Liver Fluke in Cattle

by Andrew Cribb (Cribby)

Cribby is the Director/Veterinarian at East Coast Farm Vets

March 2022

Liver Fluke Fasciola Hepatica, are flatworms that feed on the blood of their host and can destroy the liver of infected stock.

Their life cycle is complicated and involves numerous larval stages, water snails (as intermediate hosts) and can vary considerably in length, depending on environmental conditions.

Early immature fluke (2 weeks after ingestion) are crucial to keep under control as they travel through the liver causing more damage than adult fluke living in the bile ducts. Clinical signs observed range from anaemia and weight loss (<200 adult fluke) to sudden death (<1000 immature fluke).

Cattle are particularly prone to liver fluke infections because they often feed in the wet areas that suit the water snail immediate host and the infective fluke stage. Young stock is particularly at risk.

A degree of immunity is acquired over time; however this is often associated with extensive prior damage to the liver. Unfortunately, this type of resistance is not a protective immune response, having little ability to control immature flukes. Although fluke numbers can be suppressed, liver damage and consequently production loss will occur.

Sheep on the other hand avoid wet areas but graze the grass lower and so therefore can pick up significant infection in contaminated pasture. Farms with persistent wet areas and those in parts of the country that experience long, hot summers are most at risk. Periods of extended drought force sheep to graze contaminated wet areas, thereby greatly increasing the risk of infection. Sheep also develop little resistance to liver fluke meaning all age groups are susceptible to repeated seasonal exposure and therefore require treatment.

Other than monitoring stock for clinical signs or examination of the liver post-mortem, diagnosis can be achieved through blood testing (liver function, ELISA) and faecal egg counts.

Correct timing of treatment and product selection is based on the biology of the fluke and likely parasite challenge to stock. The two core treatments are in late autumn/early winter and late winter/early spring.

The spring treatment is an essential preventative treatment that helps to break the fluke life-cycle by removing any flukes that have infected the animals throughout the winter. By preventing the contamination of the pastures with fluke eggs as temperatures warm up, the snail intermediate hosts do not immediately become infected as they become active.

Spring treatment should therefore primarily target adult fluke, however; the mild and wet winters of the East Coast mean fluke infection can continue throughout the year. As a result, consideration should be given to treating for immature fluke using a combination drench.

Please contact your vet team to discuss the best options for treating liver fluke at their various larval stages.

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