Therapeutic and prophylactic measures for winter saprolegniosis in channel catfish

Abstract

LVlnter s a p r o l e g n~o s~s In channel c a t f~s h Ictalurus punctatus is associated with low temperature (-12°C) Induced ~mmunosuppress~on and ~nvaslon by a ubiqu~tous opportunistic water mold, Identified as a S a p~o l e g n~a sp In t h~s study 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 sThe 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 A d m l n~s t r a t~o n and 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 ~n e f f e c t~v e , 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~k e l y d u e 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 w e l e efficac~ous In preventing the onset of winter saprolegn~osis In channel catf~sh K E Y WORDS: Channel catflsh . Saprolegn~osis . Temperature .

Antagonistic activity of Aeromonas media strain A199 against Saprolegnia sp., an opportunistic pathogen of the eel, Anguilla australis Richardson

“…The intricate associations of such factors reflect the difficulty of establishing controlled infection studies to observe such opportunistic fungal infections and any benefit this potential probiotic might deliver. Existing methods for inducing saprolegniosis in fish (Hatai & Hoshiai 1993; Bly, Quiniou, Lawson & Clem 1996; Howe & Stehly 1998) use a combination of stresses suitable for studying the pathogenesis of the disease. These are, however, likely to be inapplicable for probiotic investigations, where a constant reproducible percentage of infection is required for statistical validity.…”

Comparative Therapeutic Effects of Natural Compounds Against Saprolegnia spp. (Oomycota) and Amyloodinium ocellatum (Dinophyceae)

“…Fajer-Ávila et al (20), surveying the antiparasitic properties of the compound against ectoparasites (among which A. ocellatum) of bullseye puffer fish (Sphoeroides annulatus), reported 4 mg/L as the dose at which the compound had less adverse effects on fish in long-term exposure and reduced the parasite burden on skin and gills after 7 h of treatment. With respect to Saprolegnia, formalin has been effectively employed for egg disinfection in aquaculture to both treat and prevent infection in fish eggs (21). These authors observed that it is capable of inhibiting Saprolegnia cyst germination at a concentration of 250 mg/L.…”

In vitro activity of chemicals and commercial products against Saprolegnia parasitica and Saprolegnia delica strains

“…Formalin, a solution of 37% formaldehyde, has been effectively employed to prevent (Bly, Quiniou, Lawson, & Clem, ; Schreier, Rach, & Howe, ) and treat (Cline & Post, ; Marking, Rach, & Schreier, ; Walser & Phelps, ) Saprolegnia infection in fish eggs. As a prophylactic measure, it inhibits cyst germination at a concentration of 250 mg/L (Bly et al., ). Daily flushes of formalin with 100, 200 and 400 mg/L increased per cent hatch of channel catfish Ictalurus punctatus eggs in comparison with non‐treated eggs (Walser & Phelps, ).…”