Once cattle are housed, they are no longer at risk of becoming infected with worms (stomach or gut worms, lungworm and liver fluke) as these occur mainly at grazing on pasture.

Effective treatment at housing can therefore keep animals virtually free of worms and liver fluke until they are back on grass in spring. This is also a good time to consider the performance of the stock over the grazing season.

In younger animals, growth rates are the main performance indicator and in adults, milk yield, body condition and fertility are key indicators. If cattle are not performing well on these indicators or have had clinical signs of parasitic disease such as scour over the season, review your parasite control programme with your veterinary practitioner to see where improvements could be made.

Young stock

Young animals usually need to be treated for stomach and gut worms at housing. Faecal sampling and testing a number of weeks after treatment can give an indication whether the wormer product is effective.

Stomach worm larvae that have been picked up at pasture can become dormant over the winter and emerge in large numbers in the spring (Type II ostertagiosis) causing severe disease.

Products containing a yellow drench (levamisole) are not effective against these dormant larvae. Instead, use a product from the clear drenches (macrocyclic lactones) or certain white drenches (benzimidazoles).

Lungworm (hoose) may still be a possibility within the first few weeks after housing if an infection was picked up at the end of the grazing period, but other respiratory conditions should be considered if animals are showing clinical signs such as coughing or breathing difficulties.


Adult cattle usually develop immunity to stomach and gut worms over time and so these worms rarely cause clinical signs.

Bulk milk samples in dairy animals can indicate if the herd has been exposed to lung worm, stomach worms or liver fluke. These tests can remain positive for many months after treating even if there is no longer an active infection, so these tests need careful interpretation to decide if a treatment has been effective or if treatment is needed.

Liver fluke

Animals are usually infected with liver fluke at pasture in the late autumn and these parasites can take up to 12 weeks to mature into adult fluke. Many flukicides are only effective against the adult stage of the liver fluke and so timing and product choice are important for treatment to be effective.

Always check the product label for the targeted fluke stage. This could be early immature, late immature and adult.

Within the first few weeks of housing, only a product containing triclabendazole will be effective against all stages including the early immature liver fluke.

If using a product effective against late-stage immature or adult liver fluke soon after housing, a second treatment would be needed six to 10 weeks later.

Earlier treatments may be needed to prevent production losses if the fluke burdens on the farm are high.

Cattle do not develop immunity to liver fluke with age and all animals should be treated on farms with a risk of liver fluke, usually towards the end of the grazing season or going into housing.

High-risk regions for liver fluke are the west and northwest of Ireland but the risk is variable per farm.

A history of liver fluke and wet, waterlogged areas place a farm at higher risk.

Check the history of liver fluke in animals slaughtered from your farm as part of the Beef HealthCheck programme on beefhealthcheck.icbf.com.

Faecal testing can help inform if treatment is needed but liver fluke eggs are shed erratically and in small numbers, so a number of animals should be sampled in a group.

Eggs are only detected if liver fluke have matured into adults, up to 12 weeks after infection. Alternative tests are available that may detect liver fluke before they are producing eggs. These should be discussed with your vet.

Rumen fluke detected on a faecal sample do not usually require treatment unless the animals are showing clinical signs such as scouring or weight loss.

External parasites

Lice and mites can become a problem in the housing period causing scratching and hair loss in cattle. The itching and scratching can be so troublesome that it affects the animals’ welfare and performance.

It is important to treat all animals that are in contact with each other, not only those that are showing clinical signs. For controlling lice, it is best to use an externally applied product, eg pour-on, particularly for chewing/biting lice.

Apply these products to a clean, dry animal, according to the package instructions. Injectable products are preferable for mites and if mites are present or if there is a heavy infestation of lice, a second treatment is usually needed.

Ideally, get a diagnosis and identify which parasites are causing problems on the farm, particularly if a treatment does not seem to be working.

Key points

  • Treat young stock at housing using a product effective against inhibited stomach worm larvae.
  • Older animals do not develop immunity to liver fluke and all age groups should be treated if this is a risk on-farm.
  • The timing of the flukicide treatment depends on the product used and a repeated treatment may be necessary.
  • If treating for lice and mites, all in-contact animals should be treated in the group.
  • Always check the withdrawal period for any antiparasitics used in finishing or dairy animals.