“Since 2000 the incidence of liver fluke has been increasing and it is estimated that 20% of livers are condemned in UK abattoirs at a cost of over £1 million annually”, Aurelie Moralis, Veterinary Consultant with Zoetis told a meeting of animal health SQP’s organised by Agrihealth.
She explained that immature fluke migrates through the liver to the bile ducts where they mature and lay eggs which pass down into the intestines and are deposited unto pasture in the sheep’s faeces.
Adult fluke can lay hundreds of eggs per day. As the lifecycle outside of the sheep is dependent on the presence of the mud snail the disease is more common in wet regions. Climatic factors likely to increase the risk of fluke infection are a mild winter followed by a wet, warm summer.
The clinical signs of the acute fluke in sheep are a result of immature fluke migrating through the liver tissue and can lead to a rapid loss of condition and sudden death. Chronic fluke is caused by adult flukes in the bile ducts feeding on the host’s tissue and blood and is characterised by ill-thrift, anaemia, bottle jaw and terminal diarrhoea.
Aurelie emphasised: “When choosing a treatment for liver fluke it is crucial to use the right product for the stage of liver fluke in the animal.”
Most flukicides on the market are effective for treating adult fluke but few are effective in treating immature fluke. Triclabendazole is the drug of choice for very immature fluke but it is recommended to rotate with alternatives in late winter/spring to reduce the potential development of triclabendazole resistance.
She advised: “To delay the development of flukicide resistance generally, use the full dose rate with correctly functioning equipment and avoid using one chemical family exclusively for a number of years.”
For mixed infections only use combination fluke and worm products. Cydectin ® TriclaMox Oral Solution for sheep contains moxidectin and triclabendazole and is the only combination fluke and worm treatment with persistent action against stomach worms which is also effective against all stages of fluke.
Aurelie added: “The flukicide programme has to be on a ‘know your farm’ basis. The effectiveness of anthelmintic treatments on individual farms can be checked by taking dung samples after treatment and submitting them through your vet for laboratory examination.”