Liver Fluke

General description 

  • Liver fluke (Fasciola hepatica) are large, flat leaf-shaped parasites found in the liver. 
  • Adults are approximately 2cm long and 1cm wide, whilst immature fluke are millimetres long. 
  • Liver fluke require a freshwater snail to complete their lifecycle; hence the problem occurs where there is open water which allows the survival of snails. 
  • Liver fluke reduces animal productivity on farm. It is also an economic cost to the meat industry due to condemnations of livers.  

 Cause 

  • Intermediate stages released from snails form cysts on pasture which are then ingested by grazing livestock. 
  • The ingested immature-stage fluke migrate from the small intestines through the liver tissue to mature in the bile ducts. 

 Clinical signs 

  • Liver fluke disease (fasciolosis) is classed as either acute or chronic. 
  • Acute fasciolosis often does not show obvious clinical signs; affected animal simply die suddenly without any sign of struggle. Affected animals may go down and die within minutes if driven at pace. On close examination anaemia and abdominal pain may be detected. 
  • Chronic disease is more common in cattle and occurs at any time, but is most common from autumn to spring. Cattle generally display ill thrift, anaemia (pale gums and membranes around eyes), scouring and bottle jaw may develop. 
  • Where liver flukeare present, deaths from Black disease may occur if cattle have not been vaccinated. 

Diagnosis 

  • Based on flock history, environment and post-mortem findings. 
  • Where mature fluke are present, testing for eggs in the faeces is a reliable method of confirmation; however egg numbers do not correlate to the liver damage being caused, nor to the fluke burden. 

Treatment 

  • Triclabendazole is the only drench which can be used to kill all stages of the liver fluke within the cattle. Others will kill the mature parasite (in the bile ducts) but will have varying degrees of effectiveness on migrating stages. 

Prevention 

  • Good biosecurity measures when introducing new stock on farm.  
  • Effective, strategically-timed oral drenching of cattle is very important for the control of liver fluke to reduce pasture contamination as infected animals shed eggs in their faeces. 
  • Drenching stock when they exit a paddock with marshy ground which supports a snail population will both reduce the parasite burden on the cattle as well as prevent them from shedding eggs in subsequent paddocks. 
  • Avoid exposing animals to marshy areas infested with snails, especially in dry periods when water levels in the marshy areas are lower and animals have easier access to contaminated herbage. Graze such paddocks with adult sheep and cattle as they have a greater tolerance to the parasite and preferably when water levels are high. 
  • Clean water troughs regularly to prevent the establishment of snail colonies. Where possible, fence off marshy areas and stream banks which offer a suitable habitat for snail survival. 
  • Monitoring the fluke status of livestock using either faecal samples to check for fluke eggs, a blood test, or reports on liver condemnations of animals sent for slaughter. 

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