Diagnosis and Detection

The threat of liver fluke varies from year to year, from farm to farm, and even from field to field. Therefore, it is really important to risk-assess and test for liver fluke in individual flocks before treatment with a flukicide. It is also important to understand the liver fluke lifecycle, because the detection (and treatment) options vary according to the level of maturity of the liver fluke present.

A risk assessment must take into account the farm history, topography, geographical location and weather patterns, using fluke forecasts where possible. SCOPS works with the Control Of Worms Sustainably (COWS) group to issue fluke forecasts/warnings through autumn and winter. The National Animal Disease Information Service (NADIS) also provides free forecasting services.

Diagnostic tools

The presence of liver fluke can be monitored in a number of ways:-

• The blood antibody ELISA test shows whether or not a sheep has been exposed to liver fluke. If this test is carried out on lambs (or calves) in their first grazing season they can be used as ‘sentinels’, giving information of the presence of liver fluke on the farm in that season. This helps to guide both the need and the timing of treatments, providing an early warning system before other tests can be utilised.
• The coproantigen ELISA test is carried out on dung samples and is useful in late autumn/winter to test for mid to late-stage infection. It is generally expected to give two to three weeks advance warning over and above a faecal egg test (see below) but a negaitive result must be interpreted carefully and testing repeated. This test is ideally done on individual samples rather than a pooled sample so seek advice if you’re using this test for the first time.
• Faecal fluke egg counts also have an important role in the monitoring process. This test can only detect liver fluke when egg-laying adults are present, so should not be used later in the autumn, when the flukes have had 10-12 weeks to develop into adults.
• A post mortem on fallen stock will give a definitive diagnosis of all stages of fluke infection. Abattoir feedback on condemned livers can also provide very useful information regarding the presence of liver fluke.

In addition to testing, keeping records of areas on the farm most likely to present a risk of liver fluke can be a very useful tool.

Overuse of flukicides speeds up the development of anthelmintic resistance, can pose a risk to the environment and wastes time and money. Therefore, it is vital to monitor the situation each year even on farms that have a history of fluke infection. Continued monitoring can help determine the need for any further treatments.

For vets/advisers, find more information on diagnosis and treatment in the SCOPS Technial Manual. Chaper 3.4.3.