Parasiticidal effects of Tanacetum vulgare extract against Ichthyophthirius multifiliis.

Ichthyophthiriasis, which is caused by Ichthyophthirius multifiliis (Ich) infections, has a severe impact on productivity in freshwater aquaculture. These infections were previously treated effectively with malachite green, a compound that is now banned on fish farms due to its carcinogenicity. To find efficacious drugs to control Ich, flowers of tansy Tanacetum vulgare were evaluated for their antiprotozoal activity. Tanacetum vulgare extract significantly reduced the survival of Ich trophonts and theronts. In vitro, the extract killed all trophonts at 3200 mg l-1, terminated tomont reproduction at 50 mg l-1, and caused mortality of all theronts at 100 mg l-1. T. vulgare extract may be a new and efficacious drug for the control of Ich.