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Wettest summer in years means high fluke and worm risk for sheep and cattle

15 January 2018
Boehringer Ingelheim

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. While Eastern Scotland and parts of North and South-West England are at medium risk of liver fluke.

Higher than average rainfall from May to October has created the 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.

Sheep are most at risk of acute fluke disease in the autumn. This disease is caused by migrating juvenile liver fluke. 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’).

Boehringer Ingelheim Animal Health’s Ruminant Technical Manager, Sioned Timothy, advises: “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 week after infection."

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.

Farmers in lower risk fluke regions, such as the east of England, should consult their veterinary surgeon about fluke control measure before deciding whether treatment is necessary. 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 also increase the risk of Parasitic Gastroenteritis (PGE). Outbreaks of trichostrongylosis in store and replacement lambs, as well as gimmers, is not uncommon. Farmers are advised to 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.

Sheep scab and lice can present during the housing. 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.

Sheep Scab is caused by the presence of psoroptic mites. Infection can be very debilitating leading to significant loss of condition, secondary infections and eventually death if not treated. Farmers in Scotland are reminded that scab 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 therefore farmers should consider using alternatives to TCBZ where possible, such as closantel or nitroxynil (Trodax®).

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 retreatment 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,” advises Ms Timothy.

First and, less frequently, second season grazing cattle that were exposed to pastures contaminated with gutworm larvae late in the grazing season may be at risk from winter scour (type 2 ostertagiosis) from late winter onwards. If these animals were not dosed at housing consideration should be given to treating them with a suitable product before temperatures start to increase. Autumn-born calves that have grazed little are unlikely to require anthelmintic treatment over the housing period.

Lice are very common in the coats of cattle during winter months but low numbers are typically not considered significant. Both chewing and sucking lice are found on cattle in the UK, and when populations increase rapidly this can cause intense itching and irritation. Heavy burdens of sucking lice, which feed on blood, may even lead to anaemia.

Ms. Timothy advises that: “If cattle require lice treatment product selection should take into account the production system and whether any other classes of parasite require treatment. Injectable macrocyclic lactone treatments, such as IVOMEC® Classic Injection, and topical treatments containing either macrocyclic lactones or synthetic pyrethroids can be used as part of a lice control plan. It is essential to make sure that all the animals in the group are treated. Farmers should take advice on the most appropriate option from their vet or local animal health adviser.”

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