Treatment of liver fluke in cattle and sheep this winter
November 10, 2021
With the majority of cattle housed from late October through early November many farmers are now addressing their herd health plan again, in particular for the treatment of liver fluke. In this article Dominic Mason, CAFRE Beef and Sheep Advisers looks at the signs, lifecycle and treatment of liver fluke in cattle and sheep.
Liver fluke disease (fasciolosis) is a widespread problem within the UK and Ireland which can have a massive impact on the overall productivity and profitability of cattle and sheep, with the estimated cost to the UK cattle industry alone reaching a staggering £40.4 million annually.
In late October 2021 the Agri-Food and Biosciences institute (AFBI) brought to our attention that the farmers of Northern Ireland “need to consider a medium to high risk of liver fluke infection in cattle and sheep this autumn and winter”. This prediction was made via the use of a forecasting system based on climate data and have predicted that the fluke infection will be “moderate to high in central, southern and eastern parts of the province and that high prevalence of the disease is likely in the west”
Many will be aware of Liver Fluke due to past experiences of this parasite within their stock, leading to ill thrift and reduced daily live-weight gain (DLWG). It is a parasite with a rather complex life cycle which can cause 3 forms of infection; acute, sub-acute and chronic. Timing of the forms depends on when infestation occurs but traditionally acute fluke would be seen from August through to October, sub-acute from October onwards and Chronic from December onwards.
Chronic liver fluke disease is more common than acute cases and can occur in both cattle and sheep usually during the winter and spring months. Acute disease would be more commonly seen in sheep and is often fatal. All 3 forms however will display signs within cattle and sheep and these signs are classed as either sub clinical or clinical signs.
Clinical Signs in beef cattle & sheep:
- Overall weight loss/reduced body condition
- Anaemia caused by liver damage as a result of the activity of adult fluke once in the bile duct.
- Bottle jaw
- Ewes in late pregnancy would be more susceptible to metabolic diseases such as twin lamb and staggers. Also likely to produce less colostrum and perform poorly in their lactation.
Liver Fluke. The cycle
The liver fluke life cycle is complex and requires an intermediate host to continue, which in this case is the mud snail. For the mud snail to survive and thrive they require a damp habitat. Below Dominic outlines the Liver fluke life cycle.
- The adult fluke lay eggs in the hosts which are then passed out in the dung.
- Once temperatures are suitable (above 10 ), fluke eggs will develop and hatch. Once hatched these larvae or miracidium swim and attach themselves to the mud snail.
- Each of the miracidium burrow themselves into the mud snail’s body and undergo 2 developmental stages which eventually lead to the production of infective cercariae.
- The cercariae will emerge from the mud snail when the temperatures and moisture levels are suitable. It’s at this point that they attach themselves to the grass plant and other vegetation forming cysts known as metacercariae.
- These metacercariae/cysts can live and remain viable on pasture for several months. Ultimately they are eaten by the grazing animals and hatch within the cow/ewe/beef animal eventually burrowing through the gut and into the animals liver. At this point they ingest blood within the liver, causing severe anaemia and chronic inflammation of the bile ducts.
Patent liver fluke infection, or when the adult fluke start to lay eggs commonly occurs at 10-12 weeks after the metacercariae are ingested. In some cases clinical signs can be visually seen before adult fluke lay their eggs and therefore be detected within a dung sample.
Dominic confirms that the housing period marks the end of exposure to contaminated pasture for the season. Considering this, you now have the ideal time to look at your options for diagnosis or treatment.
There are several flukicide products on the market and they are generally classified based on the stage of liver fluke that they are active against. It is important to have recorded housing dates and historical treatments in an effort to target the correct stage of liver fluke with the correct flukicide.
There are 2 methods in which liver fluke can be treated at the point of housing:
- Delay treatment for a number of weeks from housing to allow the immature fluke to develop into mature fluke allowing you to treat with a product which covers that stage of fluke.
- Alternatively, if you are concerned of a heavy fluke burden due to historical information or observations consult your veterinarian who may recommend treating straight away.
In recent years there have been reported cases of resistance to some flukicides such as triclabendazole. With this is mind it is essential that all veterinary products including flukicides are used responsibly in an effort to reduce Antimicrobial Resistance (AMR) and it is advised that you work with your local vet to discuss a suitable parasite control plan.
A disciplined approach involving a strategic flukicide choice to reduce pasture contamination and resistance is essential. Grazing management, according to Dominic, is also important taking into account the restriction of stock from wetter areas where the mud snail would thrive as the intermediate host.
On farm data can be collected and reviewed through items such as abattoir feedback reports, detailing if liver fluke were found on the livers of your cattle even if clinical signs were not visible. Diagnosis and consultation with your veterinarian through Faecal Egg Count (FEC) reports is also another option.
Ultimately, Dominic summarises, the fight against fluke will depend greatly on your location, rainfall and average temperatures. Grazing protocol and historical fluke treatments throughout the year are also very important in an effort to reduce the number of adult fluke laying their eggs and starting the cycle once again.
AFBI publish liver fluke forecasts through the local farming press and their own website which can be accessed via www.afbini.gov.uk.