Anthelmintic resistance is a growing problem on sheep farms here in Ireland and actions need to be taken at farm level to slow this down.
Tom Coll of Teagasc said during a webinar that over the years, resistance has been detected, particularly in the white, yellow and clear drenches – with the two prescription-only products also witnessing worrying trends with regards to resistance and its effectiveness.
Anthelmintic resistance is the genetic ability of a worm to survive a dose of anthelmintics that should kill it and it is a big concern for the sheep sector here in Ireland.
Tom added that if the drench is killing 95% of the worms, then generally lamb performance is not affected; however, if it drops below 95%, then lamb performance will suffer.
There are a number of wormer products available on the market for farmers to choose from – which can be seen below.
These include:
- Benzimidazole: commonly known as a white drench;
- Levamisole: commonly known as a yellow drench;
- Macrocyclic lactone: commonly known as a clear drench;
- Amino-acetonitrile derivative: commonly known as an orange drench (prescription-only);
- Spiroindole: commonly known as a purple drench (prescription-only).
Good practices to carry out on sheep farms
- Don’t dose mature animals for worms unless there is a demonstrated need to do so;
- Drench test/faecal egg count – find out how effective the products you are using are and use faecal egg counting to determine the need for dosing;
- Use only Benzimadazoles (white drenches) to treat for Nematodirus; no resistance to white drenches detected for Nematodirus (generally not that effective late in the season);
- Quarantine drench all bought-in sheep; avoid buying in resistant worms.