Abstract: To investigate the effects of Houttuynia cordata Thunb. on the disease resistance of the black-spotted pond frog (Pelophylax nigromaculatus) against Elizabethkingia miricola infection, graded concentrations of H. cordata were supplemented into formulated feeds in the present trial. Blood biochemical and hepatic physiological parameters were determined, and the survival rate was recorded post artificial challenge with E. miricola. The results showed that after 9 weeks of dietary administration, dietary H. cordata significantly elevated serum lysozyme (LYS) activity as well as complement C3 and C4 contents in P. nigromaculatus. No significant variations were observed in hepatic alanine transaminase (ALT) and antioxidant capacity (AOC), whereas hepatic superoxide dismutase (SOD) activity was markedly reduced. All tested supplemental levels of H. cordata significantly improved the survival rate of frogs following E. miricola challenge. Relative to the blank control group, dietary supplementation with 1%, 3% and 5% H. cordata powder improved survival rates by 39.13, 28.42 and 28.42 percentage points, respectively; supplementation with 0.4% H. cordata crude extract increased survival by 14.13 percentage points. Collectively, dietary H. cordata effectively enhanced the innate immunity of P. nigromaculatus against E. miricola, with 1% H. cordata powder identified as the optimal dosage. These findings provided fundamental references for the prevention and control of Elizabethkingia infection in the culture of black-spotted pond frogs.

Key words: black-spotted pond frog （Pelophylax nigromaculatus）, Elizabethkingia miricola, Houttuynia cordata Thunb., immunity