Immature fluke still a threat, surveillance farms show

Experts are predicting a relatively high challenge of fluke this spring due to the mud snail intermediate host remaining active as a result of the warm winter weather.

The warning comes after results from five fluke surveillance farms show sub-acute and acute fluke disease risk has remained present throughout the winter.

Sheep vet Matt Colston from Elanco Animal Health, who has been overseeing the trial, says the results show sheep farmers still need to be mindful of the threat of immature fluke, even though it is almost spring.

See also: Fluke survey reveals only 8% of farmers are treating correctly

In a normal year, when temperatures drop below 10C in the winter, the mud snail goes into hibernation and stops releasing the infectious stages of fluke on to pasture.

But this year that hasn’t happened because of the mild, wet weather conditions, says Mr Colston.

“This season is different from average. Normally we would expect to see challenge on pasture rising through the autumn to peak around October/November and declining over Christmas.

“But this year because of the cold summer there wasn’t much challenge until October/November so we are getting peak challenge now. The season has been shifted by a couple of months.

“Just because it is February it doesn’t mean you can stop thinking about immature fluke,” he warns.

Surveillance farms

Elanco set up five surveillance farms to monitor fluke risk in response to the Farming Against Liver Fluke (Falf) campaign.

The farms have been working with industry experts and their vets to test, monitor and help manage a sustainable approach to liver fluke control on their farm.

Farm profiles

  • Farm one George Milne, Kinaldy Farm, Fife: 120 pedigree ewes and lambs, 500 gimmers and 250 fattening hogs. Experienced large losses to fluke in the winter of 2012-13.
  • Farm two John Harrison, Croftheads, Dumfries and Galloway: 200 Lleyns and Hampshires ewes.
  • Farm three Paul Capstick, Parkhouse Farm, Heversham, Cumbria: 1,000 mule ewes.
  • Farm four Carwyn Roberts, Garn Fach, Llanelli: 270 ewes.
  • Farm five Mr Peter Derryman, Peterhayes Farm, Honiton, Devon: 100 pedigree Hampshire Downs, 120 pedigree Suffolks and a commercial flock of 250 Romneys.


Results for January show newly acquired liver fluke infection has been detected on four out of five farms.

Commenting on the results (see “Samples taken from November to January to determine liver fluke risk”), Mr Colston says: “For our five farms, where there is a fluke challenge, the level of challenge has been maintained or is increasing, with the risk of acute or sub-acute disease still present.

“In these circumstances treatment with an active effective against early immature fluke is advisable.

“This would normally be triclabendazole, or closantel where triclabendazole resistance has been established.”

Samples taken from November to January to determine liver fluke risk     

Test taken

Farm one: Fife, Scotland.

Farm two: Croftheads, Dumfries and Galloway.

Farm three: Heversham, Cumbria.

Farm four: Llanelli, South Wales.

Farm five: Honiton, Devon.

Copro-antigen test taken in November

Six lambs positive, but no fluke eggs present

Lambs: One positive, nine negative

No test taken

All negative (check which test)

Ewes only – Negative

Copro-antigen test taken in December

No test taken

Seven lambs positive, three negative

Ewes: positive bulk sample

Lambs: three positive, seven negative

Ewes: Positive bulk sample for the first time

Lambs: Five positive, five negative.

Ewes only -Negative

Fluke egg test taken in December

No sample taken

Ewes: Large numbers positive in bulk sample

Lambs: two positive, eight negative.

Ewes: Large numbers in bulk sample for first time

Lambs: 10 negative

Ewes only – negative

Copro-antigen test taken in January

Treated lambs: three positive, 7 negative

Untreated lambs: four positive, six negative

Ewes: positive bulk sample

10 lambs positive

No sample taken

Lambs: 10 positive


Fluke egg test taken in January

Treated lambs: All samples negative

Untreated lambs: two positive, eight negative

Ewes: Large numbers positive in bulk sample



Lambs: nine positive, one negative.



Closantel in November

Triclabendazole in December

Ewes treated in December with Triclabendazole and lambs housed in December and treated with Closantel mid-January.

Closantel treatment in November

No Fluke challenge yet

What does it mean?

Evidence of active infection and continual challenge

Increasing level of infection. Treatment was ineffective.

Liver fluke challenge

Liver fluke challenge

No treatment needed

What next?

All groups would benefit from treatment

All groups treated with Closantel

February samples being analysed to determine treatment options

All groups would benefit from a treatment

Continue to monitor.


Mr Colston advises farmers to speak with their vet to see what the level of challenge is like in the area.

“These results show the impact that weather can have on liver fluke levels and the need to stay alert to the challenge”, advises Mr Colston.

“I urge famers, including those in areas previously thought of as fluke-free, to learn from these surveillance farms and to consult with their vets and animal health advisers to establish similar control measures for sustainable liver fluke control if they have not done so already.”

What the tests show




Fluke antibody test

Indicates lambs have met a liver fluke challenge. It means there is liver fluke on the farm, but does not mean you should treat right at this time, but is a helpful indicator of fluke infection.

No exposure to liver fluke yet. This suggests there has been no liver fluke challenge with the tested group, and treatment is not necessary. Other groups on the farm could still be at risk, depending where they have been grazing.

Copro-antigen: This test is specific for Fasciola hepatica, and will detect the presence of active liver fluke when the volume of “excretions” from the fluke passes a certain threshold

Indicates active liver fluke infection.

Indicates no fluke present or very low numbers, or very small fluke such that fluke secretions are not great enough to make the test positive.

Fluke egg detection (faecal egg count)

This tells us egg-laying adult liver fluke are present.

This means no egg-laying liver fluke are present. A fluke needs to be in the animal for 10-12 weeks before it lays eggs so no eggs does not mean there are no liver fluke, they may just be too young to lay eggs.