Lethal effect of ammonia on metacercariae of Clonorchis sinensis.

The effect of endogenous ammonia produced in dead fish or ammonia in ammonium bicarbonate solutions was evaluated on the viability of Clonorchis sinensis metacercariae. Viability was determined by worm recovery in rats infected with metacercariae exposed to ammonia in decaying fish or in vitro solutions. The recovery rates were 58%, 48%, 44% and 2% in fish that had been allowed to decay for 5, 10, 20 and 30 days at 4 degrees C, respectively, and this rate ( Y) was inversely correlated with the ammonia concentration ( X) in fish muscle extract ( Y=80.62-0.0667 X, r(2)=0.905, P=0.049). C. sinensis metacercariae barely survived in ammonia solutions with concentrations exceeding 1 g N/l. Our results indicate that the ammonia produced in dead fish is lethal to the viability of C. sinensis metacercariae.