Snieszko and associates (1950b) tried another sulfonamide, 

 sulfamethazine, which sho^ved considerable promise. Although definitely 

 not more effective than sulf ameraaine in yearling brook trout with 

 furunculosis, it was slightly so with fingerlings. In spite of these 

 results authors still consider sulfamerazine to be the best drug in an 

 acute epizootic. 



Sulfonamide therapy has been found to be very much more effective 

 in the treatment of fingerling brook trout vath furunculosis than with 

 yearling brook trout (Snieszko and associates 1950b). Vfolf (194-7) found 

 that sulfamerazine was decidedly beneficial in the treatm.ent of 

 furunculosis in lake trout and brovm trout. 



Toxicity and tissue levels of siilfonamides in fish 



Pharmacological investigations of sulfonamides in fish Trere first 

 carried out by Litchfield in 1939. Of a number of sulfonamides 

 sulfathiazole has been shovm to be the least to.xic, although unfortunately, 

 as already indicated, one of the least beneficial in the treatment of 

 furiinculosiso Sn)ith and Nigrelli (1947) carried out toxicity tests Tri.th 

 sulfathiazole, sulfadiazine, sulfamerazine, and sulfamethazine. They 

 found in one experiment using Tilapia m.acrocephala (bleeker) as a test 

 fish, that the non-toxic concentration for sulfathiazole was 0.1 

 percent, for sulfadiazine and sulfamerazine 0. 5 percent and for 

 sulfamethazine, it was 0.14, percent. In a second experiment, five fish 

 were placed in 20-gallon tanks containing 62 liters of water. The drug 

 concentration was 0,3 mg. per cc. This concentration remained more or 

 less constant throughout the experiment. For sulfamethazine a toxic 

 reaction was obtained in 16 days; for sulfamerazine in 11 days; for 

 sulfadiazine in 20 days; and no toxic effects were obtained with 

 sulfathiazole. Except for sulfathiazole, therefore, all other 

 sulfonamides used were toxic at this concentration. Changes in pH were 

 not found to be a factor in these toxicity tests as there were no 

 deaths at the non-toxic levels even though there was a change in pH. 



It has been shovm (Outsell and Snieszko 1949b) that sulfamerazine 

 is not lethal to trout. Given sulfamerazine at daily dosage rates of 

 5, 10, and 15 gm. per 100 pounds of fish per day, these authors found 

 that in the case of brook trout and rainbow trout, mortalities were as 

 low in groups treated at the highest rate as in any lot. Moreover, 

 mortalities did not increase towards the end of the treatments. 

 Similarly, with brown trout deaths could not be attributed to sulfamerazine 

 poisoning when treated at these rates. 



?/here there was evidence of growth retardation, consumption of 

 sulfam.erazine-treated food was poor. Wien consumption of treated food 

 was good, growth was equal or nearly equal to that in controls. The 

 apparent ejq^lanation of rediiced food consumption when sulfamerazine vfas 

 m.ixed with food was that certain species of trout (especially brown 



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