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Increasing areas of Ireland and the UK are now classified as high risk for the Nematodirus battus worm based on weather patterns. Lambs born in February and early-March are most at risk.
In these areas, eggs that were on pasture have likely now hatched or will do so soon.
What is Nematodirus?
While the SCOPS group lists 15 gastrointestinal worms that affect sheep in Ireland and the UK, four are commercially importance to farmers, merchants and vets.
- Nematodirus battus
- Teladorsagia circumcincta
- Trichostrongylus spp.
- Haemonchus contortus
Of these, Nematodirus is generally the first worm that a lamb will encounter in significant numbers. It is very different to the other three listed worms.
For one, its lifecycle is very long – the infective larvae that lambs ingest from pasture in 2020 come from eggs laid by lambs in 2019.
The other worm lifecycles can complete in less than a month.
Also, it is these larvae that damage the lamb’s intestine, as opposed to the adult stages being pathogenic in other species of worms.
For this reason, FECs are not always a reliable indicator when diagnosing infection.
When?
Lambs are at risk in the period following a ‘mass hatch’ of eggs into larvae. External conditions provide the stimulus to hatch and an ideal scenario would be a cold snap, followed by three or more consecutive days with temperatures averaging above 10°C.
Expectedly, an individual farm’s risk will be governed by geography – e.g. risk is generally earlier in the year on more southerly farms – and height above sea level - every 100m increase in altitude delays hatch by ~one week.
Hatches usually occur between April and June. Where infective larvae are ingested in significant numbers, we can see symptoms in as little as two weeks.
Who?
Adult sheep will be immune to Nematodirus, but lambs will be at risk between six and 12 weeks of age. Multiple lambs and/or lambs from ewes with limited milk will be at risk sooner. Agricultural media outlets will generally report on timing of risk periods by region, based on weather patterns. The SCOPS website boats a ‘Nematodirus Forecast’ page where data is pulled from 140 weather stations across Britain and Ireland to give detailed risk-by-area information.
What?
Scour is the most common symptom farmers will see, as fluid exchange in the intestine is compromised. Note that symptoms can be similar to coccidiosis and no one product treats both. Also, FECs will pick up coccidia oocysts.
The dehydration that follows can be lethal and lambs are often seen congregating around drinkers. There can be well over 10,000 worms present in a significant infection.
Treatment
White wormers, or Benzimidazoles (1-BZ) are recommended by SCOPS when targeting Nematodirus infections. Resistance to BZs in Nematodirus populations is extremely rare and they are typically cheap relative to other active ingredients. Rotation of active ingredients throughout the season is recommended, so best practice would be to save BZs, such as Albex 2.5%, for lambs’ first dose and follow up later in the year with a yellow, e.g. Chanaverm Plus, or clear drench, e.g. Animec Oral, as needed.
When using Albex 2.5%, ensure your drencher is delivering the correct volume by testing with a measuring jug.
The dosage rate is 2ml/10kg.
Never under dose – pick the heaviest lamb in the group and dose all at this rate.
Read more
Increasing areas of the UK and Ireland are now classified as high risk for the Nematodirus battus worm based on weather patterns. Lambs born in February and early-March are most at risk.
In these areas, eggs that were on pasture have likely now hatched or will do so soon.
What is Nematodirus?
While the SCOPS group lists 15 gastrointestinal worms that affect sheep in the UK and Ireland, four are commercially importance to farmers, merchants and vets.
- Nematodirus battus
- Teladorsagia circumcincta
- Trichostrongylus spp.
- Haemonchus contortus
Of these, Nematodirus is generally the first worm that a lamb will encounter in significant numbers. It is very different to the other three listed worms.
For one, its lifecycle is very long – the infective larvae that lambs ingest from pasture in 2020 come from eggs laid by lambs in 2019.
The other worm lifecycles can complete in less than a month.
Also, it is these larvae that damage the lamb’s intestine, as opposed to the adult stages being pathogenic in other species of worms.
For this reason, FECs are not always a reliable indicator when diagnosing infection.
When?
Lambs are at risk in the period following a ‘mass hatch’ of eggs into larvae. External conditions provide the stimulus to hatch and an ideal scenario would be a cold snap, followed by three or more consecutive days with temperatures averaging above 10°C.
Expectedly, an individual farm’s risk will be governed by geography – e.g. risk is generally earlier in the year on more southerly farms – and height above sea level - every 100m increase in altitude delays hatch by ~one week.
Hatches usually occur between April and June. Where infective larvae are ingested in significant numbers, we can see symptoms in as little as two weeks.
Who?
Adult sheep will be immune to Nematodirus, but lambs will be at risk between six and 12 weeks of age. Multiple lambs and/or lambs from ewes with limited milk will be at risk sooner. Agricultural media outlets will generally report on timing of risk periods by region, based on weather patterns. The SCOPS website boats a ‘Nematodirus Forecast’ page where data is pulled from 140 weather stations across the British Isles to give detailed risk-by-area information.
What?
Scour is the most common symptom farmers will see, as fluid exchange in the intestine is compromised. Note that symptoms can be similar to coccidiosis and no one product treats both. Also, FECs will pick up coccidia oocysts.
The dehydration that follows can be lethal and lambs are often seen congregating around drinkers. There can be well over 10,000 worms present in a significant infection.
Treatment
White wormers, or Benzimidazoles (1-BZ) are recommended by SCOPS when targeting Nematodirus infections. Resistance to BZs in Nematodirus populations is extremely rare and they are typically cheap relative to other active ingredients. Rotation of active ingredients throughout the season is recommended, so best practice would be to save BZs, such as Albex 2.5% SC, for lambs’ first dose and follow up later in the year with a yellow, e.g. Chanaverm 7.5%, or clear drench, e.g. Animec Oral, as needed.
When using Albex 2.5% SC, ensure your drencher is delivering the correct volume by testing with a measuring jug.
The dosage rate is 2ml/10kg.
Never under dose – pick the heaviest lamb in the group and dose all at this rate.
Read more
Learn more about worms in sheep