Welcome to NADIS. This map will only appear on the initial visit to the website. Please select your region, and you will be automatically be taken to your region on future visits

UK Map Northern Ireland North Scotland South East Scotland South West Scotland North East England Yorkshire & Humber East Midlands East of England South East England North West England Wales West Midlands South West England
Download this page as a PDF

Download now

NADIS Parasite Forecast - June


At the start of April, the UK's weather was unsettled and dominated by low pressure, with frequent showers and some longer spells of rain. This unsettled regime continued into the second week, with low pressure to the south-west in the Atlantic drawing in an easterly airstream. The second half of April was mostly cold, bright and showery with frequent northerly winds, although there was a brief warm sunny spell in central and northern areas between the 19th and 22nd. Sleet and snow fell unusually widely for late-April between the 26th and 29th, with some accumulations even at lower levels in the north-east accompanied by sharp frosts. (

June Parasite Forecast/Update

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

Parasitic gastroenteritis (PGE)

Contaminated (permanent) grazing:

  • Lambs grazing contaminated pastures will likely have been treated with a Group 1 anthelmintic to prevent nematodirosis during May because 2016 has been a high risk year due to the cold weather throughout April in many regions.  However, group 1 anthemintics are often not effective against other nematode species therefore treatment(s) to limit the build-up of infective larvae on contaminated pasture ('mid-summer rise') will still be necessary.  The timing of such suppressive anthelmintic treatment(s) for lambs will depend upon the ewe anthelmintic treatment at lambing time (whether a short- or long-acting preparation), grazing conditions, stocking density, and weather over the coming weeks.
  • Performance (see targeted anthelmintic treatment section below) and worm egg counts of lambs taken every two weeks from June onwards can be used to guide anthelmintic treatments.  Pooled faecal samples from approximately 10-12 lambs will guide treatment.  Treatment is generally recommended when counts exceed 500-700 epg.
  • Prolonged local dry weather conditions during summer can delay larval challenge to lambs grazing contaminated pastures with a return to infectivity when wet weather arrives.
  • Remember to include rams in the farm's parasite control programme because they are fully susceptible to PGE. It will take at least two months of good grazing for a ram to gain one unit of condition score with a target of 3.5 at mating in October/November. Rams typically graze the same field every year with significant build-up of infection on this pasture.


Remember to include rams in the farm's parasite control programme because they are fully susceptible to PGE; these rams need to start gaining condition before mating from September onwards.

Safe Grazing

  • Lambs grazing safe pastures should not require anthelmintic treatment until around 3-4 month-old.

Pasture that has not been grazed by sheep until mid-summer (e.g. silage aftermath) may then be regarded as 'safe grazing' and used for weaned lambs because over-wintered larvae will have exhausted their energy stores and died before mid-summer. "Safe grazing" is an important component of the farm's sustainable parasite control programme and must be used to greatest benefit.


Planning ahead - silage aftermath should be grazed by weaned lambs as part of the sustainable parasite control programme on your farm.

Targeted Anthelmintic Treatment

  • Targeted anthelmintic treatment selects only those lambs for treatment that are failing to meet expected growth rates.
  • Lambs are weighed every 3-4 weeks.
  • In general, only 40-60 per cent of lambs require anthelmintic treatment which saves money.
  • This strategy greatly reduces the likelihood of selecting for resistant strains of worms because such a large number of lambs are not treated.
  • Most importantly, targeted anthelmintic treatment should prolong the efficacy of Groups 2 and 3 anthelmintics without recourse to Group 4 and 5 anthelmintics which are much more expensive.
  • Electronic identification and automated weight recording simplifies TST.
  • Regular weighing also identifies poor growth which may be caused by overstocking, trace element deficiencies etc. and prompt management review.
  • Accurate record keeping also allows selection of the best genetics in your flock with breeding stock kept on the basis of performance not appearance.



Targeted anthelmintic treatment selects only those lambs for treatment that are failing to meet expected growth rates.


  • Shearing reduces the risk of blowfly strike in adults
  • Treat all shearing cuts otherwise flies can cause severe irritation and disrupt grazing.

Shearing allows direct assessment of body condition scores of the whole flock and thereby ewe nutrition during the first 2-3 months of lactation.


Shearing reduces the risk of blowfly strike in adults


Treat all shearing cuts immediately to prevent flies and further self-inflicted injury by the sheep.


  • Cattle receiving prophylactic anthelmintic treatments must remain on the same pasture during the entire grazing season or be moved to safe grazing such as silage aftermath.
  • Strategic regimes based on products with prolonged persistence against Ostertagia ostertagi may allow the build-up of pasture populations of those worm species against which they have poorer efficacy or little persistent effect, for example Cooperia species and Nematodirus helvetianus, which may cause problems later in the year.
  • Incidents of clinical PGE in cattle peak during August/September.



Strategic regimes are commonly used to control Ostertagia ostertagi infestation in autumn-born beef cattle during their second grazing season.


Lungworm disease appears from June onwards in unvaccinated calves, those cattle without an effective anthelmintic programme, and naïve adults.

  • Early signs include coughing, initially after exercise then at rest, and an increased respiratory rate.
  • Affected cattle rapidly lose weight and body condition



Lungworm infestation from a farm where vaccination was not used has caused marked condition loss; convalescence will be prolonged causing considerable financial loss.


Large numbers of lungworm in the airways causing death of this steer.

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