Student case report: Evaluation of anthelmintic efficacy on a sheep farm, and practices that contribute to anthelmintic resistance

Authors: Fannin S
Publication: Grazing Gazette, Volume Issue 69, pp 18-24, May 2025
Publisher: Sheep and Beef Cattle Veterinarians Branch of the New Zealand Veterinary Association

Animal type: Sheep
Article class: Case Study

---

Abstract:

A sheep and beef farm in the Manawatu completed a faecal egg count reduction test (FECRT) in February 2024, to establish an effective parasite control plan in their sheep flock. The farmer had become aware of anthelmintic resistance issues in New Zealand, and wanted to determine how efficacious the anthelmintics being used on the farm were, and if any steps could have been taken to stop, or slow down, the development of anthelmintic resistance on their property. No monitoring of lamb faecal egg output or anthelmintic effectiveness had been completed until this time.

Parasitology results from faecal egg counts and subsequent larval cultures suggested that all of the anthelmintics on this property were currently effective against all Strongylid genera– which is fairly uncommon on New Zealand sheep and beef farms (Riddy, 2023). However, the increasing frequency of anthelmintic resistance in New Zealand is of great concern, so the parasite control practices on this property were discussed and evaluated at length, with the veterinarian. It was then found that very few of the known high-risk practices for the development of anthelmintic resistance, were not occurring on this farm, but opportunities to fine-tune their parasite control strategies were still identified.

---