Inadequate control during high risk periods for acute disease can lead to stock losses of up to 10% in an affected flock through internal bleeding and anaemia or secondary complications caused by extensive liver damage. Unsurprisingly, fluke is a bigger problem in parts of the UK with suitable weather conditions, although it also appears to be increasingly common in areas previously considered lower risk as a result of changing weather patterns.Īdditionally, and again unlike roundworms, both sheep and cattle are susceptible to infection with liver fluke meaning pastures grazed by one species can be a source of infection for the other, including drug resistant strains of the parasite.įasciolosis can have a serious impact on sheep health and welfare. Due to the biology of the external life stages, and its mud snail host, fluke risk is greater when there has been sustained warm, wet weather. Unlike roundworms, sheep of all ages are susceptible to infection with liver fluke, as protective immunity does not develop against this parasite. Once ingested, the juvenile flukes migrate to, and then through the liver causing tissue damage as they go before reaching the liver bile ducts, where they mature to adults and begin producing eggs at around 10-12 weeks post-infection. Consequently, pastures are usually at their most infectious from August to October, although due to the long-lived nature of the infective “cyst” stages, and survival of infected mud snails over winter, pastures can remain infective for most of the year. The development time of liver fluke within the mud snail host can be prolonged, taking six weeks or more depending on weather conditions. Mud snails and the external life stages of liver fluke are only active when temperatures rise above 10 oC, meaning development of liver fluke on pastures in the UK generally occurs from mid- to late-Spring through to early Autumn. These snails are only present in damp, muddy areas such as the borders of permanent water bodies, wet flushes (often identifiable through presence of rushes and other water loving plant species), ditches, boggy areas etc. Unlike other parasites of grazing animals, the liver fluke life cycle requires an intermediate host, the mud snail ( Galba truncatula). The liver fluke, Fasciola hepatica, infects a number of animals including cattle, sheep, goats and horses. This is reflected in an increasing number of cases identified through laboratory surveillance and abattoir inspection in sheep and its emergence in parts of the UK previously considered to be low risk. Changing weather patterns appear to favour development of this parasite. This also makes disease more common in wetter parts of the UK. Due to its complex life cycle disease is seasonal in nature, with wet, warm conditions favouring its development on pastures. In sheep, disease can range from seemingly unaffected animals with sub-clinical infection to sudden death in heavy, acute infections.
This parasite is capable of infecting a range of animal species including cattle, sheep, goats and horses. Fasciolosis is the disease caused by liver fluke ( Fasciola hepatica) infection.
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