Liver Fluke (Fasciola hepatica) is an ever-present concern in livestock farming, particularly in dairy where treatments are limited due to long withdrawal periods. Unlike worms, animals do not develop any immunity to fluke infection and can be reinfected each year or even every few weeks in particularly high-risk areas. Winter is an ideal time to assess and treat animals as the likelihood of immature fluke being present at this time is low, which opens up the range of suitable treatments. The latest parasite forecast indicated a low risk of a fluke for the end of Autumn, based on the rainfall we had and temperature from May-October. Although, it’s still worth being vigilant.
The fluke life cycle relies on four main criteria:
- Initial pasture contamination with fluke eggs
- Ensure you have a robust quarantine procedure in place, choose a product that will treat all stages of fluke.
- Remember that the same species of fluke can infect cattle and sheep, so if you offer winter grazing, ensure any incoming animals are treated prior to arrival.
2. The presence of the mud snail, the intermediate host for fluke, without which the fluke life cycle cannot be completed.
3. Standing water in pastures to create the habitat for the mud snails – most people think of ponds/marshy areas, but even standing water wheel ruts can be enough
- Use wetter pastures in the spring/ summer where risks are lower and reserve drier fields for grazing in autumn/winter.
- Fencing off snail habitats can be helpful where possible.
4. Correct weather conditions for larvae to hatch, adequate moisture and temperatures greater than 10ºc
- Infective larvae are primarily shed by snails onto pasture during late summer and early autumn with the highest of infection is in animals
grazed throughout the autumn.
- The highest risk is when animals are grazed throughout the autumn.
- Less commonly, snails can become infected late summer/ early autumn and then lay dormant until spring, which can lead to significant infection.
Sheep are at high risk of acute fluke where large numbers of immature fluke in autumn migrate through the liver, which can lead to rapid weight loss and death. A treatment that treats all stages of fluke is needed.
Cattle, however, tend to develop chronic disease as they have larger livers that allow the fluke to develop to the adult stages. Evidence of chronic liver disease tends to show itself in late winter and early spring and can be treated with a suitable adulticide.
Black disease is a clostridial disease typically associated with migration of immature liver fluke and can affect unvaccinated cattle and sheep of all ages. There is no effective treatment and clinical signs are rarely seen and livestock are simply found dead. Using an appropriate clostridial vaccination plan, alongside an effective fluke control plan, should effectively control black disease.
The key to good liver fluke control is know the risks on your farm:
- Fluke antibodies can be detected in bulk milk samples and are routinely tested for as part of our infectious diseases checks.
- Check abattoir reports for condemned livers.
- Blood or muck can be tested for fluke antibodies and muck can also be sampled for the presence of fluke eggs
- Assess your pasture and know which are your high-risk fields.
Winter housing can be the perfect time to treat animals for fluke and worms as they will not become re-infected. Speak to your vet or SQP to discuss your options for fluke treatments and future control plans.
Summary of different flukicidal products licensed for use in cattle**
** Note: Not all products licenced in cattle producing milk for human consumption