Are you informed about liver fluke?
Fluke, Fasciola hepatica, is a parasite traditionally found in the wetter, western parts of the UK but, in recent years it has spread across the country. Fluke can affect both sheep and cattle but recent reports of cases in sheep
Symptoms for Sheep
- Clinical signs:
- sudden death
- dullness and anaemia
Acute disease in sheep usually occurs in late summer and autumn from large numbers of immature flukes migrating through the liver with little or no sign of fluke eggs in faeces.
The sub-acute form of the disease is usually associated with late autumn and early winter, with both mature and immature flukes present and faecal egg count of less than 100 eggs per gram.
- Sub-acute infection clinical signs:
- rapid weight loss
- anaemia and oedema, usually under the jaw
Chronic infection which is normally seen from January to April occurs when a population of adult flukes becomes established in the bile ducts with egg counts generally above 100 per gram (though it is not uncommon to find no eggs in some samples).
- chronic infection clinical signs:
- anaemia (visible as pale membranes around the eye or vulva)
- loss of body condition
Definitive diagnosis is based on post-mortem examination. Fluke egg counts in faeces can be useful indicators of infection, although false negatives do occur as the infection may not be spread evenly throughout a herd or flock. A blood test is also available, although this only indicates previous exposure, not a current infection. Antibodies against fluke can be detected in milk, and a positive result on bulk milk indicates that fluke is present in the herd and control should be considered.
Control and prevention
Fluke prevention and control should be part of an integrated approach to parasite control in the herd or flock health plan developed in conjunction with your vet. The following elements should be included in a fluke control and prevention plan:
- quarantine any new animals brought onto the holding - The quarantine procedure for any bought-in animals should include two treatments with a different flukicide to avoid increasing fluke burden or introducing resistant fluke. Sheep can pass fluke eggs up to three weeks after the adults have been killed, so even if treated, stock should be kept on quarantine pasture and away from fields with a fluke habitat for at least a month.
- cultural control can be achieved by drainage, but where farmers are involved in agri-environmental schemes this may prohibit drainage.
- keep susceptible stock, e.g. young calves and sheep, away from the wettest fields that could be infested by the mud snail from late summer onwards, or graze only less infected animals on those areas in spring to minimize infection of the snails.
- consider conserving forage from low lying fields rather than grazing them, this can be useful in reducing the risk of fluke as the infective larval stage dies quickly in silage.
Shared grazing of cattle with sheep, when fluke is present is a risk factor as the same fluke infects cattle and sheep. Mixed grazing or mixed use of land is only beneficial if pigs or horses are rotated with sheep and cattle. Horses can become infected with fluke but usually at low levels. Alpacas and llamas are very susceptible.