Liver fluke is a parasitic disease of grazing animals caused by Fasciola Hepatica (a flat worm) and has a major economic impact on cattle and sheep farms.

Due to the dry weather experienced over the summer months the risk posed by liver fluke this year is expected to be low – but that does not mean fluke will not pose a threat.

According to Animal Health Ireland (AHI) losses due to liver fluke are estimated to cost €90 million/year to the Irish agriculture industry, mainly due to decreased production associated with an infection.

Dairy cows are estimated to have a decreased milk production of 8%, while this can be between 20% and 30% in meat production of cattle and sheep.

Liver fluke symptoms

Infection can be an issue at any time of the year, however most infections occur during the winter period.

This is usually caused by animals becoming infected during late summer and early autumn.

Mild weather and above average rainfall provide the best environment for liver fluke to develop.

Clinical signs of an infection include:

  • Reduced liveweight gains through reduced feed conversion efficiency;
  • Reduced milk yields;
  • Reduced fertility;
  • Bottle Jaw;
  • Diarrhoea;
  • Anaemia.

Clinical signs can be an indication of an infection within a herd. It should be noted that if there are clinical signs present, the worm burden is generally quite high.

Continued monitoring using faecal egg counts or bulk milk sampling is best and control measures should be implemented before clinical signs develop.


There are several control measures that can be used on farms to limit livestock’s contact with liver fluke worms.

Wet areas should be either fenced off during high risk periods or drainage improved. The pouching of fields and areas where liver fluke worms are likely to be located should be avoided.

Newly purchased animals should be quarantined and dosed before introduction to the herd.

Continued monitoring of fluke infestation is advised, this can be done by checking faecal egg counts or by bulk milk tank sampling.

Cows are generally not dosed for fluke during lactation, due to the withdrawal period required by the products.

For this reason, most farmers will dose animals at drying off for liver fluke, but if faecal egg counts show a high level of infection, targeted treatment is advised.