title: Anthelmintic efficacy of ivermectin against immature gastrointestinal pulmonary nematodes of calves.
abstract: Anthelmintic efficacy of ivermectin (greater than or equal to 80% 22,23-dihydroavermectin B1a and less than or equal to 20% 22,23-dihydroavermectin B1b) was evaluated in a controlled experiment against immature nematodes. Twenty calves raised to about 8 weeks of age under nematode-free conditions were allocated into 4 groups. Infective larvae of Haemonchus contortus, Ostertagia ostertagi, Trichostrongylus axei, T colubriformis, Cooperia oncophora, C punctata, Oesophagostomum radiatum, and Dictyocaulus viviparus were given orally to each calf on a staggered schedule 6 to 14 days before treatments. The drug was given subcutaneously when the nematodes were in the early 4th stage of development, and the calves were killed 23 or 24 days later. Group 1 nonmedicated control calves had a geometric mean of 25,102 nematodes; groups 2, 3, and 4 calves given ivermectin at dose rates of 50, 100, or 200 micrograms/kg had reductions of 88.2%, 98.0%, and 99.8%, respectively.
mesh_terms: D000818:Animals; D000871:Anthelmintics / Q000494:pharmacology* / Q000627:therapeutic use; D002417:Cattle; D002418:Cattle Diseases / Q000517:prevention & control*; D005243:Feces / Q000469:parasitology; D007559:Ivermectin; D007783:Lactones / Q000494:pharmacology* / Q000627:therapeutic use; D007814:Larva / Q000187:drug effects; D009348:Nematoda / Q000187:drug effects*; D009349:Nematode Infections / Q000517:prevention & control / Q000662:veterinary*; D013045:Species Specificity
chemical_list: D000871:Anthelmintics; D007783:Lactones; D007559:Ivermectin