A liver fluke is a parasitic worm that commonly live off of cattle, sheep and other livestock.

Cattle can pick them up while out at pasture, and if not treated can drastically affect their performance, and cause liver damage.

The disease they cause is called fasciolosis. Cattle typically develop chronic disease and classically show loss of weight, condition and become anaemic.

Liver fluke-related disease can become acute and even fatal in sheep, but it rarely becomes acute in Irish cattle.

Liver Fluke picture

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However, if the offending liver flukes mature into adult egg-laying parasites, it can lead to severe liver damage depending on how many there are.

As well as this, cattle infected with liver fluke are considered to be more susceptible to other infections.

That is why it is so important to deal with liver fluke early.



If you are aware of high risk areas for liver fluke, then deal with them as soon as possible.

Fence off wet areas, attend to leaky troughs and pipes, drainage or housing early

If you have lost any sheep, investigate this, as this can be an early indication of fluke risk for your cattle.

liver fluke cycle

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Cattle cannot pick up liver fluke when they are housed, meaning they should be free of the parasite for the winter if they are treated correctly.

However if they are not, it has the potential to put their growth rates well below target.

Correct treatment means using the right product, at the right time, using the correct dose rate and administering it the right way.

Never underdose your cattle for liver fluke, and do not assume that one size fits all when you’re measuring doses.

liver fluke cycle

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Base your measurement off your heaviest animal for a group of cattle.

Do not overdose your cattle either as this can encourace resistance to liver fluke treatments. If you have a large variation in weights, group them to ensure an accurate dose rate.

If the treatment comes in the form of an injection, ensure it goes under the skin and not into the muscle

Bear in mind that just one treatment for liver fluke at winter isn’t always enough.

Liver Fluke treatment needle triclabendazole

According to Teagasc, if you are using a product two weeks after housing (which is a common time to treat for stomach worms and lice) that controls immature and adult fluke, you will have to treat them again five weeks later.

The only 3 scenarios Teagasc say you can use a single treatment for liver fluke are:

  • Drench cattle two weeks after housing with a product that has triclabendazole in it
  • If you are using a product that kills immature fluke (these are mostly injection and pour-on products) you wait for at least seven weeks after housing before you give it
  • If you are using a product that only kills mature fluke (these are mostly injection and oral drench products) you wait for at least 10 weeks after housing before you give it.

Consider reducing pasture contamination levels in spring/summer using a drug that kills adult fluke to stop eggs passing onto pasture.

Animals can pick up infection straight after treatment as none of the flukicidal products aren’t protective.


Over-reliance on triclabendazole as a flukicide has led to drug resistance growing in liver fluke.

It is important that you have an effective plan for cattle that reduces the risk of resistance spreading. If you suspect resistance, arrange a drench test with your vet.

As mentioned before, try and prevent resistance by splitting up your herd into weight groups when you are treating for liver fluke if there is a large variation.

All of these careful steps can be undone if you simply import resistant liver fluke from another farm.

To prevent this, quarantine all incoming stock from potential fluke areas for liver fluke and roundworms.

Be proactive in fighting liver fluke, rather than wait until the problem mounts up. As with many things in farming, being well prepared before you go in can save you from a raft of problems.

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