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NADIS Parasite Forecast - February

Use of meteorological data to predict the prevalence of parasitic diseases

PF Capture

December 2014 was mild with a mean temperature around 0.5°C above the 1961-90 long-term average adding to the average rolling three month mean temperature between1-1.5°C above the 1961-90 long-term average. December rainfall was slightly below normal in most regions. The first half of January has also seen mild temperatures but stormy with wet conditions in many areas (

February Parasite Forecast/Update

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


  • Winter is a good time to review the parasite control plan for the forthcoming grazing season especially for those flocks with large areas of permanent grazing.
  • Safe grazing available at turnout (e.g. last year's pastures grazed by cattle 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.

Check now for chronic liver fluke in sheep and beef cattle

  • While this winter has generally seen a low to moderate risk for liver fluke disease, chronic liver fluke will still be encountered in some flocks during late winter/early spring.
  • 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 the digestive enzymes that are released into the bile by migrating (late immature) and adult flukes in sheep faeces. Using this test, active fluke infestation can be detected as early as 3-4 weeks after infestation, but more reliably after 6-9 weeks. This is approximately 3-6 weeks before eggs can be detected in faeces.
  • If sheep have not been treated this autumn/winter then faecal samples from around 10 ewes will identify patent fluke infection if present, and indicate the need to treat the group.
  • All efforts must be taken to reduce reliance on triclabendazole through husbandry measures, and the use of other fasciolicides as appropriate.
  • Closantel and nitroxynil are very effective against flukes from around 7 weeks post infestation and should be used for treatment before lambing time.
  • 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 2015.

Fig 1

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

Fig 2

Sheep affected by chronic liver fluke show significant weight loss.


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.

Fig 3

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

Fig 4

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


Watch out for: Parasitic gastroenteritis (PGE) in fattening lambs and yearlings

  • The continuing mild weather may lead to PGE in store lambs and yearlings particularly on paddocks heavily contaminated earlier in the season by grazing lambs.
  • This risk period can continue into February given the present mild weather conditions. The need to dose out-wintered store or replacement lambs during the winter can be reliably assessed by monitoring pooled faecal egg counts.

Fig 5

The continuing mild weather may lead to the risk of PGE in store lambs this winter - typically black foetid diarrhoea.

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 flanks 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.

Fig 6

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

Fig 7

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.

Watch out for: Lice in Sheep

  • 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.
  • Lice infestations are widespread in most sheep flocks.
  • Use of plunge dipping for other reasons, such as control of sheep scab, cutaneous myiasis and headfly problems, also effectively controls louse infestations.
  • Louse infestations can also be controlled with topical application of high cis cypermethrin or deltamethrin best used soon after shearing.

Fig 8

Louse populations are highest during late winter and may cause disrupted feeding patterns, fleece damage/loss, and self-inflicted trauma.

Fig 9

Poor flock husbandry - heavy louse infestation affecting a ewe in poor condition.


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