivation. Fish should be washed with 

 dilute formalin and then with spirit (methyl alcohol) which is allowed to 

 dry before cutting into lesions or viscera. The surface through which 

 an incision is made is also cauterized by a red-hot copper spatula. 

 Cutting instrumentsn forceps, etc. are sterilized in boiling water or by 

 dry heat. Specimens for film preparations and for inoculating culture 

 media are taken with a wire loop from lesions, heart blood, kidneys, 

 spleen, liver, and intestine., Films are stained by Gram's method or by 

 simple stains, and inoculations are made on plates of nutrient agar. The 

 addition of blood serum to the medium intensifies pigment production by 

 the organism and facilitates its recognition in culture „ Plates are 



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