Higher sensitivity of the developing larvae of Angiostrongylus cantonensis than the adult worms to flubendazole and mebendazole.

Two kinds of benzimidazoles, flubendazole and mebendazole were each administered at 10 mg/kg to rats harbouring the developing larvae of the rat lungworm, Angiostrongylus cantonensis 3 or 10 days post-infection and to those harbouring the adult worms 70 days post-infection. Almost all of the larvae were eliminated from the rats mediated 3 days post-infection. The larvicidal effects of the drugs administered 10 days post-infection were not so high as those 3 days post-infection. However, the growth of larvae in rats medicated 10 days post-infection were significantly inhibited as judged from their length, width and weight except the length of the larvae in rats given mebendazole. An inhibition of their growth was also demonstrated by the observation that no first-stage larvae were released from the rats medicated 10 days post-infection and examined 66 days post-infection at which the first-stage larvae were released from non-medicated rats. On the other hand, when the drugs were administered 70 days post-infection, no effects were seen on the number, body size and weight of recovered worms, and the release of the first-stage larvae. A sound conclusion was drawn that the developing larvae are more sensitive to the drugs than the adult worms.