Evaluation of medicated feeds with antiparasitical and immune-enhanced Chinese herbal medicines against Ichthyophthirius multifiliis in grass carp (Ctenopharyngodon idellus)

Authors: LIN, DE-JIE - Jiangnan University; ZHANG, QI-ZHONG - Jiangnan University; Xu, Dehai; FU, YAO-WU - Jiangnan University; LIU, YAN-MENG - Jiangnan University; ZHOU, SHENG-YU - Jiangnan University

Submitted to: Parasitology Research
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 3/9/2016
Publication Date: 3/22/2016
Citation: Lin, D., Zhang, Q., Xu, D., Fu, Y., Liu, Y., Zhou, S. 2016. Evaluation of medicated feeds with antiparasitical and immune-enhanced Chinese herbal medicines against Ichthyophthirius multifiliis in grass carp (Ctenopharyngodon idellus). Parasitology Research. 115:2473-2483.

Interpretive Summary: The protozoa Ichthyophthirius multifiliis (Ich) is a widespread fish ciliated parasite that results in significant losses in aquaculture. Currently there is no drug available to treat Ich effectively and economically and the search of new drug to treat Ich becomes urgent. This study aimed to (1) evaluate the ethanol extracts of medicinal plants and immunostimulants for their efficacy against Ich and (2) determine effects of medicated feeds with plant extracts or immunostimulants to treat Ich in fish. This study showed that ethanol extracts from 3 selected medicinal plants could kill all young parasite in water at a concentration of 16 mg/L. When fish were fed medicated feeds containing medicinal plant extracts for 10 days, infective intensity of the parasite on fish was significantly reduced. Fish fed medicated feed with immunostimulant(A) for 21 days showed no parasite infection and 100% survival during a 15 days of parasite exposure. The immunostimulant(A) is a combination of 10 medicinal plants. The trial results demonstrated that immunostimulant(A) is a promising feed supplements to treated I. multifiliis with good anti-parasitic efficacy. The study results are important to the aquaculture and pharmaceutical industry and will help researchers to develop effective parasiticides against the parasite Ich.

Technical Abstract: Ichthyophthirius multifiliis (Ich) is a widespread ciliated ectoparasite and results in severe economic loss in the aquaculture industry. Since malachite green was banned for using in food fish due to its carcinogenic and teratogenic effects on human, the search of alternative drug to treat I. multifiliis becomes urgent. Previous studies have shown that medicinal plants have promising effect against I. multifiliis in vitro or in vivo and immunostimulants could enhance fish immunity to treat disease in the aquaculture. This study aimed to (1) evaluate the ethanol extracts of medicinal plants Cynanchum atratum, Zingiber officinale, and Cynanchum paniculatum, immunostimulant(A), and immunostimulant(B) for their efficacy against I. multifiliis and (2) determine effects of medicated feeds with C. atratum, Z. officinale, C. paniculatum, and immunostimulant(A) to treat I. multifiliis in grass carp. The results in this study showed that the minimum concentrations of C. atratum, Z. officinale, and C. paniculatum extracts for killing all theronts were 16 mg/L, 8 mg/L, and 16 mg/L, respectively. The 4-h median effective concentrations (EC50) of C. atratum, Z. officinale, and C. paniculatum to theronts were 4.69 mg/L, 2.53 mg/L, and 6.45 mg/L, respectively and higher than the EC50 of immunostimulant(A) (407.32 mg/L), and immunostimulant(B) (419.65 mg/L) to theronts. In vivo experiments, fish fed with medicated feeds of C. atratum for 10 days, or Z. officinale for 3 days, or combination of 3 plant extracts for 10 days resulted in a significant reduction in the I. multifiliis infective intensity on grass carp after theronts exposure. Grass carp fed with medicated feeds of immunostimulant(A) for 21 days showed no infection and 100% of survival 15 days post theront exposure. Therefore, immunostimulant(A) is a promising feed supplement to treated I. multifiliis with good antiparasitic efficacy.