Therapeutic and prophylactic measures for winter saprolegniosis in channel catfish.

LVlnter s ap ro l egn~os~s In channel ca t f~sh Ictalurus punctatus is associated with low temperature (-12°C) Induced ~mmunosuppress~on and ~nvas lon by a ubiqu~tous opportunistic water mold, Identified as a S a p ~ o l e g n ~ a sp In t h ~ s tudy attempts were made to identify antiinicrob~als/chemlcals w h ~ c h may (1) be effect~ve for the therapeut~c treatment of xvlnter saprolegniosis and (2) prophylact~cally control water concentrations of Saprolegn~a and hence prevent the onset of dlsease under laboratory challenge c o n d ~ t ~ o n s The antlmicrobials used were amphotencln B and the cecroplns A. B, and P1 While amphotericln B halted Saplolegn~a growth, the cecroplns were lneffect~ve The chemlcals and he] b~cides approved for use by the U S Food and Drug Admln~s t r a t~on a d considered In t h ~ s study for the prevention of Saproleyn~a zoospore ploduction or cyst germination were used at concentrations less than or equal to those recommended for use In commercial catflsh ponds for other purposes Compared wlth malachite green ( a positlve control only) sodium chloride and potasslum permanganate were ~ne f f ec t~ve , w h ~ l e copper sulphate and formalln l n h ~ b ~ t e d both zoospore production and cyst geimlnation Hoivever, at the lowest lnh~bltory dosage, copper sulphate was t o x ~ c to catflsh challenged under laboratory c o n d ~ t ~ o n s , this was l~ke ly due to the low alkalin~ty of our tank water when compared to that of catflsh ponds Several herbicides were tested ~ncludlng diquat simazlne hydrothol 191 and aquathol K Only dlquat had an inhibitory effect on Saprolegn~a growth In subsequent laboratory challenge expenments both formalln and diquat we le efficac~ous In preventing the onset of winter saprolegn~osis In channel ca t f~sh K E Y WORDS: Channel catflsh . Saprolegn~osis . Temperature . I n ~ m u n ~ t y . Chemotherapy. Antlm~croblals