In this final instalment in the Beat the Parasites series, we look at the new prescription rules for wormers, and what farmers need to know before December 2025.

From December 1, 2025, livestock farmers in Ireland will need a veterinary prescription for all antiparasitic medicines.

This change means that cattle, sheep and dairy farmers will need to work more closely with their vets to get the right treatment for worms, fluke, and other parasites.

The aim is to improve animal health and welfare, reduce the risk of resistance to wormers, and protect the wider environment.

But to get the most from each prescription, farmers will need to be ready with the right information when they speak to their vet.

In this article, Peter Howard, veterinary adviser at Boehringer Ingelheim explains what your vet will need to know to help them prescribe the most effective and responsible treatment for your animals.

1. Animal and herd history

Your vet will start by asking about the type and age of animals on your farm and any recent movements or purchases.

If you have brought in stock, they will want to know whether those animals were quarantined or treated on arrival.

This helps assess the risk of introducing parasites from other farms.

Howard explained: “It’s important to share with your vet any history of parasite problems.

"For example, if you’ve had issues with lungworm, fluke, or Nematodirus, or if you’ve noticed scours or coughing in any youngstock.

"And don’t forget external parasites such as lice, mites, or flystrike, as they may also influence your vet’s advice.”

Having an idea of average weights or growth rates is also helpful, not only to ensure correct dosing but also to highlight performance issues that could be linked to parasites.

2. Previous treatments

“Your vet will ask about what wormers you’ve used before, and when and why you used them,” Howard said.

Overusing the same type of wormer can increase the risk of resistance, meaning treatments become less effective over time.

"This is why it’s important to go through your treatment history with your vet,” Howard explained.

If you suspect that wormers are no longer working as well as they used to, mention this.

Your vet may suggest a Faecal Egg Count Reduction Test (FECRT) to check whether resistance is developing on your farm.

3. Diagnostic tests and results

To prescribe responsibly, your vet will look for evidence of parasite infection before recommending treatment.

You might be asked to collect dung so your vet can carry out a Faecal Egg Count (FEC) test to check worm levels in cattle or sheep.

In sheep, FECs can guide whether treatment is necessary.

In cattle, they are most useful in youngstock early in the grazing season, and can help track changes in gutworm burden.

Later in the year, or for adult cattle, FECs may not be as reliable, but they can still be useful for identifying fluke burdens, especially towards the end of the housing period.

“If you’re a dairy farmer, your milk processor may provide bulk milk ELISA tests on collected milk," Howard said.

"The results from these tests can show whether antibodies from the pathogenic gut worm Ostertagia ostertagi are present at low, medium, or high levels.

"These provide another valuable clue for your vet, alongside any treatment history."

And do not overlook abattoir feedback. Reports showing liver damage from fluke can indicate whether your current control programme is working or not.

4. Pasture management and grazing

Good grazing management plays a big role in parasite control, and your vet will likely ask about how different groups of animals use the land.

Be ready to talk about:

Which animals and age groups graze each paddock and for how long;
Whether ground was used for silage or rested;
How animals are moved between fields.

In sheep, for example, Nematodirus risk can be reduced by using clean grazing for lambs.

Similarly, young cattle can benefit from being moved to cleaner paddocks from mid-summer onwards to lower the parasite challenge they face.

This information helps your vet assess risk levels and recommend timing for any treatments.

5. Prescribing the right product

After reviewing your herd history, test results, and grazing management, your vet can narrow down which products will work best, and when.

Different wormers and flukicides target parasites at different life stages, so timing matters.

For instance, some flukicides only kill adult fluke, while others are effective against immature stages.

“Your vet will also consider whether multiple parasites are present,” Howard said.

Another key factor is meat and milk withdrawal periods.

Your vet will need to know if animals are close to slaughter or calving, to ensure withdrawal times do not cause costly delays or milk waste.

Finally, practical issues matter too. Your vet may ask what handling facilities you have, such as a crush or race, and what labour is available.

This helps ensure that whatever product is prescribed can be administered safely and effectively.

6. Working together

“From 1 December 2025, vets and farmers will need to work even more closely to manage parasites in livestock.

"But these conversations don’t have to be complicated,  and they’re a great opportunity to review what’s working, and what’s not, on your farm,” Howard added.

By keeping good records, carrying out simple diagnostic tests, and talking openly with your vet, you will be able to:

Target treatments more accurately;
Avoid unnecessary use of wormers;
Protect the effectiveness of products for the future.

“As always, use medicines responsibly, and remember that the right product, at the right time, for the right animal is the best protection for your herd, your land, and your livelihood,” Howard stressed.