Efficacy of 6-, 12-, and 24-h Praziquantel Bath Treatments against Asian Tapeworms Bothriocephalus acheilognathi in Grass Carp

Abstract

Praziquantel is an effective anthelmintic treatment that has been used in dogs Canis lupus familiaris and cats Felis catus. It has also been used successfully against tapeworms and trematodes in fish. This study tested the efficacy of praziquantel bath treatments (6, 12, or 24 h) at various concentrations (0.187, 0.375, 0.75, 1.5, 3.0, 6.0, 9.0, and 12.0 mg of praziquantel/L of water) for controlling natural infestations of Asian tapeworms Bothriocephalus acheilognathi in grass carp Ctenopharyngodon idella (60–100% of the fish were infested). Treatments either were given as a single application or were applied twice (3 d apart) at fish densities of 60 or 120 g/L. The objective of the study was to find a treatment that would completely eliminate Asian tapeworms from all infested fish, as a number of states now require imported fish to be completely free of this parasite. Most of the praziquantel treatments reduced the percentage containing Asian tapeworms. Single, 24-h bath treatments at praziquantel concentrations of 0.75 mg/L or higher applied to fish held at a density of 60 g/L were the only treatments that completely eliminated Asian tapeworms. Raising the fish density from 60 to 120 g/L affected treatment success; the 24-h, 0.75-mg/L praziquantel treatment at the higher fish density did not completely eliminate Asian tapeworms (prevalence = 15%). A 12-h, 1.5-mg/L praziquantel treatment applied twice to fish held at a density of 60 g/L resulted in low Asian tapeworm prevalence (3.3%).