The Thai Journal of Veterinary Medicine


The safety of trichlorfon at a therapeutic dose for ectoparasitic treatment in healthy carp (Cyprinus carpio) was evaluated by the measurement of serum cholinesterase (ChE) activity. Three groups of juvenile carp (70-80 g b.w., n =30 each) were bathed with 0.5 ppm trichlorfon 1, 2 or 3 times, respectively, at 5-day intervals. Serum ChE activity in each fish were compared pre and post-treatment. A significant post-treatment reduction of serum ChE activity (p < 0.05) was found in all groups, although they, resumed their pre-treatment levels 14 days after trichlorfon was withdrawn. All fish were clinically healthy throughout the experiment, suggesting, that the doses of trichlorfon applied in this study were safe.

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