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Anthelmintic Resistance

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Internal parasites, in particular gut worms, are a major challenge to sheep production systems. Parasite control is largely based on suppression of the parasitic burden using anthelmintic products. Nationally anthelmintic resistance i.e. the ability of parasites to survive a dose that should kill them, is increasing for the 3 most common products we use for control; namely, group 1-BZ (white), group 2-LV (yellow) and group 3-ML (clear).

Latest Videos

  • Liver Fluke animation

    Liver Fluke is an internal parasite that infects grazing livestock. This video gives an outline of the life cycle of liver fluke and when different categories of flukicides should be used.

  • Addressing anthelmintic resistance

    There are five classes of wormer drugs currently in use: white, yellow, clear, orange and purple. However, anthelmintic resistance (the ability of worms to survive a wormer dose that should kill them) is increasing, so care should be taken when deciding which wormer to use.

  • Effect of dosing on pasture worm population

    Over time the population of worms on pasture will change as we continually dose lambs with ineffective products with an increasing number of resistant ones present as the susceptible ones are killed off. Michael Gottstein, Head of Sheep, Teagasc tells us more in this video.

  • Understanding Pasture Contamination

    On sheep farms the parasite challenge or burden that lambs are exposed to varies depending on how the pasture was managed previously as this influences the worm population. Michael Gottstein, Teagasc explains that it helps to better understand this as it has an influence on lamb performance.

  • Quarantine Treatment - Avoid buying in resistant worms

    As new sheep come on to a farm they could be carrying resistant worms and you don’t want those spread on your farm. So in order to prevent that you need to quarantine treat the incoming sheep up on arrival, Dr Orla Keane explains this process in more detail.


  Control of Stomach Worms – improving sustainability

 Products licensed for control of parasites in sheep in the Republic of Ireland


Understanding and delaying the development of anthelmintic resistant parasites on sheep farms

Stomach worms are a significant cause of production loss in lambs The infective larvae are picked up as sheep graze. The larvae mature in the sheep's digestive tract, mate, lay eggs and pass out in the faeces onto the pasture. The lifecycle completes with eggs hatching as infected larvae.

  • Drench Test - Checking Product Efficacy

    The drench test is a very simple procedure to check and see if the drench is working and killing the worms in the lambs. Sheep specialist Michael Gottstein goes through how to check product efficacy of drench in this short video

  • Identifying worm burden - routine faecal sampling

    In this video Michael Gottstein, Head of Sheep, Teagasc outlines how carrying out routine dung samples from a batch of lambs will help identify whether or not the lambs need a dose. Michael also goes through the process of how to take a sample.

  • Dosing gun calibration

    Teagasc Sheep Specialist Damian Costello goes through the process of calibrating your dosing gun when drenching lambs.

  • Stomach worm control - Anthelmintic groups

    In this video Damian Costello, Teagasc Sheep Specialist outlines the five anthelmintic classes that we rely on for the control of stomach worms.