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NADIS Parasite Forecast - February

Capture 2

December was an exceptional and record-breaking month. The UK was in a warm and moist tropical air mass for most of the month, bringing unseasonably mild conditions to England and Wales, although Scotland and Northern Ireland were colder at times, particularly in the second week. It was also exceptionally wet and often windy, with frequent deep depressions and frontal systems - including storms Desmond, Eva and Frank - bringing record-breaking rainfall over much of Scotland, Wales and northern England. Severe flooding affected Cumbria for much of December, and became widespread across North Wales, northern England and Scotland after Christmas. (

February Parasite Forecast/Update

The most recent version of this monthly parasite forecast may be accessed at


The very mild and extremely wet conditions that we have seen throughout the UK this winter has meant that the survival of all the internal parasites of sheep and cattle on pasture has been prolonged. This means we have been seeing more cases of PGE in lambs and more Liver Fluke cases than we might otherwise have expected and the risk of further disease remains high especially in those areas of Scotland, Wales and Western England with a higher Liver Fluke forecast this season.

Review of flock and herd health plan

  • Winter is a good time to review the parasite control plan for the forthcoming grazing season with your veterinary adviser especially for those flocks and herds with large areas of permanent pasture grazing.
  • Safe grazing available at turnout (e.g.  pasture grazed by cattle last year and re-seeded pastures) will avoid the risk of nematodirosis in young lambs.  In midsummer, silage aftermaths can be utilised to reduce reliance on anthelmintics to control internal parasites in weaned lambs.
  • Intergrating your grazing management and treatment plans for cattle and sheep on a holding can reduce the need for treatment and allow stock to perform better if done well.


Check now for chronic liver fluke in sheep and beef cattle


  • This winter has seen a moderate to high risk for liver fluke disease in western region of the UK, especially in Scotland.
  • Chronic liver fluke will be encountered in flocks during late winter/early spring unless action is taken now.
  • Poor scanning results may be the first indication that there is a liver fluke problem on the farm and may be limited to only one group of sheep depending upon its autumn/winter grazing.
  • Be aware that not all sheep with fluke infestation develop 'bottle-jaw'.
  • The new coproantigen ELISA test detects digestive enzymes that are released into the bile by migrating (late immature) and adult flukes and detected in sheep faeces.  Active fluke infestation can be detected 3-4 weeks after infestation but more reliably after 6-9 weeks. This is ~3-6 weeks before eggs can be detected in faeces.
  • Care must be taken to ensure that all sheep are drenched correctly especially when working with sheep in a pen rather than a race.
  • All efforts must be taken to reduce reliance on triclabendazole by husbandry measures, and the use of other fasciolicides as appropriate.
  • Closantel and nitroxynil are very effective against immature flukes from around 7 weeks post infestation and can be used for treatment from December onwards.
  • Care should be taken to ensure sheep are not overdosed with clostantel or nitroxynil.   Weigh a representative number of sheep to gauge the correct bodyweight range within the group/flock.  If there is a significant difference between breeds etc; separate and  treat as two groups.
  • Sheep should always be moved to clean pastures after treatment; supplementary feeding may be necessary to maintain condition.
  • Albendazole and oxyclozanide are effective from 10-14 weeks post infestation and can be used when treatment is recommended to remove adult flukes in late spring (often in May).
  • Limiting pasture contamination with fluke eggs now from patent infestations will reduce fluke larval challenge during late summer/autumn 2016.


Poor scanning results (image shows resorption of lower foetus) may be the first indication that there is a liver fluke problem on the farm.


Sheep affected by chronic liver fluke show significant weight loss. The mature flukes live in the bile ducts but are shown here on the surface of the liver.


Sheep affected by chronic liver fluke show significant weight loss. The mature flukes live in the bile ducts but are shown here on the surface of the liver. Compare with a normal sheep's liver below.


A normal sheep's liver.

Beef cattle

More than 25% of bovine livers are condemned at slaughter because of liver fluke damage.

  • Fluke infestation increases the time taken to reach slaughter weight by several weeks.
  • Un-dosed beef cattle grazing potentially infected pastures, should either be checked for the presence of fluke eggs in faeces or treated.


Out-wintered cattle should be checked for the presence of fluke eggs in faeces.


This bovine liver at the slaughterhouse shows extensive liver fluke damage.

Watch out for sheep scab

Sheep scab is typically encountered during the autumn/winter months from September to April.

  • Sheep have disturbed grazing patterns and are observed kicking at their chest with their hind feet and/or rubbing themselves against fence posts.
  • The fleece is wet, sticky, yellow, and frequently contaminated with dirt from the hind feet.
  • Typically after eight weeks' infestation or so the hair loss on the flanks may extend to 20 cm diameter surrounded by an area of inflammation and serum exudation. The skin is often thrown into thickened corrugations.

NB: Different rules apply in England and Wales vs Scotland on reporting of Sheep Scab, consult your vet or local APHA for details.


Early sheep scab - rubbing causing breakage of wool over the chest wall.


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.


Local farm conditions may vary so consult your veterinary surgeon. Parasite control should be part of your veterinary health plan.