Multiple resistance to ivermectin and oxfendazole in Cooperia species of cattle in New Zealand
Vermunt, J.J.; West, D.M.; Pomroy, W.E.
Veterinary Record 137(2): 43-45
1995
ISSN/ISBN: 0042-4900 PMID: 8525583 Document Number: 443982
Persistent scouring and ill-thrift in a herd of 17 calves (5-6 months old) which continued despite treatments with benzimidazoles and ivermectin prompted an investigation into anthelmintic resistance. The calves were allocated to one of 2 treatment groups to receive either topical ivermectin (Ivomec Pour-On) at a dose rate of 500 mg/kg or oral oxfendazole (Oxfen C) at a dose rate of 4.5 mg/kg. The faecal egg count reductions (FECR), 14 days after treatment was 0% for the ivermectin group and 59% for the oxfendazole group. Larval cultures indicated that more than 99% of larvae in post treatment samples were Cooperia species. The calves were then treated as one group with oral ivermectin at a dose rate of 200 micro g/kg; the FECR 7 days later was 14%. The calves were then treated with topical moxidectin (Vetdectin Pour On) at 500 micro g/kg; the FECR 8 days later was 99%. Although moxidectin had not been used on the farm previously the FECR 19 days after treatment had fallen to 54%. The calves were then treated with oral levamisole at 8 mg/kg; faecal egg counts were negative in all calves 7 days after treatment. Strategies for limiting the spread of multiple resistance, including the use of levamisole are discussed.