Each year, the Department of Agriculture, Food and the Marine advises farmers of the predicted risk of disease caused by liver fluke (Fasciola hepatica) infection in livestock based on advice received from the Liver Fluke Advisory Group.

The Disease Forecast

The risk of disease due to liver fluke infection this winter is high for all parts of the country. This forecast is based on meteorological data provided by Met Éireann with regard to weather conditions and rainfall during the summer and autumn of this year.

Other Information Sources

Animal Health Ireland

Further to the disease forecast, preliminary information from the Animal Health Ireland Beef HealthCheck programme indicates that nationally the frequency of fluke damaged livers in cattle at slaughter has increased slightly over the summer months and into the autumn, with live fluke detected at low but consistent levels throughout this period. The frequency of these findings is greatest in cattle going to slaughter from north western and western counties. The Beef HealthCheck programme now provides a high level of coverage of cattle nationally, and work is ongoing to analyse the information it provides.

Regional Veterinary Laboratories (RVLs) Liver Fluke Abattoir ELISA Survey

Blood samples collected by Department staff from a selection of lambs (n=4,129) entering abattoirs in September and October were tested for antibodies to liver fluke to determine their level of exposure. Preliminary data from this survey indicates greatest exposure of lambs to liver fluke from counties on the western seaboard.

Farm-to-Farm Variation

In assessing the risk of liver fluke disease on any particular farm, variation between individual farms in their soil type (whether soils are heavy or free-draining) must be taken into account, in addition to weather. The intermediate host of the parasite, which is a mud snail, tends to be located in soil that is slightly acidic and muddy. Thus, areas of fields with rushes are a particularly common location for mud snails to be found.

Aside from local conditions on the farm and prior weather conditions, it is important that livestock owners also factor in prior liver fluke history on the farm. This can be an important indicator of future disease patterns.

Monitoring of Disease

Liver fluke infection tends to be chronic in cattle, resulting in ill thrift and poor performance. In sheep, similarly, chronic disease can occur. However, infection in sheep can 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 stock 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 submitted to a RVL for post mortem examination in cases where the cause of death is not obvious.

Information from abattoir examination of livers (Beef HealthCheck reports for cattle) 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 program.

Treatment and Control

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

In 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 or prior 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 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 such 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.

Where it is feasible, and as a long term control option, areas of fields which are suitable habitats for the intermediate host (wet muddy areas often containing clumps of rushes) should be either fenced off or drained. This will result in a permanent reduction of snail habitat.

What about Rumen Fluke?

This parasite, which shares the same intermediate host as liver fluke, has become more prevalent in Ireland over the last number of years. The pathogenicity of rumen fluke is due to the activity of the juvenile stages in the intestine.

If clinical signs such as rapid weight loss or diarrhoea are seen, or if there is a history of previous disease from rumen fluke on the farm, consult with your veterinary advisor as to whether treatment for rumen fluke is required. The finding of rumen fluke eggs in faecal samples of animals that are thriving and producing well is not reason enough to warrant treatment of these animals for rumen fluke.

Further Information Sources

Further details on liver fluke and its control, and information on flukicide selection along with further information on the Beef HealthCheck programme are available at http://animalhealthireland.ie/?page_id=405.

 ENDS

Date Released: 21 November 2017