The wettest summer for many years has led to a high risk of liver fluke infection in sheep and cattle across large areas of the UK, including the north, west and central Scotland, west Wales and Cornwall.

Even eastern Scotland and parts of north and south-west England are being viewed as being at medium risk of liver fluke.

The higher than average rainfall from May to October created ideal conditions for the liver fluke’s intermediate host, the mud snail, to thrive, leading to an increased number of infective larvae on pasture. This, coupled with 2017’s long grazing season on pasture, has led to greater fluke burdens in pastured animals, according to Boehringer Ingelheim Animal Health's ruminant technical manager, Sioned Timothy.

She said that sheep were most at risk of acute fluke disease in the autumn. This disease is caused by migrating juvenile liver fluke and sheep may simply be found dead with no prior signs of illness. However, chronic liver fluke disease caused by the presence of adult fluke, peaks in the late winter/early spring. Affected sheep may show varying signs of infection, such as progressive loss of condition, weakness, lowered appetite, emaciation, a brittle open fleece, the development of anaemia and low blood protein levels, characterised by pale mucous membranes, and submandibular oedema (‘bottle jaw’), she added.

“Farmers in high fluke risk regions of the country who have already administered a first treatment for acute fluke earlier in the year, may be able to delay a second triclabendazole (TCBZ) treatment until January.

“However, where TCBZ-resistance has been confirmed, or suspected, farmers should consider the use of either closantel, or nitroxynil-based products, which are active on the late immature stages of fluke, from 7-8 weeks after infection."

She added: "The aim of any spring treatments should be to remove any surviving adult flukes and prevent pasture contamination by fluke eggs reducing the risk of disease later in the year. In these cases, choosing an alternative to TCBZ is advised in all cases, to reduce the likelihood of resistance."

Faecal egg samples from around 10 animals will identify patent fluke infection acquired during the autumn and indicate the need to treat the flock.

Mild, wet winters are also known to increase the risk of parasitic gastroenteritis (PGE), said Ms Timothy. Outbreaks of trichostrongylosis in store and replacement lambs, as well as gimmers, is not uncommon.

"Farmers should continue to monitor worm egg counts on pooled faecal samples where there is a risk of disease. Heavy infestations are typically associated with black foetid diarrhoea (black scour) and rapid weight loss," she said.

Sheep scab and lice can by present during the housing period, but the similarities in the symptoms for both conditions mean that correct diagnosis is important before deciding on treatment. "Farmers should consult their vet or local animal health adviser for information if unsure," she pointed out.

Sheep scab is caused by the presence of psoroptic mites. Infection can be debilitating leading to significant loss of condition, secondary infections and eventually death if not treated. In Scotland, it is a notifiable disease.

"Out-wintered cattle in areas with a high risk of liver fluke may need dosing in December. However, acute fluke is rare in cattle and farmers should consider using alternatives to TCBZ where possible, such as closantel or nitroxynil (Trodax)," she said.

"Cattle treated for fluke at housing should be tested for the presence of the adult stage of the parasite mid-winter and re-treated if necessary, to ensure all fluke are removed. The interval between housing and testing or re-treatment will depend on the product used.

"For closantel or nitroxynil the interval is 6-7 weeks, and 10-12 weeks for oxyclozanide or albendazole. Even where TCBZ was used, juvenile fluke may have infected cattle 1-2 weeks before housing. In these cases cattle may require re-treatment.

“Faecal egg counting, blood or milk ELISA testing, and slaughterhouse liver reports are practical methods of detecting fluke challenge within a herd. Farmers should seek advice and base treatments on local farm conditions, as well as the NADIS fluke forecast,” advised Ms Timothy.