Laboratory Dose Confirmation of Copper Sulfate for Treating Fungus on Channel Catfish Eggs

Two dose confirmation studies are required by the U.S. Food and Drug Administration to verify the effectiveness of a candidate before approval as a new animal drug is awarded; the two studies provide independent substantiation of the results. This laboratory study was designed to compare an untreated control and a 10-mg/L copper sulfate (CuSO4) treatment to control fungus (Saprolegnia spp.) on eggs of channel catfish Ictalurus punctatus at 23.5°C in a flow-through system. The eggs were treated once daily until the embryos reached the eyed stage (five treatments). When hatching was complete for all viable eggs (day 10), the fry were counted to determine the percent survival in each treatment. Infestation by a fungus identified morphologically and by polymerase chain reaction as Saprolegnia spp. was severe in the control fish, resulting in 8% survival. The mean percent survival of fry hatched from the CuSO4-treated eggs was significantly higher (mean, 55%; range, 27–71%).