Janssen Animal Health is advising farmers not to leave it too late to treat for fluke and to think about their choice of flukicide this autumn. The company recently warned sheep farmers to be on the look out for sudden deaths in their flocks this autumn as acute fascioliasis due to liver fluke was predicted to reach high levels. Since then both NADIS and SAC have produced their latest data which supports the prediction that in Northern England and Scotland fluke threat has reached its highest level yet. April to August statistics show diagnosis of the disease in sheep is already up 5 per cent.
An EU funded project (DeLiver) is also underway, bringing together 12 European and three South American research groups to investigate the main issues of concern regarding fluke: these include how the changing climate has led to geographical spread of the disease and the appearance of triclabendazole resistant strains. The group say that the extent of triclabendazole resistance is currently difficult to identify and aim to develop a test to establish resistance in reported cases. In the meantime they suggest that farmers avoid under-dosing and too frequent treatments with the same licensed drug year on year. SAC has also been emphasizing the risk in its latest report which points out that since triclabendazole resistance was first reported in Scotland in 1998, the number of farms where resistance has been detected has risen.
Janssen say that both acute and chronic fascioliasis can be controlled by implementing a strategic control programme using effective flukicides on a rotational basis as well as management programmes. This approach can both minimize the risk of resistance developing to flukicides, and can be effective in reducing pasture contamination and subsequent fluke infections.
Vet Nigel Underwood says that farmers need to seek advice and think carefully before electing to treat with their usual product, “We should be bracing for a surge of new cases of fluke and resurgence in areas where the disease has been endemic but previously controlled. In the panic, it’s easy to reach for the familiar products but every farm is different with regard to climatic conditions, the incidence of fluke and the appearance of resistant populations. There is some evidence that some fluke strains have shorter lifecycles and variable degrees of resistance to triclabendazole1. In choosing how to treat, farmers need to consider many variables. There have been no reports of resistance to closantel in the UK, it will kill fluke and also cause marked stunting of earlier immature fluke i.e. they never develop fully, lay fewer eggs and the eggs they do lay have reduced viability. Closantel disrupts egg laying and the viability of eggs for 13 weeks – longer than any other flukicide. With many experts recommending follow up treatments just one to two months after initial doses, it’s clear that this year is a high risk situation where everyone needs to be doing everything they can to reduce deaths from acute disease and to minimise the burden of fluke within over-wintered animals as soon as possible.”
Mr Underwood also added that late cases of Haemonchus (Barber’s Pole worm) attributed to the mild start to winter have also been reported and warned farmers to be on the look out for unexplained anaemia or sudden death which could be attributed to fluke in the absence of a post mortem, “The blood sucking nature of the parasite means that it is very susceptible to anthelmintics, such as closantel, that are carried in the blood and dosing now will give six weeks duration of effect against Haemonchus, providing protection for these late season cases.”
For more advice on strategic control of fluke and minimising the risk of resistance to flukicides farmers should speak to their animal health adviser or vet.
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