Selection of different genotype larvae and adult worms for anthelmintic resistance by persistent and short-acting avermectin/milbemycins May 17, 2001 E Barnes R Dobson P Stein L Le Jambre I Lenane Avermectin/Milbemycin Haemonchus Contortus Ivermectin Moxidectin Persistent Drugs/Capsules Resistance