05/11/2024
Liver Fluke Information Note
Understanding Liver Fluke in Cattle and Sheep: A Guide for Farmers
Liver fluke infection, caused by the parasitic flatworm Fasciola hepatica, is a widespread and serious issue affecting both cattle and sheep. The parasite can lead to significant health problems in livestock, ultimately impacting farm productivity and profitability.
The Lifecycle of Liver Fluke
Understanding the lifecycle of liver fluke is crucial for effective control. The parasite has a complex life cycle that involves both definitive hosts (cattle and sheep) and an intermediate host, the mud snail (Galba truncatula).
Adult liver flukes live in the bile ducts of infected animals, where they lay eggs that are passed out in the host’s faeces. In wet and damp conditions, the eggs hatch into larvae (miracidia), which must find and infect a mud snail within a few hours. After a period of 6-8 weeks the larvae are released from the mudsnail and infect pasture. Once ingested, these larvae (metacercariae) migrate through the animal’s gut wall and liver tissue, eventually settling in the bile ducts of the liver, where they mature into adult flukes and begin the cycle again.
Negative Impact and Health Issues
Liver fluke infestation can have a range of detrimental effects on both cattle and sheep:
Acute Liver Fluke: This occurs primarily in sheep but can also affect young cattle. Large numbers of immature flukes migrate through the liver, causing severe liver damage, hemorrhage, and in some cases, sudden death. Symptoms include weakness, anemia, and rapid weight loss.
Chronic Liver Fluke: More common in cattle, chronic liver fluke results from long-term infection. Adult flukes in the bile ducts cause inflammation, fibrosis, and blockage, leading to reduced feed conversion efficiency, poor growth rates, decreased milk production, and reduced fertility. In severe cases, it can also lead to liver failure.
Economic Impact: The economic consequences of liver fluke infection are significant, including reduced productivity and negative health impacts associated with liver damage such as poor response to vaccination or susceptibility to other infectious diseases, e.g. salmonellosis.
Controlling Liver Fluke
Effective control of liver fluke requires an integrated approach that combines pasture management, strategic treatment, and monitoring. Here are some key strategies:
Pasture Management:
Drainage: Improving pasture drainage can make habitats less favourable for mud snails. However, this may not always be feasible or sufficient on its own.
Avoidance: If possible, avoid grazing livestock on wet, boggy pastures, especially during peak risk periods (late summer to early winter), when metacercariae are most abundant.
Strategic Treatment:
Anthelmintics: Administering flukicides at strategic times of the year can help reduce the burden of liver fluke in the herd or flock. The choice of flukicide and timing of treatment should be based on the lifecycle stage of the fluke and local risk factors. Different flukicide groups are effective against different stages of liver fluke, for example triclabendozole is effective against early immature, and mature fluke where as oxyclozanide is only effective against mature (adult) fluke.
Treatment Timing: Typically, treatment is recommended in the autumn (to target immature flukes) and late winter or early spring (to target adult flukes). In some cases, additional treatments may be necessary during high-risk periods.
Resistance Management: To reduce the risk of drug resistance, rotate the use of different classes of flukicides and follow veterinary guidance on dosing and treatment intervals.
Monitoring and Diagnosis:
F***l Egg Counts (FEC): Regular f***l egg counts can help assess the level of liver fluke infection in your animals and guide treatment decisions. Be aware that it takes at least 13 or 14 weeks from the time of the animal being infected for fluke to become mature and start shedding eggs, therefore faecal egg counts are not useful for detecting early infections
Blood tests. Fasciola antibody elisa tests are a useful tool for detecting Liver fluke in cattle from about 3 weeks post infection. Elevated blood liver enzyme tests (GLDH and GGT) can also be indicative of liver damage relating to liver fluke infection
Bulk tank milk. Measuring Fasciola antibody levels in the bulk tank are a useful monitoring tool for liver fluke in dairy herds. They can also be used (with caution) to assess the response to treatment- herds with high bulk tank fasciola antibody levels at drying off should see a reduction in the bulk tank antibody levels in spring if treatment was successfully implemented. It should be noted that it can take up to 3 months for milk antibody levels to return to low levels post treatment.
Liver Fluke Forecasting: Utilize liver fluke forecasting services, which use weather data to predict fluke risk, helping you time treatments more effectively.
Post-Mortem Inspection: When animals are slaughtered, request a liver inspection report. This can provide valuable information on the presence of liver fluke in your herd or flock.
Conclusion
Liver fluke is a challenging parasite, but with the right management strategies, its impact can be minimized. By understanding the lifecycle of the parasite, recognizing the health issues it causes, and implementing effective control measures, you can protect your livestock and maintain farm productivity. Regular monitoring, combined with strategic treatment and good pasture management, are your best defenses against this costly parasite.
For personalized advice and treatment plans, always consult with your vet, who can help develop a tailored liver fluke control program based on the specific conditions of your farm.
