The Department of Agriculture has warned that there is an increased risk of liver fluke in cattle and sheep in the north and west of the country this winter.

Each year, the Department, in collaboration with Met Éireann, UCD, Teagasc and Animal Health Ireland, advises farmers of the predicted risk of disease caused by liver fluke infection in livestock based on meteorological data gathered between May and October.

While liver fluke levels have generally remained low for the last few years, this year has seen the first increase since the programme began in 2016.

This year’s Ollerenshaw summer index has predicted that infections will be most prevalent in the west and northern half of the country, with a somewhat lower disease prevalence in the southeast of the country.

To date this year, abattoir examinations showed an average of 39% of herds with at least one animal with liver fluke damage. Active infection in one or more animals was seen in 17% of herds, compared with only 13% last year.

Prevalence

Counties in the northwest of Ireland were more heavily affected, with 70% to 80% of herds in Sligo, Leitrim, Roscommon and Donegal reported to have signs of liver fluke at slaughter.

The prevalence within herds is typically low depending on the farm, with 7% of animals presented to slaughter showing signs of liver fluke damage and 2% of animals showing live liver fluke parasites.

Environmental factors such as climate, landform and soil type are taken into account to assess the risk of liver fluke on a particular farm because the intermediate host of the parasite, which is a mud snail (Galba truncatula), occurs in soil that is slightly acidic and muddy.

Thus, areas with rushes or wet patches (for example, around gates or troughs) are particularly important with regard to liver fluke risk, as they can help to maintain a population of the infective stage of the parasite.

The Department is advising livestock owners to factor in prior liver fluke history on the farm, as this is an important indicator of future disease risks.

Monitoring and treatment

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

Livestock owners should be vigilant for any signs of illness or ill-thrift in their animals and consult with their private veterinary practitioner (PVP) if they are concerned.

When using flukicides to control and treat liver fluke infection, particular attention should be given to dosing cattle at the time of housing or shortly thereafter and sheep in autumn or earlier in the year.

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.

Given that flukicides do not have persistent activity, any cattle or sheep that are out-wintered are at risk of further infection post-treatment and follow-up flukicide treatments may be necessary.

Veterinary advice should be sought on treatment protocols and on the appropriate interval at which such treatments should be given, as resistance to flukicides is becoming increasingly widespread.

The Department also advice that as a long-term control option, areas of farms that provide suitable habitat for the mud snail such as wet muddy areas should be fenced off.

Rumen fluke

The rumen fluke, which has become more prevalent in Ireland over the last number of years in both cattle and sheep, uses the same intermediate host as the liver fluke.

However, rumen fluke infection is extremely common, especially in cattle, and only produces disease rarely.

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, livestock owners should consult with their PVP as to whether treatment for rumen fluke is required.