Trial of avermectin B1a, mebendazole and melarsoprol against pre-cardiac Dirofilaria immitis in the ferret (Mustela putorius furo).

Avermectin B1a was found active against the pre-cardiac stage of Dirofilaria immitis in ferrets. The drug was given orally, at 0.2 mg/kg, on days 38--42 of infection. At necropsy, 5 1/2 months after inoculation, worms were almost totally absent from the hearts of these ferrets. The efficacy of melarsoprol against developing Dirofilaria, which has been demonstrated in dogs by other workers, was demonstrated in ferrets given oral doses, at 100 mg/kg, on days 38--42 of infection. The reported efficacy of mebendazole was not evident in the ferret host in this study, probably because the treatment (100 mg/kg, orally, on days 38--42) was shorter and later than that reported for dogs.