Nematodirus Forecast

Powered by Forecast ( and the Met Office Datapoint

Risk at a Glance

Each dot on the map represents a weather station. Zoom in on the map to find your area and then click on the weather station closest to your holding for more detailed information and advice on how to protect your lambs - but read the information below on how this information relates to your holding.

Negligible Risk

Low Risk

Moderate Risk

High Risk

Very High Risk

The SCOPS Nematodirus Forecast 2018 is sponsored by Bimeda and FECPACK




How does the SCOPS Nematodirus Forecast work?

The forecast predicts the hatch date for nematodirus based on temperature data from 140 weather stations throughout the UK and should be used in combination with your grazing history (more below) to assess the risk of nematodirus infection in your lambs. To use the forecast:-

  1. Zoom in on the map to locate the station(s) closest to your holding. Use knowledge of your farm and the surrounding area to choose the weather station that is most relevant to you. In most cases this will be the nearest station but if, for example, there is a large difference in the height above sea level between your holding and the nearest weather station, then look to see if another station further away may be more representative. (If you click on a station it will give the height above sea level). Alternatively take a view across a combination of stations in your area.
  2. Click on the station(s). Each station has more detailed information on the current risk level, guidance on what to do next, and information on when the forecast was last updated.
  3. Carry out a risk assessment and take action if needed. Nematodirosis can strike very quickly so you can’t afford to have a ‘wait and see’ policy. And because the damage is done by large numbers of immature larvae that are not producing eggs, faecal egg counts (FECs) are not a reliable indicator of risk. Rapid action is often required and this has to be based on a risk assessment and the forecast for your area.

Main risk factors

If your lambs are grazing pasture that carried lambs last spring and you answer yes to one or more of these questions, your lambs are at risk.

  • Are they old enough to be eating significant amounts of grass? (generally 6-12 weeks of age but may be younger if ewes are not milking well)
  • Do you have groups where there is also likely to be a challenge from coccidiosis? For example, mixed aged lambs are a higher risk
  • Has there been a sudden, cold snap recently followed by a period of warm weather?
  • Have you got lambs that are under other stresses e.g. triplets, fostered, on young or older ewes.

Recommended actions

If possible, avoid infection. Move at-risk lambs (as determined by the risk assessment) to low risk pastures (i.e. pasture that was not grazed by lambs the previous spring).

If you cannot avoid high risk pasture grazed by lambs the previous spring and decide you need to treat for nematodirus, SCOPS advises farmers to use a white (1-BZ) drench. Use the SCOPS ‘Know Your Anthelmintics’ Guide to select a product. These are still highly effective against this parasite on most farms and suitable for young lambs. Check that treatment is effective by taking a FEC 10 days after treatment. Remember, it may be necessary to treat lambs more than once depending on the spread of ages in a group and subsequent weather conditions.

Understanding nematodirus  

Nematodirosis is a particularly nasty disease in lambs, causing a high number of mortalities and stunting the growth of many others. It is caused by the Nematodirus battus worm, which has a different lifecycle to other sheep worms. Under certain climatic conditions it can strike very quickly, with little or no warning. The main difference in the lifecycle of Nematodirus battus compared with other parasitic worms is that development to infective larvae takes place within the egg and infection passes from one lamb crop to the next year’s crop. Cold weather delays hatching so when we get a sudden change in temperature it can trigger a mass hatch. If this coincides with the time when lambs are starting to take in significant amounts of grass (over about six weeks old), the result can be devastating.