As a general rule of thumb, liver fluke is most prevalent in a wet and mild summer, much the same as we see with increased worm burden. The drier summer experienced this year means it has not posed a threat as of yet, but rainfall in the last two months will see cattle going indoors with early immature, immature and/or adult fluke in them, while sheep, due to often being grazed on heavier and wetter land, are hugely prone to liver fluke in the autumn and winter months.

Sampling and diagnosing

Routine dosing should not be completed where there are no clinical signs or presence of fluke eggs in a faecal sample. A fresh, pooled (from several animals) sample should be taken and presented to your vet or to a lab as soon as possible. Results received should dictate dosing protocol, although farmers should also use their own initiative and watch for clinical signs of liver fluke.

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Clinical signs are less pronounced in sheep than in cattle. However, the presence of liver fluke can present issues such as reduced liveweight gain and feed conversion efficiency (FCE) and reduced fertility in autumn-calving cows. While bottle jaw is more common in sheep flocks, it can present itself in cattle and is similar to timber tongue with a swelling of fluid beneath the jaw, although the tongue will not swell if it is a fluke problem.

Dosing protocol

If a fluke drench is required, the efficacy of the product against different life cycles of the fluke need to be considered before drawing up a drenching programme. An early/mid-summer dose is sometimes recommended where fluke is a recurring problem; this reduces the volume of mud snails (primary host of fluke) thereby reducing the prevalence in autumn/winter months.

Certain products are only effective against the adult stage of liver fluke. Where a drench like this is used at housing, farmers should follow up 10 weeks later with a second drench. All early immature and immature fluke that were not killed at the first drenching will now have become adults, with the second drench required to kill these. Alternatively, farmers can use a drench that will cover all three stages that will not require a follow-up drench.

Caution should be urged with regard to dairy cows or in-calf heifers who are treated for fluke in the dry period, as some active ingredients can carry long withdrawal periods or may not be appropriate for use in dairy cows producing milk for human consumption. Your vet will be able to advise on timing and the appropriate active ingredient for your herd.

The inappropriate use or overuse of some flukicides such as triclabendazole has led to the emergence of resistant strains of F. hepatica (liver fluke); this has been reported in several countries including Ireland, the Netherlands and the UK. Therefore, annual rotation of anthelmintics, plus post-treatment assessment of effectiveness of dosing should form part of fluke control programmes. Again, consult with your own veterinary practitioner as to the best strategy for your farm.

Rumen fluke

Traditionally, rumen fluke was not considered to be a significant parasite of Irish cattle, mainly because it was only seen in very low numbers, and was not associated with clinical disease.

In recent years, however, a number of very severe outbreaks, with multiple fatalities, have focused attention on the rumen fluke.

It is important to remember that the detection of rumen fluke eggs in faecal samples, or the detection of the adults in small numbers in the rumen is not in itself a reason to institute specific control measures, as light infections appear to have no effect on animal health or productivity.

It is estimated that up to 50% of herds in Ireland may have rumen fluke present, but just 5% require intervention.

The routine implementation of a preventive dosing regime for rumen fluke is rarely justified, except on farms where severe disease and losses have been confirmed in the past.

Due to the rarity of severe outbreaks, such a control programme would be best designed and tailored for the specific farm in question, following consultation with your own veterinary practitioner.

Such a programme would aim to use treatment in a strategic manner to reduce the pasture contamination, in association with other measures mentioned previously.

With all fluke treatments, a tailored approach should be carried out as opposed to a blanket treatment to reduce the risk of on-farm resistance to flukicides.