The efficacy of ivermectin on experimental infections of P. malaysiensis in rats was determined. Ivermectin was 99·4% and 97·9% effective at a dosage of 400 mcg and 800 mcg respectively at seven days post-infection. The same two dosages of ivermectin when given at 14 days post infection had an efficacy of 100%. However, as an adulticide it had only 40·7% efficacy. Ivermectin may therefore be useful for the treatment of parastrongyliasis due to the larval stages of the worm which can cause significant pathology in man and animals.
