Anthelmintic activities of ivermectin against immature and adult Dictyocaulus viviparus.

Eighteen calves about 3 months old were inoculated with 3,000 Dictyocaulus viviparus infective larvae. Three groups of 6 calves each were formed. Thirteen days after inoculations, 3 of the 6 group 1 control calves were given vehicle subcutaneously (SC) and the group 2 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Thirty-five days after inoculation, the remaining 3 calves in group 1 were given vehicle SC and the group 3 calves were given ivermectin at the dose rate of 200 micrograms/kg, SC. Necropsies were performed 42 days after inoculations. A total of 474 D viviparus was recovered from the group 1 control calves, whereas none was recovered from the calves treated when the nematodes were in the 4th stage of development (group 2) or adult stage (group 3).