Fluke infection already costs UK agriculture approximately £300 million per year due to production losses, with liver condemnations alone costing over £3 million per year.
How Is Liver Fluke Spread?
Infection can be spread from sheep to cattle and vice versa, and is most common on wet, muddy pastures.
For the fluke life cycle to occur, certain species of snail are required to support fluke development from egg to larvae, which can only live in muddy areas or slow moving pools of water. Snails can hibernate over winter and fluke can then resume development once again in the spring. Once developed, larvae are ingested by grazing cattle. It then takes 10-12 weeks for fluke to reach the liver and mature enough to start producing eggs that can be diagnosed in faecal samples.
Liver fluke is a seasonal disease in the UK and development of the above stages occurs most commonly between May and October, with largest numbers of larvae being released from snails at the end of the summer months if the weather remains warm and wet.
Acute fluke in the autumn/early winter months is rarely seen in cattle, but much more common in sheep. Cattle more commonly develop chronic disease, seen in late winter or early spring, including in housed cattle if left untreated.
Signs Of Liver Fluke
Signs seen can range from obvious weight/condition loss, scour and anaemia to less obvious reduced growth rates, fertility, and can cause changes in carcass composition and milk yields.
Cattle infected with fluke are thought to be more susceptible to Salmonella infection and Clostridial disease (Black disease). Cattle do not tend to develop immunity to liver fluke and so infection can be picked up at any age, multiple times.
Diagnosing Liver Fluke
When investigating production loss/diarrhoea, liver fluke can be diagnosed in a variety of ways, depending on the stage of disease.
Blood or milk antibody ELISA tests can detect early infection before eggs are produced, however antibodies are also known to persist for 4-10 weeks after treatment so can simply mean the animal has been only exposed to the parasite.
For dairy herds, bulk milk ELISAs can be used routinely on a quarterly basis to monitor infection/exposure levels within the herd. Faecal egg counts are also commonly used in individual animals or pooled for groups of animals, however lack sensitivity and can only detect infection when adult flukes that can produce eggs are present.
It is important to remember that farm details such as herd history, pasture type, time of year and weather conditions over summer impact on the likelihood of fluke infection on farm. NADIS do provide regional monthly updates on fluke risk, however individual farm risk factors must always be taken into account.
Controlling Liver Fluke
Control depends on farm type/level of infection and will vary year on year depending on weather conditions.
A good control plan would include reducing pasture contamination/use of grazing strategies to avoid contaminated pasture in autumn, and drying out wet areas of pasture alongside use of drugs to target the stage of fluke likely to be present in the animal at the time.
Remember that many flukicides are not licensed for use in lactating dairy cattle or have a long milk withdrawal. Therefore, it is important to consult one of our vets next time they are on farm to discuss best control strategies and drugs suitable for your farm this season!