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Assessing the Liver Fluke Risk on your Farm

01 October 2019
Type Media Article

Joanne Masterson, B&T Drystock Adviser, Teagasc Galway/Clare

The month of August was a particularly wet month in the west of Ireland. Rainfall in Mellows Campus, Athenry for the month of August totalled 297mm of rainfall; when you compare this to August 2018 total rainfall for the month was 126mm. This high rain fall and mild temperatures are the ideal conditions for fluke to thrive in. The west and north-west of the country traditionally have higher burdens of fluke; this is mainly due to higher rainfall and land type.

Liver Fluke is caused by a flat leaf-like worm called Fasciola Hepatica. An intermediate host, the mud snail is also involved in the life cycle. Infection with liver fluke occurs when pasture that is contaminated with fluke is eaten by the animal. Once eaten fluke starts to feed and grow. It takes approximately twelve weeks for the flukes to grow to adult stage when they start to lay eggs. These eggs pass out in the faeces of the animal and when conditions are suitable (when temperatures go above 10 degrees) they hatch and use the mud snail to continue the life cycle. During this twelve week period the fluke are classified according to their stage of development:

  • First 5-6 weeks – early immature fluke
  • Weeks 6-10/11 – Immature fluke
  • Week 11 + - Adult fluke

Types of Liver Fluke Disease:

Acute Fluke – this occurs when large amounts of immature fluke burrow through the animals liver and can lead to rapid death.

Chronic Fluke – this occurs due to adult fluke sucking blood in the liver. Clinical signs of chronic fluke include anaemia and loss of condition. You may also notice paleness around the eyes and gums this may mean the animal is suffering from anaemia. There may also be abdominal pain and swelling such as ‘bottle jaw’ due to fluids that are retained. Clinical signs in cattle may be more subtle than in sheep; along with the signs above they also include reduced milk yields, reduced fertility, and diarrhoea. In some cases you may not know that you have a fluke problem until it is detected in animals in the abattoir due to condemnation of livers as a result of damage caused by fluke travelling through the liver. Animal Health Ireland have developed a Beef HealthCheck programme which analyses and reports abattoir data from post mortem meat inspections. It also looks at regional and national trends and if the incidence of liver fluke increases in slaughtered animals it is possible to issue alerts to the farming community where they can then make decisions on dosing their animals.

Controlling Liver Fluke:

The following guidelines are useful in control of Liver Fluke on the farm:

  • If possible try to improve drainage on the farm and fence off any muddy areas during risk periods (areas where rushes may be growing).
  • Any bought in animals should be quarantined for at least 4 weeks after arriving on the farm.
  • Strategic Dosing – in early to mid-summer may reduce the number of snails becoming infected.
  • Faecal Egg Counts – to determine if the product you are using is being effective.
  • Dose animals if possible at housing and if needed 4-6 weeks after housing.
  • Look out for the annual Department of Agriculture Food and the Marine (DAFM) Liver Fluke forecast which advises farmers of the predicted risk of disease by Liver Fluke infection in livestock. This will be released in early November.

Treatment of Liver Fluke:

There a numerous products on the market that are available to treat liver fluke, however, in some cases it may not kill all fluke in the animal. This could be because the product used is only killing part of the fluke burden; resistance may have built up, under dosing animals and not using equipment correctly.

Treatment for liver fluke has to be specific to your farm. Flukicides can be divided into a number of groups according to the active ingredient. Triclabendazole is the only group that has activity against early immature fluke; however, there have been cases of resistance to these products. When choosing a product to treat liver fluke it is important to look for these ingredients as you will then know which stage of fluke will be targeted.

Anthelmintic resistance is becoming more of an issue on Irish farms due to overuse of certain products and not using best practice when administering these products. To help slow down resistance farmers should follow proper administration of products, only use when necessary, use the most appropriate product, and avoid bringing resistance onto the farm by treating stock on arrival. When dosing try to accurately estimate the weight of the animals you are treating to decide on the correct dose rate as you do not want to under or over dose animals, and have equipment in good working order and calibrated before use. If you want to make sure that the product you are using is being effective, it would be a good idea to send off dung samples for testing. It is also important to be aware of withdrawal periods in particular when animals are to be slaughtered. Keeping these guidelines in mind over the winter months will help you to have a plan in place when treating fluke on your farm.