Guard against nematodirus in lambs

Make sure you are using a risk assessment and forecasting tool to guard against nematodirus in lambs.

Nematodiriosis in lambs can strike quickly and with little to no warning, resulting in stunted growth and high mortality rates.

While, traditionally, nematodirus was an issue in April/May for southern England and June for northern England, increasingly unpredictable weather means the timing now varies from region to region and year to year.

Knowing the risks and grazing history, and using the SCOPS nematodirus forecast tool, can help you take rapid action as needed.

Nematodiriosis life cycle

The life cycle of the Nematodirus battus worm is different to other worm species. Infection passes from last year’s lamb crop to the next as larvae development takes place inside the egg.

The eggs must have a period of cold weather followed by temperatures of 10°C and above to hatch. If these conditions occur within a short period, they trigger a mass hatch.

The impact of a mass hatch on a group of lambs can be substantial if it happens as lambs are starting to eat significant quantities of grass. The risk will vary depending on your location and the age of your lambs.

Recent analysis by SCOPS shows the peak risk period has varied by six weeks over the last five years, highlighting the need to assess risk by year and by farm.

Risk factors

Lambs grazing pasture that also carried lambs last spring and where one or more of the following apply:

• Lambs are old enough to eat significant amounts of grass (6–12 weeks old but can be younger if ewes are not milking well)
• There is likely to be a challenge from coccidiosis, e.g. groups of mixed-aged lambs
• There has been a sudden cold period followed by warm weather
• Lambs are under additional stress, e.g. triplets, fostered lambs or lambs on young or older ewes

Recommended actions

Where possible, move at-risk lambs to low-risk pastures, i.e. pasture not grazed by lambs last spring.

If this is not practical, speak to your vet or SQP and use the forecasting tool for your area to support any decisions around the need for treatment.

If you decide to treat lambs, follow the SCOPS guidance to ensure you select the most appropriate product for treatment.

Take a faecal egg count (FEC) 7–10 days after treatment to make sure it has been effective; lambs may need to be treated more than once depending on the spread of ages in the group and subsequent weather conditions.

Further information