In vitro and in vivo assessment of Nelumbo nucifera, Glycines testa, and Agrimonia eupatoria extracts against different developmental stages of Ichthyophthirius multifiliis

Abstract

The ciliate Ichthyophthirius multifiiis is one of the most pathogenic parasites of freshwater fish, has three life cycle stages. The use of natural plants for prevention and treatment of ichthyophthiriasis has a good prospect. In the present study, Nelumbo nucifera, Glycines testa, and Agrimonia eupatoria ethanolic extracts were selected among 70 extracts through screening experiment targeting theronts. Then, we evaluated in vitro parasiticidal effects of the three extracts against three life stages of I. multifiiis. The EC₅₀ values of N. nucifera, G. testa, and A. eupatoria extracts against theronts were 2.18, 3.63, 2.63 mg/L, respectively, and the corresponding EC₅₀ values against protomonts were 11.02, 10.02, 10.08 mg/L, and against tomonts were 34.68, 21.48, 32.50 mg/L. To achieve a comprehensive assessment of these three extracts, we investigated their therapeutic effect in vivo and the toxicity to goldfish (Carassius auratus). After continuous immersion at the maximum nonlethal concentration (50, 30, 50 mg/L) of N. nucifera, G. testa, and A. eupatoria extracts for 17 days, the infection intensity of caudal fin was reduced by 90.98 %, 91.95 %, 85.08 % compared to the control group, and the survival rate of infected goldfish was increased by 13.33 %, 46.67 %, 66.67 %. The 96 h acute toxicity test to goldfish showed that the LC₅₀ values of N. nucifera, G. testa, and A. eupatoria extracts were 95.16, 53.42, 90.76 mg/L, respectively, demonstrating three extracts were safe to host. Collectively, our findings highlight A. eupatoria extract has the promising application prospects in prevention and control of ichthyophthiriasis.