Prevalence of anthelmintic resistance on 62 beef cattle farms in the North Island of New Zealand

Prevalence of anthelmintic resistance on 62 beef cattle farms in the North Island of New Zealand
Peer reviewed

Abstract

AIM: To establish the prevalence of anthelmintic resistance in parasitic nematodes on a random sample of beef cattle herds in the North Island of New Zealand.
METHODS: A cross-sectional prevalence study was conducted using a standardised faecal nematode egg count (FEC) reduction (FECR) test (FECRT) for ivermectin, levamisole and albendazole on 60 calves on each of 62 farms in the North Island chosen at random from farms that conformed with the selection criteria. Resistance to an anthelmintic was inferred when there was <95% reduction in FEC 7–10 days after treatment. Larval cultures were performed for all control groups and for treated groups for which resistance was evident.
RESULTS: Of the farms that completed the FECRT, 4/61 (7%) showed ≥95% reduction in FEC for all anthelmintics tested. Resistance to ivermectin was evident on 56/61 (92%) farms, to albendazole on 47/62 (76%) farms, and to both ivermectin and albendazole on 45/61 (74%) farms. Resistance to levamisole was evident on only 4/62 (6%) farms. The parasites most prevalent in resistant populations cultured were Cooperia spp. On 45/61 (74%) farms where Cooperia spp were present in sufficient numbers, resistance to both ivermectin and albendazole was evident. No cases of levamisole-resistant Cooperia spp were detected. Resistance of Ostertagia spp to ivermectin was evident on 4/45 (9%) farms, to albendazole on 15/46 (35%) farms, and to levamisole on 4/46 (9%) farms.
CONCLUSION: Anthelmintic resistance in parasitic nematodes of cattle is common in the North Island of New Zealand. Beef farmers need to be aware of the risks posed by anthelmintic resistance, and routine FECR testing is recommended to ensure optimal productivity and to guide decision-making when purchasing anthelmintics to be used on-farm.
KEY WORDS: Cattle, anthelmintic resistance, survey, macrocyclic lactone, ivermectin, benzimidazole, albendazole, levamisole

Access to the full text of this article is available:

If you're a member or subscriber and believe you should have access:

login

Otherwise:

Register for an account

Request new password

The whole of the literary matter of the New Zealand Veterinary Journal is copyright Taylor and Francis, Downloading this article signifies agreement with the terms and conditions of electronic access.