Killing effects of extracts of six Chinese herbal medicines on Crytocaryon irritans in vitro and preventive effect of Fructus mume

We evaluated the killing effects of water extracts of six Chinese herbal medicines on Crytocaryon irritans in vitro, and found out that treating theronts for 5 min with 7.14 mg·mL^–1 of Fructus mume, Areca catechu, Dryopteris setosa and Punica granatum, respectively, had rendered the theronts mortality rate of 100%. Moreover, treating tomonts with the above water extracts at a concentration of 28.57 mg·mL^–1 for 4 h could lead to the tomonts mortality rate of over 84.1%. To evaluate the preventive effect of water extract of F.mume on C.irritans infection, we studied the weight gain, lysozyme activity, hemolytic activity of alternative pathway CH50 (ACH₅₀), number of fish trophozoites and mortality rate of Epinephelus lanceolatus♀×E.fuscoguttatus♂ after having fed with water extract of F.mume for 14 d. No significant difference was observed in weight gain and hemolytic activity of ACH₅₀ between medicine groups and control group (P>0.05). In addition, lysozyme activity was all significantly higher than that in control group (P<0.05), and number of trophozoites after infection with C.irritans was significantly lower than that in control group (P<0.05). Furthermore, the survival rate in medicine groups (11.4 g·kg^–1, 6.84 g·kg^–1, 3.42 g·kg^–1) and the control group were 40%, 20%, 46.67% and 0% with lethal dose infection, respectively. It is indicated that F.mume has developmental prospects for preventing C.irritans infection.