Sheep farmers should be aware of the growing prevalence of liver fluke and the parasite's increasing resistance to triclabendazole throughout the UK.
With such significant production and financial consequences of fluke for farmers, these are both challenges of serious concern for the industry and need to be tackled, says veterinary surgeon Dudley Gradwell. The sheep industry can not afford to lose one of the major weapons against liver fluke by allowing resistant strains of fluke to spread widely over the country.
As far back as November 2003 an SAC report stated that triclabendazole-resistant fluke had been recorded in sheep "over the past few years" in Scotland, England, Wales and Ireland.
Scotland's Helminth Control Group puts the nation's sheep industry losses at £50 million a year, on average, from deaths and poor production in sheep and liver condemnations caused by the liver fluke, Fasciola hepatica.
Underlining the extent of the problem, Max Bonniwell a partner with Oban Veterinary Surgeons, says triclabendazole resistance is so widespread in the region that many sheep farmers could not survive without using an alternative flukicide.
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"More and more farmers are using closantel to ensure triclabendazole-resistant fluke are killed and the fluke problem on their farms is brought under control," he states. "Where farmers are unsure if their sheep are challenged by resistant fluke, we are encouraging them to carry out tests. It is important the industry takes steps to attempt to slow the growth of this resistance."
Dudley Gradwell, technical manager with Janssen Animal Health, says milder winters have allowed more mud snails to survive, and they are the intermediate hosts that enable fluke to complete their life cycle and get into sheep at an earlier stage in the year – often with dire financial consequences for farmers.
"Liver fluke can seriously raise lamb mortality rates, cut weight gain by up to five per cent, cut the number of multiple births by up to 10 per cent and reduce birth weight," he says. Wool production can also be adversely affected, by as much as 40 per cent.
It is important that farms which have an actual or potential fluke problem include a strategic fluke treatment programme as part of their farm health plan, based on an effective flukicide and a rotational dosing programme, he states. Closantel, the active ingredient in Flukiver™, for example, controls immature and adult fluke. It also severely stunts early immature fluke1. It also prevents egg laying for 13 weeks – significantly longer than any other flukicide.
An added assurance for sheep farmers is the fact that closantel has no history of fluke resistance in the UK, making it ideal for treatment of flocks, for new stock brought on to a farm and for killing triclabendazole-resistant fluke.
Achievements 'wiped out'
The production and financial losses caused by liver fluke are a concern to industry organisations and UK meat processors. Peter Morris, chief executive of the National Sheep Association, says farmers are continually striving to improve efficiency and product quality. "Failing to act to control this parasite can wipe out in a season the advances it has taken years to achieve," he says. more . . .
A report published by the English Beef and Lamb Executive (Eblex) puts the annual cost of gastro-intestinal parasites, including liver fluke, for British sheep farmers at an estimated average £84 million.
Phil Saunders of Eblex says: "Reduced lamb growth is responsible for about 75 per cent of the costs, and so reducing the severity or the incidence of infection with these parasites will have a large beneficial impact on costs of production."
Meat processors are hit by the loss of sales when livers are condemned and then the cost of their disposal. In extreme cases, all livers in a consignment of lambs can be condemned. There is also the loss of lamb quality, at times making it difficult for processors to meet the specifications required by their retail customers.
A spokesperson for the British Meat Processors Association says the industry works on very low margins and cannot afford the burden of extra costs. "Ultimately, costs such as these have to be passed back where possible. Financial penalties for lambs that do not meet specification are an example."
Says Dudley Gradwell: "The extra productivity gained from having a strategic fluke treatment programme in place makes it a sound investment for sheep farmers. In regions where fluke is known to be a problem, it is vital that farmers draw up a good fluke control programme with their veterinarians. If farmers wait until they see symptoms, the disease will already have caused significant financial losses."
