Parasite Forecast January 2017 – NADIS Summary

Local farm conditions may change, consult your Severn Edge Vet.
Effective worm control should be part of your veterinary health plan.

For the full forecast please go to

The weather in November started off mild in the south, but turned colder with snow in parts of Scotland and northern England and thereafter remained, generally unsettled with heavy rain and flooding in the south-west, followed by a further spell of dry but cold weather in most regions.

Liver Fluke
For regions of the UK with a predicted high risk of liver fluke disease (Scotland, NW England, and north Wales), the recommendations for January are:

  • Efforts should be taken to reduce reliance on triclabendazole by husbandry measures and by the use of other flukicide treatments when appropriate.
  • Closantel and nitroxynil are highly effective against adult and late immature flukes and should be used now for the treatment of fasciolosis in sheep.
  • Where possible, treated sheep and cattle should be moved to fluke-free pastures after treatment.
  • Where triclabendazole resistance is suspected, a fluke faecal egg count reduction test should be considered at 3-weeks post treatment. The alternative, is the coproantigen ELISA test, which can be used two to three weeks after dosing. Farmers should contact their veterinary practitioner for further advice where such drug resistance is suspected.
  • Quarantine treatments must be carefully considered for all introduced sheep and cattle.

For moderate or low risk areas:
If animals have not been treated, then faecal samples from around 10 animals will identify patent fluke infection acquired during the autumn and indicate the need to treat the group. The above recommendations equally apply for those animals requiring treatment.

Signs of Liver Fluke

  • Chronic liver fluke in sheep and cattle peaks in the late winter/early spring.
  • Affected sheep may show a progressive loss of condition, weakness, lowered appetite, emaciation, a brittle open fleece, and the development of anaemia characterised by pale mucous membranes.
  • Cattle with chronic liver fluke typically show signs of chronic weight loss and diarrhoea.

More than 25% of bovine livers are condemned because of liver fluke damage; positive results from the slaughterhouse should be discussed with your veterinary surgeon.

Parasitic gastroenteritis (PGE)

  • There is a continued risk of PGE in store lambs and yearlings throughout the winter, particularly on paddocks heavily contaminated earlier in the season by grazing lambs.
  • The need to dose out-wintered store or replacement lambs during the winter can be reliably assessed by monitoring pooled faecal egg counts.

Continuing mild weather may lead to PGE, especially from Trichostrongylus vitrinus, in store and replacement lambs this winter. Heavy infestations of this parasite cause black foetid diarrhoea (black scour) and rapid weight loss.

Sheep scab and lice
The symptoms of both sheep scab and lice can be similar and so diagnosis is important before advising on treatment.

  • Sheep scab, caused by the presence of psoroptic mites, can be very debilitating with significant loss of condition, secondary infections and eventually deaths if not treated and is typically encountered during the autumn/winter months from September to April.
  • Affected sheep may be restless, have disturbed grazing patterns and are observed kicking at their flanks with their hind feet and/or rubbing themselves against fence posts.
  • As the disease progresses there is hair loss on the flanks with areas of inflammation and serum exudation. The skin is often thrown into thickened corrugations.

Advanced sheep scab, there is extensive fleece loss over the chest, which is wet, sticky and yellow at the edges due to serum leaking from the skin.


  • Like sheep scab, louse populations are highest in sheep during late winter.
  • Lice infestation is commonly mistaken for sheep scab and vice versa.
  • Spread occurs by close contact with other sheep.
  • Infestations of chewing lice are widespread in most sheep flocks. Sucking lice are not a problem in the UK.

Treatments for Scab and Lice

  • Plunge dipping in diazinon is an effective control for sheep scab and louse infestations.
  • Sheep scab can also be treated by injection of a macrocyclic lactone (ML). Treatment requires either a single, or repeat injection 7-10 days apart, depending of the product and active ingredient.
  • Louse infestations can also be controlled with topical application of high cis cypermethrin or deltamethrin.
  • For more information on ectoparasite treatments consult the product literature, or the SCOPS website ( for specific product recommendations.

Parasite Control should be part of your veterinary health plan, consult your Severn Edge Vet for more details.

Related SEV Branch