comparison of anti-ichthyophthirius multifiliis effects of some medicinal plants with malachite green

The most common treatment for the parasite ichthyophthirius multifiliis is malachite green, which has carcinogenic effects and causes environmental pollution. therefore, using alternative treatments, especially medicinal plants, seems logical (1). in this study, the anti-parasitic effects of five herbal extracts of lawsonia inermis, satureja khuzestanica, citrullus colocynthis, garlic, and thyme on i. multifiliis, the causative organism of white spot syndrome, were investigated. first, hydroalcoholic extracts of all plants were prepared using the maceration method (2). next, the theront and tomont stages of the parasite, being isolated from heavily infected rainbow trout, were exposed to serial two-fold dilutions of each extract. immobilized (dead) parasites were recorded every 3 hr for 12 hr at each dilution, and the 12-hr ld50 of each extract was calculated using the probit method. malachite green was used as a positive control. the results showed that the 12 hr ld50 values of l. inermis, s. khuzestanica, c. colocynthis, garlic, thyme, and malachite green on parasite tomonts were 4.68, 2.32, 5.21, 1.00, 2.50, and 0.24 mg/l, respectively. meanwhile, the 12 hr ld50 values on theronts were 0.57, 0.45, 2.37, 1.66, 0.57 mg/l, and 0.121 mg/l, respectively. among the five medicinal plant extracts used in this study, garlic and thyme extracts demonstrated the highest anti-parasitic effects. however, the anti-parasitic effects of these extracts were negligible compared to the malachite green, a commonly used conventional chemical treatment for ichthyophthiriasis (3). these extracts can be used as complementary treatments alongside chemical treatment.