Control of psoroptic scabies on calves with ivermectin.

Eleven Hereford or Angus-cross calves slightly to severely infested with common scabies mites (Psoroptes ovis) were treated with 22,23-dihydroavermectin B1a (ivermectin) at dosages given subcutaneously (SC)--300 micrograms/kg; orally--400 micrograms/kg; or IM--50, 100, or 200 micrograms/kg. At 14 days after treatment, live mites were not found on any of the calves treated SC or IM, but live mites were found on all of the orally treated calves at 14 days and on 1 of them at 28 days after treatment. Four nontreated calves retained their mite infestations during the course of the IM test. Biting lice (Bovicola bovis) were eliminated from 1 calf treated SC, but not from calves treated IM. Ear ticks (Otobius megnini) were not noticeably affected.