Compared with the 0 g/kg group, after infection with A. veronii, the activity of CAT in the hepatopancreas of red claw crayfish significantly increased at the 0 h and 48 h time points in the 0.1 g/kg, 1.0 g/kg, and 10.0 g/kg groups (p < 0.05), with increases of 27.6%, 45.9%, and 38.7% at 0 h and 35.7%, 38.9%, and 32.8% at 48 h respectively. The gene discussed is CAT; the disease is infection.