Article Text

Mutual resistance to avermectins and milbemycins: oral activity of ivermectin and moxidectin against ivermectin-resistant and susceptible nematodes
  1. WL Shoop,
  2. HW Haines,
  3. BF Michael and
  4. CH Eary
  1. Merck Research Laboratories, Merck and Co Inc, Rahway, New Jersey 07065.

Abstract

To determine whether there is mutual resistance to avermectin and milbemycin anthelmintics, ivermectin and moxidectin sheep drenches were tested against ivermectin-resistant and susceptible isolates of Ostertagia circumcincta and Trichostrongylus colubriformis in sheep. None of the isolates had been exposed to moxidectin previously. The dosage of ivermectin required to remove 95 per cent of the ivermectin-resistant O circumcincta and T colubriformis were 23 times and six times larger, respectively, than the dosages required to remove the same percentage of susceptible isolates. The dosages of moxidectin required to remove 95 per cent of the ivermectin-resistant O circumcincta and T colubriformis were 31 times and nine times larger, respectively, than the dosages required to remove the same percentage of susceptible isolates. It is concluded that the worms resistant to ivermectin were also resistant to moxidectin.

    Statistics from Altmetric.com

      Request permissions

      If you wish to reuse any or all of this article please use the link below which will take you to the Copyright Clearance Center’s RightsLink service. You will be able to get a quick price and instant permission to reuse the content in many different ways.