Department issues liver fluke forecast for winter 2018

The Department of Agriculture, Food and the Marine has issued its advice for farmers of the predicted risk of disease caused by liver fluke infection in livestock, in collaboration with Met Eireann.

Due to the dry weather conditions experienced in many parts of the country this summer, there is a moderate risk of liver fluke-related disease this winter for the north, west, south-west and midlands, with a lower disease risk expected for the east and parts of the south.

However, farmers in these lower-risk areas should still remain vigilant for signs of disease, according to the department.

This is based on meteorological data gathered between May and October by Met Eireann. Other risk prediction tools have also been consulted.

Preliminary data from lamb blood samples taken by Regional Veterinary Labs (RVLs) from 348 flocks across 25 counties indicate that the majority of moderately-infected flocks are from counties on the western seaboard, with a small number of heavily-infected flocks in the north-west.

Meanwhile, based on survey data collected between 2014 and 2015 from sheep flocks, dairy and beef herds, a model of exposure to the liver fluke in Ireland has also been developed by UCD.

The model highlighted temperature, rainfall and vegetation indexes among the main risk factors.

In addition, the risk map indicated that the predicted probability of exposure to liver fluke was greater in the western parts of the country.

Monitoring liver fluke

Liver fluke infection tends to be chronic in cattle, resulting in ill-thrift and poor performance. In sheep, chronic disease can occur but infection may also result in more acute clinical signs, and can cause sudden death in cases of heavy challenge.

Livestock owners should continue to be vigilant for any signs of illness or ill-thrift in their animals and should consult with their veterinary practitioner for diagnosis of liver fluke infection or other potential cause(s) of these clinical signs.

It is recommended that carcasses be referred by a veterinary practitioner to an RVL for necropsy in cases where the cause of death is not obvious.

Information from abattoir examination of livers of previously-sold fattened stock is also a valuable source of information to inform livestock owners of the prevalence of liver fluke infection on their own farm or on the efficacy of their control programme.

Treatment and Control

In areas of high risk and on farms where liver fluke infection has been diagnosed or where there is a prior history, livestock owners should consult with their veterinary practitioner to devise an appropriate treatment and control programme.

When using flukicides to control and treat liver fluke infection, particular attention should be given to dosing cattle at the time of housing, and sheep in autumn or earlier in the year if there are concerns based on faecal examination results or prior disease history.

For sheep, a drug effective against early immature as well as late immature and mature flukes should be used to protect against acute disease, and sheep should also be removed from affected pasture to prevent re-infection.

If the flukicide given to cattle at housing is not effective against early immature fluke, then faecal samples should be taken six to eight weeks after housing and tested for the presence of liver fluke eggs.

This will determine whether a follow-up flukicide treatment is necessary.

Advice should always be sought on treatment protocols and the appropriate interval at which such treatments should be given.

Testing faecal samples for the presence of liver fluke eggs can help determine both the necessity and success of flukicide treatments.

This is especially important given that resistance to flukicides is becoming an increasing concern.

In addition, bulk milk tests for antibodies to the parasite in dairy herds can be useful in monitoring year-to-year variation in exposure (please note that bulk milk tests cannot be used to judge the success of any treatment given).