The effects of trichlorfon, praziquantel and copper sulphate on various stages of the monogenean Benedeniella posterocolpa, a skin parasite of the cownose ray, Rhinoptera bonasus (Mitchill)

Abstract

Monogeneans of the superfamily Capsa)oidca have been a severe problem in maintaining both teleosts and elasmobranchs in eaptivity. Infestations of Benedeniella posterocolpa on the skin of the cownose ray, Rhinoptera bonasus, provided an excellent model for testing the effects of triehlorfon (0-7ppm), praziquantel (20ppm) and eopper sulphate (0-25 ppm) on adult monogeneans in situ, and on adult monogeneans. oncomiraeidia and eggs in vitro. One treatment with praziquantel eliminated i(K)% of the worms from the skin of rays. Two treatments with triehlorfon only eliminated 81% of the worms. Praziquantel killed all worms tested in vitro within 6h and prevented egg deposition. Triehlorfon killed all worms within 21 h, but some eggs were deposited. Copper sulphate had little effeet on worms in vitro. Both triehlorfon and praziquantel immobilized oneomiraeidia while copper sulphate had httle effeet. Eggs were relatively resistant to these chemieals; however, triehlorfon and praziquantel were the most effective in killing eggs.

The efficacy of four common anthelmintic drugs and traditional Chinese medicinal plant extracts to control Dactylogyrus vastator (Monogenea)

“…This result was similar to that shown by Thoney (1990) who demonstrated that trichlorfon killed all B. posterocolpa within 21 h in vitro, but did not prevent egg laying. In this study, trichlorfon at a concentration of 2.5 mg/L was the most effective drug tested in vivo.…”

“…Therefore, in the present study the effects of various treatments on the egg hatching and embryonic development of D. vastator were also investigated. Previously praziquantel was shown to be ineffective for reducing the hatching success or inhibiting the embryonic development of monogenean eggs (Chisholm and Whittington, 2002;Sharp et al, 2004;Sitjà-Bobadilla et al, 2006;Thoney, 1990). This contrasted with our results and suggested that the effect of praziquantel on egg viability might depend on the monogenean species.…”

“…Schmahl and Mehlhorn (1985) revealed that praziquantel was effective against D. vastator when administered at a concentration of 10 mg/L for 3 h at 22°C. In addition, high anthelmintic effectiveness of praziquantel against various monogeneans in vivo had also been reported (FajerÁvila et al, 2007;Santamarina et al, 1991;Sharp et al, 2004;Stephens et al, 2003;Thoney, 1990). So it supposed that praziquantel was an effective drug to control adult D. vastator in vitro and in vivo.…”

“…Many previous studies have demonstrated the anthelmintic effectiveness of praziquantel on adult parasites with particularly high success in vitro (Chisholm and Whittington, 2002;Santamarina et al, 1991;Sitjà-Bobadilla et al, 2006). For example, Thoney (1990) demonstrated that exposure to 20 mg/L praziquantel killed Benedeniella posterocolpa in vitro within 6 h and also prevented egg deposition. In the in vivo anthelmintic test, praziquantel was also effective to kill D. vastator.…”

Treatment of Microcotyle sebastis (Monogenea:Polyopisthocotylea) infestation with praziquantel in an experimental cage simulating commercial rockfish Sebastes schlegeli culture conditions

“…Bath treatment with praziquantel has been tested against monogenean infections in fish (Schmahl & Mehlhorn 1985, Moser et al 1986, Buchmann 1987, Schmahl & Taraschewski 1987, Schmahl et al 1989, Buchmann et al 1990, Szekely & Molnar 1990, Thoney 1990, Santamarina et al 1991, and in many cases has proved effective. The common treatment scheme in these studies was exposure of fish to a concentration of less than 30 ppm praziquantel for at least 3 h. In commercial rockfish culture farms, however, the bathing of fish for such a long time is very laborious and severely stressful to the fish.…”