Page 3 - Parasite Control - Liver Fluke, The Facts

PAGE 3 Liver Fluke - the facts

Figure1 illustrates the life cycle of Liver fuke, which depends on an external host as well as catle or sheep. In the
bowel, the larvae are freed from the cysts, penetrate the intestnal wall and move to the liver.

In the liver they travel for 8-12 weeks causing signifcant liver damage. Immature fukes reach the bile ducts where
they mature into adults and in the absence of treatment, they may live for months in catle and years in sheep,
feeding on blood and producing thousands of eggs that are released with the bile into the small intestne, fnally
reaching the pasture in the faeces.

In the egg, a small larval stage (miracidium) develops that, afer leaving the egg, must penetrate a snail (the so-called
liver fuke snail or mud snail). In the snail the larva grows via the sporocyst and redia stages.

Finally 500-1000 larval stages (cercariae) leave the snail and setle on the grass as encapsulated infectve larvae
(metacercariae).

What are the signs that liver fuke infecton may be present in your herd?

Animals may show a variety of obvious signs such as oedema (dropsy) under the jaw (botle jaw), anaemia, poor coat
conditon and lack of appette. Liver fuke infestaton can cause decreased fertlity and wool producton. However, the
animal with weight loss and botle jaw represents the ‘tp of the iceberg’. Detecton of Subclinical infecton with its
adverse efect on growth rate, milk yield and fertlity requires diagnostc tests such as blood tests (elevated globulins,
low albumins, elevated GGT) and assessment of faecal egg counts.
Diagnostc data relatng to liver condemnaton collected at abatoirs is
invaluable and bulk milk testng may be used to confrm that infecton
is present in dairy herds, but the later method should be backed up by
faecal egg countng prior to initaton of a dosing programme.

In Ireland, Liver fuke infecton can be a problem all year round. However,
most infectons occur during the winter, as a result of infectons acquired
in the autumn from snails that build up over the summer on pastures.
Occasionally, snails become infected in the autumn and may hibernate
over winter. They will then shed infecton onto the pasture the following
spring thus infestng animals early in spring tme. Most herds in Ireland
show evidence of infecton, with prevalence greatest in the West. Mature Liver Flukes in Gall bladder of an
infected animal
Recommendatons for control

• Improve drainage and fence-of wet areas with poor drainage, where possible

• Reasonable measures should be taken to prevent poaching and avoid grazing “fukey areas” partcularly
when metacercariae are likely to be present

• Dose bought-in animals with an appropriate fukicide before introducing to pastures. All bought-in animals
should be quarantned for at least 4 weeks afer arriving on farm - see the AHI Biosecurity Purchasing Stock
Guidelines for more informaton on quarantning of newly arrived animals.

• A strategic dose, in early - mid summer, designed to reduce the number of snails becoming infected, is also
recommended

• Fluke burdens can be monitored by using a combinaton of faecal egg counts, bulk milk ELISA and data
relatng to liver condemnatons from the factory. Discuss these results with your vet to ensure your control
strategy is efectve and appropriate.

• Dose animals, where possible, at housing, and if required, again 4-6 weeks afer housing - refer to the AHI
leafet ‘Parasite Control at Housing’ for more informaton on treatment at this tme.
• Treatment of dairy catle is a partcular problem. Dosing with an authorized product during the dry period
should be considered. See below regarding withholding periods.
• Heed the annual DAFM liver fuke forecast, issued in autumn each year htp://www.agriculture.gov.ie