AFBI warns of the risks of liver fluke infection this winter

The Agri-Food and Biosciences Institute (AFBI) wishes to bring to the attention of farmers the need to consider the risk of liver fluke infection in cattle and sheep this autumn and winter.

Using a forecasting system based on climate data, staff at the institute have predicted that the overall risk of liver fluke infection during this autumn and winter will be high across Northern Ireland.

This year saw significant levels of rainfall during the summer months, higher than last year in the months of key importance, June and July, and, in general, considerably higher than in 2019.

Liver fluke disease can occur in either acute or chronic forms. The acute form occurs in sheep and is caused by the migration of large numbers of immature flukes through the liver. Acute liver fluke is often fatal and has serious welfare implications.

Signs of severe infections include distended painful abdomen, anaemia and sudden death. In less severe cases, poor production and growth, coupled with reduced appetite and abdominal pain, are apparent.

Chronic liver fluke disease is more common than the acute form and occurs in both sheep and cattle, usually during the winter and spring, although infection can persist throughout the year. Affected animals may exhibit “bottle jaw” (swelling under the jaw).

Reduction of milk yield

Fluke infection can cause a reduction of 5-15% in the milk yield of dairy cows and reduction of growth in fattening lambs and cattle. It is therefore a source of considerable financial loss to the local agricultural industry.

Fluke infections in dairy cattle can also predispose to metabolic conditions such as ketosis and infectious diseases such as salmonellosis. The same is likely to be true for sheep.

Migrating liver fluke can also predispose animals to the clostridial infection, black disease, and care should be taken to ensure that cattle and sheep in fluke-affected areas are fully vaccinated against this disease.

All farmers should review their fluke control measures at this time of year. Access to snail habitats (wet and poorly drained areas) should be reduced or sheep taken off the land and housed or moved to new clean pasture.

However, in most cases, control will be based on the strategic use of anthelmintics, employing a product effective against the life cycle stages likely to be present in the flock or herd at the time of treatment.

This is particularly important in autumn when acute fluke infection occurs in sheep and pick-up of infection by sheep and cattle is still taking place.

At this time of year a product effective against both immature and mature forms is needed. Use of such a product on out-wintered sheep once or twice in autumn, with possible follow up in January, coupled with a treatment effective against adult flukes in early spring, should significantly reduce the fluke burden on individual farms.