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
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 |
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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. |
|
Treatments |
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. |
Advice
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 |
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Test |
Positive |
Negative |
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. |